Bump postgres version

2026-06-02 13:00:37 +00:00 · 2021-09-27 12:08:55 +03:00 · 2021-09-24 19:21:16 +03:00 · 2021-09-24 19:10:18 +03:00 · 2021-09-24 19:07:30 +03:00 · 2021-09-24 18:19:41 +03:00
91 changed files with 4819 additions and 2252 deletions
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -128,6 +128,14 @@ jobs:
            - ~/.cargo/git
            - target

+        # Run style checks
+        # has to run separately from cargo fmt section
+        # since needs to run with dependencies
+      - run:
+          name: clippy
+          command: |
+            ./run_clippy.sh
+
        # Run rust unit tests
      - run: cargo test

@@ -193,6 +201,9 @@ jobs:
      needs_postgres_source:
        type: boolean
        default: false
+      run_in_parallel:
+        type: boolean
+        default: true
    steps:
      - attach_workspace:
          at: /tmp/zenith
@@ -221,6 +232,9 @@ jobs:
              echo "test_selection must be set"
              exit 1
            fi
+            if << parameters.run_in_parallel >>; then
+              EXTRA_PARAMS="-n4 $EXTRA_PARAMS"
+            fi;
            # Run the tests.
            #
            # The junit.xml file allows CircleCI to display more fine-grained test information
@@ -230,6 +244,7 @@ jobs:
            # --verbose prints name of each test (helpful when there are
            # multiple tests in one file)
            # -rA prints summary in the end
+            # -n4 uses four processes to run tests via pytest-xdist
            pipenv run pytest --junitxml=$TEST_OUTPUT/junit.xml --tb=short -s --verbose -rA $TEST_SELECTION $EXTRA_PARAMS
      - run:
          # CircleCI artifacts are preserved one file at a time, so skipping
@@ -239,7 +254,7 @@ jobs:
          when: always
          command: |
            du -sh /tmp/test_output/*
-            find /tmp/test_output -type f ! -name "pg.log" ! -name "pageserver.log" ! -name "wal_acceptor.log" ! -name "regression.diffs" ! -name "junit.xml" -delete
+            find /tmp/test_output -type f ! -name "pg.log" ! -name "pageserver.log" ! -name "wal_acceptor.log" ! -name "regression.diffs" ! -name "junit.xml" ! -name "*.filediff" -delete
            du -sh /tmp/test_output/*
      - store_artifacts:
          path: /tmp/test_output
@@ -264,6 +279,51 @@ jobs:
            echo $DOCKER_PWD | docker login -u $DOCKER_LOGIN --password-stdin
            docker build -t zenithdb/zenith:latest . && docker push zenithdb/zenith:latest

+  # Trigger a new remote CI job
+  remote-ci-trigger:
+    docker:
+      - image: cimg/base:2021.04
+    parameters:
+      remote_repo:
+        type: string
+    environment:
+      REMOTE_REPO: << parameters.remote_repo >>
+    steps:
+      - run:
+          name: Set PR's status to pending
+          command: |
+            LOCAL_REPO=$CIRCLE_PROJECT_USERNAME/$CIRCLE_PROJECT_REPONAME
+
+            curl -f -X POST \
+            https://api.github.com/repos/$LOCAL_REPO/statuses/$CIRCLE_SHA1 \
+            -H "Accept: application/vnd.github.v3+json" \
+            --user "$CI_ACCESS_TOKEN" \
+            --data \
+              "{
+                \"state\": \"pending\",
+                \"context\": \"zenith-remote-ci\",
+                \"description\": \"[$REMOTE_REPO] Remote CI job is about to start\"
+              }"
+      - run:
+          name: Request a remote CI test
+          command: |
+            LOCAL_REPO=$CIRCLE_PROJECT_USERNAME/$CIRCLE_PROJECT_REPONAME
+
+            curl -f -X POST \
+            https://api.github.com/repos/$REMOTE_REPO/actions/workflows/testing.yml/dispatches \
+            -H "Accept: application/vnd.github.v3+json" \
+            --user "$CI_ACCESS_TOKEN" \
+            --data \
+              "{
+                \"ref\": \"main\",
+                \"inputs\": {
+                  \"ci_job_name\": \"zenith-remote-ci\",
+                  \"commit_hash\": \"$CIRCLE_SHA1\",
+                  \"remote_repo\": \"$LOCAL_REPO\",
+                  \"zenith_image_branch\": \"$CIRCLE_BRANCH\"
+                }
+              }"
+
 workflows:
  build_and_test:
    jobs:
@@ -277,7 +337,7 @@ workflows:
          requires:
            - build-postgres
      - run-pytest:
-          name: pg_regress tests << matrix.build_type >>
+          name: pg_regress-tests-<< matrix.build_type >>
          matrix:
            parameters:
              build_type: ["debug", "release"]
@@ -286,7 +346,7 @@ workflows:
          requires:
            - build-zenith-<< matrix.build_type >>
      - run-pytest:
-          name: other tests << matrix.build_type >>
+          name: other-tests-<< matrix.build_type >>
          matrix:
            parameters:
              build_type: ["debug", "release"]
@@ -297,6 +357,7 @@ workflows:
          name: benchmarks
          build_type: release
          test_selection: performance
+          run_in_parallel: false
          requires:
            - build-zenith-release
      - docker-image:
@@ -308,5 +369,16 @@ workflows:
              only:
                - main
          requires:
-            - pg_regress tests release
-            - other tests release
+            - pg_regress-tests-release
+            - other-tests-release
+      - remote-ci-trigger:
+          # Context passes credentials for gh api
+          context: CI_ACCESS_TOKEN
+          remote_repo: "zenithdb/console"
+          requires:
+            # XXX: Successful build doesn't mean everything is OK, but
+            # the job to be triggered takes so much time to complete (~22 min)
+            # that it's better not to wait for the commented-out steps
+            - build-zenith-debug
+            # - pg_regress-tests-release
+            # - other-tests-release
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -325,6 +325,7 @@ dependencies = [
 "serde",
 "serde_json",
 "tar",
+ "thiserror",
 "toml",
 "url",
 "walkeeper",
@@ -1172,6 +1173,7 @@ name = "pageserver"
 version = "0.1.0"
 dependencies = [
 "anyhow",
+ "async-trait",
 "bookfile",
 "byteorder",
 "bytes",
@@ -1186,19 +1188,16 @@ dependencies = [
 "lazy_static",
 "log",
 "postgres",
- "postgres-protocol 0.6.1 (git+https://github.com/zenithdb/rust-postgres.git?rev=9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858)",
- "postgres-types 0.2.1 (git+https://github.com/zenithdb/rust-postgres.git?rev=9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858)",
+ "postgres-protocol",
+ "postgres-types",
 "postgres_ffi",
 "rand",
 "regex",
 "routerify",
+ "rust-s3",
 "scopeguard",
 "serde",
 "serde_json",
- "slog",
- "slog-scope",
- "slog-stdlog",
- "slog-term",
 "tar",
 "thiserror",
 "tokio",
@@ -1301,27 +1300,9 @@ dependencies = [
 "fallible-iterator",
 "futures",
 "log",
- "postgres-protocol 0.6.1 (git+https://github.com/zenithdb/rust-postgres.git?rev=9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858)",
+ "postgres-protocol",
 "tokio",
- "tokio-postgres 0.7.1",
-]
-
-[[package]]
-name = "postgres-protocol"
-version = "0.6.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ff3e0f70d32e20923cabf2df02913be7c1842d4c772db8065c00fcfdd1d1bff3"
-dependencies = [
- "base64 0.13.0",
- "byteorder",
- "bytes",
- "fallible-iterator",
- "hmac",
- "md-5",
- "memchr",
- "rand",
- "sha2",
- "stringprep",
+ "tokio-postgres",
 ]

 [[package]]
@@ -1342,17 +1323,6 @@ dependencies = [
 "stringprep",
 ]

-[[package]]
-name = "postgres-types"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "430f4131e1b7657b0cd9a2b0c3408d77c9a43a042d300b8c77f981dffcc43a2f"
-dependencies = [
- "bytes",
- "fallible-iterator",
- "postgres-protocol 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
 [[package]]
 name = "postgres-types"
 version = "0.2.1"
@@ -1360,7 +1330,7 @@ source = "git+https://github.com/zenithdb/rust-postgres.git?rev=9eb0dbfbeb6a6c1b
 dependencies = [
 "bytes",
 "fallible-iterator",
- "postgres-protocol 0.6.1 (git+https://github.com/zenithdb/rust-postgres.git?rev=9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858)",
+ "postgres-protocol",
 ]

 [[package]]
@@ -1423,16 +1393,9 @@ dependencies = [
 "lazy_static",
 "memchr",
 "parking_lot",
- "protobuf",
 "thiserror",
 ]

-[[package]]
-name = "protobuf"
-version = "2.24.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "db50e77ae196458ccd3dc58a31ea1a90b0698ab1b7928d89f644c25d72070267"
-
 [[package]]
 name = "proxy"
 version = "0.1.0"
@@ -1447,7 +1410,7 @@ dependencies = [
 "serde",
 "serde_json",
 "tokio",
- "tokio-postgres 0.7.2",
+ "tokio-postgres",
 "zenith_utils",
 ]

@@ -2135,9 +2098,9 @@ checksum = "cda74da7e1a664f795bb1f8a87ec406fb89a02522cf6e50620d016add6dbbf5c"

 [[package]]
 name = "tokio"
-version = "1.8.1"
+version = "1.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "98c8b05dc14c75ea83d63dd391100353789f5f24b8b3866542a5e85c8be8e985"
+checksum = "b4efe6fc2395938c8155973d7be49fe8d03a843726e285e100a8a383cc0154ce"
 dependencies = [
 "autocfg",
 "bytes",
@@ -2146,7 +2109,6 @@ dependencies = [
 "mio",
 "num_cpus",
 "once_cell",
- "parking_lot",
 "pin-project-lite",
 "signal-hook-registry",
 "tokio-macros",
@@ -2189,31 +2151,8 @@ dependencies = [
 "percent-encoding",
 "phf",
 "pin-project-lite",
- "postgres-protocol 0.6.1 (git+https://github.com/zenithdb/rust-postgres.git?rev=9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858)",
- "postgres-types 0.2.1 (git+https://github.com/zenithdb/rust-postgres.git?rev=9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858)",
- "socket2",
- "tokio",
- "tokio-util",
-]
-
-[[package]]
-name = "tokio-postgres"
-version = "0.7.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2d2b1383c7e4fb9a09e292c7c6afb7da54418d53b045f1c1fac7a911411a2b8b"
-dependencies = [
- "async-trait",
- "byteorder",
- "bytes",
- "fallible-iterator",
- "futures",
- "log",
- "parking_lot",
- "percent-encoding",
- "phf",
- "pin-project-lite",
- "postgres-protocol 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "postgres-types 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "postgres-protocol",
+ "postgres-types",
 "socket2",
 "tokio",
 "tokio-util",
@@ -2386,16 +2325,11 @@ dependencies = [
 "log",
 "pageserver",
 "postgres",
- "postgres-protocol 0.6.1 (git+https://github.com/zenithdb/rust-postgres.git?rev=9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858)",
+ "postgres-protocol",
 "postgres_ffi",
 "regex",
 "rust-s3",
 "serde",
- "slog",
- "slog-async",
- "slog-scope",
- "slog-stdlog",
- "slog-term",
 "tokio",
 "tokio-stream",
 "walkdir",
@@ -2644,6 +2578,11 @@ dependencies = [
 "rustls-split",
 "serde",
 "serde_json",
+ "slog",
+ "slog-async",
+ "slog-scope",
+ "slog-stdlog",
+ "slog-term",
 "thiserror",
 "tokio",
 "webpki",
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ Zenith substitutes PostgreSQL storage layer and redistributes data across a clus

 A Zenith installation consists of Compute nodes and Storage engine.

-Compute nodes are stateles PostgreSQL nodes, backed by zenith storage.
+Compute nodes are stateless PostgreSQL nodes, backed by zenith storage.

 Zenith storage engine consists of two major components:
 - Pageserver. Scalable storage backend for compute nodes.
@@ -125,9 +125,19 @@ Now we use README files to cover design ideas and overall architecture for each

 To view your `rustdoc` documentation in a browser, try running `cargo doc --no-deps --open`

+### Postgres-specific terms
+
+Due to Zenith's very close relation with PostgreSQL internals, there are numerous specific terms used.
+Same applies to certain spelling: i.e. we use MB to denote 1024 * 1024 bytes, while MiB would be technically more correct, it's inconsistent with what PostgreSQL code and its documentation use.
+
+To get more familiar with this aspect, refer to:
+
+- [Zenith glossary](/docs/glossary.md)
+- [PostgreSQL glossary](https://www.postgresql.org/docs/13/glossary.html)
+- Other PostgreSQL documentation and sources (Zenith fork sources can be found [here](https://github.com/zenithdb/postgres))
+
 ## Join the development

 - Read `CONTRIBUTING.md` to learn about project code style and practices.
- Use glossary in [/docs/glossary.md](/docs/glossary.md)
 - To get familiar with a source tree layout, use [/docs/sourcetree.md](/docs/sourcetree.md).
 - To learn more about PostgreSQL internals, check http://www.interdb.jp/pg/index.html
--- a/control_plane/Cargo.toml
+++ b/control_plane/Cargo.toml
@@ -16,6 +16,7 @@ toml = "0.5"
 lazy_static = "1.4"
 regex = "1"
 anyhow = "1.0"
+thiserror = "1"
 bytes = "1.0.1"
 nix = "0.20"
 url = "2.2.2"
--- a/control_plane/src/compute.rs
+++ b/control_plane/src/compute.rs
@@ -3,7 +3,8 @@ use std::io::Write;
 use std::net::SocketAddr;
 use std::net::TcpStream;
 use std::os::unix::fs::PermissionsExt;
-use std::process::Command;
+use std::process::{Command, Stdio};
+use std::str::FromStr;
 use std::sync::Arc;
 use std::time::Duration;
 use std::{collections::BTreeMap, path::PathBuf};
@@ -12,6 +13,7 @@ use anyhow::{Context, Result};
 use lazy_static::lazy_static;
 use regex::Regex;
 use zenith_utils::connstring::connection_host_port;
+use zenith_utils::lsn::Lsn;
 use zenith_utils::postgres_backend::AuthType;
 use zenith_utils::zid::ZTenantId;
 use zenith_utils::zid::ZTimelineId;
@@ -86,40 +88,31 @@ impl ComputeControlPlane {
        &mut self,
        tenantid: ZTenantId,
        branch_name: &str,
-        config_only: bool,
+        port: Option<u16>,
    ) -> Result<Arc<PostgresNode>> {
        let timeline_id = self
            .pageserver
            .branch_get_by_name(&tenantid, branch_name)?
            .timeline_id;

+        let port = port.unwrap_or_else(|| self.get_port());
        let node = Arc::new(PostgresNode {
            name: branch_name.to_owned(),
-            address: SocketAddr::new("127.0.0.1".parse().unwrap(), self.get_port()),
+            address: SocketAddr::new("127.0.0.1".parse().unwrap(), port),
            env: self.env.clone(),
            pageserver: Arc::clone(&self.pageserver),
            is_test: false,
            timelineid: timeline_id,
            tenantid,
+            uses_wal_proposer: false,
        });

-        node.init_from_page_server(self.env.auth_type, config_only)?;
+        node.create_pgdata()?;
+        node.setup_pg_conf(self.env.auth_type)?;
+
        self.nodes
            .insert((tenantid, node.name.clone()), Arc::clone(&node));

-        // Configure the node to stream WAL directly to the pageserver
-        node.append_conf(
-            "postgresql.conf",
-            format!(
-                concat!(
-                    "synchronous_standby_names = 'pageserver'\n", // TODO: add a new function arg?
-                    "zenith.callmemaybe_connstring = '{}'\n",     // FIXME escaping
-                ),
-                node.connstr(),
-            )
-            .as_str(),
-        )?;
-
        Ok(node)
    }
 }
@@ -135,6 +128,7 @@ pub struct PostgresNode {
    is_test: bool,
    pub timelineid: ZTimelineId,
    pub tenantid: ZTenantId,
+    uses_wal_proposer: bool,
 }

 impl PostgresNode {
@@ -219,6 +213,8 @@ impl PostgresNode {
            .parse()
            .with_context(|| err_msg)?;

+        let uses_wal_proposer = config.contains("wal_acceptors");
+
        // ok now
        Ok(PostgresNode {
            address: SocketAddr::new("127.0.0.1".parse().unwrap(), port),
@@ -228,15 +224,54 @@ impl PostgresNode {
            is_test: false,
            timelineid,
            tenantid,
+            uses_wal_proposer,
        })
    }

+    fn sync_walkeepers(&self) -> Result<Lsn> {
+        let pg_path = self.env.pg_bin_dir().join("postgres");
+        let sync_handle = Command::new(pg_path)
+            .arg("--sync-safekeepers")
+            .env_clear()
+            .env("LD_LIBRARY_PATH", self.env.pg_lib_dir().to_str().unwrap())
+            .env("DYLD_LIBRARY_PATH", self.env.pg_lib_dir().to_str().unwrap())
+            .env("PGDATA", self.pgdata().to_str().unwrap())
+            .stdout(Stdio::piped())
+            // Comment this to avoid capturing stderr (useful if command hangs)
+            .stderr(Stdio::piped())
+            .spawn()
+            .expect("postgres --sync-safekeepers failed to start");
+
+        let sync_output = sync_handle
+            .wait_with_output()
+            .expect("postgres --sync-safekeepers failed");
+        if !sync_output.status.success() {
+            anyhow::bail!(
+                "sync-safekeepers failed: '{}'",
+                String::from_utf8_lossy(&sync_output.stderr)
+            );
+        }
+
+        let lsn = Lsn::from_str(std::str::from_utf8(&sync_output.stdout)?.trim())?;
+        println!("Walkeepers synced on {}", lsn);
+        Ok(lsn)
+    }
+
    /// Get basebackup from the pageserver as a tar archive and extract it
    /// to the `self.pgdata()` directory.
-    pub fn do_basebackup(&self) -> Result<()> {
-        let pgdata = self.pgdata();
+    fn do_basebackup(&self, lsn: Option<Lsn>) -> Result<()> {
+        println!(
+            "Extracting base backup to create postgres instance: path={} port={}",
+            self.pgdata().display(),
+            self.address.port()
+        );
+
+        let sql = if let Some(lsn) = lsn {
+            format!("basebackup {} {} {}", self.tenantid, self.timelineid, lsn)
+        } else {
+            format!("basebackup {} {}", self.tenantid, self.timelineid)
+        };

-        let sql = format!("basebackup {} {}", self.tenantid, self.timelineid);
        let mut client = self
            .pageserver
            .page_server_psql_client()
@@ -248,47 +283,32 @@ impl PostgresNode {

        // Read the archive directly from the `CopyOutReader`
        tar::Archive::new(copyreader)
-            .unpack(&pgdata)
+            .unpack(&self.pgdata())
            .with_context(|| "extracting page backup failed")?;

        Ok(())
    }

-    /// Connect to a pageserver, get basebackup, and untar it to initialize a
-    /// new data directory
-    pub fn init_from_page_server(&self, auth_type: AuthType, config_only: bool) -> Result<()> {
-        let pgdata = self.pgdata();
-
-        println!(
-            "Extracting base backup to create postgres instance: path={} port={}",
-            pgdata.display(),
-            self.address.port()
-        );
-
-        // initialize data directory
-        if self.is_test {
-            fs::remove_dir_all(&pgdata).ok();
-        }
-
-        fs::create_dir_all(&pgdata)
-            .with_context(|| format!("could not create data directory {}", pgdata.display()))?;
-        fs::set_permissions(pgdata.as_path(), fs::Permissions::from_mode(0o700)).with_context(
-            || {
+    fn create_pgdata(&self) -> Result<()> {
+        fs::create_dir_all(&self.pgdata()).with_context(|| {
+            format!(
+                "could not create data directory {}",
+                self.pgdata().display()
+            )
+        })?;
+        fs::set_permissions(self.pgdata().as_path(), fs::Permissions::from_mode(0o700))
+            .with_context(|| {
                format!(
                    "could not set permissions in data directory {}",
-                    pgdata.display()
+                    self.pgdata().display()
                )
-            },
-        )?;
+            })
+    }

-        if config_only {
-            //Just create an empty config file
-            File::create(self.pgdata().join("postgresql.conf").to_str().unwrap())?;
-        } else {
-            self.do_basebackup()?;
-            fs::create_dir_all(self.pgdata().join("pg_wal"))?;
-            fs::create_dir_all(self.pgdata().join("pg_wal").join("archive_status"))?;
-        }
+    // Connect to a page server, get base backup, and untar it to initialize a
+    // new data directory
+    fn setup_pg_conf(&self, auth_type: AuthType) -> Result<()> {
+        File::create(self.pgdata().join("postgresql.conf").to_str().unwrap())?;

        // wal_log_hints is mandatory when running against pageserver (see gh issue#192)
        // TODO: is it possible to check wal_log_hints at pageserver side via XLOG_PARAMETER_CHANGE?
@@ -304,6 +324,8 @@ impl PostgresNode {
                 max_connections = 100\n\
                 wal_sender_timeout = 0\n\
                 wal_level = replica\n\
+                 zenith.file_cache_size = 4096\n\
+                 zenith.file_cache_path = '/tmp/file.cache'\n\
                 listen_addresses = '{address}'\n\
                 port = {port}\n",
                address = self.address.ip(),
@@ -342,6 +364,40 @@ impl PostgresNode {
            .as_str(),
        )?;

+        // Configure the node to stream WAL directly to the pageserver
+        self.append_conf(
+            "postgresql.conf",
+            format!(
+                concat!(
+                    "synchronous_standby_names = 'pageserver'\n", // TODO: add a new function arg?
+                    "zenith.callmemaybe_connstring = '{}'\n",     // FIXME escaping
+                ),
+                self.connstr(),
+            )
+            .as_str(),
+        )?;
+
+        Ok(())
+    }
+
+    fn load_basebackup(&self) -> Result<()> {
+        let lsn = if self.uses_wal_proposer {
+            // LSN 0 means that it is bootstrap and we need to download just
+            // latest data from the pageserver. That is a bit clumsy but whole bootstrap
+            // procedure evolves quite actively right now, so let's think about it again
+            // when things would be more stable (TODO).
+            let lsn = self.sync_walkeepers()?;
+            if lsn == Lsn(0) {
+                None
+            } else {
+                Some(lsn)
+            }
+        } else {
+            None
+        };
+
+        self.do_basebackup(lsn)?;
+
        Ok(())
    }

@@ -408,38 +464,22 @@ impl PostgresNode {
        }

        // 1. We always start compute node from scratch, so
-        // if old dir exists, preserve config files and drop the directory
-
-        // XXX Now we only use 'postgresql.conf'.
-        // If we will need 'pg_hba.conf', support it here too
-
+        // if old dir exists, preserve 'postgresql.conf' and drop the directory
        let postgresql_conf_path = self.pgdata().join("postgresql.conf");
-        let postgresql_conf = fs::read(postgresql_conf_path.clone()).with_context(|| {
+        let postgresql_conf = fs::read(&postgresql_conf_path).with_context(|| {
            format!(
                "failed to read config file in {}",
                postgresql_conf_path.to_str().unwrap()
            )
        })?;
-
-        println!(
-            "Destroying postgres data directory '{}'",
-            self.pgdata().to_str().unwrap()
-        );
        fs::remove_dir_all(&self.pgdata())?;
+        self.create_pgdata()?;

-        // 2. Create new node
-        self.init_from_page_server(self.env.auth_type, false)?;
+        // 2. Bring back config files
+        fs::write(&postgresql_conf_path, postgresql_conf)?;

-        // 3. Bring back config files
-
-        if let Ok(mut file) = OpenOptions::new()
-            .append(false)
-            .write(true)
-            .open(&postgresql_conf_path)
-        {
-            file.write_all(&postgresql_conf)?;
-            file.sync_all()?;
-        }
+        // 3. Load basebackup
+        self.load_basebackup()?;

        // 4. Finally start the compute node postgres
        println!("Starting postgres node at '{}'", self.connstr());
@@ -451,13 +491,22 @@ impl PostgresNode {
    }

    pub fn stop(&self, destroy: bool) -> Result<()> {
-        self.pg_ctl(&["-m", "immediate", "stop"], &None)?;
+        // If we are going to destroy data directory,
+        // use immediate shutdown mode, otherwise,
+        // shutdown gracefully to leave the data directory sane.
+        //
+        // Compute node always starts from scratch, so stop
+        // without destroy only used for testing and debugging.
+        //
        if destroy {
+            self.pg_ctl(&["-m", "immediate", "stop"], &None)?;
            println!(
                "Destroying postgres data directory '{}'",
                self.pgdata().to_str().unwrap()
            );
            fs::remove_dir_all(&self.pgdata())?;
+        } else {
+            self.pg_ctl(&["stop"], &None)?;
        }
        Ok(())
    }
--- a/control_plane/src/local_env.rs
+++ b/control_plane/src/local_env.rs
@@ -4,27 +4,24 @@
 // Now it also provides init method which acts like a stub for proper installation
 // script which will use local paths.
 //
-use anyhow::{anyhow, Context, Result};
-use hex;
+use anyhow::{Context, Result};
 use serde::{Deserialize, Serialize};
+use std::env;
 use std::fs;
 use std::path::PathBuf;
 use std::process::{Command, Stdio};
-use std::{collections::BTreeMap, env};
-use url::Url;
 use zenith_utils::auth::{encode_from_key_path, Claims, Scope};
 use zenith_utils::postgres_backend::AuthType;
 use zenith_utils::zid::ZTenantId;

-pub type Remotes = BTreeMap<String, String>;
-
 //
 // This data structures represent deserialized zenith CLI config
 //
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct LocalEnv {
-    // Pageserver connection strings
-    pub pageserver_connstring: String,
+    // Pageserver connection settings
+    pub pageserver_pg_port: u16,
+    pub pageserver_http_port: u16,

    // Base directory for both pageserver and compute nodes
    pub base_data_dir: PathBuf,
@@ -35,8 +32,8 @@ pub struct LocalEnv {
    // to four separate paths and match OS-specific installation layout.
    pub pg_distrib_dir: PathBuf,

-    // Path to pageserver binary. Empty for remote pageserver.
-    pub zenith_distrib_dir: Option<PathBuf>,
+    // Path to pageserver binary.
+    pub zenith_distrib_dir: PathBuf,

    // keeping tenant id in config to reduce copy paste when running zenith locally with single tenant
    #[serde(with = "hex")]
@@ -50,8 +47,6 @@ pub struct LocalEnv {

    // used to issue tokens during e.g pg start
    pub private_key_path: PathBuf,
-
-    pub remotes: Remotes,
 }

 impl LocalEnv {
@@ -64,11 +59,7 @@ impl LocalEnv {
    }

    pub fn pageserver_bin(&self) -> Result<PathBuf> {
-        Ok(self
-            .zenith_distrib_dir
-            .as_ref()
-            .ok_or_else(|| anyhow!("Can not manage remote pageserver"))?
-            .join("pageserver"))
+        Ok(self.zenith_distrib_dir.join("pageserver"))
    }

    pub fn pg_data_dirs_path(&self) -> PathBuf {
@@ -98,7 +89,8 @@ fn base_path() -> PathBuf {
 // Initialize a new Zenith repository
 //
 pub fn init(
-    remote_pageserver: Option<&str>,
+    pageserver_pg_port: u16,
+    pageserver_http_port: u16,
    tenantid: ZTenantId,
    auth_type: AuthType,
 ) -> Result<()> {
@@ -165,39 +157,22 @@ pub fn init(
    let auth_token =
        encode_from_key_path(&Claims::new(None, Scope::PageServerApi), &private_key_path)?;

-    let conf = if let Some(addr) = remote_pageserver {
-        // check that addr is parsable
-        let _uri = Url::parse(addr).map_err(|e| anyhow!("{}: {}", addr, e))?;
+    // Find zenith binaries.
+    let zenith_distrib_dir = env::current_exe()?.parent().unwrap().to_owned();
+    if !zenith_distrib_dir.join("pageserver").exists() {
+        anyhow::bail!("Can't find pageserver binary.",);
+    }

-        LocalEnv {
-            pageserver_connstring: format!("postgresql://{}/", addr),
-            pg_distrib_dir,
-            zenith_distrib_dir: None,
-            base_data_dir: base_path,
-            remotes: BTreeMap::default(),
-            tenantid,
-            auth_token,
-            auth_type,
-            private_key_path,
-        }
-    } else {
-        // Find zenith binaries.
-        let zenith_distrib_dir = env::current_exe()?.parent().unwrap().to_owned();
-        if !zenith_distrib_dir.join("pageserver").exists() {
-            anyhow::bail!("Can't find pageserver binary.",);
-        }
-
-        LocalEnv {
-            pageserver_connstring: "postgresql://127.0.0.1:6400".to_string(),
-            pg_distrib_dir,
-            zenith_distrib_dir: Some(zenith_distrib_dir),
-            base_data_dir: base_path,
-            remotes: BTreeMap::default(),
-            tenantid,
-            auth_token,
-            auth_type,
-            private_key_path,
-        }
+    let conf = LocalEnv {
+        pageserver_pg_port,
+        pageserver_http_port,
+        pg_distrib_dir,
+        zenith_distrib_dir,
+        base_data_dir: base_path,
+        tenantid,
+        auth_token,
+        auth_type,
+        private_key_path,
    };

    fs::create_dir_all(conf.pg_data_dirs_path())?;
@@ -225,12 +200,3 @@ pub fn load_config() -> Result<LocalEnv> {
    let config = fs::read_to_string(repopath.join("config"))?;
    toml::from_str(config.as_str()).map_err(|e| e.into())
 }
-
-// Save config. We use that to change set of remotes from CLI itself.
-pub fn save_config(conf: &LocalEnv) -> Result<()> {
-    let config_path = base_path().join("config");
-    let conf_str = toml::to_string_pretty(conf)?;
-
-    fs::write(config_path, conf_str)?;
-    Ok(())
-}
--- a/control_plane/src/storage.rs
+++ b/control_plane/src/storage.rs
@@ -1,17 +1,19 @@
-use std::collections::HashMap;
+use std::io::Write;
 use std::net::TcpStream;
 use std::path::PathBuf;
 use std::process::Command;
-use std::thread;
 use std::time::Duration;
+use std::{io, result, thread};

-use anyhow::{anyhow, bail, ensure, Result};
+use anyhow::{anyhow, bail};
 use nix::sys::signal::{kill, Signal};
 use nix::unistd::Pid;
 use pageserver::http::models::{BranchCreateRequest, TenantCreateRequest};
 use postgres::{Config, NoTls};
-use reqwest::blocking::{Client, RequestBuilder};
-use reqwest::{IntoUrl, Method, StatusCode};
+use reqwest::blocking::{Client, RequestBuilder, Response};
+use reqwest::{IntoUrl, Method};
+use thiserror::Error;
+use zenith_utils::http::error::HttpErrorBody;
 use zenith_utils::postgres_backend::AuthType;
 use zenith_utils::zid::ZTenantId;

@@ -20,7 +22,38 @@ use crate::read_pidfile;
 use pageserver::branches::BranchInfo;
 use zenith_utils::connstring::connection_address;

-const HTTP_BASE_URL: &str = "http://127.0.0.1:9898/v1";
+#[derive(Error, Debug)]
+pub enum PageserverHttpError {
+    #[error("Reqwest error: {0}")]
+    Transport(#[from] reqwest::Error),
+
+    #[error("Error: {0}")]
+    Response(String),
+}
+
+type Result<T> = result::Result<T, PageserverHttpError>;
+
+pub trait ResponseErrorMessageExt: Sized {
+    fn error_from_body(self) -> Result<Self>;
+}
+
+impl ResponseErrorMessageExt for Response {
+    fn error_from_body(self) -> Result<Self> {
+        let status = self.status();
+        if !(status.is_client_error() || status.is_server_error()) {
+            return Ok(self);
+        }
+
+        // reqwest do not export it's error construction utility functions, so lets craft the message ourselves
+        let url = self.url().to_owned();
+        Err(PageserverHttpError::Response(
+            match self.json::<HttpErrorBody>() {
+                Ok(err_body) => format!("Error: {}", err_body.msg),
+                Err(_) => format!("Http error ({}) at {}.", status.as_u16(), url),
+            },
+        ))
+    }
+}

 //
 // Control routines for pageserver.
@@ -46,27 +79,36 @@ impl PageServerNode {

        PageServerNode {
            kill_on_exit: false,
-            pg_connection_config: Self::default_config(password), // default
+            pg_connection_config: Self::pageserver_connection_config(
+                password,
+                env.pageserver_pg_port,
+            ),
            env: env.clone(),
            http_client: Client::new(),
-            http_base_url: HTTP_BASE_URL.to_owned(),
+            http_base_url: format!("http://localhost:{}/v1", env.pageserver_http_port),
        }
    }

-    fn default_config(password: &str) -> Config {
-        format!("postgresql://no_user:{}@localhost:64000/no_db", password)
+    fn pageserver_connection_config(password: &str, port: u16) -> Config {
+        format!("postgresql://no_user:{}@localhost:{}/no_db", password, port)
            .parse()
            .unwrap()
    }

-    pub fn init(&self, create_tenant: Option<&str>, enable_auth: bool) -> Result<()> {
+    pub fn init(&self, create_tenant: Option<&str>, enable_auth: bool) -> anyhow::Result<()> {
        let mut cmd = Command::new(self.env.pageserver_bin()?);
+        let listen_pg = format!("localhost:{}", self.env.pageserver_pg_port);
+        let listen_http = format!("localhost:{}", self.env.pageserver_http_port);
        let mut args = vec![
            "--init",
            "-D",
            self.env.base_data_dir.to_str().unwrap(),
            "--postgres-distrib",
            self.env.pg_distrib_dir.to_str().unwrap(),
+            "--listen-pg",
+            &listen_pg,
+            "--listen-http",
+            &listen_http,
        ];

        if enable_auth {
@@ -74,7 +116,10 @@ impl PageServerNode {
            args.extend(&["--auth-type", "ZenithJWT"]);
        }

-        create_tenant.map(|tenantid| args.extend(&["--create-tenant", tenantid]));
+        if let Some(tenantid) = create_tenant {
+            args.extend(&["--create-tenant", tenantid])
+        }
+
        let status = cmd
            .args(args)
            .env_clear()
@@ -97,12 +142,13 @@ impl PageServerNode {
        self.repo_path().join("pageserver.pid")
    }

-    pub fn start(&self) -> Result<()> {
-        println!(
-            "Starting pageserver at '{}' in {}",
+    pub fn start(&self) -> anyhow::Result<()> {
+        print!(
+            "Starting pageserver at '{}' in '{}'",
            connection_address(&self.pg_connection_config),
            self.repo_path().display()
        );
+        io::stdout().flush().unwrap();

        let mut cmd = Command::new(self.env.pageserver_bin()?);
        cmd.args(&["-D", self.repo_path().to_str().unwrap()])
@@ -119,25 +165,41 @@ impl PageServerNode {

        // It takes a while for the page server to start up. Wait until it is
        // open for business.
-        for retries in 1..15 {
+        const RETRIES: i8 = 15;
+        for retries in 1..RETRIES {
            match self.check_status() {
                Ok(_) => {
-                    println!("Pageserver started");
+                    println!("\nPageserver started");
                    return Ok(());
                }
                Err(err) => {
-                    println!(
-                        "Pageserver not responding yet, err {} retrying ({})...",
-                        err, retries
-                    );
+                    match err {
+                        PageserverHttpError::Transport(err) => {
+                            if err.is_connect() && retries < 5 {
+                                print!(".");
+                                io::stdout().flush().unwrap();
+                            } else {
+                                if retries == 5 {
+                                    println!() // put a line break after dots for second message
+                                }
+                                println!(
+                                    "Pageserver not responding yet, err {} retrying ({})...",
+                                    err, retries
+                                );
+                            }
+                        }
+                        PageserverHttpError::Response(msg) => {
+                            bail!("pageserver failed to start: {} ", msg)
+                        }
+                    }
                    thread::sleep(Duration::from_secs(1));
                }
            }
        }
-        bail!("pageserver failed to start");
+        bail!("pageserver failed to start in {} seconds", RETRIES);
    }

-    pub fn stop(&self) -> Result<()> {
+    pub fn stop(&self) -> anyhow::Result<()> {
        let pid = read_pidfile(&self.pid_file())?;
        let pid = Pid::from_raw(pid);
        if kill(pid, Signal::SIGTERM).is_err() {
@@ -166,7 +228,7 @@ impl PageServerNode {
        client.simple_query(sql).unwrap()
    }

-    pub fn page_server_psql_client(&self) -> Result<postgres::Client, postgres::Error> {
+    pub fn page_server_psql_client(&self) -> result::Result<postgres::Client, postgres::Error> {
        self.pg_connection_config.connect(NoTls)
    }

@@ -179,14 +241,9 @@ impl PageServerNode {
    }

    pub fn check_status(&self) -> Result<()> {
-        let status = self
-            .http_request(Method::GET, format!("{}/{}", self.http_base_url, "status"))
+        self.http_request(Method::GET, format!("{}/{}", self.http_base_url, "status"))
            .send()?
-            .status();
-        ensure!(
-            status == StatusCode::OK,
-            format!("got unexpected response status {}", status)
-        );
+            .error_from_body()?;
        Ok(())
    }

@@ -194,7 +251,7 @@ impl PageServerNode {
        Ok(self
            .http_request(Method::GET, format!("{}/{}", self.http_base_url, "tenant"))
            .send()?
-            .error_for_status()?
+            .error_from_body()?
            .json()?)
    }

@@ -205,7 +262,7 @@ impl PageServerNode {
                tenant_id: tenantid,
            })
            .send()?
-            .error_for_status()?
+            .error_from_body()?
            .json()?)
    }

@@ -216,7 +273,7 @@ impl PageServerNode {
                format!("{}/branch/{}", self.http_base_url, tenantid),
            )
            .send()?
-            .error_for_status()?
+            .error_from_body()?
            .json()?)
    }

@@ -227,35 +284,30 @@ impl PageServerNode {
        tenantid: &ZTenantId,
    ) -> Result<BranchInfo> {
        Ok(self
-            .http_request(Method::POST, format!("{}/{}", self.http_base_url, "branch"))
+            .http_request(Method::POST, format!("{}/branch", self.http_base_url))
            .json(&BranchCreateRequest {
                tenant_id: tenantid.to_owned(),
                name: branch_name.to_owned(),
                start_point: startpoint.to_owned(),
            })
            .send()?
-            .error_for_status()?
+            .error_from_body()?
            .json()?)
    }

-    // TODO: make this a separate request type and avoid loading all the branches
    pub fn branch_get_by_name(
        &self,
        tenantid: &ZTenantId,
        branch_name: &str,
    ) -> Result<BranchInfo> {
-        let branch_infos = self.branch_list(tenantid)?;
-        let branch_by_name: Result<HashMap<String, BranchInfo>> = branch_infos
-            .into_iter()
-            .map(|branch_info| Ok((branch_info.name.clone(), branch_info)))
-            .collect();
-        let branch_by_name = branch_by_name?;
-
-        let branch = branch_by_name
-            .get(branch_name)
-            .ok_or_else(|| anyhow!("Branch {} not found", branch_name))?;
-
-        Ok(branch.clone())
+        Ok(self
+            .http_request(
+                Method::GET,
+                format!("{}/branch/{}/{}", self.http_base_url, tenantid, branch_name),
+            )
+            .send()?
+            .error_for_status()?
+            .json()?)
    }
 }

--- a/docs/README.md
+++ b/docs/README.md
@@ -11,3 +11,4 @@
 - [postgres_ffi/README](/postgres_ffi/README) — Postgres FFI overview.
 - [test_runner/README.md](/test_runner/README.md) — tests infrastructure overview.
 - [walkeeper/README](/walkeeper/README.md) — WAL service overview.
+- [core_changes.md](core_changes.md) - Description of Zenith changes in Postgres core
--- a/docs/core_changes.md
+++ b/docs/core_changes.md
@@ -0,0 +1,202 @@
+1. Add t_cid to XLOG record
+- Why?
+  The cmin/cmax on a heap page is a real bummer. I don't see any other way to fix that than bite the bullet and modify the WAL-logging routine to include the cmin/cmax.
+
+  To recap, the problem is that the XLOG_HEAP_INSERT record does not include the command id of the inserted row. And same with deletion/update. So in the primary, a row is inserted with current xmin + cmin. But in the replica, the cmin is always set to 1. That works, because the command id is only relevant to the inserting transaction itself. After commit/abort, no one cares abut it anymore.
+
+- Alternatives?
+  I don't know
+
+2. Add PD_WAL_LOGGED.
+- Why?
+  Postgres sometimes writes data to the page before it is wal-logged. If such page ais swapped out, we  will loose this change. The problem is currently solved by setting PD_WAL_LOGGED bit in page header. When page without this bit set is written to the SMGR, then it is forced to be written to the WAL as FPI using log_newpage_copy() function.
+
+  There was wrong assumption that it can happen only during construction of some exotic indexes (like gist). It is not true. The same situation can happen with COPY,VACUUM and when record hint bits are set.
+
+- Discussion:
+  https://discord.com/channels/869525774699462656/882681420986851359
+
+- Alternatives:
+  Do not store this flag in page header, but associate this bit with shared buffer. Logically it is more correct but in practice we will get not advantages: neither in space, neither in CPU overhead.
+
+
+3. XLogReadBufferForRedo not always loads and pins requested buffer. So we need to add extra checks that buffer is really pinned. Also do not use BufferGetBlockNumber for buffer returned by XLogReadBufferForRedo.
+- Why?
+  XLogReadBufferForRedo is not pinning pages which are not requested by wal-redo. It is specific only for wal-redo Postgres.
+
+- Alternatives?
+  No
+
+
+4. Eliminate reporting of some warnings related with hint bits, for example
+"page is not marked all-visible but visibility map bit is set in relation".
+- Why?
+  Hint bit may be not WAL logged.
+
+- Alternative?
+  Always wal log any page changes.
+
+
+5. Maintain last written LSN.
+- Why?
+  When compute node requests page from page server, we need to specify LSN. Ideally it should be LSN
+  of WAL record performing last update of this pages. But we do not know it, because we do not have page.
+  We can use current WAL flush position, but in this case there is high probability that page server
+  will be blocked until this peace of WAL is delivered.
+  As better approximation we can keep max LSN of written page. It will be better to take in account LSNs only of evicted pages,
+  but SMGR API doesn't provide such knowledge.
+
+- Alternatives?
+  Maintain map of LSNs of evicted pages.
+
+
+6. Launching Postgres without WAL.
+- Why?
+  According to Zenith architecture compute node is stateless. So when we are launching
+  compute node, we need to provide some dummy PG_DATADIR. Relation pages
+  can be requested on demand from page server. But Postgres still need some non-relational data:
+  control and configuration files, SLRUs,...
+  It is currently implemented  using basebackup (do not mix with pg_basebackup) which is created
+  by pageserver. It includes in this tarball config/control files, SLRUs and required directories.
+  As far as pageserver do not have original (non-scattered) WAL segments, it includes in
+  this tarball dummy WAL segment which contains only SHUTDOWN_CHECKPOINT record at the beginning of segment,
+  which redo field points to the end of wal. It allows to load checkpoint record in more or less
+  standard way with minimal changes of Postgres, but then some special handling is needed,
+  including restoring previous record position from zenith.signal file.
+  Also we have to correctly initialize header of last WAL page (pointed by checkpoint.redo)
+  to pass checks performed by XLogReader.
+
+- Alternatives?
+  We may not include fake WAL segment in tarball at all and modify xlog.c to load checkpoint record
+  in special way. But it may only increase number of changes in xlog.c
+
+7. Add redo_read_buffer_filter callback to XLogReadBufferForRedoExtended
+- Why?
+  We need a way in wal-redo Postgres to ignore pages which are not requested by pageserver.
+  So wal-redo Postgres reconstructs only requested page and for all other returns BLK_DONE
+  which means that recovery for them is not needed.
+
+- Alternatives?
+  No
+
+8. Enforce WAL logging of sequence updates.
+- Why?
+  Due to performance reasons Postgres don't want to log each fetching of a value from a sequence,
+  so we pre-log a few fetches in advance. In the event of crash we can lose
+  (skip over) as many values as we pre-logged.
+  But it doesn't work with Zenith because page with sequence value can be evicted from buffer cache
+  and we will get a gap in sequence values even without crash.
+
+- Alternatives:
+  Do not try to preserve sequential order but avoid performance penalty.
+
+
+9. Treat unlogged tables as normal (permanent) tables.
+- Why?
+  Unlogged tables are not transient, so them have to survive node restart (unlike temporary tables).
+  But as far as compute node is stateless, we need to persist their data to storage node.
+  And it can only be done through the WAL.
+
+- Alternatives?
+  * Store unlogged tables locally (violates requirement of stateless compute nodes).
+  * Prohibit unlogged tables at all.
+
+
+10. Support start Postgres in wal-redo mode
+- Why?
+  To be able to apply WAL record and reconstruct pages at page server.
+
+- Alternatives?
+  * Rewrite redo handlers in Rust
+  * Do not reconstruct pages at page server at all and do it at compute node.
+
+
+11. WAL proposer
+- Why?
+  WAL proposer is communicating with safekeeper and ensures WAL durability by quorum writes.
+  It is currently implemented as patch to standard WAL sender.
+
+- Alternatives?
+  Can be moved to extension if some extra callbacks will be added to wal sender code.
+
+
+12. Secure Computing BPF API wrapper.
+- Why?
+  Pageserver delegates complex WAL decoding duties to Postgres,
+  which means that the latter might fall victim to carefully designed
+  malicious WAL records and start doing harmful things to the system.
+  To prevent this, it has been decided to limit possible interactions
+  with the outside world using the Secure Computing BPF mode.
+
+- Alternatives:
+  * Rewrite redo handlers in Rust.
+  * Add more checks to guarantee correctness of WAL records.
+  * Move seccomp.c to extension
+  * Many other discussed approaches to neutralize incorrect WAL records vulnerabilities.
+
+
+13. Callbacks for replica feedbacks
+- Why?
+  Allowing waproposer to interact with walsender code.
+
+- Alternatives
+  Copy walsender code to walproposer.
+
+
+14. Support multiple SMGR implementations.
+- Why?
+  Postgres provides abstract API for storage manager but it has only one implementation
+  and provides no way to replace it with custom storage manager.
+
+- Alternatives?
+  None.
+
+
+15. Calculate database size as sum of all database relations.
+- Why?
+  Postgres is calculating database size by traversing data directory
+  but as far as Zenith compute node is stateless we can not do it.
+
+- Alternatives?
+  Send this request directly to pageserver and calculate real (physical) size
+  of Zenith representation of database/timeline, rather than sum logical size of all relations.
+
+
+-----------------------------------------------
+Not currently committed but proposed:
+
+1. Disable ring buffer buffer manager strategies
+- Why?
+  Postgres tries to avoid cache flushing by bulk operations (copy, seqscan, vacuum,...).
+  Even if there are free space in buffer cache, pages may be evicted.
+  Negative effect of it can be somehow compensated by file system cache, but in case of Zenith
+  cost of requesting page from page server is much higher.
+
+- Alternatives?
+  Instead of just prohibiting ring buffer we may try to implement more flexible eviction policy,
+  for example copy evicted page from ring buffer to some other buffer if there is free space
+  in buffer cache.
+
+2. Disable marking page as dirty when hint bits are set.
+- Why?
+  Postgres has to modify page twice: first time when some tuple is updated and second time when
+  hint bits are set. Wal logging hint bits updates requires FPI which significantly increase size of WAL.
+
+- Alternatives?
+  Add special WAL record for setting page hints.
+
+3. Prefetching
+- Why?
+  As far as pages in Zenith are loaded on demand, to reduce node startup time
+  and also sppedup some massive queries we need some mechanism for bulk loading to
+  reduce page request round-trip overhead.
+
+  Currently Postgres is supporting prefetching only for bitmap scan.
+  In Zenith we also use prefetch for sequential and index scan. For sequential scan we prefetch
+  some number of following pages. For index scan we prefetch pages of heap relation addressed by TIDs.
+
+4. Prewarming.
+- Why?
+  Short downtime (or, in other words, fast compute node restart time) is one of the key feature of Zenith.
+  But overhead of request-response round-trip for loading pages on demand can make started node warm-up quite slow.
+  We can capture state of compute node buffer cache and send bulk request for this pages at startup.
--- a/docs/glossary.md
+++ b/docs/glossary.md
@@ -26,32 +26,51 @@ A checkpoint record in the WAL marks a point in the WAL sequence at which it is
 NOTE: This is an overloaded term.

 Whenever enough WAL has been accumulated in memory, the page server []
-writes out the changes in memory into new layer files[]. This process
+writes out the changes from in-memory layers into new layer files[]. This process
 is called "checkpointing". The page server only creates layer files for
 relations that have been modified since the last checkpoint. 

+Configuration parameter `checkpoint_distance` defines the distance
+from current LSN to perform checkpoint of in-memory layers.
+Default is `DEFAULT_CHECKPOINT_DISTANCE`.
+Set this parameter to `0` to force checkpoint of every layer.
+
+Configuration parameter `checkpoint_period` defines the interval between checkpoint iterations.
+Default is `DEFAULT_CHECKPOINT_PERIOD`.
 ### Compute node

 Stateless Postgres node that stores data in pageserver.

 ### Garbage collection

+The process of removing old on-disk layers that are not needed by any timeline anymore.
 ### Fork

 Each of the separate segmented file sets in which a relation is stored. The main fork is where the actual data resides. There also exist two secondary forks for metadata: the free space map and the visibility map.
 Each PostgreSQL fork is considered a separate relish.

-### Layer file
+### Layer
+
+Each layer corresponds to the specific version of a relish Segment in a range of LSNs.
+There are two kinds of layers, in-memory and on-disk layers. In-memory
+layers are used to ingest incoming WAL, and provide fast access
+to the recent page versions. On-disk layers are stored as files on disk, and
+are immutable.
+### Layer file (on-disk layer)

 Layered repository on-disk format is based on immutable files.  The
-files are called "layer files". Each file corresponds to one 10 MB
+files are called "layer files". Each file corresponds to one RELISH_SEG_SIZE
 segment of a PostgreSQL relation fork. There are two kinds of layer
 files: image files and delta files. An image file contains a
 "snapshot" of the segment at a particular LSN, and a delta file
 contains WAL records applicable to the segment, in a range of LSNs.

+### Layer map
+
+The layer map tracks what layers exist for all the relishes in a timeline.
 ### Layered repository

+Zenith repository implementation that keeps data in layers.
 ### LSN


@@ -111,6 +130,20 @@ One repository corresponds to one Tenant.

 How much history do we need to keep around for PITR and read-only nodes?

+### Segment (PostgreSQL)
+
+NOTE: This is an overloaded term.
+
+A physical file that stores data for a given relation. File segments are
+limited in size by a compile-time setting (1 gigabyte by default), so if a
+relation exceeds that size, it is split into multiple segments.
+
+### Segment (Layered Repository)
+
+NOTE: This is an overloaded term.
+
+Segment is a RELISH_SEG_SIZE slice of relish (identified by a SegmentTag).
+
 ### SLRU

 SLRUs include pg_clog, pg_multixact/members, and
@@ -121,7 +154,7 @@ Each SLRU segment is considered a separate relish[].

 ### Tenant (Multitenancy)
 Tenant represents a single customer, interacting with Zenith.
-Wal redo[] activity, timelines[], snapshots[] are managed for each tenant independently.
+Wal redo[] activity, timelines[], layers[] are managed for each tenant independently.
 One pageserver[] can serve multiple tenants at once.
 One safekeeper 

--- a/docs/multitenancy.md
+++ b/docs/multitenancy.md
@@ -37,7 +37,7 @@ On the page server tenants introduce one level of indirection, so data directory
   ├── de182bc61fb11a5a6b390a8aed3a804a
   └── ee6016ec31116c1b7c33dfdfca38891f
 ```
-Wal redo activity, timelines, snapshots are managed for each tenant independently.
+Wal redo activity and timelines are managed for each tenant independently.

 For local environment used for example in tests there also new level of indirection for tenants. It touches `pgdatadirs` directory. Now it contains `tenants` subdirectory so the structure looks the following way:

--- a/pageserver/Cargo.toml
+++ b/pageserver/Cargo.toml
@@ -4,8 +4,6 @@ version = "0.1.0"
 authors = ["Stas Kelvich <stas@zenith.tech>"]
 edition = "2018"

-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
 [dependencies]
 bookfile = "^0.3"
 chrono = "0.4.19"
@@ -16,14 +14,10 @@ byteorder = "1.4.3"
 futures = "0.3.13"
 hyper = "0.14"
 lazy_static = "1.4.0"
-slog-stdlog = "4.1.0"
-slog-scope = "4.4.0"
-slog-term = "2.8.0"
-slog = "2.7.0"
 log = "0.4.14"
 clap = "2.33.0"
 daemonize = "0.4.1"
-tokio = { version = "1.5.0", features = ["full"] }
+tokio = { version = "1.11", features = ["process", "macros", "fs"] }
 postgres-types = { git = "https://github.com/zenithdb/rust-postgres.git", rev="9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858" }
 postgres-protocol = { git = "https://github.com/zenithdb/rust-postgres.git", rev="9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858" }
 postgres = { git = "https://github.com/zenithdb/rust-postgres.git", rev="9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858" }
@@ -38,6 +32,8 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1"
 toml = "0.5"
 scopeguard = "1.1.0"
+rust-s3 = { version = "0.27.0-rc4", features = ["no-verify-ssl"] }
+async-trait = "0.1"

 postgres_ffi = { path = "../postgres_ffi" }
 zenith_metrics = { path = "../zenith_metrics" }
--- a/pageserver/src/basebackup.rs
+++ b/pageserver/src/basebackup.rs
@@ -10,6 +10,7 @@
 //! This module is responsible for creation of such tarball
 //! from data stored in object storage.
 //!
+use anyhow::Result;
 use bytes::{BufMut, BytesMut};
 use log::*;
 use std::io;
@@ -22,7 +23,7 @@ use crate::relish::*;
 use crate::repository::Timeline;
 use postgres_ffi::xlog_utils::*;
 use postgres_ffi::*;
-use zenith_utils::lsn::{Lsn, RecordLsn};
+use zenith_utils::lsn::Lsn;

 /// This is short-living object only for the time of tarball creation,
 /// created mostly to avoid passing a lot of parameters between various functions
@@ -46,30 +47,51 @@ impl<'a> Basebackup<'a> {
        write: &'a mut dyn Write,
        timeline: &'a Arc<dyn Timeline>,
        req_lsn: Option<Lsn>,
-    ) -> Basebackup<'a> {
-        let RecordLsn {
-            last: lsn,
-            prev: prev_record_lsn,
-        } = if let Some(lsn) = req_lsn {
-            // FIXME: that wouldn't work since we don't know prev for old LSN's.
-            // Probably it is better to avoid using prev in compute node start
-            // at all and acept the fact that first WAL record in the timeline would
-            // have zero as prev. https://github.com/zenithdb/zenith/issues/506
-            RecordLsn {
-                last: lsn,
-                prev: lsn,
+    ) -> Result<Basebackup<'a>> {
+        // Compute postgres doesn't have any previous WAL files, but the first
+        // record that it's going to write needs to include the LSN of the
+        // previous record (xl_prev). We include prev_record_lsn in the
+        // "zenith.signal" file, so that postgres can read it during startup.
+        //
+        // We don't keep full history of record boundaries in the page server,
+        // however, only the predecessor of the latest record on each
+        // timeline. So we can only provide prev_record_lsn when you take a
+        // base backup at the end of the timeline, i.e. at last_record_lsn.
+        // Even at the end of the timeline, we sometimes don't have a valid
+        // prev_lsn value; that happens if the timeline was just branched from
+        // an old LSN and it doesn't have any WAL of its own yet. We will set
+        // prev_lsn to Lsn(0) if we cannot provide the correct value.
+        let (backup_prev, backup_lsn) = if let Some(req_lsn) = req_lsn {
+            // Backup was requested at a particular LSN. Wait for it to arrive.
+            timeline.wait_lsn(req_lsn)?;
+
+            // If the requested point is the end of the timeline, we can
+            // provide prev_lsn. (get_last_record_rlsn() might return it as
+            // zero, though, if no WAL has been generated on this timeline
+            // yet.)
+            let end_of_timeline = timeline.get_last_record_rlsn();
+            if req_lsn == end_of_timeline.last {
+                (end_of_timeline.prev, req_lsn)
+            } else {
+                (Lsn(0), req_lsn)
            }
        } else {
-            // Atomically get last and prev LSN's
-            timeline.get_last_record_rlsn()
+            // Backup was requested at end of the timeline.
+            let end_of_timeline = timeline.get_last_record_rlsn();
+            (end_of_timeline.prev, end_of_timeline.last)
        };

-        Basebackup {
+        info!(
+            "taking basebackup lsn={}, prev_lsn={}",
+            backup_prev, backup_lsn
+        );
+
+        Ok(Basebackup {
            ar: Builder::new(write),
            timeline,
-            lsn,
-            prev_record_lsn,
-        }
+            lsn: backup_lsn,
+            prev_record_lsn: backup_prev,
+        })
    }

    pub fn send_tarball(&mut self) -> anyhow::Result<()> {
@@ -84,10 +106,10 @@ impl<'a> Basebackup<'a> {
        for filepath in pg_constants::PGDATA_SPECIAL_FILES.iter() {
            if *filepath == "pg_hba.conf" {
                let data = pg_constants::PG_HBA.as_bytes();
-                let header = new_tar_header(&filepath, data.len() as u64)?;
-                self.ar.append(&header, &data[..])?;
+                let header = new_tar_header(filepath, data.len() as u64)?;
+                self.ar.append(&header, data)?;
            } else {
-                let header = new_tar_header(&filepath, 0)?;
+                let header = new_tar_header(filepath, 0)?;
                self.ar.append(&header, &mut io::empty())?;
            }
        }
@@ -137,11 +159,9 @@ impl<'a> Basebackup<'a> {
        let mut slru_buf: Vec<u8> =
            Vec::with_capacity(nblocks as usize * pg_constants::BLCKSZ as usize);
        for blknum in 0..nblocks {
-            let img = self.timeline.get_page_at_lsn_nowait(
-                RelishTag::Slru { slru, segno },
-                blknum,
-                self.lsn,
-            )?;
+            let img =
+                self.timeline
+                    .get_page_at_lsn(RelishTag::Slru { slru, segno }, blknum, self.lsn)?;
            assert!(img.len() == pg_constants::BLCKSZ as usize);

            slru_buf.extend_from_slice(&img);
@@ -160,20 +180,18 @@ impl<'a> Basebackup<'a> {
    // Along with them also send PG_VERSION for each database.
    //
    fn add_relmap_file(&mut self, spcnode: u32, dbnode: u32) -> anyhow::Result<()> {
-        let img = self.timeline.get_page_at_lsn_nowait(
+        let img = self.timeline.get_page_at_lsn(
            RelishTag::FileNodeMap { spcnode, dbnode },
            0,
            self.lsn,
        )?;
        let path = if spcnode == pg_constants::GLOBALTABLESPACE_OID {
-            let dst_path = "PG_VERSION";
            let version_bytes = pg_constants::PG_MAJORVERSION.as_bytes();
-            let header = new_tar_header(&dst_path, version_bytes.len() as u64)?;
-            self.ar.append(&header, &version_bytes[..])?;
+            let header = new_tar_header("PG_VERSION", version_bytes.len() as u64)?;
+            self.ar.append(&header, version_bytes)?;

-            let dst_path = format!("global/PG_VERSION");
-            let header = new_tar_header(&dst_path, version_bytes.len() as u64)?;
-            self.ar.append(&header, &version_bytes[..])?;
+            let header = new_tar_header("global/PG_VERSION", version_bytes.len() as u64)?;
+            self.ar.append(&header, version_bytes)?;

            String::from("global/pg_filenode.map") // filenode map for global tablespace
        } else {
@@ -188,7 +206,7 @@ impl<'a> Basebackup<'a> {
            let dst_path = format!("base/{}/PG_VERSION", dbnode);
            let version_bytes = pg_constants::PG_MAJORVERSION.as_bytes();
            let header = new_tar_header(&dst_path, version_bytes.len() as u64)?;
-            self.ar.append(&header, &version_bytes[..])?;
+            self.ar.append(&header, version_bytes)?;

            format!("base/{}/pg_filenode.map", dbnode)
        };
@@ -204,7 +222,7 @@ impl<'a> Basebackup<'a> {
    fn add_twophase_file(&mut self, xid: TransactionId) -> anyhow::Result<()> {
        let img = self
            .timeline
-            .get_page_at_lsn_nowait(RelishTag::TwoPhase { xid }, 0, self.lsn)?;
+            .get_page_at_lsn(RelishTag::TwoPhase { xid }, 0, self.lsn)?;

        let mut buf = BytesMut::new();
        buf.extend_from_slice(&img[..]);
@@ -222,12 +240,12 @@ impl<'a> Basebackup<'a> {
    // Also send zenith.signal file with extra bootstrap data.
    //
    fn add_pgcontrol_file(&mut self) -> anyhow::Result<()> {
-        let checkpoint_bytes =
-            self.timeline
-                .get_page_at_lsn_nowait(RelishTag::Checkpoint, 0, self.lsn)?;
+        let checkpoint_bytes = self
+            .timeline
+            .get_page_at_lsn(RelishTag::Checkpoint, 0, self.lsn)?;
        let pg_control_bytes =
            self.timeline
-                .get_page_at_lsn_nowait(RelishTag::ControlFile, 0, self.lsn)?;
+                .get_page_at_lsn(RelishTag::ControlFile, 0, self.lsn)?;
        let mut pg_control = ControlFileData::decode(&pg_control_bytes)?;
        let mut checkpoint = CheckPoint::decode(&checkpoint_bytes)?;

@@ -238,7 +256,7 @@ impl<'a> Basebackup<'a> {
            XLOG_SIZE_OF_XLOG_LONG_PHD as u32,
            pg_constants::WAL_SEGMENT_SIZE,
        );
-        checkpoint.redo = self.lsn.0 + self.lsn.calc_padding(8u32);
+        checkpoint.redo = normalize_lsn(self.lsn, pg_constants::WAL_SEGMENT_SIZE).0;

        //reset some fields we don't want to preserve
        //TODO Check this.
@@ -251,9 +269,14 @@ impl<'a> Basebackup<'a> {
        pg_control.state = pg_constants::DB_SHUTDOWNED;

        // add zenith.signal file
+        let xl_prev = if self.prev_record_lsn == Lsn(0) {
+            0xBAD0 // magic value to indicate that we don't know prev_lsn
+        } else {
+            self.prev_record_lsn.0
+        };
        self.ar.append(
            &new_tar_header("zenith.signal", 8)?,
-            &self.prev_record_lsn.0.to_le_bytes()[..],
+            &xl_prev.to_le_bytes()[..],
        )?;

        //send pg_control
--- a/pageserver/src/bin/pageserver.rs
+++ b/pageserver/src/bin/pageserver.rs
@@ -3,6 +3,7 @@
 //

 use log::*;
+use pageserver::defaults::*;
 use serde::{Deserialize, Serialize};
 use std::{
    env,
@@ -11,35 +12,48 @@ use std::{
    process::exit,
    str::FromStr,
    thread,
-    time::Duration,
 };
-use zenith_utils::{auth::JwtAuth, postgres_backend::AuthType};
+use zenith_utils::{auth::JwtAuth, logging, postgres_backend::AuthType};

-use anyhow::{ensure, Result};
+use anyhow::{bail, ensure, Result};
 use clap::{App, Arg, ArgMatches};
 use daemonize::Daemonize;

-use pageserver::{branches, http, logger, page_service, tenant_mgr, PageServerConf};
+use pageserver::{
+    branches, http, page_service, tenant_mgr, PageServerConf, RelishStorageConfig, S3Config,
+    LOG_FILE_NAME,
+};
 use zenith_utils::http::endpoint;

-const DEFAULT_LISTEN_ADDR: &str = "127.0.0.1:64000";
-const DEFAULT_HTTP_ENDPOINT_ADDR: &str = "127.0.0.1:9898";
-
-const DEFAULT_GC_HORIZON: u64 = 64 * 1024 * 1024;
-const DEFAULT_GC_PERIOD: Duration = Duration::from_secs(10);
-
-const DEFAULT_SUPERUSER: &str = "zenith_admin";
-
 /// String arguments that can be declared via CLI or config file
 #[derive(Serialize, Deserialize)]
 struct CfgFileParams {
-    listen_addr: Option<String>,
-    http_endpoint_addr: Option<String>,
+    listen_pg_addr: Option<String>,
+    listen_http_addr: Option<String>,
+    checkpoint_distance: Option<String>,
+    checkpoint_period: Option<String>,
    gc_horizon: Option<String>,
    gc_period: Option<String>,
    pg_distrib_dir: Option<String>,
    auth_validation_public_key_path: Option<String>,
    auth_type: Option<String>,
+    // see https://github.com/alexcrichton/toml-rs/blob/6c162e6562c3e432bf04c82a3d1d789d80761a86/examples/enum_external.rs for enum deserialisation examples
+    relish_storage: Option<RelishStorage>,
+}
+
+#[derive(Serialize, Deserialize, Clone)]
+enum RelishStorage {
+    Local {
+        local_path: String,
+    },
+    AwsS3 {
+        bucket_name: String,
+        bucket_region: String,
+        #[serde(skip_serializing)]
+        access_key_id: Option<String>,
+        #[serde(skip_serializing)]
+        secret_access_key: Option<String>,
+    },
 }

 impl CfgFileParams {
@@ -49,14 +63,32 @@ impl CfgFileParams {
            arg_matches.value_of(arg_name).map(str::to_owned)
        };

+        let relish_storage = if let Some(local_path) = get_arg("relish-storage-local-path") {
+            Some(RelishStorage::Local { local_path })
+        } else if let Some((bucket_name, bucket_region)) =
+            get_arg("relish-storage-s3-bucket").zip(get_arg("relish-storage-region"))
+        {
+            Some(RelishStorage::AwsS3 {
+                bucket_name,
+                bucket_region,
+                access_key_id: get_arg("relish-storage-access-key"),
+                secret_access_key: get_arg("relish-storage-secret-access-key"),
+            })
+        } else {
+            None
+        };
+
        Self {
-            listen_addr: get_arg("listen"),
-            http_endpoint_addr: get_arg("http_endpoint"),
+            listen_pg_addr: get_arg("listen-pg"),
+            listen_http_addr: get_arg("listen-http"),
+            checkpoint_distance: get_arg("checkpoint_distance"),
+            checkpoint_period: get_arg("checkpoint_period"),
            gc_horizon: get_arg("gc_horizon"),
            gc_period: get_arg("gc_period"),
            pg_distrib_dir: get_arg("postgres-distrib"),
            auth_validation_public_key_path: get_arg("auth-validation-public-key-path"),
            auth_type: get_arg("auth-type"),
+            relish_storage,
        }
    }

@@ -64,8 +96,10 @@ impl CfgFileParams {
    fn or(self, other: CfgFileParams) -> Self {
        // TODO cleaner way to do this
        Self {
-            listen_addr: self.listen_addr.or(other.listen_addr),
-            http_endpoint_addr: self.http_endpoint_addr.or(other.http_endpoint_addr),
+            listen_pg_addr: self.listen_pg_addr.or(other.listen_pg_addr),
+            listen_http_addr: self.listen_http_addr.or(other.listen_http_addr),
+            checkpoint_distance: self.checkpoint_distance.or(other.checkpoint_distance),
+            checkpoint_period: self.checkpoint_period.or(other.checkpoint_period),
            gc_horizon: self.gc_horizon.or(other.gc_horizon),
            gc_period: self.gc_period.or(other.gc_period),
            pg_distrib_dir: self.pg_distrib_dir.or(other.pg_distrib_dir),
@@ -73,6 +107,7 @@ impl CfgFileParams {
                .auth_validation_public_key_path
                .or(other.auth_validation_public_key_path),
            auth_type: self.auth_type.or(other.auth_type),
+            relish_storage: self.relish_storage.or(other.relish_storage),
        }
    }

@@ -80,14 +115,23 @@ impl CfgFileParams {
    fn try_into_config(&self) -> Result<PageServerConf> {
        let workdir = PathBuf::from(".");

-        let listen_addr = match self.listen_addr.as_ref() {
+        let listen_pg_addr = match self.listen_pg_addr.as_ref() {
            Some(addr) => addr.clone(),
-            None => DEFAULT_LISTEN_ADDR.to_owned(),
+            None => DEFAULT_PG_LISTEN_ADDR.to_owned(),
        };

-        let http_endpoint_addr = match self.http_endpoint_addr.as_ref() {
+        let listen_http_addr = match self.listen_http_addr.as_ref() {
            Some(addr) => addr.clone(),
-            None => DEFAULT_HTTP_ENDPOINT_ADDR.to_owned(),
+            None => DEFAULT_HTTP_LISTEN_ADDR.to_owned(),
+        };
+
+        let checkpoint_distance: u64 = match self.checkpoint_distance.as_ref() {
+            Some(checkpoint_distance_str) => checkpoint_distance_str.parse()?,
+            None => DEFAULT_CHECKPOINT_DISTANCE,
+        };
+        let checkpoint_period = match self.checkpoint_period.as_ref() {
+            Some(checkpoint_period_str) => humantime::parse_duration(checkpoint_period_str)?,
+            None => DEFAULT_CHECKPOINT_PERIOD,
        };

        let gc_horizon: u64 = match self.gc_horizon.as_ref() {
@@ -113,11 +157,11 @@ impl CfgFileParams {
            .auth_type
            .as_ref()
            .map_or(Ok(AuthType::Trust), |auth_type| {
-                AuthType::from_str(&auth_type)
+                AuthType::from_str(auth_type)
            })?;

        if !pg_distrib_dir.join("bin/postgres").exists() {
-            anyhow::bail!("Can't find postgres binary at {:?}", pg_distrib_dir);
+            bail!("Can't find postgres binary at {:?}", pg_distrib_dir);
        }

        if auth_type == AuthType::ZenithJWT {
@@ -132,11 +176,33 @@ impl CfgFileParams {
            );
        }

+        let relish_storage_config =
+            self.relish_storage
+                .as_ref()
+                .map(|storage_params| match storage_params.clone() {
+                    RelishStorage::Local { local_path } => {
+                        RelishStorageConfig::LocalFs(PathBuf::from(local_path))
+                    }
+                    RelishStorage::AwsS3 {
+                        bucket_name,
+                        bucket_region,
+                        access_key_id,
+                        secret_access_key,
+                    } => RelishStorageConfig::AwsS3(S3Config {
+                        bucket_name,
+                        bucket_region,
+                        access_key_id,
+                        secret_access_key,
+                    }),
+                });
+
        Ok(PageServerConf {
            daemonize: false,

-            listen_addr,
-            http_endpoint_addr,
+            listen_pg_addr,
+            listen_http_addr,
+            checkpoint_distance,
+            checkpoint_period,
            gc_horizon,
            gc_period,

@@ -148,6 +214,7 @@ impl CfgFileParams {

            auth_validation_public_key_path,
            auth_type,
+            relish_storage_config,
        })
    }
 }
@@ -156,12 +223,20 @@ fn main() -> Result<()> {
    let arg_matches = App::new("Zenith page server")
        .about("Materializes WAL stream to pages and serves them to the postgres")
        .arg(
-            Arg::with_name("listen")
+            Arg::with_name("listen-pg")
                .short("l")
-                .long("listen")
+                .long("listen-pg")
+                .alias("listen") // keep some compatibility
                .takes_value(true)
                .help("listen for incoming page requests on ip:port (default: 127.0.0.1:5430)"),
        )
+        .arg(
+            Arg::with_name("listen-http")
+                .long("listen-http")
+                .alias("http_endpoint") // keep some compatibility
+                .takes_value(true)
+                .help("http endpoint address for for metrics and management API calls ip:port (default: 127.0.0.1:5430)"),
+        )
        .arg(
            Arg::with_name("daemonize")
                .short("d")
@@ -175,6 +250,18 @@ fn main() -> Result<()> {
                .takes_value(false)
                .help("Initialize pageserver repo"),
        )
+        .arg(
+            Arg::with_name("checkpoint_distance")
+                .long("checkpoint_distance")
+                .takes_value(true)
+                .help("Distance from current LSN to perform checkpoint of in-memory layers"),
+        )
+        .arg(
+            Arg::with_name("checkpoint_period")
+                .long("checkpoint_period")
+                .takes_value(true)
+                .help("Interval between checkpoint iterations"),
+        )
        .arg(
            Arg::with_name("gc_horizon")
                .long("gc_horizon")
@@ -219,6 +306,43 @@ fn main() -> Result<()> {
                .takes_value(true)
                .help("Authentication scheme type. One of: Trust, MD5, ZenithJWT"),
        )
+        .arg(
+            Arg::with_name("relish-storage-local-path")
+                .long("relish-storage-local-path")
+                .takes_value(true)
+                .help("Path to the local directory, to be used as an external relish storage")
+                .conflicts_with_all(&[
+                    "relish-storage-s3-bucket",
+                    "relish-storage-region",
+                    "relish-storage-access-key",
+                    "relish-storage-secret-access-key",
+                ]),
+        )
+        .arg(
+            Arg::with_name("relish-storage-s3-bucket")
+                .long("relish-storage-s3-bucket")
+                .takes_value(true)
+                .help("Name of the AWS S3 bucket to use an external relish storage")
+                .requires("relish-storage-region"),
+        )
+        .arg(
+            Arg::with_name("relish-storage-region")
+                .long("relish-storage-region")
+                .takes_value(true)
+                .help("Region of the AWS S3 bucket"),
+        )
+        .arg(
+            Arg::with_name("relish-storage-access-key")
+                .long("relish-storage-access-key")
+                .takes_value(true)
+                .help("Credentials to access the AWS S3 bucket"),
+        )
+        .arg(
+            Arg::with_name("relish-storage-secret-access-key")
+                .long("relish-storage-secret-access-key")
+                .takes_value(true)
+                .help("Credentials to access the AWS S3 bucket"),
+        )
        .get_matches();

    let workdir = Path::new(arg_matches.value_of("workdir").unwrap_or(".zenith"));
@@ -273,18 +397,27 @@ fn main() -> Result<()> {

 fn start_pageserver(conf: &'static PageServerConf) -> Result<()> {
    // Initialize logger
-    let (_scope_guard, log_file) = logger::init_logging(&conf, "pageserver.log")?;
-    let _log_guard = slog_stdlog::init()?;
-
-    // Note: this `info!(...)` macro comes from `log` crate
-    info!("standard logging redirected to slog");
+    let (_scope_guard, log_file) = logging::init(LOG_FILE_NAME, conf.daemonize)?;

    // TODO: Check that it looks like a valid repository before going further

+    // bind sockets before daemonizing so we report errors early and do not return until we are listening
+    info!(
+        "Starting pageserver http handler on {}",
+        conf.listen_http_addr
+    );
+    let http_listener = TcpListener::bind(conf.listen_http_addr.clone())?;
+
+    info!(
+        "Starting pageserver pg protocol handler on {}",
+        conf.listen_pg_addr
+    );
+    let pageserver_listener = TcpListener::bind(conf.listen_pg_addr.clone())?;
+
    if conf.daemonize {
        info!("daemonizing...");

-        // There should'n be any logging to stdin/stdout. Redirect it to the main log so
+        // There shouldn't be any logging to stdin/stdout. Redirect it to the main log so
        // that we will see any accidental manual fprintf's or backtraces.
        let stdout = log_file.try_clone().unwrap();
        let stderr = log_file;
@@ -301,6 +434,12 @@ fn start_pageserver(conf: &'static PageServerConf) -> Result<()> {
        }
    }

+    // Initialize tenant manager.
+    tenant_mgr::init(conf);
+
+    // keep join handles for spawned threads
+    let mut join_handles = vec![];
+
    // initialize authentication for incoming connections
    let auth = match &conf.auth_type {
        AuthType::Trust | AuthType::MD5 => None,
@@ -313,21 +452,16 @@ fn start_pageserver(conf: &'static PageServerConf) -> Result<()> {
    info!("Using auth: {:#?}", conf.auth_type);

    // Spawn a new thread for the http endpoint
+    // bind before launching separate thread so the error reported before startup exits
    let cloned = auth.clone();
-    thread::Builder::new()
+    let http_endpoint_thread = thread::Builder::new()
        .name("http_endpoint_thread".into())
        .spawn(move || {
            let router = http::make_router(conf, cloned);
-            endpoint::serve_thread_main(router, conf.http_endpoint_addr.clone())
+            endpoint::serve_thread_main(router, http_listener)
        })?;

-    // Check that we can bind to address before starting threads to simplify shutdown
-    // sequence if port is occupied.
-    info!("Starting pageserver on {}", conf.listen_addr);
-    let pageserver_listener = TcpListener::bind(conf.listen_addr.clone())?;
-
-    // Initialize tenant manager.
-    tenant_mgr::init(conf);
+    join_handles.push(http_endpoint_thread);

    // Spawn a thread to listen for connections. It will spawn further threads
    // for each connection.
@@ -337,9 +471,13 @@ fn start_pageserver(conf: &'static PageServerConf) -> Result<()> {
            page_service::thread_main(conf, auth, pageserver_listener, conf.auth_type)
        })?;

-    page_service_thread
-        .join()
-        .expect("Page service thread has panicked")?;
+    join_handles.push(page_service_thread);

+    for handle in join_handles.into_iter() {
+        handle
+            .join()
+            .expect("thread panicked")
+            .expect("thread exited with an error")
+    }
    Ok(())
 }
--- a/pageserver/src/branches.rs
+++ b/pageserver/src/branches.rs
@@ -17,22 +17,77 @@ use std::{
 use zenith_utils::zid::{ZTenantId, ZTimelineId};

 use log::*;
+use zenith_utils::logging;
 use zenith_utils::lsn::Lsn;

-use crate::logger;
-use crate::restore_local_repo;
 use crate::tenant_mgr;
 use crate::walredo::WalRedoManager;
 use crate::{repository::Repository, PageServerConf};
+use crate::{restore_local_repo, LOG_FILE_NAME};

 #[derive(Serialize, Deserialize, Clone)]
 pub struct BranchInfo {
    pub name: String,
    #[serde(with = "hex")]
    pub timeline_id: ZTimelineId,
-    pub latest_valid_lsn: Option<Lsn>,
+    pub latest_valid_lsn: Lsn,
    pub ancestor_id: Option<String>,
    pub ancestor_lsn: Option<String>,
+    pub current_logical_size: usize,
+    pub current_logical_size_non_incremental: usize,
+}
+
+impl BranchInfo {
+    pub fn from_path<T: AsRef<Path>>(
+        path: T,
+        conf: &PageServerConf,
+        tenantid: &ZTenantId,
+        repo: &Arc<dyn Repository>,
+    ) -> Result<Self> {
+        let name = path
+            .as_ref()
+            .file_name()
+            .unwrap()
+            .to_str()
+            .unwrap()
+            .to_string();
+        let timeline_id = std::fs::read_to_string(path)?.parse::<ZTimelineId>()?;
+
+        let timeline = repo.get_timeline(timeline_id)?;
+
+        let ancestor_path = conf.ancestor_path(&timeline_id, tenantid);
+        let mut ancestor_id: Option<String> = None;
+        let mut ancestor_lsn: Option<String> = None;
+
+        if ancestor_path.exists() {
+            let ancestor = std::fs::read_to_string(ancestor_path)?;
+            let mut strings = ancestor.split('@');
+
+            ancestor_id = Some(
+                strings
+                    .next()
+                    .with_context(|| "wrong branch ancestor point in time format")?
+                    .to_owned(),
+            );
+            ancestor_lsn = Some(
+                strings
+                    .next()
+                    .with_context(|| "wrong branch ancestor point in time format")?
+                    .to_owned(),
+            );
+        }
+
+        Ok(BranchInfo {
+            name,
+            timeline_id,
+            latest_valid_lsn: timeline.get_last_record_lsn(),
+            ancestor_id,
+            ancestor_lsn,
+            current_logical_size: timeline.get_current_logical_size(),
+            current_logical_size_non_incremental: timeline
+                .get_current_logical_size_non_incremental(timeline.get_last_record_lsn())?,
+        })
+    }
 }

 #[derive(Debug, Clone, Copy)]
@@ -43,8 +98,8 @@ pub struct PointInTime {

 pub fn init_pageserver(conf: &'static PageServerConf, create_tenant: Option<&str>) -> Result<()> {
    // Initialize logger
-    let (_scope_guard, _log_file) = logger::init_logging(&conf, "pageserver.log")?;
-    let _log_guard = slog_stdlog::init()?;
+    // use true as daemonize parameter because otherwise we pollute zenith cli output with a few pages long output of info messages
+    let (_scope_guard, _log_file) = logging::init(LOG_FILE_NAME, true)?;

    // We don't use the real WAL redo manager, because we don't want to spawn the WAL redo
    // process during repository initialization.
@@ -83,9 +138,6 @@ pub fn create_repo(
    fs::create_dir_all(&repo_dir)
        .with_context(|| format!("could not create directory {}", repo_dir.display()))?;

-    // Note: this `info!(...)` macro comes from `log` crate
-    info!("standard logging redirected to slog");
-
    fs::create_dir(conf.timelines_path(&tenantid))?;
    fs::create_dir_all(conf.branches_path(&tenantid))?;
    fs::create_dir_all(conf.tags_path(&tenantid))?;
@@ -118,7 +170,7 @@ fn get_lsn_from_controlfile(path: &Path) -> Result<Lsn> {
    Ok(Lsn(lsn))
 }

-// Create the cluster temporarily in a initdbpath directory inside the repository
+// Create the cluster temporarily in 'initdbpath' directory inside the repository
 // to get bootstrap data for timeline initialization.
 //
 fn run_initdb(conf: &'static PageServerConf, initdbpath: &Path) -> Result<()> {
@@ -166,11 +218,11 @@ fn bootstrap_timeline(

    info!("bootstrap_timeline {:?} at lsn {}", pgdata_path, lsn);

-    let timeline = repo.create_empty_timeline(tli, lsn)?;
+    // Import the contents of the data directory at the initial checkpoint
+    // LSN, and any WAL after that.
+    let timeline = repo.create_empty_timeline(tli)?;
    restore_local_repo::import_timeline_from_postgres_datadir(&pgdata_path, &*timeline, lsn)?;
-
-    let wal_dir = pgdata_path.join("pg_wal");
-    restore_local_repo::import_timeline_wal(&wal_dir, &*timeline, timeline.get_last_record_lsn())?;
+    timeline.checkpoint()?;

    println!(
        "created initial timeline {} timeline.lsn {}",
@@ -201,7 +253,7 @@ pub(crate) fn get_tenants(conf: &PageServerConf) -> Result<Vec<String>> {
 }

 pub(crate) fn get_branches(conf: &PageServerConf, tenantid: &ZTenantId) -> Result<Vec<BranchInfo>> {
-    let repo = tenant_mgr::get_repository_for_tenant(tenantid)?;
+    let repo = tenant_mgr::get_repository_for_tenant(*tenantid)?;

    // Each branch has a corresponding record (text file) in the refs/branches
    // with timeline_id.
@@ -210,43 +262,7 @@ pub(crate) fn get_branches(conf: &PageServerConf, tenantid: &ZTenantId) -> Resul
    std::fs::read_dir(&branches_dir)?
        .map(|dir_entry_res| {
            let dir_entry = dir_entry_res?;
-            let name = dir_entry.file_name().to_str().unwrap().to_string();
-            let timeline_id = std::fs::read_to_string(dir_entry.path())?.parse::<ZTimelineId>()?;
-
-            let latest_valid_lsn = repo
-                .get_timeline(timeline_id)
-                .map(|timeline| timeline.get_last_record_lsn())
-                .ok();
-
-            let ancestor_path = conf.ancestor_path(&timeline_id, tenantid);
-            let mut ancestor_id: Option<String> = None;
-            let mut ancestor_lsn: Option<String> = None;
-
-            if ancestor_path.exists() {
-                let ancestor = std::fs::read_to_string(ancestor_path)?;
-                let mut strings = ancestor.split('@');
-
-                ancestor_id = Some(
-                    strings
-                        .next()
-                        .with_context(|| "wrong branch ancestor point in time format")?
-                        .to_owned(),
-                );
-                ancestor_lsn = Some(
-                    strings
-                        .next()
-                        .with_context(|| "wrong branch ancestor point in time format")?
-                        .to_owned(),
-                );
-            }
-
-            Ok(BranchInfo {
-                name,
-                timeline_id,
-                latest_valid_lsn,
-                ancestor_id,
-                ancestor_lsn,
-            })
+            BranchInfo::from_path(dir_entry.path(), conf, tenantid, &repo)
        })
        .collect()
 }
@@ -257,21 +273,36 @@ pub(crate) fn create_branch(
    startpoint_str: &str,
    tenantid: &ZTenantId,
 ) -> Result<BranchInfo> {
-    let repo = tenant_mgr::get_repository_for_tenant(tenantid)?;
+    let repo = tenant_mgr::get_repository_for_tenant(*tenantid)?;

    if conf.branch_path(branchname, tenantid).exists() {
        anyhow::bail!("branch {} already exists", branchname);
    }

    let mut startpoint = parse_point_in_time(conf, startpoint_str, tenantid)?;
-
+    let timeline = repo.get_timeline(startpoint.timelineid)?;
    if startpoint.lsn == Lsn(0) {
        // Find end of WAL on the old timeline
-        let end_of_wal = repo
-            .get_timeline(startpoint.timelineid)?
-            .get_last_record_lsn();
+        let end_of_wal = timeline.get_last_record_lsn();
        info!("branching at end of WAL: {}", end_of_wal);
        startpoint.lsn = end_of_wal;
+    } else {
+        // Wait for the WAL to arrive and be processed on the parent branch up
+        // to the requested branch point. The repository code itself doesn't
+        // require it, but if we start to receive WAL on the new timeline,
+        // decoding the new WAL might need to look up previous pages, relation
+        // sizes etc. and that would get confused if the previous page versions
+        // are not in the repository yet.
+        timeline.wait_lsn(startpoint.lsn)?;
+    }
+    startpoint.lsn = startpoint.lsn.align();
+    if timeline.get_start_lsn() > startpoint.lsn {
+        anyhow::bail!(
+            "invalid startpoint {} for the branch {}: less than timeline start {}",
+            startpoint.lsn,
+            branchname,
+            timeline.get_start_lsn()
+        );
    }

    // create a new timeline directory for it
@@ -284,14 +315,16 @@ pub(crate) fn create_branch(
    // FIXME: there's a race condition, if you create a branch with the same
    // name concurrently.
    let data = newtli.to_string();
-    fs::write(conf.branch_path(&branchname, tenantid), data)?;
+    fs::write(conf.branch_path(branchname, tenantid), data)?;

    Ok(BranchInfo {
        name: branchname.to_string(),
        timeline_id: newtli,
-        latest_valid_lsn: Some(startpoint.lsn),
+        latest_valid_lsn: startpoint.lsn,
        ancestor_id: None,
        ancestor_lsn: None,
+        current_logical_size: 0,
+        current_logical_size_non_incremental: 0,
    })
 }

@@ -333,21 +366,21 @@ fn parse_point_in_time(

    // Check if it's a tag
    if lsn.is_none() {
-        let tagpath = conf.tag_path(name, &tenantid);
+        let tagpath = conf.tag_path(name, tenantid);
        if tagpath.exists() {
            let pointstr = fs::read_to_string(tagpath)?;

-            return parse_point_in_time(conf, &pointstr, &tenantid);
+            return parse_point_in_time(conf, &pointstr, tenantid);
        }
    }

    // Check if it's a branch
    // Check if it's branch @ LSN
-    let branchpath = conf.branch_path(name, &tenantid);
+    let branchpath = conf.branch_path(name, tenantid);
    if branchpath.exists() {
        let pointstr = fs::read_to_string(branchpath)?;

-        let mut result = parse_point_in_time(conf, &pointstr, &tenantid)?;
+        let mut result = parse_point_in_time(conf, &pointstr, tenantid)?;

        result.lsn = lsn.unwrap_or(Lsn(0));
        return Ok(result);
@@ -356,7 +389,7 @@ fn parse_point_in_time(
    // Check if it's a timelineid
    // Check if it's timelineid @ LSN
    if let Ok(timelineid) = ZTimelineId::from_str(name) {
-        let tlipath = conf.timeline_path(&timelineid, &tenantid);
+        let tlipath = conf.timeline_path(&timelineid, tenantid);
        if tlipath.exists() {
            return Ok(PointInTime {
                timelineid,
--- a/pageserver/src/http/openapi_spec.yml
+++ b/pageserver/src/http/openapi_spec.yml
@@ -54,7 +54,52 @@ paths:
            application/json:
              schema:
                $ref: "#/components/schemas/ForbiddenError"
-
+        "500":
+          description: Generic operation error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+  /v1/branch/{tenant_id}/{branch_name}:
+    parameters:
+      - name: tenant_id
+        in: path
+        required: true
+        schema:
+          type: string
+          format: hex
+      - name: branch_name
+        in: path
+        required: true
+        schema:
+          type: string
+    get:
+      description: Get branches for tenant
+      responses:
+        "200":
+          description: BranchInfo
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/BranchInfo"
+        "400":
+          description: Error when no tenant id found in path or no branch name
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+        "401":
+          description: Unauthorized Error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/UnauthorizedError"
+        "403":
+          description: Forbidden Error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ForbiddenError"
        "500":
          description: Generic operation error
          content:
@@ -203,6 +248,9 @@ components:
      required:
        - name
        - timeline_id
+        - latest_valid_lsn
+        - current_logical_size
+        - current_logical_size_non_incremental
      properties:
        name:
          type: string
@@ -213,6 +261,10 @@ components:
          type: string
        ancestor_lsn:
          type: string
+        current_logical_size:
+          type: integer
+        current_logical_size_non_incremental:
+          type: integer
    Error:
      type: object
      required:
--- a/pageserver/src/http/routes.rs
+++ b/pageserver/src/http/routes.rs
@@ -1,3 +1,4 @@
+use std::str::FromStr;
 use std::sync::Arc;

 use anyhow::Result;
@@ -18,10 +19,8 @@ use zenith_utils::http::{

 use super::models::BranchCreateRequest;
 use super::models::TenantCreateRequest;
-use crate::{
-    branches::{self},
-    tenant_mgr, PageServerConf, ZTenantId,
-};
+use crate::branches::BranchInfo;
+use crate::{branches, tenant_mgr, PageServerConf, ZTenantId};

 #[derive(Debug)]
 struct State {
@@ -57,6 +56,33 @@ fn get_config(request: &Request<Body>) -> &'static PageServerConf {
    get_state(request).conf
 }

+fn get_request_param<'a>(
+    request: &'a Request<Body>,
+    param_name: &str,
+) -> Result<&'a str, ApiError> {
+    match request.param(param_name) {
+        Some(arg) => Ok(arg),
+        None => {
+            return Err(ApiError::BadRequest(format!(
+                "no {} specified in path param",
+                param_name
+            )))
+        }
+    }
+}
+
+fn parse_request_param<T: FromStr>(
+    request: &Request<Body>,
+    param_name: &str,
+) -> Result<T, ApiError> {
+    match get_request_param(request, param_name)?.parse() {
+        Ok(v) => Ok(v),
+        Err(_) => Err(ApiError::BadRequest(
+            "failed to parse tenant id".to_string(),
+        )),
+    }
+}
+
 // healthcheck handler
 async fn status_handler(_: Request<Body>) -> Result<Response<Body>, ApiError> {
    Ok(Response::builder()
@@ -85,16 +111,7 @@ async fn branch_create_handler(mut request: Request<Body>) -> Result<Response<Bo
 }

 async fn branch_list_handler(request: Request<Body>) -> Result<Response<Body>, ApiError> {
-    let tenantid: ZTenantId = match request.param("tenant_id") {
-        Some(arg) => arg
-            .parse()
-            .map_err(|_| ApiError::BadRequest("failed to parse tenant id".to_string()))?,
-        None => {
-            return Err(ApiError::BadRequest(
-                "no tenant id specified in path param".to_string(),
-            ))
-        }
-    };
+    let tenantid: ZTenantId = parse_request_param(&request, "tenant_id")?;

    check_permission(&request, Some(tenantid))?;

@@ -106,6 +123,23 @@ async fn branch_list_handler(request: Request<Body>) -> Result<Response<Body>, A
    Ok(json_response(StatusCode::OK, response_data)?)
 }

+// TODO add to swagger
+async fn branch_detail_handler(request: Request<Body>) -> Result<Response<Body>, ApiError> {
+    let tenantid: ZTenantId = parse_request_param(&request, "tenant_id")?;
+    let branch_name: &str = get_request_param(&request, "branch_name")?;
+    let conf = get_state(&request).conf;
+    let path = conf.branch_path(branch_name, &tenantid);
+
+    let response_data = tokio::task::spawn_blocking(move || {
+        let repo = tenant_mgr::get_repository_for_tenant(tenantid)?;
+        BranchInfo::from_path(path, conf, &tenantid, &repo)
+    })
+    .await
+    .map_err(ApiError::from_err)??;
+
+    Ok(json_response(StatusCode::OK, response_data)?)
+}
+
 async fn tenant_list_handler(request: Request<Body>) -> Result<Response<Body>, ApiError> {
    // check for management permission
    check_permission(&request, None)?;
@@ -159,6 +193,7 @@ pub fn make_router(
        .data(Arc::new(State::new(conf, auth)))
        .get("/v1/status", status_handler)
        .get("/v1/branch/:tenant_id", branch_list_handler)
+        .get("/v1/branch/:tenant_id/:branch_name", branch_detail_handler)
        .post("/v1/branch", branch_create_handler)
        .get("/v1/tenant", tenant_list_handler)
        .post("/v1/tenant", tenant_create_handler)
--- a/pageserver/src/layered_repository.rs
+++ b/pageserver/src/layered_repository.rs
--- a/pageserver/src/layered_repository/README.md
+++ b/pageserver/src/layered_repository/README.md
@@ -4,15 +4,67 @@ The on-disk format is based on immutable files. The page server
 receives a stream of incoming WAL, parses the WAL records to determine
 which pages they apply to, and accumulates the incoming changes in
 memory. Every now and then, the accumulated changes are written out to
-new files.
+new immutable files. This process is called checkpointing. Old versions
+of on-disk files that are not needed by any timeline are removed by GC
+process.

-The files are called "snapshot files". Each snapshot file corresponds
-to one 10 MB slice of a PostgreSQL relation fork. The snapshot files
+# Terms used in layered repository
+
+- Relish - one PostgreSQL relation or similarly treated file.
+- Segment - one slice of a Relish that is stored in a LayeredTimeline.
+- Layer -  specific version of a relish Segment in a range of LSNs.
+
+Layers can be InMemory or OnDisk:
+- InMemory layer is not durably stored and needs to rebuild from WAL on pageserver start.
+- OnDisk layer is durably stored.
+
+OnDisk layers can be Image or Delta:
+- ImageLayer represents an image or a snapshot of a segment at one particular LSN.
+- DeltaLayer represents a collection of WAL records or page images in a range of LSNs.
+
+Dropped segments are always represented on disk by DeltaLayer.
+
+LSN range defined by start_lsn and end_lsn:
+- start_lsn is always inclusive.
+- end_lsn depends on layer kind:
+	- InMemoryLayer is either unbounded (end_lsn = MAX_LSN) or dropped (end_lsn = drop_lsn)
+    - ImageLayer represents snapshot at one LSN, so end_lsn = lsn.
+    - DeltaLayer has explicit end_lsn, which represents end of incremental layer.
+
+Layers can be open or historical:
+- Open layer is a writeable one. Only InMemory layer can be open.
+FIXME: If open layer is dropped, it is not writeable, so it should be turned into historical, 
+but now it is not implemented - see bug #569.
+- Historical layer is the one that cannot be modified anymore. Now only OnDisk layers can be historical.
+
+- LayerMap - a map that tracks what layers exist for all the relishes in a timeline.
+
+LayerMap consists of two data structures:
+- segs - All the layers keyed by segment tag
+- open_layers - data structure that hold all open layers ordered by oldest_pending_lsn for quick access during checkpointing. oldest_pending_lsn is the LSN of the oldest page version stored in this layer.
+
+All operations that update InMemory Layers should update both structures to keep them up-to-date.
+
+- LayeredTimeline - implements Timeline interface.
+
+All methods of LayeredTimeline are aware of its ancestors and return data taking them into account.
+TODO: Are there any exceptions to this?
+For example, timeline.list_rels(lsn) will return all segments that are visible in this timeline at the LSN,
+including ones that were not modified in this timeline and thus don't have a layer in the timeline's LayerMap.
+
+TODO:
+Describe GC and checkpoint interval settings.
+
+# Layer files (On-disk layers)
+
+The files are called "layer files". Each layer file corresponds
+to one RELISH_SEG_SIZE slice of a PostgreSQL relation fork or
+non-rel file in a range of LSNs. The layer files
 for each timeline are stored in the timeline's subdirectory under
 .zenith/tenants/<tenantid>/timelines.

-There are two kind of snapshot file: base images, and deltas. A base
-image file contains a snapshot of a segment as it was at one LSN,
+There are two kind of layer file: base images, and deltas. A base
+image file contains a layer of a segment as it was at one LSN,
 whereas a delta file contains modifications to a segment - mostly in
 the form of WAL records - in a range of LSN

@@ -44,7 +96,7 @@ managed, except that the first part of file names is different.
 Internally, the relations and non-relation files that are managed in
 the versioned store are together called "relishes".

-If a file has been dropped, the last snapshot file for it is created
+If a file has been dropped, the last layer file for it is created
 with the _DROPPED suffix, e.g.

    rel_1663_13990_2609_0_10_000000000169C348_0000000001702000_DROPPED
@@ -67,7 +119,7 @@ for 'orders' table on 'main' branch is represented like this:
    main/orders_100_200


-# Creating snapshot files
+# Creating layer files

 Let's start with a simple example with a system that contains one
 branch called 'main' and two tables, 'orders' and 'customers'. The end
@@ -86,10 +138,10 @@ end of WAL at 250 are kept in memory. If the page server crashes, the
 latest records between 200-250 need to be re-read from the WAL.

 Whenever enough WAL has been accumulated in memory, the page server
-writes out the changes in memory into new snapshot files. This process
+writes out the changes in memory into new layer files. This process
 is called "checkpointing" (not to be confused with the PostgreSQL
 checkpoints, that's a different thing). The page server only creates
-snapshot files for relations that have been modified since the last
+layer files for relations that have been modified since the last
 checkpoint. For example, if the current end of WAL is at LSN 450, and
 the last checkpoint happened at LSN 400 but there hasn't been any
 recent changes to 'customers' table, you would have these files on
@@ -108,7 +160,7 @@ disk:

 If the customers table is modified later, a new file is created for it
 at the next checkpoint. The new file will cover the "gap" from the
-last snapshot file, so the LSN ranges are always contiguous:
+last layer file, so the LSN ranges are always contiguous:

 	main/orders_100
 	main/orders_100_200
@@ -130,13 +182,13 @@ page server needs to reconstruct the requested page, as it was at the
 requested LSN. To do that, the page server first checks the recent
 in-memory layer; if the requested page version is found there, it can
 be returned immediatedly without looking at the files on
-disk. Otherwise the page server needs to locate the snapshot file that
+disk. Otherwise the page server needs to locate the layer file that
 contains the requested page version.

 For example, if a request comes in for table 'orders' at LSN 250, the
 page server would load the 'main/orders_200_300' file into memory, and
 reconstruct and return the requested page from it, as it was at
-LSN 250. Because the snapshot file consists of a full image of the
+LSN 250. Because the layer file consists of a full image of the
 relation at the start LSN and the WAL, reconstructing the page
 involves replaying any WAL records applicable to the page between LSNs
 200-250, starting from the base image at LSN 200.
@@ -171,7 +223,7 @@ Then, the 'orders' table is updated differently on the 'main' and

 Because the 'customers' table hasn't been modified on the child
 branch, there is no file for it there. If you request a page for it on
-the 'child' branch, the page server will not find any snapshot file
+the 'child' branch, the page server will not find any layer file
 for it in the 'child' directory, so it will recurse to look into the
 parent 'main' branch instead.

@@ -217,7 +269,7 @@ branch at a historic LSN, is how we support PITR in Zenith.

 # Garbage collection

-In this scheme, we keep creating new snapshot files over time. We also
+In this scheme, we keep creating new layer files over time. We also
 need a mechanism to remove old files that are no longer needed,
 because disk space isn't infinite.

@@ -245,7 +297,7 @@ of the branch is LSN 525, so that the GC horizon is currently at
 	main/customers_200

 We can remove the following files because the end LSNs of those files are
-older than GC horizon 375, and there are more recent snapshot files for the
+older than GC horizon 375, and there are more recent layer files for the
 table:

 	main/orders_100       DELETE
@@ -262,7 +314,7 @@ table:
 	main/customers_200      KEEP, NO NEWER VERSION

 'main/customers_100_200' is old enough, but it cannot be
-removed because there is no newer snapshot file for the table.
+removed because there is no newer layer file for the table.

 Things get slightly more complicated with multiple branches. All of
 the above still holds, but in addition to recent files we must also
@@ -308,7 +360,7 @@ new base image and delta file for it on the child:

 After this, the 'main/orders_100' and 'main/orders_100_200' file could
 be removed. It is no longer needed by the child branch, because there
-is a newer snapshot file there. TODO: This optimization hasn't been
+is a newer layer file there. TODO: This optimization hasn't been
 implemented! The GC algorithm will currently keep the file on the
 'main' branch anyway, for as long as the child branch exists.

@@ -346,7 +398,7 @@ It would also be OK to have overlapping LSN ranges for the same relation:
 	main/orders_300_400
 	main/orders_400

-The code that reads the snapshot files should cope with this, but this
+The code that reads the layer files should cope with this, but this
 situation doesn't arise either, because the checkpointing code never
 does that.  It could be useful, however, as a transient state when
 garbage collecting around branch points, or explicit recovery
@@ -360,6 +412,6 @@ points. For example, if we start with this:

 And there is a branch or explicit recovery point at LSN 150, we could
 replace 'main/orders_100_200' with 'main/orders_150' to keep a
-snapshot only at that exact point that's still needed, removing the
+layer only at that exact point that's still needed, removing the
 other page versions around it. But such compaction has not been
 implemented yet.
--- a/pageserver/src/layered_repository/blob.rs
+++ b/pageserver/src/layered_repository/blob.rs
@@ -16,14 +16,14 @@ pub fn read_blob(reader: &BoundedReader<&'_ File>, range: &BlobRange) -> Result<
    Ok(buf)
 }

-pub struct BlobWriter {
-    writer: ChapterWriter<File>,
+pub struct BlobWriter<W> {
+    writer: ChapterWriter<W>,
    offset: u64,
 }

-impl BlobWriter {
+impl<W: Write> BlobWriter<W> {
    // This function takes a BookWriter and creates a new chapter to ensure offset is 0.
-    pub fn new(book_writer: BookWriter<File>, chapter_id: impl Into<ChapterId>) -> Self {
+    pub fn new(book_writer: BookWriter<W>, chapter_id: impl Into<ChapterId>) -> Self {
        let writer = book_writer.new_chapter(chapter_id);
        Self { writer, offset: 0 }
    }
@@ -39,7 +39,7 @@ impl BlobWriter {
        Ok(range)
    }

-    pub fn close(self) -> bookfile::Result<BookWriter<File>> {
+    pub fn close(self) -> bookfile::Result<BookWriter<W>> {
        self.writer.close()
    }
 }
--- a/pageserver/src/layered_repository/delta_layer.rs
+++ b/pageserver/src/layered_repository/delta_layer.rs
@@ -56,7 +56,7 @@ use std::collections::BTreeMap;
 use std::fmt::Write as _;
 use std::fs;
 use std::fs::File;
-use std::io::Write;
+use std::io::{BufWriter, Write};
 use std::ops::Bound::Included;
 use std::path::{Path, PathBuf};
 use std::sync::{Arc, Mutex, MutexGuard};
@@ -69,7 +69,7 @@ use zenith_utils::lsn::Lsn;
 use super::blob::{read_blob, BlobRange};

 // Magic constant to identify a Zenith delta file
-static DELTA_FILE_MAGIC: u32 = 0x5A616E01;
+pub const DELTA_FILE_MAGIC: u32 = 0x5A616E01;

 /// Mapping from (block #, lsn) -> page/WAL record
 /// byte ranges in PAGE_VERSIONS_CHAPTER
@@ -79,6 +79,36 @@ static PAGE_VERSION_METAS_CHAPTER: u64 = 1;
 static PAGE_VERSIONS_CHAPTER: u64 = 2;
 static REL_SIZES_CHAPTER: u64 = 3;

+/// Contains the [`Summary`] struct
+static SUMMARY_CHAPTER: u64 = 4;
+
+#[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
+struct Summary {
+    tenantid: ZTenantId,
+    timelineid: ZTimelineId,
+    seg: SegmentTag,
+
+    start_lsn: Lsn,
+    end_lsn: Lsn,
+
+    dropped: bool,
+}
+
+impl From<&DeltaLayer> for Summary {
+    fn from(layer: &DeltaLayer) -> Self {
+        Self {
+            tenantid: layer.tenantid,
+            timelineid: layer.timelineid,
+            seg: layer.seg,
+
+            start_lsn: layer.start_lsn,
+            end_lsn: layer.end_lsn,
+
+            dropped: layer.dropped,
+        }
+    }
+}
+
 #[derive(Serialize, Deserialize)]
 struct PageVersionMeta {
    page_image_range: Option<BlobRange>,
@@ -130,23 +160,23 @@ pub struct DeltaLayerInner {

 impl Layer for DeltaLayer {
    fn get_timeline_id(&self) -> ZTimelineId {
-        return self.timelineid;
+        self.timelineid
    }

    fn get_seg_tag(&self) -> SegmentTag {
-        return self.seg;
+        self.seg
    }

    fn is_dropped(&self) -> bool {
-        return self.dropped;
+        self.dropped
    }

    fn get_start_lsn(&self) -> Lsn {
-        return self.start_lsn;
+        self.start_lsn
    }

    fn get_end_lsn(&self) -> Lsn {
-        return self.end_lsn;
+        self.end_lsn
    }

    fn filename(&self) -> PathBuf {
@@ -161,6 +191,20 @@ impl Layer for DeltaLayer {
        )
    }

+    fn path(&self) -> Option<PathBuf> {
+        Some(Self::path_for(
+            &self.path_or_conf,
+            self.timelineid,
+            self.tenantid,
+            &DeltaFileName {
+                seg: self.seg,
+                start_lsn: self.start_lsn,
+                end_lsn: self.end_lsn,
+                dropped: self.dropped,
+            },
+        ))
+    }
+
    /// Look up given page in the cache.
    fn get_page_reconstruct_data(
        &self,
@@ -168,13 +212,13 @@ impl Layer for DeltaLayer {
        lsn: Lsn,
        reconstruct_data: &mut PageReconstructData,
    ) -> Result<PageReconstructResult> {
-        let mut cont_lsn: Option<Lsn> = Some(lsn);
+        let mut need_image = true;

        assert!(self.seg.blknum_in_seg(blknum));

        {
            // Open the file and lock the metadata in memory
-            // TODO: avoid opening the snapshot file for each read
+            // TODO: avoid opening the file for each read
            let (_path, book) = self.open_book()?;
            let page_version_reader = book.chapter_reader(PAGE_VERSIONS_CHAPTER)?;
            let inner = self.load()?;
@@ -185,12 +229,12 @@ impl Layer for DeltaLayer {
            let mut iter = inner
                .page_version_metas
                .range((Included(&minkey), Included(&maxkey)));
-            while let Some(((_blknum, entry_lsn), entry)) = iter.next_back() {
+            while let Some(((_blknum, _entry_lsn), entry)) = iter.next_back() {
                if let Some(img_range) = &entry.page_image_range {
                    // Found a page image, return it
                    let img = Bytes::from(read_blob(&page_version_reader, img_range)?);
                    reconstruct_data.page_img = Some(img);
-                    cont_lsn = None;
+                    need_image = false;
                    break;
                } else if let Some(rec_range) = &entry.record_range {
                    let rec = WALRecord::des(&read_blob(&page_version_reader, rec_range)?)?;
@@ -198,11 +242,8 @@ impl Layer for DeltaLayer {
                    reconstruct_data.records.push(rec);
                    if will_init {
                        // This WAL record initializes the page, so no need to go further back
-                        cont_lsn = None;
+                        need_image = false;
                        break;
-                    } else {
-                        // This WAL record needs to be applied against an older page image
-                        cont_lsn = Some(*entry_lsn);
                    }
                } else {
                    // No base image, and no WAL record. Huh?
@@ -215,14 +256,14 @@ impl Layer for DeltaLayer {

        // If an older page image is needed to reconstruct the page, let the
        // caller know about the predecessor layer.
-        if let Some(cont_lsn) = cont_lsn {
+        if need_image {
            if let Some(cont_layer) = &self.predecessor {
                Ok(PageReconstructResult::Continue(
-                    cont_lsn,
+                    self.start_lsn,
                    Arc::clone(cont_layer),
                ))
            } else {
-                Ok(PageReconstructResult::Missing(cont_lsn))
+                Ok(PageReconstructResult::Missing(self.start_lsn))
            }
        } else {
            Ok(PageReconstructResult::Complete)
@@ -274,7 +315,9 @@ impl Layer for DeltaLayer {

    fn delete(&self) -> Result<()> {
        // delete underlying file
-        fs::remove_file(self.path())?;
+        if let Some(path) = self.path() {
+            fs::remove_file(path)?;
+        }
        Ok(())
    }

@@ -285,8 +328,8 @@ impl Layer for DeltaLayer {
    /// debugging function to print out the contents of the layer
    fn dump(&self) -> Result<()> {
        println!(
-            "----- delta layer for {} {}-{} ----",
-            self.seg, self.start_lsn, self.end_lsn
+            "----- delta layer for ten {} tli {} seg {} {}-{} ----",
+            self.tenantid, self.timelineid, self.seg, self.start_lsn, self.end_lsn
        );

        println!("--- relsizes ---");
@@ -301,7 +344,7 @@ impl Layer for DeltaLayer {
            let mut desc = String::new();

            if let Some(page_image_range) = v.page_image_range.as_ref() {
-                let image = read_blob(&chapter, &page_image_range)?;
+                let image = read_blob(&chapter, page_image_range)?;
                write!(&mut desc, " img {} bytes", image.len())?;
            }
            if let Some(record_range) = v.record_range.as_ref() {
@@ -324,20 +367,6 @@ impl Layer for DeltaLayer {
 }

 impl DeltaLayer {
-    fn path(&self) -> PathBuf {
-        Self::path_for(
-            &self.path_or_conf,
-            self.timelineid,
-            self.tenantid,
-            &DeltaFileName {
-                seg: self.seg,
-                start_lsn: self.start_lsn,
-                end_lsn: self.end_lsn,
-                dropped: self.dropped,
-            },
-        )
-    }
-
    fn path_for(
        path_or_conf: &PathOrConf,
        timelineid: ZTimelineId,
@@ -358,6 +387,7 @@ impl DeltaLayer {
    /// This is used to write the in-memory layer to disk. The in-memory layer uses the same
    /// data structure with two btreemaps as we do, so passing the btreemaps is currently
    /// expedient.
+    #[allow(clippy::too_many_arguments)]
    pub fn create(
        conf: &'static PageServerConf,
        timelineid: ZTimelineId,
@@ -372,28 +402,31 @@ impl DeltaLayer {
    ) -> Result<DeltaLayer> {
        let delta_layer = DeltaLayer {
            path_or_conf: PathOrConf::Conf(conf),
-            timelineid: timelineid,
-            tenantid: tenantid,
-            seg: seg,
-            start_lsn: start_lsn,
+            timelineid,
+            tenantid,
+            seg,
+            start_lsn,
            end_lsn,
            dropped,
            inner: Mutex::new(DeltaLayerInner {
                loaded: true,
                page_version_metas: BTreeMap::new(),
-                relsizes: relsizes,
+                relsizes,
            }),
            predecessor,
        };
        let mut inner = delta_layer.inner.lock().unwrap();

        // Write the in-memory btreemaps into a file
-        let path = delta_layer.path();
+        let path = delta_layer
+            .path()
+            .expect("DeltaLayer is supposed to have a layer path on disk");

        // Note: This overwrites any existing file. There shouldn't be any.
        // FIXME: throw an error instead?
        let file = File::create(&path)?;
-        let book = BookWriter::new(file, DELTA_FILE_MAGIC)?;
+        let buf_writer = BufWriter::new(file);
+        let book = BookWriter::new(buf_writer, DELTA_FILE_MAGIC)?;

        let mut page_version_writer = BlobWriter::new(book, PAGE_VERSIONS_CHAPTER);

@@ -436,6 +469,21 @@ impl DeltaLayer {
        chapter.write_all(&buf)?;
        let book = chapter.close()?;

+        let mut chapter = book.new_chapter(SUMMARY_CHAPTER);
+        let summary = Summary {
+            tenantid,
+            timelineid,
+            seg,
+
+            start_lsn,
+            end_lsn,
+
+            dropped,
+        };
+        Summary::ser_into(&summary, &mut chapter)?;
+        let book = chapter.close()?;
+
+        // This flushes the underlying 'buf_writer'.
        book.close()?;

        trace!("saved {}", &path.display());
@@ -477,6 +525,31 @@ impl DeltaLayer {

        let (path, book) = self.open_book()?;

+        match &self.path_or_conf {
+            PathOrConf::Conf(_) => {
+                let chapter = book.read_chapter(SUMMARY_CHAPTER)?;
+                let actual_summary = Summary::des(&chapter)?;
+
+                let expected_summary = Summary::from(self);
+
+                if actual_summary != expected_summary {
+                    bail!("in-file summary does not match expected summary. actual = {:?} expected = {:?}", actual_summary, expected_summary);
+                }
+            }
+            PathOrConf::Path(path) => {
+                let actual_filename = Path::new(path.file_name().unwrap());
+                let expected_filename = self.filename();
+
+                if actual_filename != expected_filename {
+                    println!(
+                        "warning: filename does not match what is expected from in-file summary"
+                    );
+                    println!("actual: {:?}", actual_filename);
+                    println!("expected: {:?}", expected_filename);
+                }
+            }
+        }
+
        let chapter = book.read_chapter(PAGE_VERSION_METAS_CHAPTER)?;
        let page_version_metas = BTreeMap::des(&chapter)?;

@@ -522,26 +595,24 @@ impl DeltaLayer {
    /// Create a DeltaLayer struct representing an existing file on disk.
    ///
    /// This variant is only used for debugging purposes, by the 'dump_layerfile' binary.
-    pub fn new_for_path(
-        path: &Path,
-        timelineid: ZTimelineId,
-        tenantid: ZTenantId,
-        filename: &DeltaFileName,
-    ) -> DeltaLayer {
-        DeltaLayer {
+    pub fn new_for_path(path: &Path, book: &Book<File>) -> Result<Self> {
+        let chapter = book.read_chapter(SUMMARY_CHAPTER)?;
+        let summary = Summary::des(&chapter)?;
+
+        Ok(DeltaLayer {
            path_or_conf: PathOrConf::Path(path.to_path_buf()),
-            timelineid,
-            tenantid,
-            seg: filename.seg,
-            start_lsn: filename.start_lsn,
-            end_lsn: filename.end_lsn,
-            dropped: filename.dropped,
+            timelineid: summary.timelineid,
+            tenantid: summary.tenantid,
+            seg: summary.seg,
+            start_lsn: summary.start_lsn,
+            end_lsn: summary.end_lsn,
+            dropped: summary.dropped,
            inner: Mutex::new(DeltaLayerInner {
                loaded: false,
                page_version_metas: BTreeMap::new(),
                relsizes: BTreeMap::new(),
            }),
            predecessor: None,
-        }
+        })
    }
 }
--- a/pageserver/src/layered_repository/filename.rs
+++ b/pageserver/src/layered_repository/filename.rs
@@ -111,8 +111,10 @@ impl DeltaFileName {
            dropped,
        })
    }
+}

-    fn to_string(&self) -> String {
+impl fmt::Display for DeltaFileName {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let basename = match self.seg.rel {
            RelishTag::Relation(reltag) => format!(
                "rel_{}_{}_{}_{}",
@@ -134,11 +136,12 @@ impl DeltaFileName {
                format!("pg_filenodemap_{}_{}", spcnode, dbnode)
            }
            RelishTag::TwoPhase { xid } => format!("pg_twophase_{}", xid),
-            RelishTag::Checkpoint => format!("pg_control_checkpoint"),
-            RelishTag::ControlFile => format!("pg_control"),
+            RelishTag::Checkpoint => "pg_control_checkpoint".to_string(),
+            RelishTag::ControlFile => "pg_control".to_string(),
        };

-        format!(
+        write!(
+            f,
            "{}_{}_{:016X}_{:016X}{}",
            basename,
            self.seg.segno,
@@ -149,12 +152,6 @@ impl DeltaFileName {
    }
 }

-impl fmt::Display for DeltaFileName {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.to_string())
-    }
-}
-
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
 pub struct ImageFileName {
    pub seg: SegmentTag,
@@ -233,8 +230,10 @@ impl ImageFileName {

        Some(ImageFileName { seg, lsn })
    }
+}

-    fn to_string(&self) -> String {
+impl fmt::Display for ImageFileName {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let basename = match self.seg.rel {
            RelishTag::Relation(reltag) => format!(
                "rel_{}_{}_{}_{}",
@@ -256,11 +255,12 @@ impl ImageFileName {
                format!("pg_filenodemap_{}_{}", spcnode, dbnode)
            }
            RelishTag::TwoPhase { xid } => format!("pg_twophase_{}", xid),
-            RelishTag::Checkpoint => format!("pg_control_checkpoint"),
-            RelishTag::ControlFile => format!("pg_control"),
+            RelishTag::Checkpoint => "pg_control_checkpoint".to_string(),
+            RelishTag::ControlFile => "pg_control".to_string(),
        };

-        format!(
+        write!(
+            f,
            "{}_{}_{:016X}",
            basename,
            self.seg.segno,
@@ -269,12 +269,6 @@ impl ImageFileName {
    }
 }

-impl fmt::Display for ImageFileName {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.to_string())
-    }
-}
-
 /// Scan timeline directory and create ImageFileName and DeltaFilename
 /// structs representing all files on disk
 ///
@@ -302,7 +296,7 @@ pub fn list_files(
            warn!("unrecognized filename in timeline dir: {}", fname);
        }
    }
-    return Ok((imgfiles, deltafiles));
+    Ok((imgfiles, deltafiles))
 }

 /// Helper enum to hold a PageServerConf, or a path
--- a/pageserver/src/layered_repository/image_layer.rs
+++ b/pageserver/src/layered_repository/image_layer.rs
@@ -2,8 +2,9 @@
 //! It is stored in a file on disk.
 //!
 //! On disk, the image files are stored in timelines/<timelineid> directory.
-//! Currently, there are no subdirectories, and each snapshot file is named like this:
+//! Currently, there are no subdirectories, and each image layer file is named like this:
 //!
+//! Note that segno is
 //!    <spcnode>_<dbnode>_<relnode>_<forknum>_<segno>_<LSN>
 //!
 //! For example:
@@ -15,10 +16,10 @@
 //! Only metadata is loaded into memory by the load function.
 //! When images are needed, they are read directly from disk.
 //!
-//! For blocky segments, the images are stored in BLOCKY_IMAGES_CHAPTER.
+//! For blocky relishes, the images are stored in BLOCKY_IMAGES_CHAPTER.
 //! All the images are required to be BLOCK_SIZE, which allows for random access.
 //!
-//! For non-blocky segments, the image can be found in NONBLOCKY_IMAGE_CHAPTER.
+//! For non-blocky relishes, the image can be found in NONBLOCKY_IMAGE_CHAPTER.
 //!
 use crate::layered_repository::filename::{ImageFileName, PathOrConf};
 use crate::layered_repository::storage_layer::{
@@ -28,27 +29,53 @@ use crate::layered_repository::LayeredTimeline;
 use crate::layered_repository::RELISH_SEG_SIZE;
 use crate::PageServerConf;
 use crate::{ZTenantId, ZTimelineId};
-use anyhow::{anyhow, ensure, Result};
+use anyhow::{anyhow, bail, ensure, Result};
 use bytes::Bytes;
 use log::*;
+use serde::{Deserialize, Serialize};
 use std::convert::TryInto;
 use std::fs;
 use std::fs::File;
-use std::io::Write;
+use std::io::{BufWriter, Write};
 use std::path::{Path, PathBuf};
 use std::sync::{Mutex, MutexGuard};

 use bookfile::{Book, BookWriter};

+use zenith_utils::bin_ser::BeSer;
 use zenith_utils::lsn::Lsn;

 // Magic constant to identify a Zenith segment image file
-const IMAGE_FILE_MAGIC: u32 = 0x5A616E01 + 1;
+pub const IMAGE_FILE_MAGIC: u32 = 0x5A616E01 + 1;

 /// Contains each block in block # order
 const BLOCKY_IMAGES_CHAPTER: u64 = 1;
 const NONBLOCKY_IMAGE_CHAPTER: u64 = 2;

+/// Contains the [`Summary`] struct
+const SUMMARY_CHAPTER: u64 = 3;
+
+#[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
+struct Summary {
+    tenantid: ZTenantId,
+    timelineid: ZTimelineId,
+    seg: SegmentTag,
+
+    lsn: Lsn,
+}
+
+impl From<&ImageLayer> for Summary {
+    fn from(layer: &ImageLayer) -> Self {
+        Self {
+            tenantid: layer.tenantid,
+            timelineid: layer.timelineid,
+            seg: layer.seg,
+
+            lsn: layer.lsn,
+        }
+    }
+}
+
 const BLOCK_SIZE: usize = 8192;

 ///
@@ -96,24 +123,36 @@ impl Layer for ImageLayer {
        )
    }

+    fn path(&self) -> Option<PathBuf> {
+        Some(Self::path_for(
+            &self.path_or_conf,
+            self.timelineid,
+            self.tenantid,
+            &ImageFileName {
+                seg: self.seg,
+                lsn: self.lsn,
+            },
+        ))
+    }
+
    fn get_timeline_id(&self) -> ZTimelineId {
-        return self.timelineid;
+        self.timelineid
    }

    fn get_seg_tag(&self) -> SegmentTag {
-        return self.seg;
+        self.seg
    }

    fn is_dropped(&self) -> bool {
-        return false;
+        false
    }

    fn get_start_lsn(&self) -> Lsn {
-        return self.lsn;
+        self.lsn
    }

    fn get_end_lsn(&self) -> Lsn {
-        return self.lsn;
+        self.lsn
    }

    /// Look up given page in the file
@@ -182,7 +221,9 @@ impl Layer for ImageLayer {

    fn delete(&self) -> Result<()> {
        // delete underlying file
-        fs::remove_file(self.path())?;
+        if let Some(path) = self.path() {
+            fs::remove_file(path)?;
+        }
        Ok(())
    }

@@ -192,7 +233,10 @@ impl Layer for ImageLayer {

    /// debugging function to print out the contents of the layer
    fn dump(&self) -> Result<()> {
-        println!("----- image layer for {} at {} ----", self.seg, self.lsn);
+        println!(
+            "----- image layer for ten {} tli {} seg {} at {} ----",
+            self.tenantid, self.timelineid, self.seg, self.lsn
+        );

        let inner = self.load()?;

@@ -210,18 +254,6 @@ impl Layer for ImageLayer {
 }

 impl ImageLayer {
-    fn path(&self) -> PathBuf {
-        Self::path_for(
-            &self.path_or_conf,
-            self.timelineid,
-            self.tenantid,
-            &ImageFileName {
-                seg: self.seg,
-                lsn: self.lsn,
-            },
-        )
-    }
-
    fn path_for(
        path_or_conf: &PathOrConf,
        timelineid: ZTimelineId,
@@ -255,10 +287,10 @@ impl ImageLayer {

        let layer = ImageLayer {
            path_or_conf: PathOrConf::Conf(conf),
-            timelineid: timelineid,
-            tenantid: tenantid,
-            seg: seg,
-            lsn: lsn,
+            timelineid,
+            tenantid,
+            seg,
+            lsn,
            inner: Mutex::new(ImageLayerInner {
                loaded: true,
                image_type: image_type.clone(),
@@ -267,12 +299,14 @@ impl ImageLayer {
        let inner = layer.inner.lock().unwrap();

        // Write the images into a file
-        let path = layer.path();
-
+        let path = layer
+            .path()
+            .expect("ImageLayer is supposed to have a layer path on disk");
        // Note: This overwrites any existing file. There shouldn't be any.
        // FIXME: throw an error instead?
        let file = File::create(&path)?;
-        let book = BookWriter::new(file, IMAGE_FILE_MAGIC)?;
+        let buf_writer = BufWriter::new(file);
+        let book = BookWriter::new(buf_writer, IMAGE_FILE_MAGIC)?;

        let book = match &image_type {
            ImageType::Blocky { .. } => {
@@ -290,6 +324,18 @@ impl ImageLayer {
            }
        };

+        let mut chapter = book.new_chapter(SUMMARY_CHAPTER);
+        let summary = Summary {
+            tenantid,
+            timelineid,
+            seg,
+
+            lsn,
+        };
+        Summary::ser_into(&summary, &mut chapter)?;
+        let book = chapter.close()?;
+
+        // This flushes the underlying 'buf_writer'.
        book.close()?;

        trace!("saved {}", &path.display());
@@ -350,6 +396,31 @@ impl ImageLayer {

        let (path, book) = self.open_book()?;

+        match &self.path_or_conf {
+            PathOrConf::Conf(_) => {
+                let chapter = book.read_chapter(SUMMARY_CHAPTER)?;
+                let actual_summary = Summary::des(&chapter)?;
+
+                let expected_summary = Summary::from(self);
+
+                if actual_summary != expected_summary {
+                    bail!("in-file summary does not match expected summary. actual = {:?} expected = {:?}", actual_summary, expected_summary);
+                }
+            }
+            PathOrConf::Path(path) => {
+                let actual_filename = Path::new(path.file_name().unwrap());
+                let expected_filename = self.filename();
+
+                if actual_filename != expected_filename {
+                    println!(
+                        "warning: filename does not match what is expected from in-file summary"
+                    );
+                    println!("actual: {:?}", actual_filename);
+                    println!("expected: {:?}", expected_filename);
+                }
+            }
+        }
+
        let image_type = if self.seg.rel.is_blocky() {
            let chapter = book.chapter_reader(BLOCKY_IMAGES_CHAPTER)?;
            let images_len = chapter.len();
@@ -411,22 +482,20 @@ impl ImageLayer {
    /// Create an ImageLayer struct representing an existing file on disk.
    ///
    /// This variant is only used for debugging purposes, by the 'dump_layerfile' binary.
-    pub fn new_for_path(
-        path: &Path,
-        timelineid: ZTimelineId,
-        tenantid: ZTenantId,
-        filename: &ImageFileName,
-    ) -> ImageLayer {
-        ImageLayer {
+    pub fn new_for_path(path: &Path, book: &Book<File>) -> Result<ImageLayer> {
+        let chapter = book.read_chapter(SUMMARY_CHAPTER)?;
+        let summary = Summary::des(&chapter)?;
+
+        Ok(ImageLayer {
            path_or_conf: PathOrConf::Path(path.to_path_buf()),
-            timelineid,
-            tenantid,
-            seg: filename.seg,
-            lsn: filename.lsn,
+            timelineid: summary.timelineid,
+            tenantid: summary.tenantid,
+            seg: summary.seg,
+            lsn: summary.lsn,
            inner: Mutex::new(ImageLayerInner {
                loaded: false,
                image_type: ImageType::Blocky { num_blocks: 0 },
            }),
-        }
+        })
    }
 }
--- a/pageserver/src/layered_repository/inmemory_layer.rs
+++ b/pageserver/src/layered_repository/inmemory_layer.rs
@@ -7,6 +7,7 @@ use crate::layered_repository::storage_layer::{
    Layer, PageReconstructData, PageReconstructResult, PageVersion, SegmentTag, RELISH_SEG_SIZE,
 };
 use crate::layered_repository::LayeredTimeline;
+use crate::layered_repository::ZERO_PAGE;
 use crate::layered_repository::{DeltaLayer, ImageLayer};
 use crate::repository::WALRecord;
 use crate::PageServerConf;
@@ -29,20 +30,19 @@ pub struct InMemoryLayer {

    ///
    /// This layer contains all the changes from 'start_lsn'. The
-    /// start is inclusive. There is no end LSN; we only use in-memory
-    /// layer at the end of a timeline.
+    /// start is inclusive.
    ///
    start_lsn: Lsn,

+    /// Frozen in-memory layers have an inclusive end LSN.
+    end_lsn: Option<Lsn>,
+
    /// LSN of the oldest page version stored in this layer
    oldest_pending_lsn: Lsn,

    /// The above fields never change. The parts that do change are in 'inner',
    /// and protected by mutex.
    inner: Mutex<InMemoryLayerInner>,
-
-    /// Predecessor layer
-    predecessor: Option<Arc<dyn Layer>>,
 }

 pub struct InMemoryLayerInner {
@@ -59,9 +59,24 @@ pub struct InMemoryLayerInner {
    /// `segsizes` tracks the size of the segment at different points in time.
    ///
    segsizes: BTreeMap<Lsn, u32>,
+
+    /// Writes are only allowed when true.
+    /// Set to false when this layer is in the process of being replaced.
+    writeable: bool,
+
+    /// Predecessor layer
+    predecessor: Option<Arc<dyn Layer>>,
 }

 impl InMemoryLayerInner {
+    fn check_writeable(&self) -> WriteResult<()> {
+        if self.writeable {
+            Ok(())
+        } else {
+            Err(NonWriteableError)
+        }
+    }
+
    fn get_seg_size(&self, lsn: Lsn) -> u32 {
        // Scan the BTreeMap backwards, starting from the given entry.
        let mut iter = self.segsizes.range((Included(&Lsn(0)), Included(&lsn)));
@@ -93,27 +108,35 @@ impl Layer for InMemoryLayer {
        let delta_filename = DeltaFileName {
            seg: self.seg,
            start_lsn: self.start_lsn,
-            end_lsn: end_lsn,
-            dropped: dropped,
+            end_lsn,
+            dropped,
        }
        .to_string();

        PathBuf::from(format!("inmem-{}", delta_filename))
    }

+    fn path(&self) -> Option<PathBuf> {
+        None
+    }
+
    fn get_timeline_id(&self) -> ZTimelineId {
-        return self.timelineid;
+        self.timelineid
    }

    fn get_seg_tag(&self) -> SegmentTag {
-        return self.seg;
+        self.seg
    }

    fn get_start_lsn(&self) -> Lsn {
-        return self.start_lsn;
+        self.start_lsn
    }

    fn get_end_lsn(&self) -> Lsn {
+        if let Some(end_lsn) = self.end_lsn {
+            return Lsn(end_lsn.0 + 1);
+        }
+
        let inner = self.inner.lock().unwrap();

        if let Some(drop_lsn) = inner.drop_lsn {
@@ -135,10 +158,12 @@ impl Layer for InMemoryLayer {
        lsn: Lsn,
        reconstruct_data: &mut PageReconstructData,
    ) -> Result<PageReconstructResult> {
-        let mut cont_lsn: Option<Lsn> = Some(lsn);
+        let mut need_image = true;

        assert!(self.seg.blknum_in_seg(blknum));

+        let predecessor: Option<Arc<dyn Layer>>;
+
        {
            let inner = self.inner.lock().unwrap();

@@ -148,20 +173,17 @@ impl Layer for InMemoryLayer {
            let mut iter = inner
                .page_versions
                .range((Included(&minkey), Included(&maxkey)));
-            while let Some(((_blknum, entry_lsn), entry)) = iter.next_back() {
+            while let Some(((_blknum, _entry_lsn), entry)) = iter.next_back() {
                if let Some(img) = &entry.page_image {
                    reconstruct_data.page_img = Some(img.clone());
-                    cont_lsn = None;
+                    need_image = false;
                    break;
                } else if let Some(rec) = &entry.record {
                    reconstruct_data.records.push(rec.clone());
                    if rec.will_init {
                        // This WAL record initializes the page, so no need to go further back
-                        cont_lsn = None;
+                        need_image = false;
                        break;
-                    } else {
-                        // This WAL record needs to be applied against an older page image
-                        cont_lsn = Some(*entry_lsn);
                    }
                } else {
                    // No base image, and no WAL record. Huh?
@@ -169,19 +191,17 @@ impl Layer for InMemoryLayer {
                }
            }

+            predecessor = inner.predecessor.clone();
            // release lock on 'inner'
        }

        // If an older page image is needed to reconstruct the page, let the
        // caller know about the predecessor layer.
-        if let Some(cont_lsn) = cont_lsn {
-            if let Some(cont_layer) = &self.predecessor {
-                Ok(PageReconstructResult::Continue(
-                    cont_lsn,
-                    Arc::clone(cont_layer),
-                ))
+        if need_image {
+            if let Some(cont_layer) = predecessor {
+                Ok(PageReconstructResult::Continue(self.start_lsn, cont_layer))
            } else {
-                Ok(PageReconstructResult::Missing(cont_lsn))
+                Ok(PageReconstructResult::Missing(self.start_lsn))
            }
        } else {
            Ok(PageReconstructResult::Complete)
@@ -200,6 +220,11 @@ impl Layer for InMemoryLayer {
    fn get_seg_exists(&self, lsn: Lsn) -> Result<bool> {
        let inner = self.inner.lock().unwrap();

+        // If the segment created after requested LSN,
+        // it doesn't exist in the layer. But we shouldn't
+        // have requested it in the first place.
+        assert!(lsn >= self.start_lsn);
+
        // Is the requested LSN after the segment was dropped?
        if let Some(drop_lsn) = inner.drop_lsn {
            if lsn >= drop_lsn {
@@ -225,7 +250,8 @@ impl Layer for InMemoryLayer {
    }

    fn is_incremental(&self) -> bool {
-        self.predecessor.is_some()
+        let inner = self.inner.lock().unwrap();
+        inner.predecessor.is_some()
    }

    /// debugging function to print out the contents of the layer
@@ -239,22 +265,48 @@ impl Layer for InMemoryLayer {
            .unwrap_or_default();

        println!(
-            "----- in-memory layer for {} {}-{} ----",
-            self.seg, self.start_lsn, end_str
+            "----- in-memory layer for tli {} seg {} {}-{} ----",
+            self.timelineid, self.seg, self.start_lsn, end_str
        );

        for (k, v) in inner.segsizes.iter() {
-            println!("{}: {}", k, v);
+            println!("segsizes {}: {}", k, v);
+        }
+
+        for (k, v) in inner.page_versions.iter() {
+            println!(
+                "blk {} at {}: {}/{}\n",
+                k.0,
+                k.1,
+                v.page_image.is_some(),
+                v.record.is_some()
+            );
        }
-        //for (k, v) in inner.page_versions.iter() {
-        //    println!("blk {} at {}: {}/{}", k.0, k.1, v.page_image.is_some(), v.record.is_some());
-        //}

        Ok(())
    }
 }

+/// Write failed because the layer is in process of being replaced.
+/// See [`LayeredTimeline::perform_write_op`] for how to handle this error.
+#[derive(Debug)]
+pub struct NonWriteableError;
+
+pub type WriteResult<T> = std::result::Result<T, NonWriteableError>;
+
+/// Helper struct to cleanup `InMemoryLayer::freeze` return signature.
+pub struct FreezeLayers {
+    /// Replacement layer for the layer which freeze was called on.
+    pub frozen: Arc<InMemoryLayer>,
+    /// New open layer containing leftover data.
+    pub open: Option<Arc<InMemoryLayer>>,
+}
+
 impl InMemoryLayer {
+    fn assert_not_frozen(&self) {
+        assert!(self.end_lsn.is_none());
+    }
+
    /// Return the oldest page version that's stored in this layer
    pub fn get_oldest_pending_lsn(&self) -> Lsn {
        self.oldest_pending_lsn
@@ -284,20 +336,22 @@ impl InMemoryLayer {
            tenantid,
            seg,
            start_lsn,
+            end_lsn: None,
            oldest_pending_lsn,
            inner: Mutex::new(InMemoryLayerInner {
                drop_lsn: None,
                page_versions: BTreeMap::new(),
                segsizes: BTreeMap::new(),
+                writeable: true,
+                predecessor: None,
            }),
-            predecessor: None,
        })
    }

    // Write operations

    /// Remember new page version, as a WAL record over previous version
-    pub fn put_wal_record(&self, blknum: u32, rec: WALRecord) -> Result<()> {
+    pub fn put_wal_record(&self, blknum: u32, rec: WALRecord) -> WriteResult<u32> {
        self.put_page_version(
            blknum,
            rec.lsn,
@@ -309,7 +363,7 @@ impl InMemoryLayer {
    }

    /// Remember new page version, as a full page image
-    pub fn put_page_image(&self, blknum: u32, lsn: Lsn, img: Bytes) -> Result<()> {
+    pub fn put_page_image(&self, blknum: u32, lsn: Lsn, img: Bytes) -> WriteResult<u32> {
        self.put_page_version(
            blknum,
            lsn,
@@ -322,7 +376,8 @@ impl InMemoryLayer {

    /// Common subroutine of the public put_wal_record() and put_page_image() functions.
    /// Adds the page version to the in-memory tree
-    pub fn put_page_version(&self, blknum: u32, lsn: Lsn, pv: PageVersion) -> Result<()> {
+    pub fn put_page_version(&self, blknum: u32, lsn: Lsn, pv: PageVersion) -> WriteResult<u32> {
+        self.assert_not_frozen();
        assert!(self.seg.blknum_in_seg(blknum));

        trace!(
@@ -334,6 +389,8 @@ impl InMemoryLayer {
        );
        let mut inner = self.inner.lock().unwrap();

+        inner.check_writeable()?;
+
        let old = inner.page_versions.insert((blknum, lsn), pv);

        if old.is_some() {
@@ -359,16 +416,55 @@ impl InMemoryLayer {
                    newsize,
                    lsn
                );
+
+                // If we are extending the relation by more than one page, initialize the "gap"
+                // with zeros
+                //
+                // XXX: What if the caller initializes the gap with subsequent call with same LSN?
+                // I don't think that can happen currently, but that is highly dependent on how
+                // PostgreSQL writes its WAL records and there's no guarantee of it. If it does
+                // happen, we would hit the "page version already exists" warning above on the
+                // subsequent call to initialize the gap page.
+                let gapstart = self.seg.segno * RELISH_SEG_SIZE + oldsize;
+                for gapblknum in gapstart..blknum {
+                    let zeropv = PageVersion {
+                        page_image: Some(ZERO_PAGE.clone()),
+                        record: None,
+                    };
+                    trace!(
+                        "filling gap blk {} with zeros for write of {}",
+                        gapblknum,
+                        blknum
+                    );
+                    let old = inner.page_versions.insert((gapblknum, lsn), zeropv);
+                    // We already had an entry for this LSN. That's odd..
+
+                    if old.is_some() {
+                        warn!(
+                            "Page version of rel {} blk {} at {} already exists",
+                            self.seg.rel, blknum, lsn
+                        );
+                    }
+                }
+
                inner.segsizes.insert(lsn, newsize);
+                return Ok(newsize - oldsize);
            }
        }
-
-        Ok(())
+        Ok(0)
    }

    /// Remember that the relation was truncated at given LSN
-    pub fn put_truncation(&self, lsn: Lsn, segsize: u32) -> anyhow::Result<()> {
+    pub fn put_truncation(&self, lsn: Lsn, segsize: u32) -> WriteResult<()> {
+        self.assert_not_frozen();
+
        let mut inner = self.inner.lock().unwrap();
+        inner.check_writeable()?;
+
+        // check that this we truncate to a smaller size than segment was before the truncation
+        let oldsize = inner.get_seg_size(lsn);
+        assert!(segsize < oldsize);
+
        let old = inner.segsizes.insert(lsn, segsize);

        if old.is_some() {
@@ -380,9 +476,13 @@ impl InMemoryLayer {
    }

    /// Remember that the segment was dropped at given LSN
-    pub fn put_unlink(&self, lsn: Lsn) -> anyhow::Result<()> {
+    pub fn drop_segment(&self, lsn: Lsn) -> WriteResult<()> {
+        self.assert_not_frozen();
+
        let mut inner = self.inner.lock().unwrap();

+        inner.check_writeable()?;
+
        assert!(inner.drop_lsn.is_none());
        inner.drop_lsn = Some(lsn);

@@ -425,42 +525,33 @@ impl InMemoryLayer {
            tenantid,
            seg,
            start_lsn,
+            end_lsn: None,
            oldest_pending_lsn,
            inner: Mutex::new(InMemoryLayerInner {
                drop_lsn: None,
                page_versions: BTreeMap::new(),
-                segsizes: segsizes,
+                segsizes,
+                writeable: true,
+                predecessor: Some(src),
            }),
-            predecessor: Some(src),
        })
    }

-    ///
-    /// Write the this in-memory layer to disk, as a snapshot layer.
-    ///
-    /// The cutoff point for the layer that's written to disk is 'end_lsn'.
-    ///
-    /// Returns new layers that replace this one. Always returns a new image
-    /// layer containing the page versions at the cutoff LSN, that were written
-    /// to disk, and usually also a DeltaLayer that includes all the WAL records
-    /// between start LSN and the cutoff. (The delta layer is not needed when
-    /// a new relish is created with a single LSN, so that the start and end LSN
-    /// are the same.) If there were page versions newer than 'end_lsn', also
-    /// returns a new in-memory layer containing those page versions. The caller
-    /// replaces this layer with the returned layers in the layer map.
-    ///
-    pub fn freeze(
-        &self,
-        cutoff_lsn: Lsn,
-        // This is needed just to call materialize_page()
-        timeline: &LayeredTimeline,
-    ) -> Result<(Vec<Arc<dyn Layer>>, Option<Arc<InMemoryLayer>>)> {
+    /// Splits `self` into two InMemoryLayers: `frozen` and `open`.
+    /// All data up to and including `cutoff_lsn` (or the drop LSN, if dropped)
+    /// is copied to `frozen`, while the remaining data is copied to `open`.
+    /// After completion, self is non-writeable, but not frozen.
+    pub fn freeze(&self, cutoff_lsn: Lsn) -> Result<FreezeLayers> {
        info!(
            "freezing in memory layer for {} on timeline {} at {}",
            self.seg, self.timelineid, cutoff_lsn
        );

-        let inner = self.inner.lock().unwrap();
+        self.assert_not_frozen();
+
+        let mut inner = self.inner.lock().unwrap();
+        assert!(inner.writeable);
+        inner.writeable = false;

        // Normally, use the cutoff LSN as the end of the frozen layer.
        // But if the relation was dropped, we know that there are no
@@ -494,10 +585,7 @@ impl InMemoryLayer {
            before_page_versions = BTreeMap::new();
            after_page_versions = BTreeMap::new();
            for ((blknum, lsn), pv) in inner.page_versions.iter() {
-                if *lsn == end_lsn {
-                    // Page versions at the cutoff LSN will be stored in the
-                    // materialized image layer.
-                } else if *lsn > end_lsn {
+                if *lsn > end_lsn {
                    after_page_versions.insert((*blknum, *lsn), pv.clone());
                } else {
                    before_page_versions.insert((*blknum, *lsn), pv.clone());
@@ -510,7 +598,83 @@ impl InMemoryLayer {
            after_page_versions = BTreeMap::new();
        }

-        // we can release the lock now.
+        let frozen = Arc::new(InMemoryLayer {
+            conf: self.conf,
+            tenantid: self.tenantid,
+            timelineid: self.timelineid,
+            seg: self.seg,
+            start_lsn: self.start_lsn,
+            end_lsn: Some(end_lsn),
+            oldest_pending_lsn: self.start_lsn,
+            inner: Mutex::new(InMemoryLayerInner {
+                drop_lsn: inner.drop_lsn,
+                page_versions: before_page_versions,
+                segsizes: before_segsizes,
+                writeable: false,
+                predecessor: inner.predecessor.clone(),
+            }),
+        });
+
+        let open = if !dropped && (!after_segsizes.is_empty() || !after_page_versions.is_empty()) {
+            let mut new_open = Self::create_successor_layer(
+                self.conf,
+                frozen.clone(),
+                self.timelineid,
+                self.tenantid,
+                end_lsn,
+                end_lsn,
+            )?;
+
+            let new_inner = new_open.inner.get_mut().unwrap();
+            new_inner.page_versions.append(&mut after_page_versions);
+            new_inner.segsizes.append(&mut after_segsizes);
+
+            Some(Arc::new(new_open))
+        } else {
+            None
+        };
+
+        // TODO could we avoid creating the `frozen` if it contains no data
+        Ok(FreezeLayers { frozen, open })
+    }
+
+    /// Write the this frozen in-memory layer to disk.
+    ///
+    /// Returns new layers that replace this one.
+    /// If not dropped, returns a new image layer containing the page versions
+    /// at the `end_lsn`. Can also return a DeltaLayer that includes all the
+    /// WAL records between start and end LSN. (The delta layer is not needed
+    /// when a new relish is created with a single LSN, so that the start and
+    /// end LSN are the same.)
+    pub fn write_to_disk(&self, timeline: &LayeredTimeline) -> Result<Vec<Arc<dyn Layer>>> {
+        let end_lsn = self.end_lsn.expect("can only write frozen layers to disk");
+
+        let inner = self.inner.lock().unwrap();
+
+        let drop_lsn = inner.drop_lsn;
+        let predecessor = inner.predecessor.clone();
+
+        let mut before_page_versions;
+        let mut before_segsizes;
+        if inner.drop_lsn.is_none() {
+            before_segsizes = BTreeMap::new();
+            for (lsn, size) in inner.segsizes.iter() {
+                if *lsn <= end_lsn {
+                    before_segsizes.insert(*lsn, *size);
+                }
+            }
+
+            before_page_versions = BTreeMap::new();
+            for ((blknum, lsn), pv) in inner.page_versions.iter() {
+                if *lsn < end_lsn {
+                    before_page_versions.insert((*blknum, *lsn), pv.clone());
+                }
+            }
+        } else {
+            before_page_versions = inner.page_versions.clone();
+            before_segsizes = inner.segsizes.clone();
+        }
+
        drop(inner);

        let mut frozen_layers: Vec<Arc<dyn Layer>> = Vec::new();
@@ -524,13 +688,12 @@ impl InMemoryLayer {
                self.seg,
                self.start_lsn,
                end_lsn,
-                dropped,
-                self.predecessor.clone(),
+                drop_lsn.is_some(),
+                predecessor,
                before_page_versions,
                before_segsizes,
            )?;
-            let delta_layer_rc: Arc<dyn Layer> = Arc::new(delta_layer);
-            frozen_layers.push(delta_layer_rc);
+            frozen_layers.push(Arc::new(delta_layer));
            trace!(
                "freeze: created delta layer {} {}-{}",
                self.seg,
@@ -541,61 +704,18 @@ impl InMemoryLayer {
            assert!(before_page_versions.is_empty());
        }

-        let mut new_open_rc = None;
-        if !dropped {
+        if drop_lsn.is_none() {
            // Write a new base image layer at the cutoff point
-            let imgfile = ImageLayer::create_from_src(self.conf, timeline, self, end_lsn)?;
-            let imgfile_rc: Arc<dyn Layer> = Arc::new(imgfile);
-            frozen_layers.push(Arc::clone(&imgfile_rc));
+            let image_layer = ImageLayer::create_from_src(self.conf, timeline, self, end_lsn)?;
+            frozen_layers.push(Arc::new(image_layer));
            trace!("freeze: created image layer {} at {}", self.seg, end_lsn);
-
-            // If there were any page versions newer than the cutoff, initialize a new in-memory
-            // layer to hold them
-            if !after_segsizes.is_empty() || !after_page_versions.is_empty() {
-                let new_open = Self::create_successor_layer(
-                    self.conf,
-                    imgfile_rc,
-                    self.timelineid,
-                    self.tenantid,
-                    end_lsn,
-                    end_lsn,
-                )?;
-                let mut new_inner = new_open.inner.lock().unwrap();
-                new_inner.page_versions.append(&mut after_page_versions);
-                new_inner.segsizes.append(&mut after_segsizes);
-                drop(new_inner);
-                trace!("freeze: created new in-mem layer {} {}-", self.seg, end_lsn);
-
-                new_open_rc = Some(Arc::new(new_open))
-            }
        }

-        Ok((frozen_layers, new_open_rc))
+        Ok(frozen_layers)
    }

-    /// debugging function to print out the contents of the layer
-    #[allow(unused)]
-    pub fn dump(&self) -> String {
-        let mut result = format!(
-            "----- inmemory layer for {} {}-> ----\n",
-            self.seg, self.start_lsn
-        );
-
-        let inner = self.inner.lock().unwrap();
-
-        for (k, v) in inner.segsizes.iter() {
-            result += &format!("{}: {}\n", k, v);
-        }
-        for (k, v) in inner.page_versions.iter() {
-            result += &format!(
-                "blk {} at {}: {}/{}\n",
-                k.0,
-                k.1,
-                v.page_image.is_some(),
-                v.record.is_some()
-            );
-        }
-
-        result
+    pub fn update_predecessor(&self, predecessor: Arc<dyn Layer>) -> Option<Arc<dyn Layer>> {
+        let mut inner = self.inner.lock().unwrap();
+        inner.predecessor.replace(predecessor)
    }
 }
--- a/pageserver/src/layered_repository/layer_map.rs
+++ b/pageserver/src/layered_repository/layer_map.rs
@@ -1,5 +1,5 @@
 //!
-//! The layer map tracks what layers exist for all the relations in a timeline.
+//! The layer map tracks what layers exist for all the relishes in a timeline.
 //!
 //! When the timeline is first accessed, the server lists of all layer files
 //! in the timelines/<timelineid> directory, and populates this map with
@@ -14,11 +14,8 @@ use crate::layered_repository::InMemoryLayer;
 use crate::relish::*;
 use anyhow::Result;
 use lazy_static::lazy_static;
-use log::*;
 use std::cmp::Ordering;
-use std::collections::HashSet;
 use std::collections::{BTreeMap, BinaryHeap, HashMap};
-use std::ops::Bound::Included;
 use std::sync::Arc;
 use zenith_metrics::{register_int_gauge, IntGauge};
 use zenith_utils::lsn::Lsn;
@@ -35,68 +32,21 @@ lazy_static! {
 ///
 /// LayerMap tracks what layers exist on a timeline.
 ///
+#[derive(Default)]
 pub struct LayerMap {
    /// All the layers keyed by segment tag
    segs: HashMap<SegmentTag, SegEntry>,

-    /// All in-memory layers, ordered by 'oldest_pending_lsn' of each layer.
-    /// This allows easy access to the in-memory layer that contains the
-    /// oldest WAL record.
-    open_segs: BinaryHeap<OpenSegEntry>,
+    /// All in-memory layers, ordered by 'oldest_pending_lsn' and generation
+    /// of each layer. This allows easy access to the in-memory layer that
+    /// contains the oldest WAL record.
+    open_layers: BinaryHeap<OpenLayerEntry>,

    /// Generation number, used to distinguish newly inserted entries in the
    /// binary heap from older entries during checkpoint.
    current_generation: u64,
 }

-///
-/// Per-segment entry in the LayerMap.segs hash map
-///
-/// The last layer that is open for writes is always an InMemoryLayer,
-/// and is kept in a separate field, because there can be only one for
-/// each segment. The older layers, stored on disk, are kept in a
-/// BTreeMap keyed by the layer's start LSN.
-struct SegEntry {
-    pub open: Option<Arc<InMemoryLayer>>,
-    pub historic: BTreeMap<Lsn, Arc<dyn Layer>>,
-}
-
-/// Entry held LayerMap.open_segs, with boilerplate comparison
-/// routines to implement a min-heap ordered by 'oldest_pending_lsn'
-///
-/// Each entry also carries a generation number. It can be used to distinguish
-/// entries with the same 'oldest_pending_lsn'.
-struct OpenSegEntry {
-    pub oldest_pending_lsn: Lsn,
-    pub layer: Arc<InMemoryLayer>,
-    pub generation: u64,
-}
-impl Ord for OpenSegEntry {
-    fn cmp(&self, other: &Self) -> Ordering {
-        // BinaryHeap is a max-heap, and we want a min-heap. Reverse the ordering here
-        // to get that.
-        other.oldest_pending_lsn.cmp(&self.oldest_pending_lsn)
-    }
-}
-impl PartialOrd for OpenSegEntry {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        // BinaryHeap is a max-heap, and we want a min-heap. Reverse the ordering here
-        // to get that. Entries with identical oldest_pending_lsn are ordered by generation
-        Some(
-            other
-                .oldest_pending_lsn
-                .cmp(&self.oldest_pending_lsn)
-                .then_with(|| other.generation.cmp(&self.generation)),
-        )
-    }
-}
-impl PartialEq for OpenSegEntry {
-    fn eq(&self, other: &Self) -> bool {
-        self.oldest_pending_lsn.eq(&other.oldest_pending_lsn)
-    }
-}
-impl Eq for OpenSegEntry {}
-
 impl LayerMap {
    ///
    /// Look up a layer using the given segment tag and LSN. This differs from a
@@ -107,23 +57,7 @@ impl LayerMap {
    pub fn get(&self, tag: &SegmentTag, lsn: Lsn) -> Option<Arc<dyn Layer>> {
        let segentry = self.segs.get(tag)?;

-        if let Some(open) = &segentry.open {
-            if open.get_start_lsn() <= lsn {
-                let x: Arc<dyn Layer> = Arc::clone(&open) as _;
-                return Some(x);
-            }
-        }
-
-        if let Some((_k, v)) = segentry
-            .historic
-            .range((Included(Lsn(0)), Included(lsn)))
-            .next_back()
-        {
-            let x: Arc<dyn Layer> = Arc::clone(&v) as _;
-            Some(x)
-        } else {
-            None
-        }
+        segentry.get(lsn)
    }

    ///
@@ -133,49 +67,42 @@ impl LayerMap {
    pub fn get_open(&self, tag: &SegmentTag) -> Option<Arc<InMemoryLayer>> {
        let segentry = self.segs.get(tag)?;

-        if let Some(open) = &segentry.open {
-            Some(Arc::clone(open))
-        } else {
-            None
-        }
+        segentry.open.as_ref().map(Arc::clone)
    }

    ///
    /// Insert an open in-memory layer
    ///
    pub fn insert_open(&mut self, layer: Arc<InMemoryLayer>) {
-        let tag = layer.get_seg_tag();
+        let segentry = self.segs.entry(layer.get_seg_tag()).or_default();

-        if let Some(segentry) = self.segs.get_mut(&tag) {
-            if let Some(_old) = &segentry.open {
-                // FIXME: shouldn't exist, but check
-            }
-            segentry.open = Some(Arc::clone(&layer));
-        } else {
-            let segentry = SegEntry {
-                open: Some(Arc::clone(&layer)),
-                historic: BTreeMap::new(),
-            };
-            self.segs.insert(tag, segentry);
-        }
+        segentry.insert_open(Arc::clone(&layer));

-        let opensegentry = OpenSegEntry {
+        // Also add it to the binary heap
+        let open_layer_entry = OpenLayerEntry {
            oldest_pending_lsn: layer.get_oldest_pending_lsn(),
-            layer: layer,
+            layer,
            generation: self.current_generation,
        };
-        self.open_segs.push(opensegentry);
+        self.open_layers.push(open_layer_entry);

        NUM_INMEMORY_LAYERS.inc();
    }

    /// Remove the oldest in-memory layer
    pub fn pop_oldest_open(&mut self) {
-        let opensegentry = self.open_segs.pop().unwrap();
-        let segtag = opensegentry.layer.get_seg_tag();
+        // Pop it from the binary heap
+        let oldest_entry = self.open_layers.pop().unwrap();
+        let segtag = oldest_entry.layer.get_seg_tag();

+        // Also remove it from the SegEntry of this segment
        let mut segentry = self.segs.get_mut(&segtag).unwrap();
+        assert!(Arc::ptr_eq(
+            segentry.open.as_ref().unwrap(),
+            &oldest_entry.layer
+        ));
        segentry.open = None;
+
        NUM_INMEMORY_LAYERS.dec();
    }

@@ -183,21 +110,9 @@ impl LayerMap {
    /// Insert an on-disk layer
    ///
    pub fn insert_historic(&mut self, layer: Arc<dyn Layer>) {
-        let tag = layer.get_seg_tag();
-        let start_lsn = layer.get_start_lsn();
+        let segentry = self.segs.entry(layer.get_seg_tag()).or_default();
+        segentry.insert_historic(layer);

-        if let Some(segentry) = self.segs.get_mut(&tag) {
-            segentry.historic.insert(start_lsn, layer);
-        } else {
-            let mut historic = BTreeMap::new();
-            historic.insert(start_lsn, layer);
-
-            let segentry = SegEntry {
-                open: None,
-                historic,
-            };
-            self.segs.insert(tag, segentry);
-        }
        NUM_ONDISK_LAYERS.inc();
    }

@@ -216,52 +131,31 @@ impl LayerMap {
        NUM_ONDISK_LAYERS.dec();
    }

-    // List relations that exist at the lsn
-    pub fn list_rels(&self, spcnode: u32, dbnode: u32, lsn: Lsn) -> Result<HashSet<RelTag>> {
-        let mut rels: HashSet<RelTag> = HashSet::new();
+    // List relations along with a flag that marks if they exist at the given lsn.
+    // spcnode 0 and dbnode 0 have special meanings and mean all tabespaces/databases.
+    // Pass Tag if we're only interested in some relations.
+    pub fn list_relishes(&self, tag: Option<RelTag>, lsn: Lsn) -> Result<HashMap<RelishTag, bool>> {
+        let mut rels: HashMap<RelishTag, bool> = HashMap::new();

        for (seg, segentry) in self.segs.iter() {
-            if let RelishTag::Relation(reltag) = seg.rel {
-                if (spcnode == 0 || reltag.spcnode == spcnode)
-                    && (dbnode == 0 || reltag.dbnode == dbnode)
-                {
-                    // Add only if it exists at the requested LSN.
-                    if let Some(open) = &segentry.open {
-                        if open.get_end_lsn() > lsn {
-                            rels.insert(reltag);
+            match seg.rel {
+                RelishTag::Relation(reltag) => {
+                    if let Some(request_rel) = tag {
+                        if (request_rel.spcnode == 0 || reltag.spcnode == request_rel.spcnode)
+                            && (request_rel.dbnode == 0 || reltag.dbnode == request_rel.dbnode)
+                        {
+                            if let Some(exists) = segentry.exists_at_lsn(lsn) {
+                                rels.insert(seg.rel, exists);
+                            }
                        }
-                    } else if let Some((_k, _v)) = segentry
-                        .historic
-                        .range((Included(Lsn(0)), Included(lsn)))
-                        .next_back()
-                    {
-                        rels.insert(reltag);
                    }
                }
-            }
-        }
-        Ok(rels)
-    }
-
-    // List non-relation relishes that exist at the lsn
-    pub fn list_nonrels(&self, lsn: Lsn) -> Result<HashSet<RelishTag>> {
-        let mut rels: HashSet<RelishTag> = HashSet::new();
-
-        // Scan the timeline directory to get all rels in this timeline.
-        for (seg, segentry) in self.segs.iter() {
-            if let RelishTag::Relation(_) = seg.rel {
-            } else {
-                // Add only if it exists at the requested LSN.
-                if let Some(open) = &segentry.open {
-                    if open.get_end_lsn() > lsn {
-                        rels.insert(seg.rel);
+                _ => {
+                    if tag == None {
+                        if let Some(exists) = segentry.exists_at_lsn(lsn) {
+                            rels.insert(seg.rel, exists);
+                        }
                    }
-                } else if let Some((_k, _v)) = segentry
-                    .historic
-                    .range((Included(Lsn(0)), Included(lsn)))
-                    .next_back()
-                {
-                    rels.insert(seg.rel);
                }
            }
        }
@@ -271,44 +165,20 @@ impl LayerMap {
    /// Is there a newer image layer for given segment?
    ///
    /// This is used for garbage collection, to determine if an old layer can
-    /// be deleted. We ignore in-memory layers because they are not durable
-    /// on disk, and delta layers because they depend on an older layer.
+    /// be deleted.
    pub fn newer_image_layer_exists(&self, seg: SegmentTag, lsn: Lsn) -> bool {
        if let Some(segentry) = self.segs.get(&seg) {
-            for (newer_lsn, layer) in segentry
-                .historic
-                .range((Included(lsn), Included(Lsn(u64::MAX))))
-            {
-                // Ignore delta layers.
-                if layer.is_incremental() {
-                    continue;
-                }
-                if layer.get_end_lsn() > lsn {
-                    trace!(
-                        "found later layer for {}, {} {}-{}",
-                        seg,
-                        lsn,
-                        newer_lsn,
-                        layer.get_end_lsn()
-                    );
-                    return true;
-                } else {
-                    trace!("found singleton layer for {}, {} {}", seg, lsn, newer_lsn);
-                    continue;
-                }
-            }
+            segentry.newer_image_layer_exists(lsn)
+        } else {
+            false
        }
-        trace!("no later layer found for {}, {}", seg, lsn);
-        false
    }

    /// Return the oldest in-memory layer, along with its generation number.
    pub fn peek_oldest_open(&self) -> Option<(Arc<InMemoryLayer>, u64)> {
-        if let Some(opensegentry) = self.open_segs.peek() {
-            Some((Arc::clone(&opensegentry.layer), opensegentry.generation))
-        } else {
-            None
-        }
+        self.open_layers
+            .peek()
+            .map(|oldest_entry| (Arc::clone(&oldest_entry.layer), oldest_entry.generation))
    }

    /// Increment the generation number used to stamp open in-memory layers. Layers
@@ -325,18 +195,134 @@ impl LayerMap {
            iter: None,
        }
    }
-}

-impl Default for LayerMap {
-    fn default() -> Self {
-        LayerMap {
-            segs: HashMap::new(),
-            open_segs: BinaryHeap::new(),
-            current_generation: 0,
+    /// debugging function to print out the contents of the layer map
+    #[allow(unused)]
+    pub fn dump(&self) -> Result<()> {
+        println!("Begin dump LayerMap");
+        for (seg, segentry) in self.segs.iter() {
+            if let Some(open) = &segentry.open {
+                open.dump()?;
+            }
+
+            for (_, layer) in segentry.historic.iter() {
+                layer.dump()?;
+            }
        }
+        println!("End dump LayerMap");
+        Ok(())
    }
 }

+///
+/// Per-segment entry in the LayerMap::segs hash map. Holds all the layers
+/// associated with the segment.
+///
+/// The last layer that is open for writes is always an InMemoryLayer,
+/// and is kept in a separate field, because there can be only one for
+/// each segment. The older layers, stored on disk, are kept in a
+/// BTreeMap keyed by the layer's start LSN.
+#[derive(Default)]
+struct SegEntry {
+    pub open: Option<Arc<InMemoryLayer>>,
+    pub historic: BTreeMap<Lsn, Arc<dyn Layer>>,
+}
+
+impl SegEntry {
+    /// Does the segment exist at given LSN?
+    /// Return None if object is not found in this SegEntry.
+    fn exists_at_lsn(&self, lsn: Lsn) -> Option<bool> {
+        if let Some(layer) = &self.open {
+            if layer.get_start_lsn() <= lsn && lsn <= layer.get_end_lsn() {
+                let exists = layer.get_seg_exists(lsn).ok()?;
+                return Some(exists);
+            }
+        } else if let Some((_, layer)) = self.historic.range(..=lsn).next_back() {
+            let exists = layer.get_seg_exists(lsn).ok()?;
+            return Some(exists);
+        }
+        None
+    }
+
+    pub fn get(&self, lsn: Lsn) -> Option<Arc<dyn Layer>> {
+        if let Some(open) = &self.open {
+            if open.get_start_lsn() <= lsn {
+                let x: Arc<dyn Layer> = Arc::clone(open) as _;
+                return Some(x);
+            }
+        }
+
+        if let Some((_start_lsn, layer)) = self.historic.range(..=lsn).next_back() {
+            Some(Arc::clone(layer))
+        } else {
+            None
+        }
+    }
+
+    pub fn newer_image_layer_exists(&self, lsn: Lsn) -> bool {
+        // We only check on-disk layers, because
+        // in-memory layers are not durable
+
+        for (_newer_lsn, layer) in self.historic.range(lsn..) {
+            // Ignore incremental layers.
+            if layer.is_incremental() {
+                continue;
+            }
+            if layer.get_end_lsn() > lsn {
+                return true;
+            } else {
+                continue;
+            }
+        }
+        false
+    }
+
+    pub fn insert_open(&mut self, layer: Arc<InMemoryLayer>) {
+        assert!(self.open.is_none());
+        self.open = Some(layer);
+    }
+
+    pub fn insert_historic(&mut self, layer: Arc<dyn Layer>) {
+        let start_lsn = layer.get_start_lsn();
+
+        self.historic.insert(start_lsn, layer);
+    }
+}
+
+/// Entry held in LayerMap::open_layers, with boilerplate comparison routines
+/// to implement a min-heap ordered by 'oldest_pending_lsn' and 'generation'
+///
+/// The generation number associated with each entry can be used to distinguish
+/// recently-added entries (i.e after last call to increment_generation()) from older
+/// entries with the same 'oldest_pending_lsn'.
+struct OpenLayerEntry {
+    pub oldest_pending_lsn: Lsn, // copy of layer.get_oldest_pending_lsn()
+    pub generation: u64,
+    pub layer: Arc<InMemoryLayer>,
+}
+impl Ord for OpenLayerEntry {
+    fn cmp(&self, other: &Self) -> Ordering {
+        // BinaryHeap is a max-heap, and we want a min-heap. Reverse the ordering here
+        // to get that. Entries with identical oldest_pending_lsn are ordered by generation
+        other
+            .oldest_pending_lsn
+            .cmp(&self.oldest_pending_lsn)
+            .then_with(|| other.generation.cmp(&self.generation))
+    }
+}
+impl PartialOrd for OpenLayerEntry {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+impl PartialEq for OpenLayerEntry {
+    fn eq(&self, other: &Self) -> bool {
+        self.cmp(other) == Ordering::Equal
+    }
+}
+impl Eq for OpenLayerEntry {}
+
+/// Iterator returned by LayerMap::iter_historic_layers()
 pub struct HistoricLayerIter<'a> {
    segiter: std::collections::hash_map::Iter<'a, SegmentTag, SegEntry>,
    iter: Option<std::collections::btree_map::Iter<'a, Lsn, Arc<dyn Layer>>>,
@@ -361,3 +347,78 @@ impl<'a> Iterator for HistoricLayerIter<'a> {
        }
    }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::PageServerConf;
+    use std::str::FromStr;
+    use zenith_utils::zid::{ZTenantId, ZTimelineId};
+
+    /// Arbitrary relation tag, for testing.
+    const TESTREL_A: RelishTag = RelishTag::Relation(RelTag {
+        spcnode: 0,
+        dbnode: 111,
+        relnode: 1000,
+        forknum: 0,
+    });
+
+    /// Construct a dummy InMemoryLayer for testing
+    fn dummy_inmem_layer(
+        conf: &'static PageServerConf,
+        segno: u32,
+        start_lsn: Lsn,
+        oldest_pending_lsn: Lsn,
+    ) -> Arc<InMemoryLayer> {
+        Arc::new(
+            InMemoryLayer::create(
+                conf,
+                ZTimelineId::from_str("00000000000000000000000000000000").unwrap(),
+                ZTenantId::from_str("00000000000000000000000000000000").unwrap(),
+                SegmentTag {
+                    rel: TESTREL_A,
+                    segno,
+                },
+                start_lsn,
+                oldest_pending_lsn,
+            )
+            .unwrap(),
+        )
+    }
+
+    #[test]
+    fn test_open_layers() -> Result<()> {
+        let conf = PageServerConf::dummy_conf(PageServerConf::test_repo_dir("dummy_inmem_layer"));
+        let conf = Box::leak(Box::new(conf));
+
+        let mut layers = LayerMap::default();
+
+        let gen1 = layers.increment_generation();
+        layers.insert_open(dummy_inmem_layer(conf, 0, Lsn(100), Lsn(100)));
+        layers.insert_open(dummy_inmem_layer(conf, 1, Lsn(100), Lsn(200)));
+        layers.insert_open(dummy_inmem_layer(conf, 2, Lsn(100), Lsn(120)));
+        layers.insert_open(dummy_inmem_layer(conf, 3, Lsn(100), Lsn(110)));
+
+        let gen2 = layers.increment_generation();
+        layers.insert_open(dummy_inmem_layer(conf, 4, Lsn(100), Lsn(110)));
+        layers.insert_open(dummy_inmem_layer(conf, 5, Lsn(100), Lsn(100)));
+
+        // A helper function (closure) to pop the next oldest open entry from the layer map,
+        // and assert that it is what we'd expect
+        let mut assert_pop_layer = |expected_segno: u32, expected_generation: u64| {
+            let (l, generation) = layers.peek_oldest_open().unwrap();
+            assert!(l.get_seg_tag().segno == expected_segno);
+            assert!(generation == expected_generation);
+            layers.pop_oldest_open();
+        };
+
+        assert_pop_layer(0, gen1); // 100
+        assert_pop_layer(5, gen2); // 100
+        assert_pop_layer(3, gen1); // 110
+        assert_pop_layer(4, gen2); // 110
+        assert_pop_layer(2, gen1); // 120
+        assert_pop_layer(1, gen1); // 200
+
+        Ok(())
+    }
+}
--- a/pageserver/src/layered_repository/storage_layer.rs
+++ b/pageserver/src/layered_repository/storage_layer.rs
@@ -21,7 +21,7 @@ pub const RELISH_SEG_SIZE: u32 = 10 * 1024 * 1024 / 8192;
 /// Each relish stored in the repository is divided into fixed-sized "segments",
 /// with 10 MB of key-space, or 1280 8k pages each.
 ///
-#[derive(Debug, PartialEq, Eq, PartialOrd, Hash, Ord, Clone, Copy)]
+#[derive(Debug, PartialEq, Eq, PartialOrd, Hash, Ord, Clone, Copy, Serialize, Deserialize)]
 pub struct SegmentTag {
    pub rel: RelishTag,
    pub segno: u32,
@@ -97,26 +97,38 @@ pub enum PageReconstructResult {
 }

 ///
-/// A Layer holds all page versions for one segment of a relish, in a range of LSNs.
-/// There are two kinds of layers, in-memory and snapshot layers. In-memory
+/// A Layer corresponds to one RELISH_SEG_SIZE slice of a relish in a range of LSNs.
+/// There are two kinds of layers, in-memory and on-disk layers. In-memory
 /// layers are used to ingest incoming WAL, and provide fast access
-/// to the recent page versions. Snaphot layers are stored on disk, and
+/// to the recent page versions. On-disk layers are stored as files on disk, and
 /// are immutable. This trait presents the common functionality of
-/// in-memory and snapshot layers.
-///
-/// Each layer contains a full snapshot of the segment at the start
-/// LSN. In addition to that, it contains WAL (or more page images)
-/// needed to recontruct any page version up to the end LSN.
+/// in-memory and on-disk layers.
 ///
 pub trait Layer: Send + Sync {
-    // These functions identify the relish segment and the LSN range
-    // that this Layer holds.
+    /// Identify the timeline this relish belongs to
    fn get_timeline_id(&self) -> ZTimelineId;
+
+    /// Identify the relish segment
    fn get_seg_tag(&self) -> SegmentTag;
+
+    /// Inclusive start bound of the LSN range that this layer hold
    fn get_start_lsn(&self) -> Lsn;
+
+    /// 'end_lsn' meaning depends on the layer kind:
+    /// - in-memory layer is either unbounded (end_lsn = MAX_LSN) or dropped (end_lsn = drop_lsn)
+    /// - image layer represents snapshot at one LSN, so end_lsn = lsn
+    /// - delta layer has end_lsn
+    ///
+    /// TODO Is end_lsn always exclusive for all layer kinds?
    fn get_end_lsn(&self) -> Lsn;
+
+    /// Is the segment represented by this layer dropped by PostgreSQL?
    fn is_dropped(&self) -> bool;

+    /// Gets the physical location of the layer on disk.
+    /// Some layers, such as in-memory, might not have the location.
+    fn path(&self) -> Option<PathBuf>;
+
    /// Filename used to store this layer on disk. (Even in-memory layers
    /// implement this, to print a handy unique identifier for the layer for
    /// log messages, even though they're never not on disk.)
--- a/pageserver/src/lib.rs
+++ b/pageserver/src/lib.rs
@@ -11,9 +11,9 @@ pub mod basebackup;
 pub mod branches;
 pub mod http;
 pub mod layered_repository;
-pub mod logger;
 pub mod page_service;
 pub mod relish;
+mod relish_storage;
 pub mod repository;
 pub mod restore_local_repo;
 pub mod tenant_mgr;
@@ -21,6 +21,26 @@ pub mod waldecoder;
 pub mod walreceiver;
 pub mod walredo;

+pub mod defaults {
+    use std::time::Duration;
+
+    pub const DEFAULT_PG_LISTEN_PORT: u16 = 64000;
+    pub const DEFAULT_PG_LISTEN_ADDR: &str = "127.0.0.1:64000"; // can't format! const yet...
+    pub const DEFAULT_HTTP_LISTEN_PORT: u16 = 9898;
+    pub const DEFAULT_HTTP_LISTEN_ADDR: &str = "127.0.0.1:9898";
+
+    // FIXME: This current value is very low. I would imagine something like 1 GB or 10 GB
+    // would be more appropriate. But a low value forces the code to be exercised more,
+    // which is good for now to trigger bugs.
+    pub const DEFAULT_CHECKPOINT_DISTANCE: u64 = 256 * 1024 * 1024;
+    pub const DEFAULT_CHECKPOINT_PERIOD: Duration = Duration::from_secs(1);
+
+    pub const DEFAULT_GC_HORIZON: u64 = 64 * 1024 * 1024;
+    pub const DEFAULT_GC_PERIOD: Duration = Duration::from_secs(100);
+
+    pub const DEFAULT_SUPERUSER: &str = "zenith_admin";
+}
+
 lazy_static! {
    static ref LIVE_CONNECTIONS_COUNT: IntGaugeVec = register_int_gauge_vec!(
        "pageserver_live_connections_count",
@@ -30,11 +50,19 @@ lazy_static! {
    .expect("failed to define a metric");
 }

+pub const LOG_FILE_NAME: &str = "pageserver.log";
+
 #[derive(Debug, Clone)]
 pub struct PageServerConf {
    pub daemonize: bool,
-    pub listen_addr: String,
-    pub http_endpoint_addr: String,
+    pub listen_pg_addr: String,
+    pub listen_http_addr: String,
+    // Flush out an inmemory layer, if it's holding WAL older than this
+    // This puts a backstop on how much WAL needs to be re-digested if the
+    // page server crashes.
+    pub checkpoint_distance: u64,
+    pub checkpoint_period: Duration,
+
    pub gc_horizon: u64,
    pub gc_period: Duration,
    pub superuser: String,
@@ -52,6 +80,7 @@ pub struct PageServerConf {
    pub auth_type: AuthType,

    pub auth_validation_public_key_path: Option<PathBuf>,
+    pub relish_storage_config: Option<RelishStorageConfig>,
 }

 impl PageServerConf {
@@ -110,4 +139,54 @@ impl PageServerConf {
    pub fn pg_lib_dir(&self) -> PathBuf {
        self.pg_distrib_dir.join("lib")
    }
+
+    #[cfg(test)]
+    fn test_repo_dir(test_name: &str) -> PathBuf {
+        PathBuf::from(format!("../tmp_check/test_{}", test_name))
+    }
+
+    #[cfg(test)]
+    fn dummy_conf(repo_dir: PathBuf) -> Self {
+        PageServerConf {
+            daemonize: false,
+            checkpoint_distance: defaults::DEFAULT_CHECKPOINT_DISTANCE,
+            checkpoint_period: Duration::from_secs(10),
+            gc_horizon: defaults::DEFAULT_GC_HORIZON,
+            gc_period: Duration::from_secs(10),
+            listen_pg_addr: "127.0.0.1:5430".to_string(),
+            listen_http_addr: "127.0.0.1:9898".to_string(),
+            superuser: "zenith_admin".to_string(),
+            workdir: repo_dir,
+            pg_distrib_dir: "".into(),
+            auth_type: AuthType::Trust,
+            auth_validation_public_key_path: None,
+            relish_storage_config: None,
+        }
+    }
+}
+
+/// External relish storage configuration, enough for creating a client for that storage.
+#[derive(Debug, Clone)]
+pub enum RelishStorageConfig {
+    /// Root folder to place all stored relish data into.
+    LocalFs(PathBuf),
+    AwsS3(S3Config),
+}
+
+/// AWS S3 bucket coordinates and access credentials to manage the bucket contents (read and write).
+#[derive(Clone)]
+pub struct S3Config {
+    pub bucket_name: String,
+    pub bucket_region: String,
+    pub access_key_id: Option<String>,
+    pub secret_access_key: Option<String>,
+}
+
+impl std::fmt::Debug for S3Config {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("S3Config")
+            .field("bucket_name", &self.bucket_name)
+            .field("bucket_region", &self.bucket_region)
+            .finish()
+    }
 }
--- a/pageserver/src/logger.rs
+++ b/pageserver/src/logger.rs
@@ -1,45 +0,0 @@
-use crate::PageServerConf;
-
-use anyhow::{Context, Result};
-use slog::{Drain, FnValue};
-use std::fs::{File, OpenOptions};
-
-pub fn init_logging(
-    _conf: &PageServerConf,
-    log_filename: &str,
-) -> Result<(slog_scope::GlobalLoggerGuard, File)> {
-    // Don't open the same file for output multiple times;
-    // the different fds could overwrite each other's output.
-    let log_file = OpenOptions::new()
-        .create(true)
-        .append(true)
-        .open(&log_filename)
-        .with_context(|| format!("failed to open {:?}", &log_filename))?;
-
-    let logger_file = log_file.try_clone().unwrap();
-
-    let decorator = slog_term::PlainSyncDecorator::new(logger_file);
-    let drain = slog_term::FullFormat::new(decorator).build();
-    let drain = slog::Filter::new(drain, |record: &slog::Record| {
-        if record.level().is_at_least(slog::Level::Info) {
-            return true;
-        }
-        false
-    });
-    let drain = std::sync::Mutex::new(drain).fuse();
-    let logger = slog::Logger::root(
-        drain,
-        slog::o!(
-            "location" =>
-                FnValue(move |record| {
-                    format!("{}, {}:{}",
-                            record.module(),
-                            record.file(),
-                            record.line()
-                    )
-                }
-                )
-        ),
-    );
-    Ok((slog_scope::set_global_logger(logger), log_file))
-}
--- a/pageserver/src/page_service.rs
+++ b/pageserver/src/page_service.rs
@@ -10,7 +10,7 @@
 //     *callmemaybe <zenith timelineid> $url* -- ask pageserver to start walreceiver on $url
 //

-use anyhow::{anyhow, bail, ensure, Context, Result};
+use anyhow::{anyhow, bail, ensure, Result};
 use bytes::{Buf, BufMut, Bytes, BytesMut};
 use lazy_static::lazy_static;
 use log::*;
@@ -35,72 +35,110 @@ use zenith_utils::zid::{ZTenantId, ZTimelineId};
 use crate::basebackup;
 use crate::branches;
 use crate::relish::*;
+use crate::repository::Timeline;
 use crate::tenant_mgr;
 use crate::walreceiver;
 use crate::PageServerConf;

 // Wrapped in libpq CopyData
 enum PagestreamFeMessage {
-    Exists(PagestreamRequest),
-    Nblocks(PagestreamRequest),
-    Read(PagestreamRequest),
+    Exists(PagestreamExistsRequest),
+    Nblocks(PagestreamNblocksRequest),
+    GetPage(PagestreamGetPageRequest),
 }

 // Wrapped in libpq CopyData
 enum PagestreamBeMessage {
-    Status(PagestreamStatusResponse),
-    Nblocks(PagestreamStatusResponse),
-    Read(PagestreamReadResponse),
+    Exists(PagestreamExistsResponse),
+    Nblocks(PagestreamNblocksResponse),
+    GetPage(PagestreamGetPageResponse),
+    Error(PagestreamErrorResponse),
 }

 #[derive(Debug)]
-struct PagestreamRequest {
-    spcnode: u32,
-    dbnode: u32,
-    relnode: u32,
-    forknum: u8,
-    blkno: u32,
+struct PagestreamExistsRequest {
+    latest: bool,
    lsn: Lsn,
+    rel: RelTag,
 }

 #[derive(Debug)]
-struct PagestreamStatusResponse {
-    ok: bool,
+struct PagestreamNblocksRequest {
+    latest: bool,
+    lsn: Lsn,
+    rel: RelTag,
+}
+
+#[derive(Debug)]
+struct PagestreamGetPageRequest {
+    latest: bool,
+    lsn: Lsn,
+    rel: RelTag,
+    blkno: u32,
+}
+
+#[derive(Debug)]
+struct PagestreamExistsResponse {
+    exists: bool,
+}
+
+#[derive(Debug)]
+struct PagestreamNblocksResponse {
    n_blocks: u32,
 }

 #[derive(Debug)]
-struct PagestreamReadResponse {
-    ok: bool,
-    n_blocks: u32,
+struct PagestreamGetPageResponse {
    page: Bytes,
 }

+#[derive(Debug)]
+struct PagestreamErrorResponse {
+    message: String,
+}
+
 impl PagestreamFeMessage {
    fn parse(mut body: Bytes) -> anyhow::Result<PagestreamFeMessage> {
        // TODO these gets can fail

-        let smgr_tag = body.get_u8();
-        let zreq = PagestreamRequest {
-            spcnode: body.get_u32(),
-            dbnode: body.get_u32(),
-            relnode: body.get_u32(),
-            forknum: body.get_u8(),
-            blkno: body.get_u32(),
-            lsn: Lsn::from(body.get_u64()),
-        };
-
+        // these correspond to the ZenithMessageTag enum in pagestore_client.h
+        //
        // TODO: consider using protobuf or serde bincode for less error prone
        // serialization.
-        match smgr_tag {
-            0 => Ok(PagestreamFeMessage::Exists(zreq)),
-            1 => Ok(PagestreamFeMessage::Nblocks(zreq)),
-            2 => Ok(PagestreamFeMessage::Read(zreq)),
-            _ => Err(anyhow!(
-                "unknown smgr message tag: {},'{:?}'",
-                smgr_tag,
-                body
-            )),
+        let msg_tag = body.get_u8();
+        match msg_tag {
+            0 => Ok(PagestreamFeMessage::Exists(PagestreamExistsRequest {
+                latest: body.get_u8() != 0,
+                lsn: Lsn::from(body.get_u64()),
+                rel: RelTag {
+                    spcnode: body.get_u32(),
+                    dbnode: body.get_u32(),
+                    relnode: body.get_u32(),
+                    forknum: body.get_u8(),
+                },
+            })),
+            1 => Ok(PagestreamFeMessage::Nblocks(PagestreamNblocksRequest {
+                latest: body.get_u8() != 0,
+                lsn: Lsn::from(body.get_u64()),
+                rel: RelTag {
+                    spcnode: body.get_u32(),
+                    dbnode: body.get_u32(),
+                    relnode: body.get_u32(),
+                    forknum: body.get_u8(),
+                },
+            })),
+            2 => Ok(PagestreamFeMessage::GetPage(PagestreamGetPageRequest {
+                latest: body.get_u8() != 0,
+                lsn: Lsn::from(body.get_u64()),
+                rel: RelTag {
+                    spcnode: body.get_u32(),
+                    dbnode: body.get_u32(),
+                    relnode: body.get_u32(),
+                    forknum: body.get_u8(),
+                },
+                blkno: body.get_u32(),
+            })),
+            _ => bail!("unknown smgr message tag: {},'{:?}'", msg_tag, body),
        }
    }
 }
@@ -110,24 +148,26 @@ impl PagestreamBeMessage {
        let mut bytes = BytesMut::new();

        match self {
-            Self::Status(resp) => {
+            Self::Exists(resp) => {
                bytes.put_u8(100); /* tag from pagestore_client.h */
-                bytes.put_u8(resp.ok as u8);
-                bytes.put_u32(resp.n_blocks);
+                bytes.put_u8(resp.exists as u8);
            }

            Self::Nblocks(resp) => {
                bytes.put_u8(101); /* tag from pagestore_client.h */
-                bytes.put_u8(resp.ok as u8);
                bytes.put_u32(resp.n_blocks);
            }

-            Self::Read(resp) => {
+            Self::GetPage(resp) => {
                bytes.put_u8(102); /* tag from pagestore_client.h */
-                bytes.put_u8(resp.ok as u8);
-                bytes.put_u32(resp.n_blocks);
                bytes.put(&resp.page[..]);
            }
+
+            Self::Error(resp) => {
+                bytes.put_u8(103); /* tag from pagestore_client.h */
+                bytes.put(resp.message.as_bytes());
+                bytes.put_u8(0); // null terminator
+            }
        }

        bytes.into()
@@ -214,14 +254,6 @@ impl PageServerHandler {
        }
    }

-    fn handle_controlfile(&self, pgb: &mut PostgresBackend) -> io::Result<()> {
-        pgb.write_message_noflush(&SINGLE_COL_ROWDESC)?
-            .write_message_noflush(&BeMessage::ControlFile)?
-            .write_message(&BeMessage::CommandComplete(b"SELECT 1"))?;
-
-        Ok(())
-    }
-
    fn handle_pagerequests(
        &self,
        pgb: &mut PostgresBackend,
@@ -229,10 +261,7 @@ impl PageServerHandler {
        tenantid: ZTenantId,
    ) -> anyhow::Result<()> {
        // Check that the timeline exists
-        let repository = tenant_mgr::get_repository_for_tenant(&tenantid)?;
-        let timeline = repository
-            .get_timeline(timelineid)
-            .context(format!("error fetching timeline {}", timelineid))?;
+        let timeline = tenant_mgr::get_timeline_for_tenant(tenantid, timelineid)?;

        /* switch client to COPYBOTH */
        pgb.write_message(&BeMessage::CopyBothResponse)?;
@@ -248,88 +277,134 @@ impl PageServerHandler {
            let zenith_fe_msg = PagestreamFeMessage::parse(copy_data_bytes)?;

            let response = match zenith_fe_msg {
-                PagestreamFeMessage::Exists(req) => {
-                    let rel = RelTag {
-                        spcnode: req.spcnode,
-                        dbnode: req.dbnode,
-                        relnode: req.relnode,
-                        forknum: req.forknum,
-                    };
-                    let tag = RelishTag::Relation(rel);
-
-                    let exist = SMGR_QUERY_TIME
-                        .with_label_values(&["get_rel_exists"])
-                        .observe_closure_duration(|| {
-                            timeline.get_rel_exists(tag, req.lsn).unwrap_or(false)
-                        });
-
-                    PagestreamBeMessage::Status(PagestreamStatusResponse {
-                        ok: exist,
-                        n_blocks: 0,
-                    })
-                }
-                PagestreamFeMessage::Nblocks(req) => {
-                    let rel = RelTag {
-                        spcnode: req.spcnode,
-                        dbnode: req.dbnode,
-                        relnode: req.relnode,
-                        forknum: req.forknum,
-                    };
-                    let tag = RelishTag::Relation(rel);
-
-                    let n_blocks = SMGR_QUERY_TIME
-                        .with_label_values(&["get_rel_size"])
-                        .observe_closure_duration(|| {
-                            // Return 0 if relation is not found.
-                            // This is what postgres smgr expects.
-                            timeline
-                                .get_relish_size(tag, req.lsn)
-                                .unwrap_or(Some(0))
-                                .unwrap_or(0)
-                        });
-
-                    PagestreamBeMessage::Nblocks(PagestreamStatusResponse { ok: true, n_blocks })
-                }
-                PagestreamFeMessage::Read(req) => {
-                    let rel = RelTag {
-                        spcnode: req.spcnode,
-                        dbnode: req.dbnode,
-                        relnode: req.relnode,
-                        forknum: req.forknum,
-                    };
-                    let tag = RelishTag::Relation(rel);
-
-                    let read_response = SMGR_QUERY_TIME
-                        .with_label_values(&["get_page_at_lsn"])
-                        .observe_closure_duration(|| {
-                            match timeline.get_page_at_lsn(tag, req.blkno, req.lsn) {
-                                Ok(p) => PagestreamReadResponse {
-                                    ok: true,
-                                    n_blocks: 0,
-                                    page: p,
-                                },
-                                Err(e) => {
-                                    const ZERO_PAGE: [u8; 8192] = [0; 8192];
-                                    error!("get_page_at_lsn: {}", e);
-                                    PagestreamReadResponse {
-                                        ok: false,
-                                        n_blocks: 0,
-                                        page: Bytes::from_static(&ZERO_PAGE),
-                                    }
-                                }
-                            }
-                        });
-
-                    PagestreamBeMessage::Read(read_response)
-                }
+                PagestreamFeMessage::Exists(req) => SMGR_QUERY_TIME
+                    .with_label_values(&["get_rel_exists"])
+                    .observe_closure_duration(|| {
+                        self.handle_get_rel_exists_request(&*timeline, &req)
+                    }),
+                PagestreamFeMessage::Nblocks(req) => SMGR_QUERY_TIME
+                    .with_label_values(&["get_rel_size"])
+                    .observe_closure_duration(|| self.handle_get_nblocks_request(&*timeline, &req)),
+                PagestreamFeMessage::GetPage(req) => SMGR_QUERY_TIME
+                    .with_label_values(&["get_page_at_lsn"])
+                    .observe_closure_duration(|| {
+                        self.handle_get_page_at_lsn_request(&*timeline, &req)
+                    }),
            };

+            let response = response.unwrap_or_else(|e| {
+                error!("error reading relation or page version: {}", e);
+                PagestreamBeMessage::Error(PagestreamErrorResponse {
+                    message: e.to_string(),
+                })
+            });
+
            pgb.write_message(&BeMessage::CopyData(&response.serialize()))?;
        }

        Ok(())
    }

+    /// Helper function to handle the LSN from client request.
+    ///
+    /// Each GetPage (and Exists and Nblocks) request includes information about
+    /// which version of the page is being requested. The client can request the
+    /// latest version of the page, or the version that's valid at a particular
+    /// LSN. The primary compute node will always request the latest page
+    /// version, while a standby will request a version at the LSN that it's
+    /// currently caught up to.
+    ///
+    /// In either case, if the page server hasn't received the WAL up to the
+    /// requested LSN yet, we will wait for it to arrive. The return value is
+    /// the LSN that should be used to look up the page versions.
+    fn wait_or_get_last_lsn(timeline: &dyn Timeline, lsn: Lsn, latest: bool) -> Result<Lsn> {
+        if latest {
+            // Latest page version was requested. If LSN is given, it is a hint
+            // to the page server that there have been no modifications to the
+            // page after that LSN. If we haven't received WAL up to that point,
+            // wait until it arrives.
+            let last_record_lsn = timeline.get_last_record_lsn();
+
+            // Note: this covers the special case that lsn == Lsn(0). That
+            // special case means "return the latest version whatever it is",
+            // and it's used for bootstrapping purposes, when the page server is
+            // connected directly to the compute node. That is needed because
+            // when you connect to the compute node, to receive the WAL, the
+            // walsender process will do a look up in the pg_authid catalog
+            // table for authentication. That poses a deadlock problem: the
+            // catalog table lookup will send a GetPage request, but the GetPage
+            // request will block in the page server because the recent WAL
+            // hasn't been received yet, and it cannot be received until the
+            // walsender completes the authentication and starts streaming the
+            // WAL.
+            if lsn <= last_record_lsn {
+                Ok(last_record_lsn)
+            } else {
+                timeline.wait_lsn(lsn)?;
+                // Since we waited for 'lsn' to arrive, that is now the last
+                // record LSN. (Or close enough for our purposes; the
+                // last-record LSN can advance immediately after we return
+                // anyway)
+                Ok(lsn)
+            }
+        } else {
+            if lsn == Lsn(0) {
+                bail!("invalid LSN(0) in request");
+            }
+            timeline.wait_lsn(lsn)?;
+            Ok(lsn)
+        }
+    }
+
+    fn handle_get_rel_exists_request(
+        &self,
+        timeline: &dyn Timeline,
+        req: &PagestreamExistsRequest,
+    ) -> Result<PagestreamBeMessage> {
+        let tag = RelishTag::Relation(req.rel);
+        let lsn = Self::wait_or_get_last_lsn(timeline, req.lsn, req.latest)?;
+
+        let exists = timeline.get_rel_exists(tag, lsn)?;
+
+        Ok(PagestreamBeMessage::Exists(PagestreamExistsResponse {
+            exists,
+        }))
+    }
+
+    fn handle_get_nblocks_request(
+        &self,
+        timeline: &dyn Timeline,
+        req: &PagestreamNblocksRequest,
+    ) -> Result<PagestreamBeMessage> {
+        let tag = RelishTag::Relation(req.rel);
+        let lsn = Self::wait_or_get_last_lsn(timeline, req.lsn, req.latest)?;
+
+        let n_blocks = timeline.get_relish_size(tag, lsn)?;
+
+        // Return 0 if relation is not found.
+        // This is what postgres smgr expects.
+        let n_blocks = n_blocks.unwrap_or(0);
+
+        Ok(PagestreamBeMessage::Nblocks(PagestreamNblocksResponse {
+            n_blocks,
+        }))
+    }
+
+    fn handle_get_page_at_lsn_request(
+        &self,
+        timeline: &dyn Timeline,
+        req: &PagestreamGetPageRequest,
+    ) -> Result<PagestreamBeMessage> {
+        let tag = RelishTag::Relation(req.rel);
+        let lsn = Self::wait_or_get_last_lsn(timeline, req.lsn, req.latest)?;
+
+        let page = timeline.get_page_at_lsn(tag, req.blkno, lsn)?;
+
+        Ok(PagestreamBeMessage::GetPage(PagestreamGetPageResponse {
+            page,
+        }))
+    }
+
    fn handle_basebackup_request(
        &self,
        pgb: &mut PostgresBackend,
@@ -338,18 +413,16 @@ impl PageServerHandler {
        tenantid: ZTenantId,
    ) -> anyhow::Result<()> {
        // check that the timeline exists
-        let repository = tenant_mgr::get_repository_for_tenant(&tenantid)?;
-        let timeline = repository
-            .get_timeline(timelineid)
-            .context(format!("error fetching timeline {}", timelineid))?;
+        let timeline = tenant_mgr::get_timeline_for_tenant(tenantid, timelineid)?;
+
        /* switch client to COPYOUT */
        pgb.write_message(&BeMessage::CopyOutResponse)?;
        info!("sent CopyOut");

-        /* Send a tarball of the latest snapshot on the timeline */
+        /* Send a tarball of the latest layer on the timeline */
        {
            let mut writer = CopyDataSink { pgb };
-            let mut basebackup = basebackup::Basebackup::new(&mut writer, &timeline, lsn);
+            let mut basebackup = basebackup::Basebackup::new(&mut writer, &timeline, lsn)?;
            basebackup.send_tarball()?;
        }
        pgb.write_message(&BeMessage::CopyDone)?;
@@ -372,7 +445,7 @@ impl PageServerHandler {
            .claims
            .as_ref()
            .expect("claims presence already checked");
-        Ok(auth::check_permission(claims, tenantid)?)
+        auth::check_permission(claims, tenantid)
    }
 }

@@ -389,7 +462,7 @@ impl postgres_backend::Handler for PageServerHandler {
            .as_ref()
            .as_ref()
            .unwrap()
-            .decode(&str::from_utf8(jwt_response)?)?;
+            .decode(str::from_utf8(jwt_response)?)?;

        if matches!(data.claims.scope, Scope::Tenant) {
            ensure!(
@@ -421,11 +494,9 @@ impl postgres_backend::Handler for PageServerHandler {
        }
        let query_string = std::str::from_utf8(&query_string)?;

-        if query_string.starts_with("controlfile") {
-            self.handle_controlfile(pgb)?;
-        } else if query_string.starts_with("pagestream ") {
+        if query_string.starts_with("pagestream ") {
            let (_, params_raw) = query_string.split_at("pagestream ".len());
-            let params = params_raw.split(" ").collect::<Vec<_>>();
+            let params = params_raw.split(' ').collect::<Vec<_>>();
            ensure!(
                params.len() == 2,
                "invalid param number for pagestream command"
@@ -479,12 +550,9 @@ impl postgres_backend::Handler for PageServerHandler {
            self.check_permission(Some(tenantid))?;

            // Check that the timeline exists
-            let repository = tenant_mgr::get_repository_for_tenant(&tenantid)?;
-            repository
-                .get_timeline(timelineid)
-                .context(format!("error fetching timeline {}", timelineid))?;
+            tenant_mgr::get_timeline_for_tenant(tenantid, timelineid)?;

-            walreceiver::launch_wal_receiver(&self.conf, timelineid, &connstr, tenantid.to_owned());
+            walreceiver::launch_wal_receiver(self.conf, timelineid, &connstr, tenantid.to_owned());

            pgb.write_message_noflush(&BeMessage::CommandComplete(b"SELECT 1"))?;
        } else if query_string.starts_with("branch_create ") {
@@ -492,10 +560,10 @@ impl postgres_backend::Handler for PageServerHandler {

            // branch_create <tenantid> <branchname> <startpoint>
            // TODO lazy static
-            // TOOD: escaping, to allow branch names with spaces
+            // TODO: escaping, to allow branch names with spaces
            let re = Regex::new(r"^branch_create ([[:xdigit:]]+) (\S+) ([^\r\n\s;]+)[\r\n\s;]*;?$")
                .unwrap();
-            let caps = re.captures(&query_string).ok_or_else(err)?;
+            let caps = re.captures(query_string).ok_or_else(err)?;

            let tenantid = ZTenantId::from_str(caps.get(1).unwrap().as_str())?;
            let branchname = caps.get(2).ok_or_else(err)?.as_str().to_owned();
@@ -504,7 +572,7 @@ impl postgres_backend::Handler for PageServerHandler {
            self.check_permission(Some(tenantid))?;

            let branch =
-                branches::create_branch(&self.conf, &branchname, &startpoint_str, &tenantid)?;
+                branches::create_branch(self.conf, &branchname, &startpoint_str, &tenantid)?;
            let branch = serde_json::to_vec(&branch)?;

            pgb.write_message_noflush(&SINGLE_COL_ROWDESC)?
@@ -519,14 +587,14 @@ impl postgres_backend::Handler for PageServerHandler {

            let tenantid = ZTenantId::from_str(caps.get(1).unwrap().as_str())?;

-            let branches = crate::branches::get_branches(&self.conf, &tenantid)?;
+            let branches = crate::branches::get_branches(self.conf, &tenantid)?;
            let branches_buf = serde_json::to_vec(&branches)?;

            pgb.write_message_noflush(&SINGLE_COL_ROWDESC)?
                .write_message_noflush(&BeMessage::DataRow(&[Some(&branches_buf)]))?
                .write_message_noflush(&BeMessage::CommandComplete(b"SELECT 1"))?;
        } else if query_string.starts_with("tenant_list") {
-            let tenants = crate::branches::get_tenants(&self.conf)?;
+            let tenants = crate::branches::get_tenants(self.conf)?;
            let tenants_buf = serde_json::to_vec(&tenants)?;

            pgb.write_message_noflush(&SINGLE_COL_ROWDESC)?
@@ -537,13 +605,13 @@ impl postgres_backend::Handler for PageServerHandler {

            // tenant_create <tenantid>
            let re = Regex::new(r"^tenant_create ([[:xdigit:]]+)$").unwrap();
-            let caps = re.captures(&query_string).ok_or_else(err)?;
+            let caps = re.captures(query_string).ok_or_else(err)?;

            self.check_permission(None)?;

            let tenantid = ZTenantId::from_str(caps.get(1).unwrap().as_str())?;

-            tenant_mgr::create_repository_for_tenant(&self.conf, tenantid)?;
+            tenant_mgr::create_repository_for_tenant(self.conf, tenantid)?;

            pgb.write_message_noflush(&SINGLE_COL_ROWDESC)?
                .write_message_noflush(&BeMessage::CommandComplete(b"SELECT 1"))?;
@@ -577,59 +645,59 @@ impl postgres_backend::Handler for PageServerHandler {
                .map(|h| h.as_str().parse())
                .unwrap_or(Ok(self.conf.gc_horizon))?;

-            let repo = tenant_mgr::get_repository_for_tenant(&tenantid)?;
+            let repo = tenant_mgr::get_repository_for_tenant(tenantid)?;

            let result = repo.gc_iteration(Some(timelineid), gc_horizon, true)?;

            pgb.write_message_noflush(&BeMessage::RowDescription(&[
-                RowDescriptor::int8_col(b"snapshot_relfiles_total"),
-                RowDescriptor::int8_col(b"snapshot_relfiles_needed_by_cutoff"),
-                RowDescriptor::int8_col(b"snapshot_relfiles_needed_by_branches"),
-                RowDescriptor::int8_col(b"snapshot_relfiles_not_updated"),
-                RowDescriptor::int8_col(b"snapshot_relfiles_removed"),
-                RowDescriptor::int8_col(b"snapshot_relfiles_dropped"),
-                RowDescriptor::int8_col(b"snapshot_nonrelfiles_total"),
-                RowDescriptor::int8_col(b"snapshot_nonrelfiles_needed_by_cutoff"),
-                RowDescriptor::int8_col(b"snapshot_nonrelfiles_needed_by_branches"),
-                RowDescriptor::int8_col(b"snapshot_nonrelfiles_not_updated"),
-                RowDescriptor::int8_col(b"snapshot_nonrelfiles_removed"),
-                RowDescriptor::int8_col(b"snapshot_nonrelfiles_dropped"),
+                RowDescriptor::int8_col(b"layer_relfiles_total"),
+                RowDescriptor::int8_col(b"layer_relfiles_needed_by_cutoff"),
+                RowDescriptor::int8_col(b"layer_relfiles_needed_by_branches"),
+                RowDescriptor::int8_col(b"layer_relfiles_not_updated"),
+                RowDescriptor::int8_col(b"layer_relfiles_removed"),
+                RowDescriptor::int8_col(b"layer_relfiles_dropped"),
+                RowDescriptor::int8_col(b"layer_nonrelfiles_total"),
+                RowDescriptor::int8_col(b"layer_nonrelfiles_needed_by_cutoff"),
+                RowDescriptor::int8_col(b"layer_nonrelfiles_needed_by_branches"),
+                RowDescriptor::int8_col(b"layer_nonrelfiles_not_updated"),
+                RowDescriptor::int8_col(b"layer_nonrelfiles_removed"),
+                RowDescriptor::int8_col(b"layer_nonrelfiles_dropped"),
                RowDescriptor::int8_col(b"elapsed"),
            ]))?
            .write_message_noflush(&BeMessage::DataRow(&[
-                Some(&result.ondisk_relfiles_total.to_string().as_bytes()),
+                Some(result.ondisk_relfiles_total.to_string().as_bytes()),
                Some(
-                    &result
+                    result
                        .ondisk_relfiles_needed_by_cutoff
                        .to_string()
                        .as_bytes(),
                ),
                Some(
-                    &result
+                    result
                        .ondisk_relfiles_needed_by_branches
                        .to_string()
                        .as_bytes(),
                ),
-                Some(&result.ondisk_relfiles_not_updated.to_string().as_bytes()),
-                Some(&result.ondisk_relfiles_removed.to_string().as_bytes()),
-                Some(&result.ondisk_relfiles_dropped.to_string().as_bytes()),
-                Some(&result.ondisk_nonrelfiles_total.to_string().as_bytes()),
+                Some(result.ondisk_relfiles_not_updated.to_string().as_bytes()),
+                Some(result.ondisk_relfiles_removed.to_string().as_bytes()),
+                Some(result.ondisk_relfiles_dropped.to_string().as_bytes()),
+                Some(result.ondisk_nonrelfiles_total.to_string().as_bytes()),
                Some(
-                    &result
+                    result
                        .ondisk_nonrelfiles_needed_by_cutoff
                        .to_string()
                        .as_bytes(),
                ),
                Some(
-                    &result
+                    result
                        .ondisk_nonrelfiles_needed_by_branches
                        .to_string()
                        .as_bytes(),
                ),
-                Some(&result.ondisk_nonrelfiles_not_updated.to_string().as_bytes()),
-                Some(&result.ondisk_nonrelfiles_removed.to_string().as_bytes()),
-                Some(&result.ondisk_nonrelfiles_dropped.to_string().as_bytes()),
-                Some(&result.elapsed.as_millis().to_string().as_bytes()),
+                Some(result.ondisk_nonrelfiles_not_updated.to_string().as_bytes()),
+                Some(result.ondisk_nonrelfiles_removed.to_string().as_bytes()),
+                Some(result.ondisk_nonrelfiles_dropped.to_string().as_bytes()),
+                Some(result.elapsed.as_millis().to_string().as_bytes()),
            ]))?
            .write_message(&BeMessage::CommandComplete(b"SELECT 1"))?;
        } else {
--- a/pageserver/src/relish.rs
+++ b/pageserver/src/relish.rs
@@ -125,11 +125,7 @@ impl RelishTag {

    // convenience function to check if this relish is a normal relation.
    pub const fn is_relation(&self) -> bool {
-        if let RelishTag::Relation(_) = self {
-            true
-        } else {
-            false
-        }
+        matches!(self, RelishTag::Relation(_))
    }
 }

--- a/pageserver/src/relish_storage.rs
+++ b/pageserver/src/relish_storage.rs
@@ -0,0 +1,54 @@
+//! Abstractions for the page server to store its relish layer data in the external storage.
+//!
+//! Main purpose of this module subtree is to provide a set of abstractions to manage the storage state
+//! in a way, optimal for page server.
+//!
+//! The abstractions hide multiple custom external storage API implementations,
+//! such as AWS S3, local filesystem, etc., located in the submodules.
+
+mod local_fs;
+mod rust_s3;
+/// A queue and the background machinery behind it to upload
+/// local page server layer files to external storage.
+pub mod storage_uploader;
+
+use std::path::Path;
+
+use anyhow::Context;
+
+/// Storage (potentially remote) API to manage its state.
+#[async_trait::async_trait]
+pub trait RelishStorage: Send + Sync {
+    type RelishStoragePath;
+
+    fn derive_destination(
+        page_server_workdir: &Path,
+        relish_local_path: &Path,
+    ) -> anyhow::Result<Self::RelishStoragePath>;
+
+    async fn list_relishes(&self) -> anyhow::Result<Vec<Self::RelishStoragePath>>;
+
+    async fn download_relish(
+        &self,
+        from: &Self::RelishStoragePath,
+        to: &Path,
+    ) -> anyhow::Result<()>;
+
+    async fn delete_relish(&self, path: &Self::RelishStoragePath) -> anyhow::Result<()>;
+
+    async fn upload_relish(&self, from: &Path, to: &Self::RelishStoragePath) -> anyhow::Result<()>;
+}
+
+fn strip_workspace_prefix<'a>(
+    page_server_workdir: &'a Path,
+    relish_local_path: &'a Path,
+) -> anyhow::Result<&'a Path> {
+    relish_local_path
+        .strip_prefix(page_server_workdir)
+        .with_context(|| {
+            format!(
+                "Unexpected: relish local path '{}' is not relevant to server workdir",
+                relish_local_path.display(),
+            )
+        })
+}
--- a/pageserver/src/relish_storage/local_fs.rs
+++ b/pageserver/src/relish_storage/local_fs.rs
@@ -0,0 +1,158 @@
+//! Local filesystem relish storage.
+//!
+//! Page server already stores layer data on the server, when freezing it.
+//! This storage serves a way to
+//!
+//! * test things locally simply
+//! * allow to compabre both binary sets
+//! * help validating the relish storage API
+
+use std::{
+    future::Future,
+    path::{Path, PathBuf},
+    pin::Pin,
+};
+
+use anyhow::{bail, Context};
+
+use super::{strip_workspace_prefix, RelishStorage};
+
+pub struct LocalFs {
+    root: PathBuf,
+}
+
+impl LocalFs {
+    /// Atetmpts to create local FS relish storage, also creates the directory provided, if not exists.
+    pub fn new(root: PathBuf) -> anyhow::Result<Self> {
+        if !root.exists() {
+            std::fs::create_dir_all(&root).with_context(|| {
+                format!(
+                    "Failed to create all directories in the given root path {}",
+                    root.display(),
+                )
+            })?;
+        }
+        Ok(Self { root })
+    }
+
+    fn resolve_in_storage(&self, path: &Path) -> anyhow::Result<PathBuf> {
+        if path.is_relative() {
+            Ok(self.root.join(path))
+        } else if path.starts_with(&self.root) {
+            Ok(path.to_path_buf())
+        } else {
+            bail!(
+                "Path '{}' does not belong to the current storage",
+                path.display()
+            )
+        }
+    }
+}
+
+#[async_trait::async_trait]
+impl RelishStorage for LocalFs {
+    type RelishStoragePath = PathBuf;
+
+    fn derive_destination(
+        page_server_workdir: &Path,
+        relish_local_path: &Path,
+    ) -> anyhow::Result<Self::RelishStoragePath> {
+        Ok(strip_workspace_prefix(page_server_workdir, relish_local_path)?.to_path_buf())
+    }
+
+    async fn list_relishes(&self) -> anyhow::Result<Vec<Self::RelishStoragePath>> {
+        Ok(get_all_files(&self.root).await?.into_iter().collect())
+    }
+
+    async fn download_relish(
+        &self,
+        from: &Self::RelishStoragePath,
+        to: &Path,
+    ) -> anyhow::Result<()> {
+        let file_path = self.resolve_in_storage(from)?;
+        if file_path.exists() && file_path.is_file() {
+            create_target_directory(to).await?;
+            tokio::fs::copy(file_path, to).await?;
+            Ok(())
+        } else {
+            bail!(
+                "File '{}' either does not exist or is not a file",
+                file_path.display()
+            )
+        }
+    }
+
+    async fn delete_relish(&self, path: &Self::RelishStoragePath) -> anyhow::Result<()> {
+        let file_path = self.resolve_in_storage(path)?;
+        if file_path.exists() && file_path.is_file() {
+            Ok(tokio::fs::remove_file(file_path).await?)
+        } else {
+            bail!(
+                "File '{}' either does not exist or is not a file",
+                file_path.display()
+            )
+        }
+    }
+
+    async fn upload_relish(&self, from: &Path, to: &Self::RelishStoragePath) -> anyhow::Result<()> {
+        let target_file_path = self.resolve_in_storage(to)?;
+        create_target_directory(&target_file_path).await?;
+
+        tokio::fs::copy(&from, &target_file_path)
+            .await
+            .with_context(|| {
+                format!(
+                    "Failed to upload relish '{}' to local storage",
+                    from.display(),
+                )
+            })?;
+        Ok(())
+    }
+}
+
+fn get_all_files<'a, P>(
+    directory_path: P,
+) -> Pin<Box<dyn Future<Output = anyhow::Result<Vec<PathBuf>>> + Send + Sync + 'a>>
+where
+    P: AsRef<Path> + Send + Sync + 'a,
+{
+    Box::pin(async move {
+        let directory_path = directory_path.as_ref();
+        if directory_path.exists() {
+            if directory_path.is_dir() {
+                let mut paths = Vec::new();
+                let mut dir_contents = tokio::fs::read_dir(directory_path).await?;
+                while let Some(dir_entry) = dir_contents.next_entry().await? {
+                    let file_type = dir_entry.file_type().await?;
+                    let entry_path = dir_entry.path();
+                    if file_type.is_symlink() {
+                        log::debug!("{:?} us a symlink, skipping", entry_path)
+                    } else if file_type.is_dir() {
+                        paths.extend(get_all_files(entry_path).await?.into_iter())
+                    } else {
+                        paths.push(dir_entry.path());
+                    }
+                }
+                Ok(paths)
+            } else {
+                bail!("Path '{}' is not a directory", directory_path.display())
+            }
+        } else {
+            Ok(Vec::new())
+        }
+    })
+}
+
+async fn create_target_directory(target_file_path: &Path) -> anyhow::Result<()> {
+    let target_dir = match target_file_path.parent() {
+        Some(parent_dir) => parent_dir,
+        None => bail!(
+            "Relish path '{}' has no parent directory",
+            target_file_path.display()
+        ),
+    };
+    if !target_dir.exists() {
+        tokio::fs::create_dir_all(target_dir).await?;
+    }
+    Ok(())
+}
--- a/pageserver/src/relish_storage/rust_s3.rs
+++ b/pageserver/src/relish_storage/rust_s3.rs
@@ -0,0 +1,144 @@
+//! A wrapper around AWS S3 client library `rust_s3` to be used a relish storage.
+
+use std::path::Path;
+
+use anyhow::Context;
+use s3::{bucket::Bucket, creds::Credentials, region::Region};
+
+use crate::{relish_storage::strip_workspace_prefix, S3Config};
+
+use super::RelishStorage;
+
+const S3_FILE_SEPARATOR: char = '/';
+
+#[derive(Debug)]
+pub struct S3ObjectKey(String);
+
+impl S3ObjectKey {
+    fn key(&self) -> &str {
+        &self.0
+    }
+}
+
+/// AWS S3 relish storage.
+pub struct RustS3 {
+    bucket: Bucket,
+}
+
+impl RustS3 {
+    /// Creates the relish storage, errors if incorrect AWS S3 configuration provided.
+    pub fn new(aws_config: &S3Config) -> anyhow::Result<Self> {
+        let region = aws_config
+            .bucket_region
+            .parse::<Region>()
+            .context("Failed to parse the s3 region from config")?;
+        let credentials = Credentials::new(
+            aws_config.access_key_id.as_deref(),
+            aws_config.secret_access_key.as_deref(),
+            None,
+            None,
+            None,
+        )
+        .context("Failed to create the s3 credentials")?;
+        Ok(Self {
+            bucket: Bucket::new_with_path_style(
+                aws_config.bucket_name.as_str(),
+                region,
+                credentials,
+            )
+            .context("Failed to create the s3 bucket")?,
+        })
+    }
+}
+
+#[async_trait::async_trait]
+impl RelishStorage for RustS3 {
+    type RelishStoragePath = S3ObjectKey;
+
+    fn derive_destination(
+        page_server_workdir: &Path,
+        relish_local_path: &Path,
+    ) -> anyhow::Result<Self::RelishStoragePath> {
+        let relative_path = strip_workspace_prefix(page_server_workdir, relish_local_path)?;
+        let mut key = String::new();
+        for segment in relative_path {
+            key.push(S3_FILE_SEPARATOR);
+            key.push_str(&segment.to_string_lossy());
+        }
+        Ok(S3ObjectKey(key))
+    }
+
+    async fn list_relishes(&self) -> anyhow::Result<Vec<Self::RelishStoragePath>> {
+        let list_response = self
+            .bucket
+            .list(String::new(), None)
+            .await
+            .context("Failed to list s3 objects")?;
+
+        Ok(list_response
+            .into_iter()
+            .flat_map(|response| response.contents)
+            .map(|s3_object| S3ObjectKey(s3_object.key))
+            .collect())
+    }
+
+    async fn download_relish(
+        &self,
+        from: &Self::RelishStoragePath,
+        to: &Path,
+    ) -> anyhow::Result<()> {
+        let mut target_file = std::fs::OpenOptions::new()
+            .write(true)
+            .open(to)
+            .with_context(|| format!("Failed to open target s3 destination at {}", to.display()))?;
+        let code = self
+            .bucket
+            .get_object_stream(from.key(), &mut target_file)
+            .await
+            .with_context(|| format!("Failed to download s3 object with key {}", from.key()))?;
+        if code != 200 {
+            Err(anyhow::format_err!(
+                "Received non-200 exit code during downloading object from directory, code: {}",
+                code
+            ))
+        } else {
+            Ok(())
+        }
+    }
+
+    async fn delete_relish(&self, path: &Self::RelishStoragePath) -> anyhow::Result<()> {
+        let (_, code) = self
+            .bucket
+            .delete_object(path.key())
+            .await
+            .with_context(|| format!("Failed to delete s3 object with key {}", path.key()))?;
+        if code != 200 {
+            Err(anyhow::format_err!(
+                "Received non-200 exit code during deleting object with key '{}', code: {}",
+                path.key(),
+                code
+            ))
+        } else {
+            Ok(())
+        }
+    }
+
+    async fn upload_relish(&self, from: &Path, to: &Self::RelishStoragePath) -> anyhow::Result<()> {
+        let mut local_file = tokio::fs::OpenOptions::new().read(true).open(from).await?;
+
+        let code = self
+            .bucket
+            .put_object_stream(&mut local_file, to.key())
+            .await
+            .with_context(|| format!("Failed to create s3 object with key {}", to.key()))?;
+        if code != 200 {
+            Err(anyhow::format_err!(
+                "Received non-200 exit code during creating object with key '{}', code: {}",
+                to.key(),
+                code
+            ))
+        } else {
+            Ok(())
+        }
+    }
+}
--- a/pageserver/src/relish_storage/storage_uploader.rs
+++ b/pageserver/src/relish_storage/storage_uploader.rs
@@ -0,0 +1,116 @@
+use std::{
+    collections::VecDeque,
+    path::{Path, PathBuf},
+    sync::{Arc, Mutex},
+    thread,
+};
+
+use zenith_utils::zid::ZTimelineId;
+
+use crate::{relish_storage::RelishStorage, RelishStorageConfig};
+
+use super::{local_fs::LocalFs, rust_s3::RustS3};
+
+pub struct QueueBasedRelishUploader {
+    upload_queue: Arc<Mutex<VecDeque<(ZTimelineId, PathBuf)>>>,
+}
+
+impl QueueBasedRelishUploader {
+    pub fn new(
+        config: &RelishStorageConfig,
+        page_server_workdir: &'static Path,
+    ) -> anyhow::Result<Self> {
+        let upload_queue = Arc::new(Mutex::new(VecDeque::new()));
+        let _handle = match config {
+            RelishStorageConfig::LocalFs(root) => {
+                let relish_storage = LocalFs::new(root.clone())?;
+                create_upload_thread(
+                    Arc::clone(&upload_queue),
+                    relish_storage,
+                    page_server_workdir,
+                )?
+            }
+            RelishStorageConfig::AwsS3(s3_config) => {
+                let relish_storage = RustS3::new(s3_config)?;
+                create_upload_thread(
+                    Arc::clone(&upload_queue),
+                    relish_storage,
+                    page_server_workdir,
+                )?
+            }
+        };
+
+        Ok(Self { upload_queue })
+    }
+
+    pub fn schedule_upload(&self, timeline_id: ZTimelineId, relish_path: PathBuf) {
+        self.upload_queue
+            .lock()
+            .unwrap()
+            .push_back((timeline_id, relish_path))
+    }
+}
+
+fn create_upload_thread<P, S: 'static + RelishStorage<RelishStoragePath = P>>(
+    upload_queue: Arc<Mutex<VecDeque<(ZTimelineId, PathBuf)>>>,
+    relish_storage: S,
+    page_server_workdir: &'static Path,
+) -> std::io::Result<thread::JoinHandle<()>> {
+    let runtime = tokio::runtime::Builder::new_current_thread()
+        .enable_all()
+        .build()?;
+    thread::Builder::new()
+        .name("Queue based relish uploader".to_string())
+        .spawn(move || loop {
+            runtime.block_on(async {
+                upload_loop_step(&upload_queue, &relish_storage, page_server_workdir).await;
+            })
+        })
+}
+
+async fn upload_loop_step<P, S: 'static + RelishStorage<RelishStoragePath = P>>(
+    upload_queue: &Mutex<VecDeque<(ZTimelineId, PathBuf)>>,
+    relish_storage: &S,
+    page_server_workdir: &Path,
+) {
+    let mut queue_accessor = upload_queue.lock().unwrap();
+    log::debug!("current upload queue length: {}", queue_accessor.len());
+    let next_upload = queue_accessor.pop_front();
+    drop(queue_accessor);
+
+    let (relish_timeline_id, relish_local_path) = match next_upload {
+        Some(data) => data,
+        None => {
+            // Don't spin and allow others to use the queue.
+            // In future, could be improved to be more clever about delays depending on relish upload stats
+            thread::sleep(std::time::Duration::from_secs(1));
+            return;
+        }
+    };
+
+    if let Err(e) = upload_relish(relish_storage, page_server_workdir, &relish_local_path).await {
+        log::error!(
+            "Failed to upload relish '{}' for timeline {}, reason: {}",
+            relish_local_path.display(),
+            relish_timeline_id,
+            e
+        );
+        upload_queue
+            .lock()
+            .unwrap()
+            .push_back((relish_timeline_id, relish_local_path))
+    } else {
+        log::debug!("Relish successfully uploaded");
+    }
+}
+
+async fn upload_relish<P, S: RelishStorage<RelishStoragePath = P>>(
+    relish_storage: &S,
+    page_server_workdir: &Path,
+    relish_local_path: &Path,
+) -> anyhow::Result<()> {
+    let destination = S::derive_destination(page_server_workdir, relish_local_path)?;
+    relish_storage
+        .upload_relish(relish_local_path, &destination)
+        .await
+}
--- a/pageserver/src/repository.rs
+++ b/pageserver/src/repository.rs
@@ -17,11 +17,7 @@ pub trait Repository: Send + Sync {
    fn get_timeline(&self, timelineid: ZTimelineId) -> Result<Arc<dyn Timeline>>;

    /// Create a new, empty timeline. The caller is responsible for loading data into it
-    fn create_empty_timeline(
-        &self,
-        timelineid: ZTimelineId,
-        start_lsn: Lsn,
-    ) -> Result<Arc<dyn Timeline>>;
+    fn create_empty_timeline(&self, timelineid: ZTimelineId) -> Result<Arc<dyn Timeline>>;

    /// Branch a timeline
    fn branch_timeline(&self, src: ZTimelineId, dst: ZTimelineId, start_lsn: Lsn) -> Result<()>;
@@ -45,9 +41,6 @@ pub trait Repository: Send + Sync {
        horizon: u64,
        compact: bool,
    ) -> Result<GcResult>;
-
-    // TODO get timelines?
-    //fn get_stats(&self) -> RepositoryStats;
 }

 ///
@@ -97,11 +90,16 @@ pub trait Timeline: Send + Sync {
    // Public GET functions
    //------------------------------------------------------------------------------

-    /// Look up given page in the cache.
-    fn get_page_at_lsn(&self, tag: RelishTag, blknum: u32, lsn: Lsn) -> Result<Bytes>;
+    ///
+    /// Wait until WAL has been received and processed up to this LSN.
+    ///
+    /// You should call this before any of the other get_* or list_* functions. Calling
+    /// those functions with an LSN that has been processed yet is an error.
+    ///
+    fn wait_lsn(&self, lsn: Lsn) -> Result<()>;

-    /// Look up given page in the cache.
-    fn get_page_at_lsn_nowait(&self, tag: RelishTag, blknum: u32, lsn: Lsn) -> Result<Bytes>;
+    /// Look up given page version.
+    fn get_page_at_lsn(&self, tag: RelishTag, blknum: u32, lsn: Lsn) -> Result<Bytes>;

    /// Get size of a relish
    fn get_relish_size(&self, tag: RelishTag, lsn: Lsn) -> Result<Option<u32>>;
@@ -109,11 +107,15 @@ pub trait Timeline: Send + Sync {
    /// Does relation exist?
    fn get_rel_exists(&self, tag: RelishTag, lsn: Lsn) -> Result<bool>;

-    /// Get a list of all distinct relations in given tablespace and database.
-    fn list_rels(&self, spcnode: u32, dbnode: u32, lsn: Lsn) -> Result<HashSet<RelTag>>;
+    /// Get a list of all existing relations
+    /// Pass RelTag to get relation objects or None to get nonrels.
+    fn list_relishes(&self, tag: Option<RelTag>, lsn: Lsn) -> Result<HashSet<RelishTag>>;

-    /// Get a list of non-relational objects
-    fn list_nonrels<'a>(&'a self, lsn: Lsn) -> Result<HashSet<RelishTag>>;
+    /// Get a list of all existing relations in given tablespace and database.
+    fn list_rels(&self, spcnode: u32, dbnode: u32, lsn: Lsn) -> Result<HashSet<RelishTag>>;
+
+    /// Get a list of all existing non-relational objects
+    fn list_nonrels(&self, lsn: Lsn) -> Result<HashSet<RelishTag>>;

    //------------------------------------------------------------------------------
    // Public PUT functions, to update the repository with new page versions.
@@ -133,9 +135,8 @@ pub trait Timeline: Send + Sync {
    /// Truncate relation
    fn put_truncation(&self, rel: RelishTag, lsn: Lsn, nblocks: u32) -> Result<()>;

-    /// Unlink relish.
-    /// This method is used for marking dropped relations and truncated SLRU segments
-    fn put_unlink(&self, tag: RelishTag, lsn: Lsn) -> Result<()>;
+    /// This method is used for marking dropped relations and truncated SLRU files and aborted two phase records
+    fn drop_relish(&self, tag: RelishTag, lsn: Lsn) -> Result<()>;

    /// Track end of the latest digested WAL record.
    ///
@@ -147,6 +148,7 @@ pub trait Timeline: Send + Sync {
    /// Get last or prev record separately. Same as get_last_record_rlsn().last/prev.
    fn get_last_record_lsn(&self) -> Lsn;
    fn get_prev_record_lsn(&self) -> Lsn;
+    fn get_start_lsn(&self) -> Lsn;

    ///
    /// Flush to disk all data that was written with the put_* functions
@@ -154,14 +156,16 @@ pub trait Timeline: Send + Sync {
    /// NOTE: This has nothing to do with checkpoint in PostgreSQL. We don't
    /// know anything about them here in the repository.
    fn checkpoint(&self) -> Result<()>;
-}

-#[derive(Clone)]
-pub struct RepositoryStats {
-    pub num_entries: Lsn,
-    pub num_page_images: Lsn,
-    pub num_wal_records: Lsn,
-    pub num_getpage_requests: Lsn,
+    /// Retrieve current logical size of the timeline
+    ///
+    /// NOTE: counted incrementally, includes ancestors,
+    /// doesnt support TwoPhase relishes yet
+    fn get_current_logical_size(&self) -> usize;
+
+    /// Does the same as get_current_logical_size but counted on demand.
+    /// Used in tests to ensure thet incremental and non incremental variants match.
+    fn get_current_logical_size_non_incremental(&self, lsn: Lsn) -> Result<usize>;
 }

 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
@@ -201,6 +205,7 @@ impl WALRecord {
 ///
 /// Tests that should work the same with any Repository/Timeline implementation.
 ///
+#[allow(clippy::bool_assert_comparison)]
 #[cfg(test)]
 mod tests {
    use super::*;
@@ -208,11 +213,9 @@ mod tests {
    use crate::walredo::{WalRedoError, WalRedoManager};
    use crate::PageServerConf;
    use postgres_ffi::pg_constants;
+    use postgres_ffi::xlog_utils::SIZEOF_CHECKPOINT;
    use std::fs;
-    use std::path::PathBuf;
    use std::str::FromStr;
-    use std::time::Duration;
-    use zenith_utils::postgres_backend::AuthType;
    use zenith_utils::zid::ZTenantId;

    /// Arbitrary relation tag, for testing.
@@ -239,26 +242,24 @@ mod tests {
        buf.freeze()
    }

+    fn assert_current_logical_size(timeline: &Arc<dyn Timeline>, lsn: Lsn) {
+        let incremental = timeline.get_current_logical_size();
+        let non_incremental = timeline
+            .get_current_logical_size_non_incremental(lsn)
+            .unwrap();
+        assert_eq!(incremental, non_incremental);
+    }
+
    static ZERO_PAGE: Bytes = Bytes::from_static(&[0u8; 8192]);
+    static ZERO_CHECKPOINT: Bytes = Bytes::from_static(&[0u8; SIZEOF_CHECKPOINT]);

    fn get_test_repo(test_name: &str) -> Result<Box<dyn Repository>> {
-        let repo_dir = PathBuf::from(format!("../tmp_check/test_{}", test_name));
+        let repo_dir = PageServerConf::test_repo_dir(test_name);
        let _ = fs::remove_dir_all(&repo_dir);
        fs::create_dir_all(&repo_dir)?;
        fs::create_dir_all(&repo_dir.join("timelines"))?;

-        let conf = PageServerConf {
-            daemonize: false,
-            gc_horizon: 64 * 1024 * 1024,
-            gc_period: Duration::from_secs(10),
-            listen_addr: "127.0.0.1:5430".to_string(),
-            http_endpoint_addr: "127.0.0.1:9898".to_string(),
-            superuser: "zenith_admin".to_string(),
-            workdir: repo_dir,
-            pg_distrib_dir: "".into(),
-            auth_type: AuthType::Trust,
-            auth_validation_public_key_path: None,
-        };
+        let conf = PageServerConf::dummy_conf(repo_dir);
        // Make a static copy of the config. This can never be free'd, but that's
        // OK in a test.
        let conf: &'static PageServerConf = Box::leak(Box::new(conf));
@@ -284,7 +285,7 @@ mod tests {

        // Create timeline to work on
        let timelineid = ZTimelineId::from_str("11223344556677881122334455667788").unwrap();
-        let tline = repo.create_empty_timeline(timelineid, Lsn(0x00))?;
+        let tline = repo.create_empty_timeline(timelineid)?;

        tline.put_page_image(TESTREL_A, 0, Lsn(0x20), TEST_IMG("foo blk 0 at 2"))?;
        tline.put_page_image(TESTREL_A, 0, Lsn(0x20), TEST_IMG("foo blk 0 at 2"))?;
@@ -294,6 +295,8 @@ mod tests {

        tline.advance_last_record_lsn(Lsn(0x50));

+        assert_current_logical_size(&tline, Lsn(0x50));
+
        // The relation was created at LSN 2, not visible at LSN 1 yet.
        assert_eq!(tline.get_rel_exists(TESTREL_A, Lsn(0x10))?, false);
        assert!(tline.get_relish_size(TESTREL_A, Lsn(0x10))?.is_none());
@@ -338,6 +341,7 @@ mod tests {
        // Truncate last block
        tline.put_truncation(TESTREL_A, Lsn(0x60), 2)?;
        tline.advance_last_record_lsn(Lsn(0x60));
+        assert_current_logical_size(&tline, Lsn(0x60));

        // Check reported size and contents after truncation
        assert_eq!(tline.get_relish_size(TESTREL_A, Lsn(0x60))?.unwrap(), 2);
@@ -357,6 +361,37 @@ mod tests {
            TEST_IMG("foo blk 2 at 5")
        );

+        // Truncate to zero length
+        tline.put_truncation(TESTREL_A, Lsn(0x68), 0)?;
+        tline.advance_last_record_lsn(Lsn(0x68));
+        assert_eq!(tline.get_relish_size(TESTREL_A, Lsn(0x68))?.unwrap(), 0);
+
+        // Extend from 0 to 2 blocks, leaving a gap
+        tline.put_page_image(TESTREL_A, 1, Lsn(0x70), TEST_IMG("foo blk 1"))?;
+        tline.advance_last_record_lsn(Lsn(0x70));
+        assert_eq!(tline.get_relish_size(TESTREL_A, Lsn(0x70))?.unwrap(), 2);
+        assert_eq!(tline.get_page_at_lsn(TESTREL_A, 0, Lsn(0x70))?, ZERO_PAGE);
+        assert_eq!(
+            tline.get_page_at_lsn(TESTREL_A, 1, Lsn(0x70))?,
+            TEST_IMG("foo blk 1")
+        );
+
+        // Extend a lot more, leaving a big gap that spans across segments
+        // FIXME: This is currently broken, see https://github.com/zenithdb/zenith/issues/500
+        /*
+        tline.put_page_image(TESTREL_A, 1500, Lsn(0x80), TEST_IMG("foo blk 1500"))?;
+        tline.advance_last_record_lsn(Lsn(0x80));
+        assert_eq!(tline.get_relish_size(TESTREL_A, Lsn(0x80))?.unwrap(), 1501);
+        for blk in 2..1500 {
+            assert_eq!(
+                tline.get_page_at_lsn(TESTREL_A, blk, Lsn(0x80))?,
+                ZERO_PAGE);
+        }
+        assert_eq!(
+            tline.get_page_at_lsn(TESTREL_A, 1500, Lsn(0x80))?,
+            TEST_IMG("foo blk 1500"));
+         */
+
        Ok(())
    }

@@ -366,7 +401,7 @@ mod tests {
    fn test_large_rel() -> Result<()> {
        let repo = get_test_repo("test_large_rel")?;
        let timelineid = ZTimelineId::from_str("11223344556677881122334455667788").unwrap();
-        let tline = repo.create_empty_timeline(timelineid, Lsn(0x00))?;
+        let tline = repo.create_empty_timeline(timelineid)?;

        let mut lsn = 0x10;
        for blknum in 0..pg_constants::RELSEG_SIZE + 1 {
@@ -376,6 +411,8 @@ mod tests {
        }
        tline.advance_last_record_lsn(Lsn(lsn));

+        assert_current_logical_size(&tline, Lsn(lsn));
+
        assert_eq!(
            tline.get_relish_size(TESTREL_A, Lsn(lsn))?.unwrap(),
            pg_constants::RELSEG_SIZE + 1
@@ -389,6 +426,7 @@ mod tests {
            tline.get_relish_size(TESTREL_A, Lsn(lsn))?.unwrap(),
            pg_constants::RELSEG_SIZE
        );
+        assert_current_logical_size(&tline, Lsn(lsn));

        // Truncate another block
        lsn += 0x10;
@@ -398,6 +436,7 @@ mod tests {
            tline.get_relish_size(TESTREL_A, Lsn(lsn))?.unwrap(),
            pg_constants::RELSEG_SIZE - 1
        );
+        assert_current_logical_size(&tline, Lsn(lsn));

        // Truncate to 1500, and then truncate all the way down to 0, one block at a time
        // This tests the behavior at segment boundaries
@@ -413,6 +452,67 @@ mod tests {

            size -= 1;
        }
+        assert_current_logical_size(&tline, Lsn(lsn));
+
+        Ok(())
+    }
+
+    ///
+    /// Test list_rels() function, with branches and dropped relations
+    ///
+    #[test]
+    // FIXME: The last assertion in this test is currently failing, see
+    // https://github.com/zenithdb/zenith/issues/502. Ignore the failure until that's fixed.
+    #[ignore]
+    fn test_list_rels_drop() -> Result<()> {
+        let repo = get_test_repo("test_list_rels_drop")?;
+        let timelineid = ZTimelineId::from_str("11223344556677881122334455667788").unwrap();
+        let tline = repo.create_empty_timeline(timelineid)?;
+        const TESTDB: u32 = 111;
+
+        // Import initial dummy checkpoint record, otherwise the get_timeline() call
+        // after branching fails below
+        tline.put_page_image(RelishTag::Checkpoint, 0, Lsn(0x10), ZERO_CHECKPOINT.clone())?;
+
+        // Create a relation on the timeline
+        tline.put_page_image(TESTREL_A, 0, Lsn(0x20), TEST_IMG("foo blk 0 at 2"))?;
+
+        tline.advance_last_record_lsn(Lsn(0x30));
+
+        // Check that list_rels() lists it after LSN 2, but no before it
+        assert!(!tline.list_rels(0, TESTDB, Lsn(0x10))?.contains(&TESTREL_A));
+        assert!(tline.list_rels(0, TESTDB, Lsn(0x20))?.contains(&TESTREL_A));
+        assert!(tline.list_rels(0, TESTDB, Lsn(0x30))?.contains(&TESTREL_A));
+
+        // Create a branch, check that the relation is visible there
+        let newtimelineid = ZTimelineId::from_str("AA223344556677881122334455667788").unwrap();
+        repo.branch_timeline(timelineid, newtimelineid, Lsn(0x30))?;
+        let newtline = repo.get_timeline(newtimelineid)?;
+
+        assert!(newtline
+            .list_rels(0, TESTDB, Lsn(0x30))?
+            .contains(&TESTREL_A));
+
+        // Drop it on the branch
+        newtline.drop_relish(TESTREL_A, Lsn(0x40))?;
+        newtline.advance_last_record_lsn(Lsn(0x40));
+
+        // Check that it's no longer listed on the branch after the point where it was dropped
+        assert!(newtline
+            .list_rels(0, TESTDB, Lsn(0x30))?
+            .contains(&TESTREL_A));
+        assert!(!newtline
+            .list_rels(0, TESTDB, Lsn(0x40))?
+            .contains(&TESTREL_A));
+
+        // Run checkpoint and garbage collection and check that it's still not visible
+        newtline.checkpoint()?;
+        repo.gc_iteration(Some(newtimelineid), 0, true)?;
+
+        // FIXME: this is currently failing
+        assert!(!newtline
+            .list_rels(0, TESTDB, Lsn(0x40))?
+            .contains(&TESTREL_A));

        Ok(())
    }
@@ -424,11 +524,11 @@ mod tests {
    fn test_branch() -> Result<()> {
        let repo = get_test_repo("test_branch")?;
        let timelineid = ZTimelineId::from_str("11223344556677881122334455667788").unwrap();
-        let tline = repo.create_empty_timeline(timelineid, Lsn(0x00))?;
+        let tline = repo.create_empty_timeline(timelineid)?;

        // Import initial dummy checkpoint record, otherwise the get_timeline() call
        // after branching fails below
-        tline.put_page_image(RelishTag::Checkpoint, 0, Lsn(0x10), ZERO_PAGE.clone())?;
+        tline.put_page_image(RelishTag::Checkpoint, 0, Lsn(0x10), ZERO_CHECKPOINT.clone())?;

        // Create a relation on the timeline
        tline.put_page_image(TESTREL_A, 0, Lsn(0x20), TEST_IMG("foo blk 0 at 2"))?;
@@ -439,6 +539,7 @@ mod tests {
        tline.put_page_image(TESTREL_B, 0, Lsn(0x20), TEST_IMG("foobar blk 0 at 2"))?;

        tline.advance_last_record_lsn(Lsn(0x40));
+        assert_current_logical_size(&tline, Lsn(0x40));

        // Branch the history, modify relation differently on the new timeline
        let newtimelineid = ZTimelineId::from_str("AA223344556677881122334455667788").unwrap();
@@ -466,6 +567,8 @@ mod tests {

        assert_eq!(newtline.get_relish_size(TESTREL_B, Lsn(0x40))?.unwrap(), 1);

+        assert_current_logical_size(&tline, Lsn(0x40));
+
        Ok(())
    }

--- a/pageserver/src/restore_local_repo.rs
+++ b/pageserver/src/restore_local_repo.rs
@@ -9,9 +9,7 @@ use std::cmp::min;
 use std::fs;
 use std::fs::File;
 use std::io::Read;
-use std::io::Seek;
-use std::io::SeekFrom;
-use std::path::{Path, PathBuf};
+use std::path::Path;

 use anyhow::Result;
 use bytes::{Buf, Bytes};
@@ -29,7 +27,7 @@ use zenith_utils::lsn::Lsn;
 const MAX_MBR_BLKNO: u32 =
    pg_constants::MAX_MULTIXACT_ID / pg_constants::MULTIXACT_MEMBERS_PER_PAGE as u32;

-const ZERO_PAGE: Bytes = Bytes::from_static(&[0u8; 8192]);
+static ZERO_PAGE: Bytes = Bytes::from_static(&[0u8; 8192]);

 ///
 /// Import all relation data pages from local disk into the repository.
@@ -45,15 +43,8 @@ pub fn import_timeline_from_postgres_datadir(
        match direntry.file_name().to_str() {
            None => continue,

-            // These special files appear in the snapshot, but are not needed by the page server
            Some("pg_control") => {
-                import_nonrel_file(timeline, lsn, RelishTag::ControlFile, &direntry.path())?;
-                // Extract checkpoint record from pg_control and store is as separate object
-                let pg_control_bytes =
-                    timeline.get_page_at_lsn_nowait(RelishTag::ControlFile, 0, lsn)?;
-                let pg_control = ControlFileData::decode(&pg_control_bytes)?;
-                let checkpoint_bytes = pg_control.checkPointCopy.encode();
-                timeline.put_page_image(RelishTag::Checkpoint, 0, lsn, checkpoint_bytes)?;
+                import_control_file(timeline, lsn, &direntry.path())?;
            }
            Some("pg_filenode.map") => import_nonrel_file(
                timeline,
@@ -93,7 +84,6 @@ pub fn import_timeline_from_postgres_datadir(
            match direntry.file_name().to_str() {
                None => continue,

-                // These special files appear in the snapshot, but are not needed by the page server
                Some("PG_VERSION") => continue,
                Some("pg_filenode.map") => import_nonrel_file(
                    timeline,
@@ -130,13 +120,12 @@ pub fn import_timeline_from_postgres_datadir(
    }
    for entry in fs::read_dir(path.join("pg_twophase"))? {
        let entry = entry?;
-        let xid = u32::from_str_radix(&entry.path().to_str().unwrap(), 16)?;
+        let xid = u32::from_str_radix(entry.path().to_str().unwrap(), 16)?;
        import_nonrel_file(timeline, lsn, RelishTag::TwoPhase { xid }, &entry.path())?;
    }
    // TODO: Scan pg_tblspc

-    timeline.advance_last_record_lsn(lsn.align());
-    timeline.checkpoint()?;
+    timeline.advance_last_record_lsn(lsn);

    Ok(())
 }
@@ -153,7 +142,7 @@ fn import_relfile(

    let p = parse_relfilename(path.file_name().unwrap().to_str().unwrap());
    if let Err(e) = p {
-        warn!("unrecognized file in snapshot: {:?} ({})", path, e);
+        warn!("unrecognized file in postgres datadir: {:?} ({})", path, e);
        return Err(e.into());
    }
    let (relnode, forknum, segno) = p.unwrap();
@@ -218,6 +207,35 @@ fn import_nonrel_file(
    Ok(())
 }

+///
+/// Import pg_control file into the repository.
+///
+/// The control file is imported as is, but we also extract the checkpoint record
+/// from it and store it separated.
+fn import_control_file(timeline: &dyn Timeline, lsn: Lsn, path: &Path) -> Result<()> {
+    let mut file = File::open(path)?;
+    let mut buffer = Vec::new();
+    // read the whole file
+    file.read_to_end(&mut buffer)?;
+
+    info!("importing control file {}", path.display());
+
+    // Import it as ControlFile
+    timeline.put_page_image(
+        RelishTag::ControlFile,
+        0,
+        lsn,
+        Bytes::copy_from_slice(&buffer[..]),
+    )?;
+
+    // Extract the checkpoint record and import it separately.
+    let pg_control = ControlFileData::decode(&buffer)?;
+    let checkpoint_bytes = pg_control.checkPointCopy.encode();
+    timeline.put_page_image(RelishTag::Checkpoint, 0, lsn, checkpoint_bytes)?;
+
+    Ok(())
+}
+
 ///
 /// Import an SLRU segment file
 ///
@@ -263,86 +281,6 @@ fn import_slru_file(timeline: &dyn Timeline, lsn: Lsn, slru: SlruKind, path: &Pa
    Ok(())
 }

-/// Scan PostgreSQL WAL files in given directory
-/// and load all records >= 'startpoint' into the repository.
-pub fn import_timeline_wal(walpath: &Path, timeline: &dyn Timeline, startpoint: Lsn) -> Result<()> {
-    let mut waldecoder = WalStreamDecoder::new(startpoint);
-
-    let mut segno = startpoint.segment_number(pg_constants::WAL_SEGMENT_SIZE);
-    let mut offset = startpoint.segment_offset(pg_constants::WAL_SEGMENT_SIZE);
-    let mut last_lsn = startpoint;
-
-    let checkpoint_bytes = timeline.get_page_at_lsn_nowait(RelishTag::Checkpoint, 0, startpoint)?;
-    let mut checkpoint = CheckPoint::decode(&checkpoint_bytes)?;
-
-    loop {
-        // FIXME: assume postgresql tli 1 for now
-        let filename = XLogFileName(1, segno, pg_constants::WAL_SEGMENT_SIZE);
-        let mut buf = Vec::new();
-
-        //Read local file
-        let mut path = walpath.join(&filename);
-
-        // It could be as .partial
-        if !PathBuf::from(&path).exists() {
-            path = walpath.join(filename + ".partial");
-        }
-
-        // Slurp the WAL file
-        let open_result = File::open(&path);
-        if let Err(e) = &open_result {
-            if e.kind() == std::io::ErrorKind::NotFound {
-                break;
-            }
-        }
-        let mut file = open_result?;
-
-        if offset > 0 {
-            file.seek(SeekFrom::Start(offset as u64))?;
-        }
-
-        let nread = file.read_to_end(&mut buf)?;
-        if nread != pg_constants::WAL_SEGMENT_SIZE - offset as usize {
-            // Maybe allow this for .partial files?
-            error!("read only {} bytes from WAL file", nread);
-        }
-
-        waldecoder.feed_bytes(&buf);
-
-        let mut nrecords = 0;
-        loop {
-            let rec = waldecoder.poll_decode();
-            if rec.is_err() {
-                // Assume that an error means we've reached the end of
-                // a partial WAL record. So that's ok.
-                trace!("WAL decoder error {:?}", rec);
-                break;
-            }
-            if let Some((lsn, recdata)) = rec.unwrap() {
-                let decoded = decode_wal_record(recdata.clone());
-                save_decoded_record(&mut checkpoint, timeline, &decoded, recdata, lsn)?;
-                last_lsn = lsn;
-            } else {
-                break;
-            }
-            nrecords += 1;
-        }
-
-        info!("imported {} records up to {}", nrecords, last_lsn);
-
-        segno += 1;
-        offset = 0;
-    }
-
-    info!("reached end of WAL at {}", last_lsn);
-    let checkpoint_bytes = checkpoint.encode();
-    timeline.put_page_image(RelishTag::Checkpoint, 0, last_lsn, checkpoint_bytes)?;
-
-    timeline.advance_last_record_lsn(last_lsn.align());
-    timeline.checkpoint()?;
-    Ok(())
-}
-
 ///
 /// Helper function to parse a WAL record and call the Timeline's PUT functions for all the
 /// relations/pages that the record affects.
@@ -394,18 +332,22 @@ pub fn save_decoded_record(
        {
            let dropdb = XlDropDatabase::decode(&mut buf);

+            // To drop the database, we need to drop all the relations in it. Like in
+            // save_xlog_dbase_create(), use the previous record's LSN in the list_rels() call
+            let req_lsn = min(timeline.get_last_record_lsn(), lsn);
+
            for tablespace_id in dropdb.tablespace_ids {
-                let rels = timeline.list_rels(tablespace_id, dropdb.db_id, lsn)?;
+                let rels = timeline.list_rels(tablespace_id, dropdb.db_id, req_lsn)?;
                for rel in rels {
-                    timeline.put_unlink(RelishTag::Relation(rel), lsn)?;
+                    timeline.drop_relish(rel, lsn)?;
                }
                trace!(
-                    "Unlink FileNodeMap {}, {} at lsn {}",
+                    "Drop FileNodeMap {}, {} at lsn {}",
                    tablespace_id,
                    dropdb.db_id,
                    lsn
                );
-                timeline.put_unlink(
+                timeline.drop_relish(
                    RelishTag::FileNodeMap {
                        spcnode: tablespace_id,
                        dbnode: dropdb.db_id,
@@ -429,7 +371,7 @@ pub fn save_decoded_record(
                },
                rpageno,
                lsn,
-                ZERO_PAGE,
+                ZERO_PAGE.clone(),
            )?;
        } else {
            assert!(info == pg_constants::CLOG_TRUNCATE);
@@ -448,12 +390,12 @@ pub fn save_decoded_record(
            save_xact_record(timeline, lsn, &parsed_xact, decoded)?;
            // Remove twophase file. see RemoveTwoPhaseFile() in postgres code
            trace!(
-                "unlink twophaseFile for xid {} parsed_xact.xid {} here at {}",
+                "Drop twophaseFile for xid {} parsed_xact.xid {} here at {}",
                decoded.xl_xid,
                parsed_xact.xid,
                lsn
            );
-            timeline.put_unlink(
+            timeline.drop_relish(
                RelishTag::TwoPhase {
                    xid: parsed_xact.xid,
                },
@@ -486,7 +428,7 @@ pub fn save_decoded_record(
                },
                rpageno,
                lsn,
-                ZERO_PAGE,
+                ZERO_PAGE.clone(),
            )?;
        } else if info == pg_constants::XLOG_MULTIXACT_ZERO_MEM_PAGE {
            let pageno = buf.get_u32_le();
@@ -499,7 +441,7 @@ pub fn save_decoded_record(
                },
                rpageno,
                lsn,
-                ZERO_PAGE,
+                ZERO_PAGE.clone(),
            )?;
        } else if info == pg_constants::XLOG_MULTIXACT_CREATE_ID {
            let xlrec = XlMultiXactCreate::decode(&mut buf);
@@ -534,9 +476,6 @@ pub fn save_decoded_record(
            }
        }
    }
-    // Now that this record has been handled, let the repository know that
-    // it is up-to-date to this LSN
-    timeline.advance_last_record_lsn(lsn.align());
    Ok(())
 }

@@ -560,56 +499,52 @@ fn save_xlog_dbase_create(timeline: &dyn Timeline, lsn: Lsn, rec: &XlCreateDatab

    let mut num_rels_copied = 0;
    let mut num_blocks_copied = 0;
-    for src_rel in rels {
-        assert_eq!(src_rel.spcnode, src_tablespace_id);
-        assert_eq!(src_rel.dbnode, src_db_id);
+    for rel in rels {
+        if let RelishTag::Relation(src_rel) = rel {
+            assert_eq!(src_rel.spcnode, src_tablespace_id);
+            assert_eq!(src_rel.dbnode, src_db_id);

-        let nblocks = timeline
-            .get_relish_size(RelishTag::Relation(src_rel), req_lsn)?
-            .unwrap_or(0);
-        let dst_rel = RelTag {
-            spcnode: tablespace_id,
-            dbnode: db_id,
-            relnode: src_rel.relnode,
-            forknum: src_rel.forknum,
-        };
+            let nblocks = timeline.get_relish_size(rel, req_lsn)?.unwrap_or(0);
+            let dst_rel = RelTag {
+                spcnode: tablespace_id,
+                dbnode: db_id,
+                relnode: src_rel.relnode,
+                forknum: src_rel.forknum,
+            };

-        // Copy content
-        for blknum in 0..nblocks {
-            let content =
-                timeline.get_page_at_lsn_nowait(RelishTag::Relation(src_rel), blknum, req_lsn)?;
+            // Copy content
+            for blknum in 0..nblocks {
+                let content = timeline.get_page_at_lsn(rel, blknum, req_lsn)?;

-            debug!("copying block {} from {} to {}", blknum, src_rel, dst_rel);
+                debug!("copying block {} from {} to {}", blknum, src_rel, dst_rel);

-            timeline.put_page_image(RelishTag::Relation(dst_rel), blknum, lsn, content)?;
-            num_blocks_copied += 1;
+                timeline.put_page_image(RelishTag::Relation(dst_rel), blknum, lsn, content)?;
+                num_blocks_copied += 1;
+            }
+
+            if nblocks == 0 {
+                // make sure we have some trace of the relation, even if it's empty
+                timeline.put_truncation(RelishTag::Relation(dst_rel), lsn, 0)?;
+            }
+
+            num_rels_copied += 1;
        }
-
-        if nblocks == 0 {
-            // make sure we have some trace of the relation, even if it's empty
-            timeline.put_truncation(RelishTag::Relation(dst_rel), lsn, 0)?;
-        }
-
-        num_rels_copied += 1;
    }

    // Copy relfilemap
    // TODO This implementation is very inefficient -
    // it scans all non-rels only to find FileNodeMaps
    for tag in timeline.list_nonrels(req_lsn)? {
-        match tag {
-            RelishTag::FileNodeMap { spcnode, dbnode } => {
-                if spcnode == src_tablespace_id && dbnode == src_db_id {
-                    let img = timeline.get_page_at_lsn_nowait(tag, 0, req_lsn)?;
-                    let new_tag = RelishTag::FileNodeMap {
-                        spcnode: tablespace_id,
-                        dbnode: db_id,
-                    };
-                    timeline.put_page_image(new_tag, 0, lsn, img)?;
-                    break;
-                }
+        if let RelishTag::FileNodeMap { spcnode, dbnode } = tag {
+            if spcnode == src_tablespace_id && dbnode == src_db_id {
+                let img = timeline.get_page_at_lsn(tag, 0, req_lsn)?;
+                let new_tag = RelishTag::FileNodeMap {
+                    spcnode: tablespace_id,
+                    dbnode: db_id,
+                };
+                timeline.put_page_image(new_tag, 0, lsn, img)?;
+                break;
            }
-            _ => {} // do nothing
        }
    }
    info!(
@@ -733,7 +668,7 @@ fn save_xact_record(
                dbnode: xnode.dbnode,
                relnode: xnode.relnode,
            };
-            timeline.put_unlink(RelishTag::Relation(rel), lsn)?;
+            timeline.drop_relish(RelishTag::Relation(rel), lsn)?;
        }
    }
    Ok(())
@@ -775,7 +710,7 @@ fn save_clog_truncate_record(
        return Ok(());
    }

-    // Iterate via SLRU CLOG segments and unlink segments that we're ready to truncate
+    // Iterate via SLRU CLOG segments and drop segments that we're ready to truncate
    // TODO This implementation is very inefficient -
    // it scans all non-rels only to find Clog
    //
@@ -785,17 +720,14 @@ fn save_clog_truncate_record(
    // instead.
    let req_lsn = min(timeline.get_last_record_lsn(), lsn);
    for obj in timeline.list_nonrels(req_lsn)? {
-        match obj {
-            RelishTag::Slru { slru, segno } => {
-                if slru == SlruKind::Clog {
-                    let segpage = segno * pg_constants::SLRU_PAGES_PER_SEGMENT;
-                    if slru_may_delete_clogsegment(segpage, xlrec.pageno) {
-                        timeline.put_unlink(RelishTag::Slru { slru, segno }, lsn)?;
-                        trace!("unlink CLOG segment {:>04X} at lsn {}", segno, lsn);
-                    }
+        if let RelishTag::Slru { slru, segno } = obj {
+            if slru == SlruKind::Clog {
+                let segpage = segno * pg_constants::SLRU_PAGES_PER_SEGMENT;
+                if slru_may_delete_clogsegment(segpage, xlrec.pageno) {
+                    timeline.drop_relish(RelishTag::Slru { slru, segno }, lsn)?;
+                    trace!("Drop CLOG segment {:>04X} at lsn {}", segno, lsn);
                }
            }
-            _ => {}
        }
    }

@@ -894,7 +826,7 @@ fn save_multixact_truncate_record(
    // Delete all the segments except the last one. The last segment can still
    // contain, possibly partially, valid data.
    while segment != endsegment {
-        timeline.put_unlink(
+        timeline.drop_relish(
            RelishTag::Slru {
                slru: SlruKind::MultiXactMembers,
                segno: segment as u32,
--- a/pageserver/src/tenant_mgr.rs
+++ b/pageserver/src/tenant_mgr.rs
@@ -3,17 +3,17 @@

 use crate::branches;
 use crate::layered_repository::LayeredRepository;
-use crate::repository::Repository;
+use crate::repository::{Repository, Timeline};
 use crate::walredo::PostgresRedoManager;
 use crate::PageServerConf;
-use anyhow::{anyhow, bail, Result};
+use anyhow::{anyhow, bail, Context, Result};
 use lazy_static::lazy_static;
 use log::info;
 use std::collections::HashMap;
 use std::fs;
 use std::str::FromStr;
 use std::sync::{Arc, Mutex};
-use zenith_utils::zid::ZTenantId;
+use zenith_utils::zid::{ZTenantId, ZTimelineId};

 lazy_static! {
    pub static ref REPOSITORY: Mutex<HashMap<ZTenantId, Arc<dyn Repository>>> =
@@ -37,6 +37,7 @@ pub fn init(conf: &'static PageServerConf) {
            tenantid,
        ));
        LayeredRepository::launch_checkpointer_thread(conf, repo.clone());
+        LayeredRepository::launch_gc_thread(conf, repo.clone());

        info!("initialized storage for tenant: {}", &tenantid);
        m.insert(tenantid, repo);
@@ -66,9 +67,18 @@ pub fn insert_repository_for_tenant(tenantid: ZTenantId, repo: Arc<dyn Repositor
    o.insert(tenantid, repo);
 }

-pub fn get_repository_for_tenant(tenantid: &ZTenantId) -> Result<Arc<dyn Repository>> {
+pub fn get_repository_for_tenant(tenantid: ZTenantId) -> Result<Arc<dyn Repository>> {
    let o = &REPOSITORY.lock().unwrap();
-    o.get(tenantid)
+    o.get(&tenantid)
        .map(|repo| Arc::clone(repo))
        .ok_or_else(|| anyhow!("repository not found for tenant name {}", tenantid))
 }
+
+pub fn get_timeline_for_tenant(
+    tenantid: ZTenantId,
+    timelineid: ZTimelineId,
+) -> Result<Arc<dyn Timeline>> {
+    get_repository_for_tenant(tenantid)?
+        .get_timeline(timelineid)
+        .with_context(|| format!("cannot fetch timeline {}", timelineid))
+}
--- a/pageserver/src/waldecoder.rs
+++ b/pageserver/src/waldecoder.rs
@@ -54,6 +54,11 @@ impl WalStreamDecoder {
        }
    }

+    // The latest LSN position fed to the decoder.
+    pub fn available(&self) -> Lsn {
+        self.lsn + self.inputbuf.remaining() as u64
+    }
+
    pub fn feed_bytes(&mut self, buf: &[u8]) {
        self.inputbuf.extend_from_slice(buf);
    }
@@ -159,17 +164,10 @@ impl WalStreamDecoder {
                    let recordbuf = recordbuf.freeze();
                    let mut buf = recordbuf.clone();

+                    let xlogrec = XLogRecord::from_bytes(&mut buf);
+
                    // XLOG_SWITCH records are special. If we see one, we need to skip
                    // to the next WAL segment.
-                    let xlogrec = XLogRecord::from_bytes(&mut buf);
-                    let mut crc = crc32c_append(0, &recordbuf[XLOG_RECORD_CRC_OFFS + 4..]);
-                    crc = crc32c_append(crc, &recordbuf[0..XLOG_RECORD_CRC_OFFS]);
-                    if crc != xlogrec.xl_crc {
-                        return Err(WalDecodeError {
-                            msg: "WAL record crc mismatch".into(),
-                            lsn: self.lsn,
-                        });
-                    }
                    if xlogrec.is_xlog_switch_record() {
                        trace!("saw xlog switch record at {}", self.lsn);
                        self.padlen =
@@ -179,6 +177,15 @@ impl WalStreamDecoder {
                        self.padlen = self.lsn.calc_padding(8u32) as u32;
                    }

+                    let mut crc = crc32c_append(0, &recordbuf[XLOG_RECORD_CRC_OFFS + 4..]);
+                    crc = crc32c_append(crc, &recordbuf[0..XLOG_RECORD_CRC_OFFS]);
+                    if crc != xlogrec.xl_crc {
+                        return Err(WalDecodeError {
+                            msg: "WAL record crc mismatch".into(),
+                            lsn: self.lsn,
+                        });
+                    }
+
                    // Always align resulting LSN on 0x8 boundary -- that is important for getPage()
                    // and WalReceiver integration. Since this code is used both for WalReceiver and
                    // initial WAL import let's force alignment right here.
@@ -197,6 +204,7 @@ impl WalStreamDecoder {
 }

 #[allow(dead_code)]
+#[derive(Default)]
 pub struct DecodedBkpBlock {
    /* Is this block ref in use? */
    //in_use: bool,
@@ -229,25 +237,7 @@ pub struct DecodedBkpBlock {

 impl DecodedBkpBlock {
    pub fn new() -> DecodedBkpBlock {
-        DecodedBkpBlock {
-            rnode_spcnode: 0,
-            rnode_dbnode: 0,
-            rnode_relnode: 0,
-            forknum: 0,
-            blkno: 0,
-
-            flags: 0,
-            has_image: false,
-            apply_image: false,
-            will_init: false,
-            hole_offset: 0,
-            hole_length: 0,
-            bimg_len: 0,
-            bimg_info: 0,
-
-            has_data: false,
-            data_len: 0,
-        }
+        Default::default()
    }
 }

--- a/pageserver/src/walreceiver.rs
+++ b/pageserver/src/walreceiver.rs
@@ -23,8 +23,6 @@ use postgres_types::PgLsn;
 use std::cmp::{max, min};
 use std::collections::HashMap;
 use std::fs;
-use std::fs::{File, OpenOptions};
-use std::io::{Seek, SeekFrom, Write};
 use std::str::FromStr;
 use std::sync::Mutex;
 use std::thread;
@@ -66,10 +64,13 @@ pub fn launch_wal_receiver(
            receivers.insert(timelineid, receiver);

            // Also launch a new thread to handle this connection
+            //
+            // NOTE: This thread name is checked in the assertion in wait_lsn. If you change
+            // this, make sure you update the assertion too.
            let _walreceiver_thread = thread::Builder::new()
                .name("WAL receiver thread".into())
                .spawn(move || {
-                    thread_main(conf, timelineid, &tenantid);
+                    thread_main(conf, timelineid, tenantid);
                })
                .unwrap();
        }
@@ -90,7 +91,7 @@ fn get_wal_producer_connstr(timelineid: ZTimelineId) -> String {
 //
 // This is the entry point for the WAL receiver thread.
 //
-fn thread_main(conf: &'static PageServerConf, timelineid: ZTimelineId, tenantid: &ZTenantId) {
+fn thread_main(conf: &'static PageServerConf, timelineid: ZTimelineId, tenantid: ZTenantId) {
    info!(
        "WAL receiver thread started for timeline : '{}'",
        timelineid
@@ -120,7 +121,7 @@ fn walreceiver_main(
    conf: &PageServerConf,
    timelineid: ZTimelineId,
    wal_producer_connstr: &str,
-    tenantid: &ZTenantId,
+    tenantid: ZTenantId,
 ) -> Result<(), Error> {
    // Connect to the database in replication mode.
    info!("connecting to {:?}", wal_producer_connstr);
@@ -146,8 +147,7 @@ fn walreceiver_main(
    let end_of_wal = Lsn::from(u64::from(identify.xlogpos));
    let mut caught_up = false;

-    let repository = tenant_mgr::get_repository_for_tenant(tenantid)?;
-    let timeline = repository.get_timeline(timelineid).unwrap();
+    let timeline = tenant_mgr::get_timeline_for_tenant(tenantid, timelineid)?;

    //
    // Start streaming the WAL, from where we left off previously.
@@ -164,7 +164,7 @@ fn walreceiver_main(
    // There might be some padding after the last full record, skip it.
    startpoint += startpoint.calc_padding(8u32);

-    debug!(
+    info!(
        "last_record_lsn {} starting replication from {} for timeline {}, server is at {}...",
        last_rec_lsn, startpoint, timelineid, end_of_wal
    );
@@ -176,7 +176,7 @@ fn walreceiver_main(

    let mut waldecoder = WalStreamDecoder::new(startpoint);

-    let checkpoint_bytes = timeline.get_page_at_lsn_nowait(RelishTag::Checkpoint, 0, startpoint)?;
+    let checkpoint_bytes = timeline.get_page_at_lsn(RelishTag::Checkpoint, 0, startpoint)?;
    let mut checkpoint = CheckPoint::decode(&checkpoint_bytes)?;
    trace!("CheckPoint.nextXid = {}", checkpoint.nextXid.value);

@@ -190,15 +190,6 @@ fn walreceiver_main(
                let endlsn = startlsn + data.len() as u64;
                let prev_last_rec_lsn = last_rec_lsn;

-                write_wal_file(
-                    conf,
-                    startlsn,
-                    &timelineid,
-                    pg_constants::WAL_SEGMENT_SIZE,
-                    data,
-                    tenantid,
-                )?;
-
                trace!("received XLogData between {} and {}", startlsn, endlsn);

                waldecoder.feed_bytes(data);
@@ -220,7 +211,6 @@ fn walreceiver_main(
                        recdata,
                        lsn,
                    )?;
-                    last_rec_lsn = lsn;

                    let new_checkpoint_bytes = checkpoint.encode();
                    // Check if checkpoint data was updated by save_decoded_record
@@ -232,6 +222,11 @@ fn walreceiver_main(
                            new_checkpoint_bytes,
                        )?;
                    }
+
+                    // Now that this record has been fully handled, including updating the
+                    // checkpoint data, let the repository know that it is up-to-date to this LSN
+                    timeline.advance_last_record_lsn(lsn);
+                    last_rec_lsn = lsn;
                }

                // Somewhat arbitrarily, if we have at least 10 complete wal segments (16 MB each),
@@ -253,7 +248,7 @@ fn walreceiver_main(
                        &timelineid,
                        pg_constants::WAL_SEGMENT_SIZE,
                        last_rec_lsn,
-                        tenantid,
+                        &tenantid,
                    )?;

                    if newest_segno - oldest_segno >= 10 {
@@ -354,6 +349,9 @@ fn find_wal_file_range(
 ///
 /// [postgres docs]: https://www.postgresql.org/docs/current/protocol-replication.html
 #[derive(Debug)]
+// As of nightly 2021-09-11, fields that are only read by the type's `Debug` impl still count as
+// unused. Relevant issue: https://github.com/rust-lang/rust/issues/88900
+#[allow(dead_code)]
 pub struct IdentifySystem {
    systemid: u64,
    timeline: u32,
@@ -394,98 +392,3 @@ pub fn identify_system(client: &mut Client) -> Result<IdentifySystem, Error> {
        Err(IdentifyError.into())
    }
 }
-
-fn write_wal_file(
-    conf: &PageServerConf,
-    startpos: Lsn,
-    timelineid: &ZTimelineId,
-    wal_seg_size: usize,
-    buf: &[u8],
-    tenantid: &ZTenantId,
-) -> anyhow::Result<()> {
-    let mut bytes_left: usize = buf.len();
-    let mut bytes_written: usize = 0;
-    let mut partial;
-    let mut start_pos = startpos;
-    const ZERO_BLOCK: &[u8] = &[0u8; XLOG_BLCKSZ];
-
-    let wal_dir = conf.wal_dir_path(timelineid, tenantid);
-
-    /* Extract WAL location for this block */
-    let mut xlogoff = start_pos.segment_offset(wal_seg_size);
-
-    while bytes_left != 0 {
-        let bytes_to_write;
-
-        /*
-         * If crossing a WAL boundary, only write up until we reach wal
-         * segment size.
-         */
-        if xlogoff + bytes_left > wal_seg_size {
-            bytes_to_write = wal_seg_size - xlogoff;
-        } else {
-            bytes_to_write = bytes_left;
-        }
-
-        /* Open file */
-        let segno = start_pos.segment_number(wal_seg_size);
-        let wal_file_name = XLogFileName(
-            1, // FIXME: always use Postgres timeline 1
-            segno,
-            wal_seg_size,
-        );
-        let wal_file_path = wal_dir.join(wal_file_name.clone());
-        let wal_file_partial_path = wal_dir.join(wal_file_name.clone() + ".partial");
-
-        {
-            let mut wal_file: File;
-            /* Try to open already completed segment */
-            if let Ok(file) = OpenOptions::new().write(true).open(&wal_file_path) {
-                wal_file = file;
-                partial = false;
-            } else if let Ok(file) = OpenOptions::new().write(true).open(&wal_file_partial_path) {
-                /* Try to open existed partial file */
-                wal_file = file;
-                partial = true;
-            } else {
-                /* Create and fill new partial file */
-                partial = true;
-                match OpenOptions::new()
-                    .create(true)
-                    .write(true)
-                    .open(&wal_file_partial_path)
-                {
-                    Ok(mut file) => {
-                        for _ in 0..(wal_seg_size / XLOG_BLCKSZ) {
-                            file.write_all(&ZERO_BLOCK)?;
-                        }
-                        wal_file = file;
-                    }
-                    Err(e) => {
-                        error!("Failed to open log file {:?}: {}", &wal_file_path, e);
-                        return Err(e.into());
-                    }
-                }
-            }
-            wal_file.seek(SeekFrom::Start(xlogoff as u64))?;
-            wal_file.write_all(&buf[bytes_written..(bytes_written + bytes_to_write)])?;
-
-            // FIXME: Flush the file
-            //wal_file.sync_all()?;
-        }
-        /* Write was successful, advance our position */
-        bytes_written += bytes_to_write;
-        bytes_left -= bytes_to_write;
-        start_pos += bytes_to_write as u64;
-        xlogoff += bytes_to_write;
-
-        /* Did we reach the end of a WAL segment? */
-        if start_pos.segment_offset(wal_seg_size) == 0 {
-            xlogoff = 0;
-            if partial {
-                fs::rename(&wal_file_partial_path, &wal_file_path)?;
-            }
-        }
-    }
-    Ok(())
-}
--- a/pageserver/src/walredo.rs
+++ b/pageserver/src/walredo.rs
@@ -209,7 +209,7 @@ impl WalRedoManager for PostgresRedoManager {
            let process = (*process_guard).as_ref().unwrap();

            self.runtime
-                .block_on(self.handle_apply_request(&process, &request))
+                .block_on(self.handle_apply_request(process, &request))
        };
        end_time = Instant::now();

@@ -324,7 +324,7 @@ impl PostgresRedoManager {
                            if rec_segno == segno && blknum == rpageno {
                                transaction_id_set_status(
                                    *subxact,
-                                    pg_constants::TRANSACTION_STATUS_SUB_COMMITTED,
+                                    pg_constants::TRANSACTION_STATUS_COMMITTED,
                                    &mut page,
                                );
                            }
@@ -453,7 +453,7 @@ impl PostgresRedoProcess {
        // FIXME: We need a dummy Postgres cluster to run the process in. Currently, we
        // just create one with constant name. That fails if you try to launch more than
        // one WAL redo manager concurrently.
-        let datadir = conf.tenant_path(&tenantid).join("wal-redo-datadir");
+        let datadir = conf.tenant_path(tenantid).join("wal-redo-datadir");

        // Create empty data directory for wal-redo postgres, deleting old one first.
        if datadir.exists() {
--- a/postgres_ffi/src/controlfile_utils.rs
+++ b/postgres_ffi/src/controlfile_utils.rs
@@ -11,7 +11,7 @@
 //! data directory is compatible with a postgres binary. That includes
 //! a version number, configuration options that can be set at
 //! compilation time like the block size, and the platform's alignment
-//! and endianess information. (The PostgreSQL on-disk file format is
+//! and endianness information. (The PostgreSQL on-disk file format is
 //! not portable across platforms.)
 //!
 //! The control file is stored in the PostgreSQL data directory, as
@@ -58,7 +58,7 @@ impl ControlFileData {
        let expectedcrc = crc32c::crc32c(&buf[0..OFFSETOF_CRC]);

        // Use serde to deserialize the input as a ControlFileData struct.
-        let controlfile = ControlFileData::des(buf)?;
+        let controlfile = ControlFileData::des_prefix(buf)?;

        // Check the CRC
        if expectedcrc != controlfile.crc {
--- a/postgres_ffi/src/lib.rs
+++ b/postgres_ffi/src/lib.rs
@@ -32,5 +32,5 @@ pub const fn transaction_id_precedes(id1: TransactionId, id2: TransactionId) ->
    }

    let diff = id1.wrapping_sub(id2) as i32;
-    return diff < 0;
+    diff < 0
 }
--- a/postgres_ffi/src/pg_constants.rs
+++ b/postgres_ffi/src/pg_constants.rs
@@ -189,11 +189,11 @@ pub const XLOG_CHECKPOINT_SHUTDOWN: u8 = 0x00;
 pub const XLOG_CHECKPOINT_ONLINE: u8 = 0x10;
 pub const XLP_LONG_HEADER: u16 = 0x0002;

-pub const PG_MAJORVERSION: &'static str = "14";
+pub const PG_MAJORVERSION: &str = "14";

 // List of subdirectories inside pgdata.
 // Copied from src/bin/initdb/initdb.c
-pub const PGDATA_SUBDIRS: [&'static str; 22] = [
+pub const PGDATA_SUBDIRS: [&str; 22] = [
    "global",
    "pg_wal/archive_status",
    "pg_commit_ts",
@@ -218,11 +218,11 @@ pub const PGDATA_SUBDIRS: [&'static str; 22] = [
    "pg_logical/mappings",
 ];

-pub const PGDATA_SPECIAL_FILES: [&'static str; 4] = [
-    "pg_hba.conf",
-    "pg_ident.conf",
-    "postgresql.conf",
-    "postgresql.auto.conf",
-];
+// Don't include postgresql.conf as it is inconvenient on node start:
+// we need postgresql.conf before basebackup to synchronize safekeepers
+// so no point in overwriting it during backup restore. Rest of the files
+// here are not needed before backup so it is okay to edit them after.
+pub const PGDATA_SPECIAL_FILES: [&str; 3] =
+    ["pg_hba.conf", "pg_ident.conf", "postgresql.auto.conf"];

-pub static PG_HBA: &'static str = include_str!("../samples/pg_hba.conf");
+pub static PG_HBA: &str = include_str!("../samples/pg_hba.conf");
--- a/postgres_ffi/src/xlog_utils.rs
+++ b/postgres_ffi/src/xlog_utils.rs
@@ -16,16 +16,20 @@ use crate::XLogPageHeaderData;
 use crate::XLogRecord;
 use crate::XLOG_PAGE_MAGIC;

+use anyhow::{bail, Result};
 use byteorder::{ByteOrder, LittleEndian};
 use bytes::{Buf, Bytes};
 use bytes::{BufMut, BytesMut};
 use crc32c::*;
 use log::*;
+use std::cmp::max;
 use std::cmp::min;
 use std::fs::{self, File};
 use std::io::prelude::*;
+use std::io::SeekFrom;
 use std::path::{Path, PathBuf};
 use std::time::SystemTime;
+use zenith_utils::lsn::Lsn;

 pub const XLOG_FNAME_LEN: usize = 24;
 pub const XLOG_BLCKSZ: usize = 8192;
@@ -37,6 +41,7 @@ pub const MAX_SEND_SIZE: usize = XLOG_BLCKSZ * 16;
 pub const XLOG_SIZE_OF_XLOG_SHORT_PHD: usize = std::mem::size_of::<XLogPageHeaderData>();
 pub const XLOG_SIZE_OF_XLOG_LONG_PHD: usize = std::mem::size_of::<XLogLongPageHeaderData>();
 pub const XLOG_SIZE_OF_XLOG_RECORD: usize = std::mem::size_of::<XLogRecord>();
+#[allow(clippy::identity_op)]
 pub const SIZE_OF_XLOG_RECORD_DATA_HEADER_SHORT: usize = 1 * 2;

 pub type XLogRecPtr = u64;
@@ -88,6 +93,21 @@ pub fn IsPartialXLogFileName(fname: &str) -> bool {
    fname.ends_with(".partial") && IsXLogFileName(&fname[0..fname.len() - 8])
 }

+/// If LSN points to the beginning of the page, then shift it to first record,
+/// otherwise align on 8-bytes boundary (required for WAL records)
+pub fn normalize_lsn(lsn: Lsn, seg_sz: usize) -> Lsn {
+    if lsn.0 % XLOG_BLCKSZ as u64 == 0 {
+        let hdr_size = if lsn.0 % seg_sz as u64 == 0 {
+            XLOG_SIZE_OF_XLOG_LONG_PHD
+        } else {
+            XLOG_SIZE_OF_XLOG_SHORT_PHD
+        };
+        lsn + hdr_size as u64
+    } else {
+        lsn.align()
+    }
+}
+
 pub fn get_current_timestamp() -> TimestampTz {
    const UNIX_EPOCH_JDATE: u64 = 2440588; /* == date2j(1970, 1, 1) */
    const POSTGRES_EPOCH_JDATE: u64 = 2451545; /* == date2j(2000, 1, 1) */
@@ -108,8 +128,10 @@ fn find_end_of_wal_segment(
    segno: XLogSegNo,
    tli: TimeLineID,
    wal_seg_size: usize,
-) -> u32 {
-    let mut offs: usize = 0;
+    start_offset: usize, // start reading at this point
+) -> Result<u32> {
+    // step back to the beginning of the page to read it in...
+    let mut offs: usize = start_offset - start_offset % XLOG_BLCKSZ;
    let mut contlen: usize = 0;
    let mut wal_crc: u32 = 0;
    let mut crc: u32 = 0;
@@ -118,24 +140,33 @@ fn find_end_of_wal_segment(
    let file_name = XLogFileName(tli, segno, wal_seg_size);
    let mut last_valid_rec_pos: usize = 0;
    let mut file = File::open(data_dir.join(file_name.clone() + ".partial")).unwrap();
+    file.seek(SeekFrom::Start(offs as u64))?;
    let mut rec_hdr = [0u8; XLOG_RECORD_CRC_OFFS];

    while offs < wal_seg_size {
        // we are at the beginning of the page; read it in
        if offs % XLOG_BLCKSZ == 0 {
-            if let Ok(bytes_read) = file.read(&mut buf) {
-                if bytes_read != buf.len() {
-                    break;
-                }
-            } else {
-                break;
+            let bytes_read = file.read(&mut buf)?;
+            if bytes_read != buf.len() {
+                bail!(
+                    "failed to read {} bytes from {} at {}",
+                    XLOG_BLCKSZ,
+                    file_name,
+                    offs
+                );
            }
+
            let xlp_magic = LittleEndian::read_u16(&buf[0..2]);
            let xlp_info = LittleEndian::read_u16(&buf[2..4]);
            let xlp_rem_len = LittleEndian::read_u32(&buf[XLP_REM_LEN_OFFS..XLP_REM_LEN_OFFS + 4]);
+            // this is expected in current usage when valid WAL starts after page header
            if xlp_magic != XLOG_PAGE_MAGIC as u16 {
-                info!("Invalid WAL file {}.partial magic {}", file_name, xlp_magic);
-                break;
+                trace!(
+                    "invalid WAL file {}.partial magic {} at {:?}",
+                    file_name,
+                    xlp_magic,
+                    Lsn(XLogSegNoOffsetToRecPtr(segno, offs as u32, wal_seg_size)),
+                );
            }
            if offs == 0 {
                offs = XLOG_SIZE_OF_XLOG_LONG_PHD;
@@ -145,11 +176,18 @@ fn find_end_of_wal_segment(
            } else {
                offs += XLOG_SIZE_OF_XLOG_SHORT_PHD;
            }
+            // ... and step forward again if asked
+            offs = max(offs, start_offset);
+
        // beginning of the next record
        } else if contlen == 0 {
            let page_offs = offs % XLOG_BLCKSZ;
            let xl_tot_len = LittleEndian::read_u32(&buf[page_offs..page_offs + 4]) as usize;
            if xl_tot_len == 0 {
+                info!(
+                    "find_end_of_wal_segment reached zeros at {:?}",
+                    Lsn(XLogSegNoOffsetToRecPtr(segno, offs as u32, wal_seg_size))
+                );
                break; // zeros, reached the end
            }
            last_valid_rec_pos = offs;
@@ -173,12 +211,11 @@ fn find_end_of_wal_segment(
                let crc_offs = page_offs - rec_offs + XLOG_RECORD_CRC_OFFS;
                wal_crc = LittleEndian::read_u32(&buf[crc_offs..crc_offs + 4]);
                crc = crc32c_append(0, &buf[crc_offs + 4..page_offs + n]);
-                crc = !crc;
            } else {
                crc ^= 0xFFFFFFFFu32;
                crc = crc32c_append(crc, &buf[page_offs..page_offs + n]);
-                crc = !crc;
            }
+            crc = !crc;
            rec_offs += n;
            offs += n;
            contlen -= n;
@@ -201,7 +238,7 @@ fn find_end_of_wal_segment(
            }
        }
    }
-    last_valid_rec_pos as u32
+    Ok(last_valid_rec_pos as u32)
 }

 ///
@@ -214,7 +251,8 @@ pub fn find_end_of_wal(
    data_dir: &Path,
    wal_seg_size: usize,
    precise: bool,
-) -> (XLogRecPtr, TimeLineID) {
+    start_lsn: Lsn, // start reading WAL at this point or later
+) -> Result<(XLogRecPtr, TimeLineID)> {
    let mut high_segno: XLogSegNo = 0;
    let mut high_tli: TimeLineID = 0;
    let mut high_ispartial = false;
@@ -256,19 +294,32 @@ pub fn find_end_of_wal(
            high_segno += 1;
        } else if precise {
            /* otherwise locate last record in last partial segment */
-            high_offs = find_end_of_wal_segment(data_dir, high_segno, high_tli, wal_seg_size);
+            if start_lsn.segment_number(wal_seg_size) > high_segno {
+                bail!(
+                    "provided start_lsn {:?} is beyond highest segno {:?} available",
+                    start_lsn,
+                    high_segno,
+                );
+            }
+            high_offs = find_end_of_wal_segment(
+                data_dir,
+                high_segno,
+                high_tli,
+                wal_seg_size,
+                start_lsn.segment_offset(wal_seg_size),
+            )?;
        }
        let high_ptr = XLogSegNoOffsetToRecPtr(high_segno, high_offs, wal_seg_size);
-        return (high_ptr, high_tli);
+        return Ok((high_ptr, high_tli));
    }
-    (0, 0)
+    Ok((0, 0))
 }

 pub fn main() {
    let mut data_dir = PathBuf::new();
    data_dir.push(".");
    let wal_seg_size = 16 * 1024 * 1024;
-    let (wal_end, tli) = find_end_of_wal(&data_dir, wal_seg_size, true);
+    let (wal_end, tli) = find_end_of_wal(&data_dir, wal_seg_size, true, Lsn(0)).unwrap();
    println!(
        "wal_end={:>08X}{:>08X}, tli={}",
        (wal_end >> 32) as u32,
@@ -416,7 +467,6 @@ mod tests {
    use super::*;
    use regex::Regex;
    use std::{env, process::Command, str::FromStr};
-    use zenith_utils::lsn::Lsn;

    // Run find_end_of_wal against file in test_wal dir
    // Ensure that it finds last record correctly
@@ -448,7 +498,7 @@ mod tests {
        let wal_seg_size = 16 * 1024 * 1024;

        // 3. Check end_of_wal on non-partial WAL segment (we treat it as fully populated)
-        let (wal_end, tli) = find_end_of_wal(&wal_dir, wal_seg_size, true);
+        let (wal_end, tli) = find_end_of_wal(&wal_dir, wal_seg_size, true, Lsn(0)).unwrap();
        let wal_end = Lsn(wal_end);
        println!("wal_end={}, tli={}", wal_end, tli);
        assert_eq!(wal_end, "0/2000000".parse::<Lsn>().unwrap());
@@ -465,7 +515,7 @@ mod tests {
        let waldump_output = std::str::from_utf8(&waldump_output.stderr).unwrap();
        println!("waldump_output = '{}'", &waldump_output);
        let re = Regex::new(r"invalid record length at (.+):").unwrap();
-        let caps = re.captures(&waldump_output).unwrap();
+        let caps = re.captures(waldump_output).unwrap();
        let waldump_wal_end = Lsn::from_str(caps.get(1).unwrap().as_str()).unwrap();

        // 5. Rename file to partial to actually find last valid lsn
@@ -474,7 +524,7 @@ mod tests {
            wal_dir.join("000000010000000000000001.partial"),
        )
        .unwrap();
-        let (wal_end, tli) = find_end_of_wal(&wal_dir, wal_seg_size, true);
+        let (wal_end, tli) = find_end_of_wal(&wal_dir, wal_seg_size, true, Lsn(0)).unwrap();
        let wal_end = Lsn(wal_end);
        println!("wal_end={}, tli={}", wal_end, tli);
        assert_eq!(wal_end, waldump_wal_end);
--- a/proxy/Cargo.toml
+++ b/proxy/Cargo.toml
@@ -14,8 +14,8 @@ rand = "0.8.3"
 hex = "0.4.3"
 serde = "1"
 serde_json = "1"
-tokio = { version = "1.7.1", features = ["full"] }
-tokio-postgres = "0.7.2"
+tokio = "1.11"
+tokio-postgres = { git = "https://github.com/zenithdb/rust-postgres.git", rev="9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858" }
 clap = "2.33.0"
 rustls = "0.19.1"

--- a/proxy/src/cplane_api.rs
+++ b/proxy/src/cplane_api.rs
@@ -56,7 +56,7 @@ impl CPlaneApi {
            md5::compute([stored_hash.as_bytes(), salt].concat())
        );

-        let received_hash = std::str::from_utf8(&md5_response)?;
+        let received_hash = std::str::from_utf8(md5_response)?;

        println!(
            "auth: {} rh={} sh={} ssh={} {:?}",
--- a/proxy/src/main.rs
+++ b/proxy/src/main.rs
@@ -143,10 +143,10 @@ fn main() -> anyhow::Result<()> {
        // for each connection.
        thread::Builder::new()
            .name("Proxy thread".into())
-            .spawn(move || proxy::thread_main(&state, pageserver_listener))?,
+            .spawn(move || proxy::thread_main(state, pageserver_listener))?,
        thread::Builder::new()
            .name("Mgmt thread".into())
-            .spawn(move || mgmt::thread_main(&state, mgmt_listener))?,
+            .spawn(move || mgmt::thread_main(state, mgmt_listener))?,
    ];

    for t in threads.into_iter() {
--- a/run_clippy.sh
+++ b/run_clippy.sh
@@ -8,4 +8,8 @@
 # warnings and errors right in the editor.
 # In vscode, this setting is Rust-analyzer>Check On Save:Command

-cargo clippy "${@:2}" -- -A clippy::new_without_default -A clippy::manual_range_contains -A clippy::comparison_chain
+
+# * `-A unknown_lints` – do not warn about unknown lint suppressions
+#                        that people with newer toolchains might use
+# * `-D warnings`      - fail on any warnings (`cargo` returns non-zero exit status)
+cargo clippy "${@:2}" --all-targets --all-features --all --tests -- -A unknown_lints -D warnings
--- a/test_runner/Pipfile
+++ b/test_runner/Pipfile
@@ -9,6 +9,8 @@ psycopg2 = "*"
 typing-extensions = "*"
 pyjwt = {extras = ["crypto"], version = "*"}
 requests = "*"
+pytest-xdist = "*"
+asyncpg = "*"

 [dev-packages]
 yapf = "*"
--- a/test_runner/Pipfile.lock
+++ b/test_runner/Pipfile.lock
@@ -1,7 +1,7 @@
 {
    "_meta": {
        "hash": {
-            "sha256": "b666740289d9c82797e5c39b2a7f0074c865c9183ee878ce4fa5cda7928506ea"
+            "sha256": "3cdc048691824d0b93912b6b78a0aa01dc98f278212c1badb0cc2edbd2103c3a"
        },
        "pipfile-spec": 6,
        "requires": {
@@ -16,6 +16,25 @@
        ]
    },
    "default": {
+        "asyncpg": {
+            "hashes": [
+                "sha256:129d501f3d30616afd51eb8d3142ef51ba05374256bd5834cec3ef4956a9b317",
+                "sha256:29ef6ae0a617fc13cc2ac5dc8e9b367bb83cba220614b437af9b67766f4b6b20",
+                "sha256:41704c561d354bef01353835a7846e5606faabbeb846214dfcf666cf53319f18",
+                "sha256:556b0e92e2b75dc028b3c4bc9bd5162ddf0053b856437cf1f04c97f9c6837d03",
+                "sha256:8ff5073d4b654e34bd5eaadc01dc4d68b8a9609084d835acd364cd934190a08d",
+                "sha256:a458fc69051fbb67d995fdda46d75a012b5d6200f91e17d23d4751482640ed4c",
+                "sha256:a7095890c96ba36f9f668eb552bb020dddb44f8e73e932f8573efc613ee83843",
+                "sha256:a738f4807c853623d3f93f0fea11f61be6b0e5ca16ea8aeb42c2c7ee742aa853",
+                "sha256:c4fc0205fe4ddd5aeb3dfdc0f7bafd43411181e1f5650189608e5971cceacff1",
+                "sha256:dd2fa063c3344823487d9ddccb40802f02622ddf8bf8a6cc53885ee7a2c1c0c6",
+                "sha256:ddffcb85227bf39cd1bedd4603e0082b243cf3b14ced64dce506a15b05232b83",
+                "sha256:e36c6806883786b19551bb70a4882561f31135dc8105a59662e0376cf5b2cbc5",
+                "sha256:eed43abc6ccf1dc02e0d0efc06ce46a411362f3358847c6b0ec9a43426f91ece"
+            ],
+            "index": "pypi",
+            "version": "==0.24.0"
+        },
        "attrs": {
            "hashes": [
                "sha256:149e90d6d8ac20db7a955ad60cf0e6881a3f20d37096140088356da6c716b0b1",
@@ -83,30 +102,43 @@
        },
        "charset-normalizer": {
            "hashes": [
-                "sha256:0c8911edd15d19223366a194a513099a302055a962bca2cec0f54b8b63175d8b",
-                "sha256:f23667ebe1084be45f6ae0538e4a5a865206544097e4e8bbcacf42cd02a348f3"
+                "sha256:5d209c0a931f215cee683b6445e2d77677e7e75e159f78def0db09d68fafcaa6",
+                "sha256:5ec46d183433dcbd0ab716f2d7f29d8dee50505b3fdb40c6b985c7c4f5a3591f"
            ],
            "markers": "python_version >= '3'",
-            "version": "==2.0.4"
+            "version": "==2.0.6"
        },
        "cryptography": {
            "hashes": [
-                "sha256:0f1212a66329c80d68aeeb39b8a16d54ef57071bf22ff4e521657b27372e327d",
-                "sha256:1e056c28420c072c5e3cb36e2b23ee55e260cb04eee08f702e0edfec3fb51959",
-                "sha256:240f5c21aef0b73f40bb9f78d2caff73186700bf1bc6b94285699aff98cc16c6",
-                "sha256:26965837447f9c82f1855e0bc8bc4fb910240b6e0d16a664bb722df3b5b06873",
-                "sha256:37340614f8a5d2fb9aeea67fd159bfe4f5f4ed535b1090ce8ec428b2f15a11f2",
-                "sha256:3d10de8116d25649631977cb37da6cbdd2d6fa0e0281d014a5b7d337255ca713",
-                "sha256:3d8427734c781ea5f1b41d6589c293089704d4759e34597dce91014ac125aad1",
-                "sha256:7ec5d3b029f5fa2b179325908b9cd93db28ab7b85bb6c1db56b10e0b54235177",
-                "sha256:8e56e16617872b0957d1c9742a3f94b43533447fd78321514abbe7db216aa250",
-                "sha256:b01fd6f2737816cb1e08ed4807ae194404790eac7ad030b34f2ce72b332f5586",
-                "sha256:bf40af59ca2465b24e54f671b2de2c59257ddc4f7e5706dbd6930e26823668d3",
-                "sha256:de4e5f7f68220d92b7637fc99847475b59154b7a1b3868fb7385337af54ac9ca",
-                "sha256:eb8cc2afe8b05acbd84a43905832ec78e7b3873fb124ca190f574dca7389a87d",
-                "sha256:ee77aa129f481be46f8d92a1a7db57269a2f23052d5f2433b4621bb457081cc9"
+                "sha256:0a7dcbcd3f1913f664aca35d47c1331fce738d44ec34b7be8b9d332151b0b01e",
+                "sha256:1eb7bb0df6f6f583dd8e054689def236255161ebbcf62b226454ab9ec663746b",
+                "sha256:21ca464b3a4b8d8e86ba0ee5045e103a1fcfac3b39319727bc0fc58c09c6aff7",
+                "sha256:34dae04a0dce5730d8eb7894eab617d8a70d0c97da76b905de9efb7128ad7085",
+                "sha256:3520667fda779eb788ea00080124875be18f2d8f0848ec00733c0ec3bb8219fc",
+                "sha256:3c4129fc3fdc0fa8e40861b5ac0c673315b3c902bbdc05fc176764815b43dd1d",
+                "sha256:3fa3a7ccf96e826affdf1a0a9432be74dc73423125c8f96a909e3835a5ef194a",
+                "sha256:5b0fbfae7ff7febdb74b574055c7466da334a5371f253732d7e2e7525d570498",
+                "sha256:695104a9223a7239d155d7627ad912953b540929ef97ae0c34c7b8bf30857e89",
+                "sha256:8695456444f277af73a4877db9fc979849cd3ee74c198d04fc0776ebc3db52b9",
+                "sha256:94cc5ed4ceaefcbe5bf38c8fba6a21fc1d365bb8fb826ea1688e3370b2e24a1c",
+                "sha256:94fff993ee9bc1b2440d3b7243d488c6a3d9724cc2b09cdb297f6a886d040ef7",
+                "sha256:9965c46c674ba8cc572bc09a03f4c649292ee73e1b683adb1ce81e82e9a6a0fb",
+                "sha256:a00cf305f07b26c351d8d4e1af84ad7501eca8a342dedf24a7acb0e7b7406e14",
+                "sha256:a305600e7a6b7b855cd798e00278161b681ad6e9b7eca94c721d5f588ab212af",
+                "sha256:cd65b60cfe004790c795cc35f272e41a3df4631e2fb6b35aa7ac6ef2859d554e",
+                "sha256:d2a6e5ef66503da51d2110edf6c403dc6b494cc0082f85db12f54e9c5d4c3ec5",
+                "sha256:d9ec0e67a14f9d1d48dd87a2531009a9b251c02ea42851c060b25c782516ff06",
+                "sha256:f44d141b8c4ea5eb4dbc9b3ad992d45580c1d22bf5e24363f2fbf50c2d7ae8a7"
            ],
-            "version": "==3.4.7"
+            "version": "==3.4.8"
+        },
+        "execnet": {
+            "hashes": [
+                "sha256:8f694f3ba9cc92cab508b152dcfe322153975c29bda272e2fd7f3f00f36e47c5",
+                "sha256:a295f7cc774947aac58dde7fdc85f4aa00c42adf5d8f5468fc630c1acf30a142"
+            ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'",
+            "version": "==1.9.0"
        },
        "idna": {
            "hashes": [
@@ -133,11 +165,11 @@
        },
        "pluggy": {
            "hashes": [
-                "sha256:15b2acde666561e1298d71b523007ed7364de07029219b604cf808bfa1c765b0",
-                "sha256:966c145cd83c96502c3c3868f50408687b38434af77734af1e9ca461a4081d2d"
+                "sha256:4224373bacce55f955a878bf9cfa763c1e360858e330072059e10bad68531159",
+                "sha256:74134bbf457f031a36d68416e1509f34bd5ccc019f0bcc952c7b909d06b37bd3"
            ],
-            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
-            "version": "==0.13.1"
+            "markers": "python_version >= '3.6'",
+            "version": "==1.0.0"
        },
        "psycopg2": {
            "hashes": [
@@ -191,11 +223,27 @@
        },
        "pytest": {
            "hashes": [
-                "sha256:50bcad0a0b9c5a72c8e4e7c9855a3ad496ca6a881a3641b4260605450772c54b",
-                "sha256:91ef2131a9bd6be8f76f1f08eac5c5317221d6ad1e143ae03894b862e8976890"
+                "sha256:131b36680866a76e6781d13f101efb86cf674ebb9762eb70d3082b6f29889e89",
+                "sha256:7310f8d27bc79ced999e760ca304d69f6ba6c6649c0b60fb0e04a4a77cacc134"
            ],
            "index": "pypi",
-            "version": "==6.2.4"
+            "version": "==6.2.5"
+        },
+        "pytest-forked": {
+            "hashes": [
+                "sha256:6aa9ac7e00ad1a539c41bec6d21011332de671e938c7637378ec9710204e37ca",
+                "sha256:dc4147784048e70ef5d437951728825a131b81714b398d5d52f17c7c144d8815"
+            ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'",
+            "version": "==1.3.0"
+        },
+        "pytest-xdist": {
+            "hashes": [
+                "sha256:7b61ebb46997a0820a263553179d6d1e25a8c50d8a8620cd1aa1e20e3be99168",
+                "sha256:89b330316f7fc475f999c81b577c2b926c9569f3d397ae432c0c2e2496d61ff9"
+            ],
+            "index": "pypi",
+            "version": "==2.4.0"
        },
        "requests": {
            "hashes": [
@@ -215,12 +263,12 @@
        },
        "typing-extensions": {
            "hashes": [
-                "sha256:0ac0f89795dd19de6b97debb0c6af1c70987fd80a2d62d1958f7e56fcc31b497",
-                "sha256:50b6f157849174217d0656f99dc82fe932884fb250826c18350e159ec6cdf342",
-                "sha256:779383f6086d90c99ae41cf0ff39aac8a7937a9283ce0a414e5dd782f4c94a84"
+                "sha256:49f75d16ff11f1cd258e1b988ccff82a3ca5570217d7ad8c5f48205dd99a677e",
+                "sha256:d8226d10bc02a29bcc81df19a26e56a9647f8b0a6d4a83924139f4a8b01f17b7",
+                "sha256:f1d25edafde516b146ecd0613dabcc61409817af4766fbbcfb8d1ad4ec441a34"
            ],
            "index": "pypi",
-            "version": "==3.10.0.0"
+            "version": "==3.10.0.2"
        },
        "urllib3": {
            "hashes": [
@@ -309,12 +357,12 @@
        },
        "typing-extensions": {
            "hashes": [
-                "sha256:0ac0f89795dd19de6b97debb0c6af1c70987fd80a2d62d1958f7e56fcc31b497",
-                "sha256:50b6f157849174217d0656f99dc82fe932884fb250826c18350e159ec6cdf342",
-                "sha256:779383f6086d90c99ae41cf0ff39aac8a7937a9283ce0a414e5dd782f4c94a84"
+                "sha256:49f75d16ff11f1cd258e1b988ccff82a3ca5570217d7ad8c5f48205dd99a677e",
+                "sha256:d8226d10bc02a29bcc81df19a26e56a9647f8b0a6d4a83924139f4a8b01f17b7",
+                "sha256:f1d25edafde516b146ecd0613dabcc61409817af4766fbbcfb8d1ad4ec441a34"
            ],
            "index": "pypi",
-            "version": "==3.10.0.0"
+            "version": "==3.10.0.2"
        },
        "yapf": {
            "hashes": [
--- a/test_runner/batch_others/test_auth.py
+++ b/test_runner/batch_others/test_auth.py
@@ -1,11 +1,15 @@

 from contextlib import closing
+from typing import Iterator
 from uuid import uuid4
 import psycopg2
-from fixtures.zenith_fixtures import Postgres, ZenithCli, ZenithPageserver, PgBin
+from fixtures.zenith_fixtures import PortDistributor, Postgres, ZenithCli, ZenithPageserver, PgBin
 import pytest


+pytest_plugins = ("fixtures.zenith_fixtures")
+
+
 def test_pageserver_auth(pageserver_auth_enabled: ZenithPageserver):
    ps = pageserver_auth_enabled

@@ -42,7 +46,8 @@ def test_compute_auth_to_pageserver(
    pageserver_auth_enabled: ZenithPageserver,
    repo_dir: str,
    with_wal_acceptors: bool,
-    pg_bin: PgBin
+    pg_bin: PgBin,
+    port_distributor: PortDistributor,
 ):
    ps = pageserver_auth_enabled
    # since we are in progress of refactoring protocols between compute safekeeper and page server
@@ -59,7 +64,7 @@ def test_compute_auth_to_pageserver(
        repo_dir=repo_dir,
        pg_bin=pg_bin,
        tenant_id=ps.initial_tenant,
-        port=55432, # FIXME port distribution is hardcoded in tests and in cli
+        port=port_distributor.get_port(),
    ).create_start(
        branch,
        wal_acceptors=wa_factory.get_connstrs() if with_wal_acceptors else None,
--- a/test_runner/batch_others/test_branch_behind.py
+++ b/test_runner/batch_others/test_branch_behind.py
@@ -1,3 +1,4 @@
+import subprocess
 from fixtures.zenith_fixtures import PostgresFactory, ZenithPageserver


@@ -74,3 +75,18 @@ def test_branch_behind(zenith_cli, pageserver: ZenithPageserver, postgres: Postg
    # All the rows are visible on the main branch
    main_cur.execute('SELECT count(*) FROM foo')
    assert main_cur.fetchone() == (200100, )
+
+    # Check bad lsn's for branching
+
+    # branch at segment boundary
+    zenith_cli.run(["branch", "test_branch_segment_boundary", "test_branch_behind@0/3000000"])
+    pg = postgres.create_start("test_branch_segment_boundary")
+    cur = pg.connect().cursor()
+    cur.execute('SELECT 1')
+    assert cur.fetchone() == (1, )
+
+    # branch at pre-initdb lsn
+    try:
+        zenith_cli.run(["branch", "test_branch_preinitdb", "test_branch_behind@0/42"])
+    except subprocess.CalledProcessError:
+        print("Branch creation with pre-initdb LSN failed (as expected)")
--- a/test_runner/batch_others/test_createdropdb.py
+++ b/test_runner/batch_others/test_createdropdb.py
@@ -2,7 +2,7 @@ import os
 import pathlib

 from contextlib import closing
-from fixtures.zenith_fixtures import ZenithPageserver, PostgresFactory, ZenithCli
+from fixtures.zenith_fixtures import ZenithPageserver, PostgresFactory, ZenithCli, check_restored_datadir_content

 pytest_plugins = ("fixtures.zenith_fixtures")

@@ -48,6 +48,7 @@ def test_dropdb(
    pageserver: ZenithPageserver,
    postgres: PostgresFactory,
    pg_bin,
+    test_output_dir
 ):
    zenith_cli.run(["branch", "test_dropdb", "empty"])

@@ -69,6 +70,8 @@ def test_dropdb(
        with conn.cursor() as cur:
            cur.execute('DROP DATABASE foodb')

+            cur.execute('CHECKPOINT')
+
            cur.execute('SELECT pg_current_wal_insert_lsn()')
            lsn_after_drop = cur.fetchone()[0]

@@ -94,3 +97,6 @@ def test_dropdb(
    print(dbpath)

    assert os.path.isdir(dbpath) == False
+
+    # Check that we restore the content of the datadir correctly
+    check_restored_datadir_content(zenith_cli, test_output_dir, pg, pageserver.service_port.pg)
--- a/test_runner/batch_others/test_multixact.py
+++ b/test_runner/batch_others/test_multixact.py
@@ -1,4 +1,4 @@
-from fixtures.zenith_fixtures import PostgresFactory, ZenithPageserver
+from fixtures.zenith_fixtures import PostgresFactory, ZenithPageserver, check_restored_datadir_content

 pytest_plugins = ("fixtures.zenith_fixtures")

@@ -9,7 +9,8 @@ pytest_plugins = ("fixtures.zenith_fixtures")
 # it only checks next_multixact_id field in restored pg_control,
 # since we don't have functions to check multixact internals.
 #
-def test_multixact(pageserver: ZenithPageserver, postgres: PostgresFactory, pg_bin, zenith_cli, base_dir):
+def test_multixact(pageserver: ZenithPageserver, postgres: PostgresFactory,
+                    pg_bin, zenith_cli, base_dir, test_output_dir):
    # Create a branch for us
    zenith_cli.run(["branch", "test_multixact", "empty"])
    pg = postgres.create_start('test_multixact')
@@ -63,3 +64,6 @@ def test_multixact(pageserver: ZenithPageserver, postgres: PostgresFactory, pg_b

    # Check that we restored pg_controlfile correctly
    assert next_multixact_id_new == next_multixact_id
+
+    # Check that we restore the content of the datadir correctly
+    check_restored_datadir_content(zenith_cli, test_output_dir, pg_new, pageserver.service_port.pg)
--- a/test_runner/batch_others/test_old_request_lsn.py
+++ b/test_runner/batch_others/test_old_request_lsn.py
@@ -0,0 +1,65 @@
+from contextlib import closing
+
+from fixtures.zenith_fixtures import PostgresFactory, ZenithPageserver
+
+pytest_plugins = ("fixtures.zenith_fixtures")
+
+#
+# Test where Postgres generates a lot of WAL, and it's garbage collected away, but
+# no pages are evicted so that Postgres uses an old LSN in a GetPage request.
+# We had a bug where the page server failed to find the page version because it
+# thought it was already garbage collected away, because the LSN in the GetPage
+# request was very old and the WAL from that time was indeed already removed.
+# In reality, the LSN on a GetPage request coming from a primary server is
+# just a hint that the page hasn't been modified since that LSN, and the page
+# server should return the latest page version regardless of the LSN.
+#
+def test_old_request_lsn(zenith_cli, pageserver: ZenithPageserver, postgres: PostgresFactory, pg_bin):
+    # Create a branch for us
+    zenith_cli.run(["branch", "test_old_request_lsn", "empty"])
+    pg = postgres.create_start('test_old_request_lsn')
+    print('postgres is running on test_old_request_lsn branch')
+
+    pg_conn = pg.connect()
+    cur = pg_conn.cursor()
+
+    # Get the timeline ID of our branch. We need it for the 'do_gc' command
+    cur.execute("SHOW zenith.zenith_timeline")
+    timeline = cur.fetchone()[0]
+
+    psconn = pageserver.connect()
+    pscur = psconn.cursor()
+
+    # Create table, and insert some rows. Make it big enough that it doesn't fit in
+    # shared_buffers.
+    cur.execute('CREATE TABLE foo (id int4 PRIMARY KEY, val int, t text)')
+    cur.execute('''
+        INSERT INTO foo
+            SELECT g, 1, 'long string to consume some space' || g
+            FROM generate_series(1, 100000) g
+    ''')
+
+    # Verify that the table is larger than shared_buffers, so that the SELECT below
+    # will cause GetPage requests.
+    cur.execute('''
+        select setting::int * pg_size_bytes(unit) as shared_buffers, pg_relation_size('foo') as tbl_ize
+        from pg_settings where name = 'shared_buffers'
+    ''')
+    row = cur.fetchone()
+    print("shared_buffers is {}, table size {}", row[0], row[1]);
+    assert int(row[0]) < int(row[1])
+
+    cur.execute('VACUUM foo');
+
+    # Make a lot of updates on a single row, generating a lot of WAL. Trigger
+    # garbage collections so that the page server will remove old page versions.
+    for i in range(10):
+        pscur.execute(f"do_gc {pageserver.initial_tenant} {timeline} 0")
+        for j in range(100):
+            cur.execute('UPDATE foo SET val = val + 1 WHERE id = 1;');
+
+    # All (or at least most of) the updates should've been on the same page, so
+    # that we haven't had to evict any dirty pages for a long time. Now run
+    # a query that sends GetPage@LSN requests with the old LSN.
+    cur.execute("SELECT COUNT(*), SUM(val) FROM foo");
+    assert cur.fetchone() == (100000, 101000)
--- a/test_runner/batch_others/test_pgbench.py
+++ b/test_runner/batch_others/test_pgbench.py
@@ -12,5 +12,5 @@ def test_pgbench(postgres: PostgresFactory, pg_bin, zenith_cli):

    connstr = pg.connstr()

-    pg_bin.run_capture(['pgbench', '-i', connstr])
-    pg_bin.run_capture(['pgbench'] + '-c 10 -T 5 -P 1 -M prepared'.split() + [connstr])
+    pg_bin.run_capture(['pgbench', '-i', '-s', '100', connstr])
+    pg_bin.run_capture(['pgbench'] + '-c 1 -N -T 100 -P 1 -M prepared'.split() + [connstr])
--- a/test_runner/batch_others/test_snapfiles_gc.py
+++ b/test_runner/batch_others/test_snapfiles_gc.py
@@ -6,19 +6,19 @@ pytest_plugins = ("fixtures.zenith_fixtures")

 def print_gc_result(row):
    print("GC duration {elapsed} ms".format_map(row));
-    print("  REL    total: {snapshot_relfiles_total}, needed_by_cutoff {snapshot_relfiles_needed_by_cutoff}, needed_by_branches: {snapshot_relfiles_needed_by_branches}, not_updated: {snapshot_relfiles_not_updated}, removed: {snapshot_relfiles_removed}, dropped: {snapshot_relfiles_dropped}".format_map(row))
-    print("  NONREL total: {snapshot_nonrelfiles_total}, needed_by_cutoff {snapshot_nonrelfiles_needed_by_cutoff}, needed_by_branches: {snapshot_nonrelfiles_needed_by_branches}, not_updated: {snapshot_nonrelfiles_not_updated}, removed: {snapshot_nonrelfiles_removed}, dropped: {snapshot_nonrelfiles_dropped}".format_map(row))
+    print("  REL    total: {layer_relfiles_total}, needed_by_cutoff {layer_relfiles_needed_by_cutoff}, needed_by_branches: {layer_relfiles_needed_by_branches}, not_updated: {layer_relfiles_not_updated}, removed: {layer_relfiles_removed}, dropped: {layer_relfiles_dropped}".format_map(row))
+    print("  NONREL total: {layer_nonrelfiles_total}, needed_by_cutoff {layer_nonrelfiles_needed_by_cutoff}, needed_by_branches: {layer_nonrelfiles_needed_by_branches}, not_updated: {layer_nonrelfiles_not_updated}, removed: {layer_nonrelfiles_removed}, dropped: {layer_nonrelfiles_dropped}".format_map(row))


 #
-# Test Garbage Collection of old snapshot files
+# Test Garbage Collection of old layer files
 #
 # This test is pretty tightly coupled with the current implementation of layered
 # storage, in layered_repository.rs.
 #
-def test_snapfiles_gc(zenith_cli, pageserver, postgres, pg_bin):
-    zenith_cli.run(["branch", "test_snapfiles_gc", "empty"])
-    pg = postgres.create_start('test_snapfiles_gc')
+def test_layerfiles_gc(zenith_cli, pageserver, postgres, pg_bin):
+    zenith_cli.run(["branch", "test_layerfiles_gc", "empty"])
+    pg = postgres.create_start('test_layerfiles_gc')

    with closing(pg.connect()) as conn:
        with conn.cursor() as cur:
@@ -55,8 +55,8 @@ def test_snapfiles_gc(zenith_cli, pageserver, postgres, pg_bin):
                    row = pscur.fetchone()
                    print_gc_result(row);
                    # remember the number of files
-                    snapshot_relfiles_remain = row['snapshot_relfiles_total'] - row['snapshot_relfiles_removed']
-                    assert snapshot_relfiles_remain > 0
+                    layer_relfiles_remain = row['layer_relfiles_total'] - row['layer_relfiles_removed']
+                    assert layer_relfiles_remain > 0

                    # Insert a row.
                    print("Inserting one row and running GC")
@@ -64,12 +64,12 @@ def test_snapfiles_gc(zenith_cli, pageserver, postgres, pg_bin):
                    pscur.execute(f"do_gc {pageserver.initial_tenant} {timeline} 0")
                    row = pscur.fetchone()
                    print_gc_result(row);
-                    assert row['snapshot_relfiles_total'] == snapshot_relfiles_remain + 1
-                    assert row['snapshot_relfiles_removed'] == 1
-                    assert row['snapshot_relfiles_dropped'] == 0
+                    assert row['layer_relfiles_total'] == layer_relfiles_remain + 1
+                    assert row['layer_relfiles_removed'] == 1
+                    assert row['layer_relfiles_dropped'] == 0

                    # Insert two more rows and run GC.
-                    # This should create a new snapshot file with the new contents, and
+                    # This should create a new layer file with the new contents, and
                    # remove the old one.
                    print("Inserting two more rows and running GC")
                    cur.execute("INSERT INTO foo VALUES (2)")
@@ -78,11 +78,11 @@ def test_snapfiles_gc(zenith_cli, pageserver, postgres, pg_bin):
                    pscur.execute(f"do_gc {pageserver.initial_tenant} {timeline} 0")
                    row = pscur.fetchone()
                    print_gc_result(row);
-                    assert row['snapshot_relfiles_total'] == snapshot_relfiles_remain + 1
-                    assert row['snapshot_relfiles_removed'] == 1
-                    assert row['snapshot_relfiles_dropped'] == 0
+                    assert row['layer_relfiles_total'] == layer_relfiles_remain + 1
+                    assert row['layer_relfiles_removed'] == 1
+                    assert row['layer_relfiles_dropped'] == 0

-                    # Do it again. Should again create a new snapshot file and remove old one.
+                    # Do it again. Should again create a new layer file and remove old one.
                    print("Inserting two more rows and running GC")
                    cur.execute("INSERT INTO foo VALUES (2)")
                    cur.execute("INSERT INTO foo VALUES (3)")
@@ -90,18 +90,18 @@ def test_snapfiles_gc(zenith_cli, pageserver, postgres, pg_bin):
                    pscur.execute(f"do_gc {pageserver.initial_tenant} {timeline} 0")
                    row = pscur.fetchone()
                    print_gc_result(row);
-                    assert row['snapshot_relfiles_total'] == snapshot_relfiles_remain + 1
-                    assert row['snapshot_relfiles_removed'] == 1
-                    assert row['snapshot_relfiles_dropped'] == 0
+                    assert row['layer_relfiles_total'] == layer_relfiles_remain + 1
+                    assert row['layer_relfiles_removed'] == 1
+                    assert row['layer_relfiles_dropped'] == 0

                    # Run GC again, with no changes in the database. Should not remove anything.
                    print("Run GC again, with nothing to do")
                    pscur.execute(f"do_gc {pageserver.initial_tenant} {timeline} 0")
                    row = pscur.fetchone()
                    print_gc_result(row);
-                    assert row['snapshot_relfiles_total'] == snapshot_relfiles_remain
-                    assert row['snapshot_relfiles_removed'] == 0
-                    assert row['snapshot_relfiles_dropped'] == 0
+                    assert row['layer_relfiles_total'] == layer_relfiles_remain
+                    assert row['layer_relfiles_removed'] == 0
+                    assert row['layer_relfiles_dropped'] == 0

                    #
                    # Test DROP TABLE checks that relation data and metadata was deleted by GC from object storage
@@ -114,11 +114,11 @@ def test_snapfiles_gc(zenith_cli, pageserver, postgres, pg_bin):
                    print_gc_result(row);

                    # Each relation fork is counted separately, hence 3.
-                    assert row['snapshot_relfiles_dropped'] == 3
+                    assert row['layer_relfiles_dropped'] == 3

-                    # The catalog updates also create new snapshot files of the catalogs, which
+                    # The catalog updates also create new layer files of the catalogs, which
                    # are counted as 'removed'
-                    assert row['snapshot_relfiles_removed'] > 0
+                    assert row['layer_relfiles_removed'] > 0

                    # TODO: perhaps we should count catalog and user relations separately,
                    # to make this kind of testing more robust
--- a/test_runner/batch_others/test_timeline_size.py
+++ b/test_runner/batch_others/test_timeline_size.py
@@ -0,0 +1,39 @@
+from contextlib import closing
+from uuid import UUID
+import psycopg2.extras
+from fixtures.zenith_fixtures import PostgresFactory, ZenithPageserver
+
+
+def test_timeline_size(
+    zenith_cli, pageserver: ZenithPageserver, postgres: PostgresFactory, pg_bin
+):
+    # Branch at the point where only 100 rows were inserted
+    zenith_cli.run(["branch", "test_timeline_size", "empty"])
+
+    client = pageserver.http_client()
+    res = client.branch_detail(UUID(pageserver.initial_tenant), "test_timeline_size")
+    assert res["current_logical_size"] == res["current_logical_size_non_incremental"]
+
+    pgmain = postgres.create_start("test_timeline_size")
+    print("postgres is running on 'test_timeline_size' branch")
+
+    with closing(pgmain.connect()) as conn:
+        with conn.cursor() as cur:
+            cur.execute("SHOW zenith.zenith_timeline")
+
+            # Create table, and insert the first 100 rows
+            cur.execute("CREATE TABLE foo (t text)")
+            cur.execute(
+                """
+                INSERT INTO foo
+                    SELECT 'long string to consume some space' || g
+                    FROM generate_series(1, 10) g
+            """
+            )
+
+            res = client.branch_detail(UUID(pageserver.initial_tenant), "test_timeline_size")
+            assert res["current_logical_size"] == res["current_logical_size_non_incremental"]
+            cur.execute("TRUNCATE foo")
+
+            res = client.branch_detail(UUID(pageserver.initial_tenant), "test_timeline_size")
+            assert res["current_logical_size"] == res["current_logical_size_non_incremental"]
--- a/test_runner/batch_others/test_twophase.py
+++ b/test_runner/batch_others/test_twophase.py
@@ -59,9 +59,8 @@ def test_twophase(zenith_cli, pageserver: ZenithPageserver, postgres: PostgresFa
    # Create a branch with the transaction in prepared state
    zenith_cli.run(["branch", "test_twophase_prepared", "test_twophase"])

-    # Create compute node, but don't start.
-    # We want to observe pgdata before postgres starts
-    pg2 = postgres.create(
+    # Start compute on the new branch
+    pg2 = postgres.create_start(
        'test_twophase_prepared',
        config_lines=['max_prepared_transactions=5'],
    )
@@ -71,7 +70,6 @@ def test_twophase(zenith_cli, pageserver: ZenithPageserver, postgres: PostgresFa
    print(twophase_files2)
    assert twophase_files2.sort() == twophase_files.sort()

-    pg2 = pg2.start()
    conn2 = pg2.connect()
    cur2 = conn2.cursor()

--- a/test_runner/batch_others/test_wal_acceptor_async.py
+++ b/test_runner/batch_others/test_wal_acceptor_async.py
@@ -0,0 +1,154 @@
+import asyncio
+import asyncpg
+import random
+
+from fixtures.zenith_fixtures import WalAcceptor, WalAcceptorFactory, ZenithPageserver, PostgresFactory, Postgres
+from typing import List
+from fixtures.utils import debug_print
+
+pytest_plugins = ("fixtures.zenith_fixtures")
+
+
+class BankClient(object):
+    def __init__(self, conn: asyncpg.Connection, n_accounts, init_amount):
+        self.conn: asyncpg.Connection = conn
+        self.n_accounts = n_accounts
+        self.init_amount = init_amount
+
+    async def initdb(self):
+        await self.conn.execute('DROP TABLE IF EXISTS bank_accs')
+        await self.conn.execute('CREATE TABLE bank_accs(uid int primary key, amount int)')
+        await self.conn.execute('''
+            INSERT INTO bank_accs
+            SELECT *, $1 FROM generate_series(0, $2)
+        ''', self.init_amount, self.n_accounts - 1)
+        await self.conn.execute('DROP TABLE IF EXISTS bank_log')
+        await self.conn.execute('CREATE TABLE bank_log(from_uid int, to_uid int, amount int)')
+        
+        # TODO: Remove when https://github.com/zenithdb/zenith/issues/644 is fixed
+        await self.conn.execute('ALTER TABLE bank_accs SET (autovacuum_enabled = false)')
+        await self.conn.execute('ALTER TABLE bank_log SET (autovacuum_enabled = false)')
+
+    async def check_invariant(self):
+        row = await self.conn.fetchrow('SELECT sum(amount) AS sum FROM bank_accs')
+        assert row['sum'] == self.n_accounts * self.init_amount
+
+async def bank_transfer(conn: asyncpg.Connection, from_uid, to_uid, amount):
+    # avoid deadlocks by sorting uids
+    if from_uid > to_uid:
+        from_uid, to_uid, amount = to_uid, from_uid, -amount
+
+    async with conn.transaction():
+        await conn.execute(
+            'UPDATE bank_accs SET amount = amount + ($1) WHERE uid = $2',
+            amount, to_uid,
+        )
+        await conn.execute(
+            'UPDATE bank_accs SET amount = amount - ($1) WHERE uid = $2',
+            amount, from_uid,
+        )
+        await conn.execute('INSERT INTO bank_log VALUES ($1, $2, $3)',
+            from_uid, to_uid, amount,
+        )
+
+class WorkerStats(object):
+    def __init__(self, n_workers):
+        self.counters = [0] * n_workers
+        self.running = True
+
+    def reset(self):
+        self.counters = [0] * len(self.counters)
+
+    def inc_progress(self, worker_id):
+        self.counters[worker_id] += 1
+
+    def check_progress(self):
+        debug_print("Workers progress: {}".format(self.counters))
+
+        # every worker should finish at least one tx
+        assert all(cnt > 0 for cnt in self.counters)
+
+        progress = sum(self.counters)
+        print('All workers made {} transactions'.format(progress))
+
+
+async def run_random_worker(stats: WorkerStats, pg: Postgres, worker_id, n_accounts, max_transfer):
+    pg_conn = await pg.connect_async()
+    debug_print('Started worker {}'.format(worker_id))
+
+    while stats.running:
+        from_uid = random.randint(0, n_accounts - 1)
+        to_uid = (from_uid + random.randint(1, n_accounts - 1)) % n_accounts
+        amount = random.randint(1, max_transfer)
+
+        await bank_transfer(pg_conn, from_uid, to_uid, amount)
+        stats.inc_progress(worker_id)
+
+        debug_print('Executed transfer({}) {} => {}'.format(amount, from_uid, to_uid))
+
+    debug_print('Finished worker {}'.format(worker_id))
+
+    await pg_conn.close()
+
+
+# This test will run several iterations and check progress in each of them.
+# On each iteration 1 acceptor is stopped, and 2 others should allow
+# background workers execute transactions. In the end, state should remain
+# consistent.
+async def run_restarts_under_load(pg: Postgres, acceptors: List[WalAcceptor], n_workers=10):
+    n_accounts = 100
+    init_amount = 100000
+    max_transfer = 100
+    period_time = 10
+    iterations = 6
+
+    pg_conn = await pg.connect_async()
+    bank = BankClient(pg_conn, n_accounts=n_accounts, init_amount=init_amount)
+    # create tables and initial balances
+    await bank.initdb()
+
+    stats = WorkerStats(n_workers)
+    workers = []
+    for worker_id in range(n_workers):
+        worker = run_random_worker(stats, pg, worker_id, bank.n_accounts, max_transfer)
+        workers.append(asyncio.create_task(worker))
+
+
+    for it in range(iterations):
+        victim = acceptors[it % len(acceptors)]
+        victim.stop()
+
+        # wait for transactions that could have started and finished before
+        # victim acceptor was stopped
+        await asyncio.sleep(1)
+
+        stats.reset()
+        await asyncio.sleep(period_time)
+        # assert that at least one transaction has completed in every worker
+        stats.check_progress()
+
+        victim.start()
+
+    print('Iterations are finished, exiting coroutines...')
+    stats.running = False
+    # await all workers
+    await asyncio.gather(*workers)
+    # assert balances sum hasn't changed
+    await bank.check_invariant()
+    await pg_conn.close()
+
+
+# restart acceptors one by one, while executing and validating bank transactions
+def test_restarts_under_load(zenith_cli, pageserver: ZenithPageserver, postgres: PostgresFactory,
+                             wa_factory: WalAcceptorFactory):
+
+    wa_factory.start_n_new(3)
+
+    zenith_cli.run(["branch", "test_wal_acceptors_restarts_under_load", "empty"])
+    pg = postgres.create_start('test_wal_acceptors_restarts_under_load',
+                               wal_acceptors=wa_factory.get_connstrs())
+
+    asyncio.run(run_restarts_under_load(pg, wa_factory.instances))
+
+    # TODO: Remove when https://github.com/zenithdb/zenith/issues/644 is fixed
+    pg.stop()
--- a/test_runner/batch_pg_regress/test_pg_regress.py
+++ b/test_runner/batch_pg_regress/test_pg_regress.py
@@ -1,7 +1,7 @@
 import os

 from fixtures.utils import mkdir_if_needed
-from fixtures.zenith_fixtures import PostgresFactory, ZenithPageserver
+from fixtures.zenith_fixtures import PostgresFactory, ZenithPageserver, check_restored_datadir_content

 pytest_plugins = ("fixtures.zenith_fixtures")

@@ -49,3 +49,10 @@ def test_pg_regress(pageserver: ZenithPageserver, postgres: PostgresFactory, pg_
    # logs the exact same data to `regression.out` anyway.
    with capsys.disabled():
        pg_bin.run(pg_regress_command, env=env, cwd=runpath)
+
+        # checkpoint one more time to ensure that the lsn we get is the latest one
+        pg.safe_psql('CHECKPOINT')
+        lsn = pg.safe_psql('select pg_current_wal_insert_lsn()')[0][0]
+
+        # Check that we restore the content of the datadir correctly
+        check_restored_datadir_content(zenith_cli, test_output_dir, pg, pageserver.service_port.pg)
--- a/test_runner/batch_pg_regress/test_zenith_regress.py
+++ b/test_runner/batch_pg_regress/test_zenith_regress.py
@@ -1,13 +1,13 @@
 import os

 from fixtures.utils import mkdir_if_needed
-from fixtures.zenith_fixtures import PostgresFactory
+from fixtures.zenith_fixtures import PageserverPort, PostgresFactory, check_restored_datadir_content

 pytest_plugins = ("fixtures.zenith_fixtures")


 def test_zenith_regress(postgres: PostgresFactory, pg_bin, zenith_cli, test_output_dir, pg_distrib_dir,
-                        base_dir, capsys):
+                        base_dir, capsys, pageserver_port: PageserverPort):

    # Create a branch for us
    zenith_cli.run(["branch", "test_zenith_regress", "empty"])
@@ -50,3 +50,10 @@ def test_zenith_regress(postgres: PostgresFactory, pg_bin, zenith_cli, test_outp
    # logs the exact same data to `regression.out` anyway.
    with capsys.disabled():
        pg_bin.run(pg_regress_command, env=env, cwd=runpath)
+
+        # checkpoint one more time to ensure that the lsn we get is the latest one
+        pg.safe_psql('CHECKPOINT')
+        lsn = pg.safe_psql('select pg_current_wal_insert_lsn()')[0][0]
+
+        # Check that we restore the content of the datadir correctly
+        check_restored_datadir_content(zenith_cli, test_output_dir, pg, pageserver_port.pg)
--- a/test_runner/fixtures/benchmark_fixture.py
+++ b/test_runner/fixtures/benchmark_fixture.py
@@ -1,6 +1,7 @@
 from pprint import pprint

 import os
+import re
 import timeit
 import pathlib
 import uuid
@@ -78,7 +79,7 @@ class ZenithBenchmarkResults:

        self.results.append((test_name, metric_name, metric_value, unit))

-# Sesssion scope fixture that initializes the results object
+# Session scope fixture that initializes the results object
@pytest.fixture(autouse=True, scope='session')
 def zenbenchmark_global(request) -> Iterator[ZenithBenchmarkResults]:
    """
@@ -120,6 +121,35 @@ class ZenithBenchmarker:

        self.results.record(self.request.node.name, metric_name, end - start, 's')

+    def get_io_writes(self, pageserver) -> int:
+        """
+        Fetch the "cumulative # of bytes written" metric from the pageserver
+        """
+        # Fetch all the exposed prometheus metrics from page server
+        all_metrics = pageserver.http_client().get_metrics()
+        # Use a regular expression to extract the one we're interested in
+        #
+        # TODO: If we start to collect more of the prometheus metrics in the
+        # performance test suite like this, we should refactor this to load and
+        # parse all the metrics into a more convenient structure in one go.
+        #
+        # The metric should be an integer, as it's a number of bytes. But in general
+        # all prometheus metrics are floats. So to be pedantic, read it as a float
+        # and round to integer.
+        matches = re.search(r'pageserver_disk_io_bytes{io_operation="write"} (\S+)', all_metrics)
+        return int(round(float(matches.group(1))))
+
+    @contextmanager
+    def record_pageserver_writes(self, pageserver, metric_name):
+        """
+        Record bytes written by the pageserver during a test.
+        """
+        before = self.get_io_writes(pageserver)
+        yield
+        after = self.get_io_writes(pageserver)
+
+        self.results.record(self.request.node.name, metric_name, round((after - before) / (1024 * 1024)), 'MB')
+
@pytest.fixture(scope='function')
 def zenbenchmark(zenbenchmark_global, request) -> Iterator[ZenithBenchmarker]:
    """
--- a/test_runner/fixtures/utils.py
+++ b/test_runner/fixtures/utils.py
@@ -14,10 +14,11 @@ def mkdir_if_needed(path: str) -> None:

    Note this won't try to create intermediate directories.
    """
-    if os.path.exists(path):
-        assert os.path.isdir(path)
-        return
-    os.mkdir(path)
+    try:
+        os.mkdir(path)
+    except FileExistsError:
+        pass
+    assert os.path.isdir(path)


 def subprocess_capture(capture_dir: str, cmd: List[str], **kwargs: Any) -> None:
@@ -53,3 +54,11 @@ def global_counter() -> int:
    global _global_counter
    _global_counter += 1
    return _global_counter
+
+def debug_print(*args, **kwargs) -> None:
+    """ Print to the console if TEST_DEBUG_PRINT is set in env.
+    
+    All parameters are passed to print().
+    """
+    if os.environ.get('TEST_DEBUG_PRINT') is not None:
+        print(*args, **kwargs)
--- a/test_runner/fixtures/zenith_fixtures.py
+++ b/test_runner/fixtures/zenith_fixtures.py
@@ -1,5 +1,6 @@
 from dataclasses import dataclass
 from functools import cached_property
+import asyncpg
 import os
 import pathlib
 import uuid
@@ -10,6 +11,8 @@ import shutil
 import signal
 import subprocess
 import time
+import filecmp
+import difflib

 from contextlib import closing
 from pathlib import Path
@@ -47,8 +50,27 @@ Fn = TypeVar('Fn', bound=Callable[..., Any])
 DEFAULT_OUTPUT_DIR = 'test_output'
 DEFAULT_POSTGRES_DIR = 'tmp_install'

-DEFAULT_PAGESERVER_PG_PORT = 64000
-DEFAULT_PAGESERVER_HTTP_PORT = 9898
+BASE_PORT = 15000
+WORKER_PORT_NUM = 100
+
+def pytest_configure(config):
+    """
+    Ensure that no unwanted daemons are running before we start testing.
+    Check that we do not owerflow available ports range.
+    """
+    numprocesses = config.getoption('numprocesses')
+    if numprocesses is not None and BASE_PORT + numprocesses * WORKER_PORT_NUM > 32768: # do not use ephemeral ports
+         raise Exception('Too many workers configured. Cannot distrubute ports for services.')
+
+    # does not use -c as it is not supported on macOS
+    cmd = ['pgrep', 'pageserver|postgres|wal_acceptor']
+    result = subprocess.run(cmd, stdout=subprocess.DEVNULL)
+    if result.returncode == 0:
+        # returncode of 0 means it found something.
+        # This is bad; we don't want any of those processes polluting the
+        # result of the test.
+        # NOTE this shows as an internal pytest error, there might be a better way
+        raise Exception('found interfering processes running')


 def determine_scope(fixture_name: str, config: Any) -> str:
@@ -73,20 +95,6 @@ def zenfixture(func: Fn) -> Fn:
    return pytest.fixture(func, scope=scope)


-@pytest.fixture(autouse=True, scope='session')
-def safety_check() -> None:
-    """ Ensure that no unwanted daemons are running before we start testing. """
-
-    # does not use -c as it is not supported on macOS
-    cmd = ['pgrep', 'pageserver|postgres|wal_acceptor']
-    result = subprocess.run(cmd, stdout=subprocess.DEVNULL)
-    if result.returncode == 0:
-        # returncode of 0 means it found something.
-        # This is bad; we don't want any of those processes polluting the
-        # result of the test.
-        raise Exception('found interfering processes running')
-
-
 class PgProtocol:
    """ Reusable connection logic """
    def __init__(self, host: str, port: int, username: Optional[str] = None):
@@ -122,6 +130,21 @@ class PgProtocol:
        conn.autocommit = autocommit
        return conn

+    async def connect_async(self, *, dbname: str = 'postgres', username: Optional[str] = None, password: Optional[str] = None) -> asyncpg.Connection:
+        """
+        Connect to the node from async python.
+        Returns asyncpg's connection object.
+        """
+
+        conn = await asyncpg.connect(
+            host=self.host,
+            port=self.port,
+            database=dbname,
+            user=username or self.username,
+            password=password,
+        )
+        return conn
+
    def safe_psql(self, query: str, **kwargs: Any) -> List[Any]:
        """
        Execute query against the node and return all rows.
@@ -169,12 +192,27 @@ class ZenithCli:

        args = [self.bin_zenith] + arguments
        print('Running command "{}"'.format(' '.join(args)))
-        return subprocess.run(args,
-                              env=self.env,
-                              check=True,
-                              universal_newlines=True,
-                              stdout=subprocess.PIPE,
-                              stderr=subprocess.PIPE)
+
+        # Interceipt CalledProcessError and print more info
+        try:
+            res = subprocess.run(args,
+                                env=self.env,
+                                check=True,
+                                universal_newlines=True,
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.PIPE)
+        except subprocess.CalledProcessError as exc:
+            # this way command output will be in recorded and shown in CI in failure message
+            msg = f"""\
+            Run failed: {exc}
+              stdout: {exc.stdout}
+              stderr: {exc.stderr}
+            """
+            print(msg)
+
+            raise Exception(msg) from exc
+
+        return res


@zenfixture
@@ -211,6 +249,13 @@ class ZenithPageserverHttpClient(requests.Session):
        res.raise_for_status()
        return res.json()

+    def branch_detail(self, tenant_id: uuid.UUID, name: str) -> Dict:
+        res = self.get(
+            f"http://localhost:{self.port}/v1/branch/{tenant_id.hex}/{name}",
+        )
+        res.raise_for_status()
+        return res.json()
+
    def tenant_list(self) -> List[str]:
        res = self.get(f"http://localhost:{self.port}/v1/tenant")
        res.raise_for_status()
@@ -226,6 +271,11 @@ class ZenithPageserverHttpClient(requests.Session):
        res.raise_for_status()
        return res.json()

+    def get_metrics(self) -> str:
+        res = self.get(f"http://localhost:{self.port}/metrics")
+        res.raise_for_status()
+        return res.text
+

@dataclass
 class AuthKeys:
@@ -252,24 +302,60 @@ class AuthKeys:
        return token


+@zenfixture
+def worker_seq_no(worker_id: str):
+    # worker_id is a pytest-xdist fixture
+    # it can be master or gw<number>
+    # parse it to always get a number
+    if worker_id == 'master':
+        return 0
+    assert worker_id.startswith('gw')
+    return int(worker_id[2:])


+@zenfixture
+def worker_base_port(worker_seq_no: int):
+    # so we divide ports in ranges of 100 ports
+    # so workers have disjoint set of ports for services
+    return BASE_PORT + worker_seq_no * WORKER_PORT_NUM
+
+class PortDistributor:
+    def __init__(self, base_port: int, port_number: int) -> None:
+        self.iterator = iter(range(base_port, base_port + port_number))
+
+    def get_port(self) -> int:
+        try:
+            return next(self.iterator)
+        except StopIteration:
+            raise RuntimeError('port range configured for test is exhausted, consider enlarging the range')
+
+
+@zenfixture
+def port_distributor(worker_base_port):
+    return PortDistributor(base_port=worker_base_port, port_number=WORKER_PORT_NUM)
+
+@dataclass
+class PageserverPort:
+    pg: int
+    http: int
+

 class ZenithPageserver(PgProtocol):
    """ An object representing a running pageserver. """
-    def __init__(self, zenith_cli: ZenithCli, repo_dir: str):
-        super().__init__(host='localhost', port=DEFAULT_PAGESERVER_PG_PORT)
+    def __init__(self, zenith_cli: ZenithCli, repo_dir: str, port: PageserverPort):
+        super().__init__(host='localhost', port=port.pg)
        self.zenith_cli = zenith_cli
        self.running = False
        self.initial_tenant = None
        self.repo_dir = repo_dir
+        self.service_port = port # do not shadow PgProtocol.port which is just int

    def init(self, enable_auth: bool = False) -> 'ZenithPageserver':
        """
        Initialize the repository, i.e. run "zenith init".
        Returns self.
        """
-        cmd = ['init']
+        cmd = ['init', f'--pageserver-pg-port={self.service_port.pg}', f'--pageserver-http-port={self.service_port.http}']
        if enable_auth:
            cmd.append('--enable-auth')
        self.zenith_cli.run(cmd)
@@ -319,13 +405,23 @@ class ZenithPageserver(PgProtocol):

    def http_client(self, auth_token: Optional[str] = None):
        return ZenithPageserverHttpClient(
-            port=DEFAULT_PAGESERVER_HTTP_PORT,
+            port=self.service_port.http,
            auth_token=auth_token,
        )


+
+
@zenfixture
-def pageserver(zenith_cli: ZenithCli, repo_dir: str) -> Iterator[ZenithPageserver]:
+def pageserver_port(port_distributor: PortDistributor) -> PageserverPort:
+    pg = port_distributor.get_port()
+    http = port_distributor.get_port()
+    print(f"pageserver_port: pg={pg} http={http}")
+    return PageserverPort(pg=pg, http=http)
+
+
+@zenfixture
+def pageserver(zenith_cli: ZenithCli, repo_dir: str, pageserver_port: PageserverPort) -> Iterator[ZenithPageserver]:
    """
    The 'pageserver' fixture provides a Page Server that's up and running.

@@ -337,8 +433,7 @@ def pageserver(zenith_cli: ZenithCli, repo_dir: str) -> Iterator[ZenithPageserve
    By convention, the test branches are named after the tests. For example,
    test called 'test_foo' would create and use branches with the 'test_foo' prefix.
    """
-
-    ps = ZenithPageserver(zenith_cli, repo_dir).init().start()
+    ps = ZenithPageserver(zenith_cli=zenith_cli, repo_dir=repo_dir, port=pageserver_port).init().start()
    # For convenience in tests, create a branch from the freshly-initialized cluster.
    zenith_cli.run(["branch", "empty", "main"])

@@ -408,8 +503,8 @@ def pg_bin(test_output_dir: str, pg_distrib_dir: str) -> PgBin:
    return PgBin(test_output_dir, pg_distrib_dir)

@pytest.fixture
-def pageserver_auth_enabled(zenith_cli: ZenithCli, repo_dir: str):
-    with ZenithPageserver(zenith_cli, repo_dir).init(enable_auth=True).start() as ps:
+def pageserver_auth_enabled(zenith_cli: ZenithCli, repo_dir: str, pageserver_port: PageserverPort):
+    with ZenithPageserver(zenith_cli=zenith_cli, repo_dir=repo_dir, port=pageserver_port).init(enable_auth=True).start() as ps:
        # For convenience in tests, create a branch from the freshly-initialized cluster.
        zenith_cli.run(["branch", "empty", "main"])
        yield ps
@@ -434,7 +529,6 @@ class Postgres(PgProtocol):
        branch: str,
        wal_acceptors: Optional[str] = None,
        config_lines: Optional[List[str]] = None,
-        config_only: bool = False,
    ) -> 'Postgres':
        """
        Create the pg data directory.
@@ -446,10 +540,7 @@ class Postgres(PgProtocol):
        if not config_lines:
            config_lines = []

-        if config_only:
-            self.zenith_cli.run(['pg', 'create', '--config-only', branch, f'--tenantid={self.tenant_id}'])
-        else:
-            self.zenith_cli.run(['pg', 'create', branch, f'--tenantid={self.tenant_id}'])
+        self.zenith_cli.run(['pg', 'create', branch, f'--tenantid={self.tenant_id}', f'--port={self.port}'])
        self.branch = branch
        path = pathlib.Path('pgdatadirs') / 'tenants' / self.tenant_id / self.branch
        self.pgdata_dir = os.path.join(self.repo_dir, path)
@@ -470,12 +561,12 @@ class Postgres(PgProtocol):

        assert self.branch is not None

-        print(f"Starting postgres on brach {self.branch}")
+        print(f"Starting postgres on branch {self.branch}")

-        self.zenith_cli.run(['pg', 'start', self.branch, f'--tenantid={self.tenant_id}'])
+        run_result = self.zenith_cli.run(['pg', 'start', self.branch, f'--tenantid={self.tenant_id}', f'--port={self.port}'])
        self.running = True

-        self.pg_bin.run(['pg_controldata', self.pg_data_dir_path()])
+        print(f"stdout: {run_result.stdout}")

        return self

@@ -572,7 +663,6 @@ class Postgres(PgProtocol):
            branch=branch,
            wal_acceptors=wal_acceptors,
            config_lines=config_lines,
-            config_only=True,
        ).start()

        return self
@@ -583,16 +673,15 @@ class Postgres(PgProtocol):
    def __exit__(self, exc_type, exc, tb):
        self.stop()

-
 class PostgresFactory:
    """ An object representing multiple running postgres daemons. """
-    def __init__(self, zenith_cli: ZenithCli, repo_dir: str, pg_bin: PgBin, initial_tenant: str, base_port: int = 55431):
+    def __init__(self, zenith_cli: ZenithCli, repo_dir: str, pg_bin: PgBin, initial_tenant: str, port_distributor: PortDistributor):
        self.zenith_cli = zenith_cli
        self.repo_dir = repo_dir
        self.num_instances = 0
        self.instances: List[Postgres] = []
        self.initial_tenant: str = initial_tenant
-        self.base_port = base_port
+        self.port_distributor = port_distributor
        self.pg_bin = pg_bin

    def create_start(
@@ -602,15 +691,13 @@ class PostgresFactory:
        wal_acceptors: Optional[str] = None,
        config_lines: Optional[List[str]] = None
    ) -> Postgres:
-
        pg = Postgres(
            zenith_cli=self.zenith_cli,
            repo_dir=self.repo_dir,
            pg_bin=self.pg_bin,
            tenant_id=tenant_id or self.initial_tenant,
-            port=self.base_port + self.num_instances + 1,
+            port=self.port_distributor.get_port(),
        )
-
        self.num_instances += 1
        self.instances.append(pg)

@@ -633,7 +720,7 @@ class PostgresFactory:
            repo_dir=self.repo_dir,
            pg_bin=self.pg_bin,
            tenant_id=tenant_id or self.initial_tenant,
-            port=self.base_port + self.num_instances + 1,
+            port=self.port_distributor.get_port(),
        )

        self.num_instances += 1
@@ -658,7 +745,7 @@ class PostgresFactory:
            repo_dir=self.repo_dir,
            pg_bin=self.pg_bin,
            tenant_id=tenant_id or self.initial_tenant,
-            port=self.base_port + self.num_instances + 1,
+            port=self.port_distributor.get_port(),
        )

        self.num_instances += 1
@@ -682,8 +769,14 @@ def initial_tenant(pageserver: ZenithPageserver):


@zenfixture
-def postgres(zenith_cli: ZenithCli, initial_tenant: str, repo_dir: str, pg_bin: PgBin) -> Iterator[PostgresFactory]:
-    pgfactory = PostgresFactory(zenith_cli, repo_dir, pg_bin, initial_tenant=initial_tenant)
+def postgres(zenith_cli: ZenithCli, initial_tenant: str, repo_dir: str, pg_bin: PgBin, port_distributor: PortDistributor) -> Iterator[PostgresFactory]:
+    pgfactory = PostgresFactory(
+        zenith_cli=zenith_cli,
+        repo_dir=repo_dir,
+        pg_bin=pg_bin,
+        initial_tenant=initial_tenant,
+        port_distributor=port_distributor,
+    )

    yield pgfactory

@@ -699,10 +792,11 @@ def read_pid(path: Path):
@dataclass
 class WalAcceptor:
    """ An object representing a running wal acceptor daemon. """
-    bin_path: Path
+    wa_bin_path: Path
    data_dir: Path
    port: int
    num: int # identifier for logging
+    pageserver_port: int
    auth_token: Optional[str] = None

    def start(self) -> 'WalAcceptor':
@@ -710,13 +804,13 @@ class WalAcceptor:
        self.data_dir.mkdir(parents=True, exist_ok=True)
        self.pidfile.unlink(missing_ok=True)

-        cmd = [str(self.bin_path)]
+        cmd = [str(self.wa_bin_path)]
        cmd.extend(["-D", str(self.data_dir)])
-        cmd.extend(["-l", "localhost:{}".format(self.port)])
+        cmd.extend(["-l", f"localhost:{self.port}"])
        cmd.append("--daemonize")
        cmd.append("--no-sync")
        # Tell page server it can receive WAL from this WAL safekeeper
-        cmd.extend(["--pageserver", "localhost:{}".format(DEFAULT_PAGESERVER_PG_PORT)])
+        cmd.extend(["--pageserver", f"localhost:{self.pageserver_port}"])
        cmd.extend(["--recall", "1 second"])
        print('Running command "{}"'.format(' '.join(cmd)))
        env = {'PAGESERVER_AUTH_TOKEN': self.auth_token} if self.auth_token else None
@@ -763,24 +857,25 @@ class WalAcceptor:

 class WalAcceptorFactory:
    """ An object representing multiple running wal acceptors. """
-    def __init__(self, zenith_binpath: Path, data_dir: Path):
-        self.wa_binpath = zenith_binpath / 'wal_acceptor'
+    def __init__(self, zenith_binpath: Path, data_dir: Path, pageserver_port: int, port_distributor: PortDistributor):
+        self.wa_bin_path = zenith_binpath / 'wal_acceptor'
        self.data_dir = data_dir
        self.instances: List[WalAcceptor] = []
-        self.initial_port = 54321
+        self.port_distributor = port_distributor
+        self.pageserver_port = pageserver_port

    def start_new(self, auth_token: Optional[str] = None) -> WalAcceptor:
        """
        Start new wal acceptor.
        """
-
        wa_num = len(self.instances)
        wa = WalAcceptor(
-            self.wa_binpath,
-            self.data_dir / "wal_acceptor_{}".format(wa_num),
-            self.initial_port + wa_num,
-            wa_num,
-            auth_token,
+            wa_bin_path=self.wa_bin_path,
+            data_dir=self.data_dir / "wal_acceptor_{}".format(wa_num),
+            port=self.port_distributor.get_port(),
+            num=wa_num,
+            pageserver_port=self.pageserver_port,
+            auth_token=auth_token,
        )
        wa.start()
        self.instances.append(wa)
@@ -805,9 +900,14 @@ class WalAcceptorFactory:


@zenfixture
-def wa_factory(zenith_binpath: str, repo_dir: str) -> Iterator[WalAcceptorFactory]:
+def wa_factory(zenith_binpath: str, repo_dir: str, pageserver_port: PageserverPort, port_distributor: PortDistributor) -> Iterator[WalAcceptorFactory]:
    """ Gives WalAcceptorFactory providing wal acceptors. """
-    wafactory = WalAcceptorFactory(Path(zenith_binpath), Path(repo_dir) / "wal_acceptors")
+    wafactory = WalAcceptorFactory(
+        zenith_binpath=Path(zenith_binpath),
+        data_dir=Path(repo_dir) / "wal_acceptors",
+        pageserver_port=pageserver_port.pg,
+        port_distributor=port_distributor,
+    )
    yield wafactory
    # After the yield comes any cleanup code we need.
    print('Starting wal acceptors cleanup')
@@ -911,3 +1011,85 @@ class TenantFactory:
@zenfixture
 def tenant_factory(zenith_cli: ZenithCli):
    return TenantFactory(zenith_cli)
+
+#
+# Test helpers
+#
+def list_files_to_compare(pgdata_dir: str):
+    pgdata_files = []
+    for root, _file, filenames in os.walk(pgdata_dir):
+        for filename in filenames:
+            rel_dir = os.path.relpath(root, pgdata_dir)
+            # Skip some dirs and files we don't want to compare
+            skip_dirs = ['pg_wal', 'pg_stat', 'pg_stat_tmp', 'pg_subtrans', 'pg_logical']
+            skip_files = ['pg_internal.init', 'pg.log', 'zenith.signal', 'postgresql.conf',
+                        'postmaster.opts', 'postmaster.pid', 'pg_control']
+            if rel_dir not in skip_dirs and filename not in skip_files:
+                rel_file = os.path.join(rel_dir, filename)
+                pgdata_files.append(rel_file)
+
+    pgdata_files.sort()
+    print(pgdata_files)
+    return pgdata_files
+
+# pg is the existing and running compute node, that we want to compare with a basebackup
+def check_restored_datadir_content(zenith_cli: ZenithCli, test_output_dir: str, pg: Postgres, pageserver_pg_port: int):
+
+    # Get the timeline ID of our branch. We need it for the 'basebackup' command
+    with closing(pg.connect()) as conn:
+        with conn.cursor() as cur:
+            cur.execute("SHOW zenith.zenith_timeline")
+            timeline = cur.fetchone()[0]
+
+    # stop postgres to ensure that files won't change
+    pg.stop()
+
+    # Take a basebackup from pageserver
+    restored_dir_path = os.path.join(test_output_dir, f"{pg.branch}_restored_datadir")
+    mkdir_if_needed(restored_dir_path)
+
+    psql_path = os.path.join(pg.pg_bin.pg_bin_path, 'psql')
+
+    cmd = rf"""
+        {psql_path}                                    \
+            --no-psqlrc                                \
+            postgres://localhost:{pageserver_pg_port}  \
+            -c 'basebackup {pg.tenant_id} {timeline}'  \
+         | tar -x -C {restored_dir_path}
+    """
+
+    subprocess.check_call(cmd, shell=True)
+
+    # list files we're going to compare
+    pgdata_files = list_files_to_compare(pg.pgdata_dir)
+    restored_files = list_files_to_compare(restored_dir_path)
+
+    # check that file sets are equal
+    assert pgdata_files == restored_files
+
+    # compare content of the files
+    # filecmp returns (match, mismatch, error) lists
+    # We've already filtered all mismatching files in list_files_to_compare(),
+    # so here expect that the content is identical
+    (match, mismatch, error) = filecmp.cmpfiles(pg.pgdata_dir,
+                                                restored_dir_path,
+                                                pgdata_files,
+                                                shallow=False)
+    print('filecmp result mismatch and error lists:')
+    print(mismatch)
+    print(error)
+
+    for f in mismatch:
+
+        f1 = os.path.join(pg.pgdata_dir, f)
+        f2 = os.path.join(restored_dir_path, f)
+        stdout_filename = "{}.filediff".format(f2)
+
+        with open(stdout_filename, 'w') as stdout_f:
+            subprocess.run("xxd -b {} > {}.hex ".format(f1, f1), shell=True)
+            subprocess.run("xxd -b {} > {}.hex ".format(f2, f2), shell=True)
+
+            cmd = ['diff {}.hex {}.hex'.format(f1, f2)]
+            subprocess.run(cmd, stdout=stdout_f, shell=True)
+
+    assert (mismatch, error) == ([], [])
--- a/test_runner/performance/test_bulk_insert.py
+++ b/test_runner/performance/test_bulk_insert.py
@@ -0,0 +1,60 @@
+import os
+from contextlib import closing
+from fixtures.zenith_fixtures import PostgresFactory, ZenithPageserver
+
+pytest_plugins = ("fixtures.zenith_fixtures", "fixtures.benchmark_fixture")
+
+def get_timeline_size(repo_dir: str, tenantid: str, timelineid: str):
+    path = "{}/tenants/{}/timelines/{}".format(repo_dir, tenantid, timelineid)
+
+    totalbytes = 0
+    for root, dirs, files in os.walk(path):
+        for name in files:
+            totalbytes += os.path.getsize(os.path.join(root, name))
+
+        if 'wal' in dirs:
+            dirs.remove('wal')  # don't visit 'wal' subdirectory
+
+    return totalbytes
+
+#
+# Run bulk INSERT test.
+#
+# Collects metrics:
+#
+# 1. Time to INSERT 5 million rows
+# 2. Disk writes
+# 3. Disk space used
+#
+def test_bulk_insert(postgres: PostgresFactory, pageserver: ZenithPageserver, pg_bin, zenith_cli, zenbenchmark, repo_dir: str):
+    # Create a branch for us
+    zenith_cli.run(["branch", "test_bulk_insert", "empty"])
+
+    pg = postgres.create_start('test_bulk_insert')
+    print("postgres is running on 'test_bulk_insert' branch")
+
+    # Open a connection directly to the page server that we'll use to force
+    # flushing the layers to disk
+    psconn = pageserver.connect();
+    pscur = psconn.cursor()
+
+    # Get the timeline ID of our branch. We need it for the 'do_gc' command
+    with closing(pg.connect()) as conn:
+        with conn.cursor() as cur:
+            cur.execute("SHOW zenith.zenith_timeline")
+            timeline = cur.fetchone()[0]
+
+            cur.execute("create table huge (i int, j int);")
+
+            # Run INSERT, recording the time and I/O it takes
+            with zenbenchmark.record_pageserver_writes(pageserver, 'pageserver_writes'):
+                with zenbenchmark.record_duration('insert'):
+                    cur.execute("insert into huge values (generate_series(1, 5000000), 0);")
+
+                    # Flush the layers from memory to disk. This is included in the reported
+                    # time and I/O
+                    pscur.execute(f"do_gc {pageserver.initial_tenant} {timeline} 0")
+
+            # Report disk space used by the repository
+            timeline_size = get_timeline_size(repo_dir, pageserver.initial_tenant, timeline)
+            zenbenchmark.record('size', timeline_size / (1024*1024), 'MB')
--- a/test_runner/performance/test_perf_pgbench.py
+++ b/test_runner/performance/test_perf_pgbench.py
@@ -46,13 +46,14 @@ def test_pgbench(postgres: PostgresFactory, pageserver: ZenithPageserver, pg_bin

    connstr = pg.connstr()

-    # Initialize pgbench database
-    with zenbenchmark.record_duration('init'):
-        pg_bin.run_capture(['pgbench', '-s5', '-i', connstr])
+    # Initialize pgbench database, recording the time and I/O it takes
+    with zenbenchmark.record_pageserver_writes(pageserver, 'pageserver_writes'):
+        with zenbenchmark.record_duration('init'):
+            pg_bin.run_capture(['pgbench', '-s5', '-i', connstr])

-        # Flush the layers from memory to disk. The time to do that is included in the
-        # reported init time.
-        pscur.execute(f"do_gc {pageserver.initial_tenant} {timeline} 0")
+            # Flush the layers from memory to disk. This is included in the reported
+            # time and I/O
+            pscur.execute(f"do_gc {pageserver.initial_tenant} {timeline} 0")

    # Run pgbench for 5000 transactions
    with zenbenchmark.record_duration('5000_xacts'):
--- a/vendor/postgres
+++ b/vendor/postgres
--- a/walkeeper/Cargo.toml
+++ b/walkeeper/Cargo.toml
@@ -13,16 +13,11 @@ bytes = "1.0.1"
 byteorder = "1.4.3"
 fs2 = "0.4.3"
 lazy_static = "1.4.0"
-slog-stdlog = "4.1.0"
-slog-async = "2.6.0"
-slog-scope = "4.4.0"
-slog-term = "2.8.0"
-slog = "2.7.0"
 log = "0.4.14"
 clap = "2.33.0"
 daemonize = "0.4.1"
 rust-s3 = { version = "0.27.0-rc4", features = ["no-verify-ssl"] }
-tokio = { version = "1.3.0", features = ["full"] }
+tokio = "1.11"
 tokio-stream = { version = "0.1.4" }
 postgres-protocol = { git = "https://github.com/zenithdb/rust-postgres.git", rev="9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858" }
 postgres = { git = "https://github.com/zenithdb/rust-postgres.git", rev="9eb0dbfbeb6a6c1b79099b9f7ae4a8c021877858" }
--- a/walkeeper/src/bin/wal_acceptor.rs
+++ b/walkeeper/src/bin/wal_acceptor.rs
@@ -1,15 +1,14 @@
 //
 // Main entry point for the wal_acceptor executable
 //
-use anyhow::{Context, Result};
+use anyhow::Result;
 use clap::{App, Arg};
 use daemonize::Daemonize;
 use log::*;
-use slog::Drain;
+use std::env;
 use std::path::{Path, PathBuf};
 use std::thread;
-use std::{env, io};
-use std::{fs::File, fs::OpenOptions};
+use zenith_utils::logging;

 use walkeeper::s3_offload;
 use walkeeper::wal_service;
@@ -113,20 +112,7 @@ fn main() -> Result<()> {

 fn start_wal_acceptor(conf: WalAcceptorConf) -> Result<()> {
    let log_filename = conf.data_dir.join("wal_acceptor.log");
-    // Don't open the same file for output multiple times;
-    // the different fds could overwrite each other's output.
-    let log_file = OpenOptions::new()
-        .create(true)
-        .append(true)
-        .open(&log_filename)
-        .with_context(|| format!("failed to open {:?}", &log_filename))?;
-
-    // Initialize logger
-    let logger_file = log_file.try_clone().unwrap();
-    let _scope_guard = init_logging(&conf, logger_file)?;
-    let _log_guard = slog_stdlog::init().unwrap();
-    // Note: this `info!(...)` macro comes from `log` crate
-    info!("standard logging redirected to slog");
+    let (_scope_guard, log_file) = logging::init(log_filename, conf.daemonize)?;

    if conf.daemonize {
        info!("daemonizing...");
@@ -179,29 +165,3 @@ fn start_wal_acceptor(conf: WalAcceptorConf) -> Result<()> {
    }
    Ok(())
 }
-
-fn init_logging(
-    conf: &WalAcceptorConf,
-    log_file: File,
-) -> Result<slog_scope::GlobalLoggerGuard, io::Error> {
-    if conf.daemonize {
-        let decorator = slog_term::PlainSyncDecorator::new(log_file);
-        let drain = slog_term::CompactFormat::new(decorator).build();
-        let drain = slog::Filter::new(drain, |record: &slog::Record| {
-            record.level().is_at_least(slog::Level::Info)
-        });
-        let drain = std::sync::Mutex::new(drain).fuse();
-        let logger = slog::Logger::root(drain, slog::o!());
-        Ok(slog_scope::set_global_logger(logger))
-    } else {
-        let decorator = slog_term::TermDecorator::new().build();
-        let drain = slog_term::FullFormat::new(decorator).build().fuse();
-        let drain = slog::Filter::new(drain, |record: &slog::Record| {
-            record.level().is_at_least(slog::Level::Info)
-        })
-        .fuse();
-        let drain = slog_async::Async::new(drain).chan_size(1000).build().fuse();
-        let logger = slog::Logger::root(drain, slog::o!());
-        Ok(slog_scope::set_global_logger(logger))
-    }
-}
--- a/walkeeper/src/receive_wal.rs
+++ b/walkeeper/src/receive_wal.rs
@@ -74,7 +74,7 @@ fn request_callback(conf: WalAcceptorConf, timelineid: ZTimelineId, tenantid: ZT

 impl<'pg> ReceiveWalConn<'pg> {
    pub fn new(pg: &'pg mut PostgresBackend) -> Result<ReceiveWalConn<'pg>> {
-        let peer_addr = pg.get_peer_addr().clone();
+        let peer_addr = *pg.get_peer_addr();
        Ok(ReceiveWalConn {
            pg_backend: pg,
            peer_addr,
--- a/walkeeper/src/replication.rs
+++ b/walkeeper/src/replication.rs
@@ -3,7 +3,7 @@

 use crate::send_wal::SendWalHandler;
 use crate::timeline::{Timeline, TimelineTools};
-use anyhow::{anyhow, Result};
+use anyhow::{anyhow, Context, Result};
 use bytes::Bytes;
 use log::*;
 use postgres_ffi::xlog_utils::{get_current_timestamp, TimestampTz, XLogFileName, MAX_SEND_SIZE};
@@ -25,6 +25,10 @@ use zenith_utils::sock_split::ReadStream;

 pub const END_REPLICATION_MARKER: Lsn = Lsn::MAX;

+// See: https://www.postgresql.org/docs/13/protocol-replication.html
+const HOT_STANDBY_FEEDBACK_TAG_BYTE: u8 = b'h';
+const STANDBY_STATUS_UPDATE_TAG_BYTE: u8 = b'r';
+
 type FullTransactionId = u64;

 /// Hot standby feedback received from replica
@@ -81,10 +85,22 @@ impl ReplicationConn {
    ) -> Result<()> {
        // Wait for replica's feedback.
        while let Some(msg) = FeMessage::read(&mut stream_in)? {
-            match msg {
+            match &msg {
                FeMessage::CopyData(m) => {
-                    let feedback = HotStandbyFeedback::des(&m)?;
-                    subscriber.add_hs_feedback(feedback);
+                    // There's two possible data messages that the client is supposed to send here:
+                    // `HotStandbyFeedback` and `StandbyStatusUpdate`. We only handle hot standby
+                    // feedback.
+
+                    match m.first().cloned() {
+                        Some(HOT_STANDBY_FEEDBACK_TAG_BYTE) => {
+                            // Note: deserializing is on m[1..] because we skip the tag byte.
+                            let feedback = HotStandbyFeedback::des(&m[1..])
+                                .context("failed to deserialize HotStandbyFeedback")?;
+                            subscriber.add_hs_feedback(feedback);
+                        }
+                        Some(STANDBY_STATUS_UPDATE_TAG_BYTE) => (),
+                        _ => warn!("unexpected message {:?}", msg),
+                    }
                }
                FeMessage::Sync => {}
                FeMessage::CopyFail => return Err(anyhow!("Copy failed")),
@@ -105,7 +121,7 @@ impl ReplicationConn {
        let mut lsns = caps.map(|cap| cap[1].parse::<Lsn>());
        let start_pos = lsns
            .next()
-            .ok_or_else(|| anyhow!("failed to find start LSN"))??;
+            .ok_or_else(|| anyhow!("Failed to parse start LSN from command"))??;
        let stop_pos = lsns.next().transpose()?.unwrap_or(Lsn(0));
        Ok((start_pos, stop_pos))
    }
@@ -120,13 +136,12 @@ impl ReplicationConn {
        }

        // If that failed, try it without the .partial extension.
-        match File::open(&wal_file_path) {
-            Ok(opened_file) => Ok(opened_file),
-            Err(e) => {
-                error!("Failed to open log file {:?}: {}", &wal_file_path, e);
-                Err(e.into())
-            }
-        }
+        File::open(&wal_file_path)
+            .with_context(|| format!("Failed to open WAL file {:?}", wal_file_path))
+            .map_err(|e| {
+                error!("{}", e);
+                e
+            })
    }

    ///
@@ -144,17 +159,17 @@ impl ReplicationConn {

        thread::spawn(move || {
            if let Err(err) = Self::background_thread(bg_stream_in, bg_timeline) {
-                error!("socket error: {}", err);
+                error!("Replication background thread failed: {}", err);
            }
        });

-        let (mut start_pos, mut stop_pos) = Self::parse_start_stop(&cmd)?;
+        let (mut start_pos, mut stop_pos) = Self::parse_start_stop(cmd)?;

        let mut wal_seg_size: usize;
        loop {
            wal_seg_size = swh.timeline.get().get_info().server.wal_seg_size as usize;
            if wal_seg_size == 0 {
-                error!("Can not start replication before connecting to wal_proposer");
+                error!("Cannot start replication before connecting to wal_proposer");
                sleep(Duration::from_secs(1));
            } else {
                break;
@@ -216,8 +231,9 @@ impl ReplicationConn {

            // Read some data from the file.
            let mut file_buf = vec![0u8; send_size];
-            file.seek(SeekFrom::Start(xlogoff as u64))?;
-            file.read_exact(&mut file_buf)?;
+            file.seek(SeekFrom::Start(xlogoff as u64))
+                .and_then(|_| file.read_exact(&mut file_buf))
+                .context("Failed to read data from WAL file")?;

            // Write some data to the network socket.
            pgb.write_message(&BeMessage::XLogData(XLogDataBody {
@@ -225,11 +241,12 @@ impl ReplicationConn {
                wal_end: end_pos.0,
                timestamp: get_current_timestamp(),
                data: &file_buf,
-            }))?;
+            }))
+            .context("Failed to send XLogData")?;

            start_pos += send_size as u64;

-            debug!("Sent WAL to page server up to {}", end_pos);
+            debug!("sent WAL up to {}", end_pos);

            // Decide whether to reuse this file. If we don't set wal_file here
            // a new file will be opened next time.
--- a/walkeeper/src/safekeeper.rs
+++ b/walkeeper/src/safekeeper.rs
@@ -7,9 +7,11 @@ use byteorder::WriteBytesExt;
 use bytes::Buf;
 use bytes::Bytes;
 use log::*;
+use pageserver::waldecoder::WalStreamDecoder;
 use postgres_ffi::xlog_utils::TimeLineID;
 use serde::{Deserialize, Serialize};
 use std::cmp::max;
+use std::cmp::min;
 use std::io;
 use std::io::Read;

@@ -47,6 +49,7 @@ pub struct ServerInfo {
    /// Postgres server version
    pub pg_version: u32,
    pub system_id: SystemId,
+    pub tenant_id: ZTenantId,
    /// Zenith timelineid
    pub ztli: ZTimelineId,
    pub tli: TimeLineID,
@@ -65,14 +68,16 @@ pub struct SafeKeeperState {
    /// information about server
    pub server: ServerInfo,
    /// Unique id of the last *elected* proposer we dealed with. Not needed
-    /// correctness, exists for monitoring purposes.
+    /// for correctness, exists for monitoring purposes.
    pub proposer_uuid: PgUuid,
-    /// part of WAL acknowledged by quorum (note that we might not have wal to
-    /// up this point locally)
+    /// part of WAL acknowledged by quorum and available locally
    pub commit_lsn: Lsn,
-    /// minimal LSN which may be needed for recovery of some safekeeper (end lsn
-    /// + 1 of last record streamed to everyone)
+    /// minimal LSN which may be needed for recovery of some safekeeper (end_lsn
+    /// of last record streamed to everyone)
    pub truncate_lsn: Lsn,
+    // Safekeeper starts receiving WAL from this LSN, zeros before it ought to
+    // be skipped during decoding.
+    pub wal_start_lsn: Lsn,
 }

 impl SafeKeeperState {
@@ -84,6 +89,7 @@ impl SafeKeeperState {
            server: ServerInfo {
                pg_version: UNKNOWN_SERVER_VERSION, /* Postgres server version */
                system_id: 0,                       /* Postgres system identifier */
+                tenant_id: ZTenantId::from([0u8; 16]),
                ztli: ZTimelineId::from([0u8; 16]),
                tli: 0,
                wal_seg_size: 0,
@@ -91,10 +97,17 @@ impl SafeKeeperState {
            proposer_uuid: [0; 16],
            commit_lsn: Lsn(0),   /* part of WAL acknowledged by quorum */
            truncate_lsn: Lsn(0), /* minimal LSN which may be needed for recovery of some safekeeper */
+            wal_start_lsn: Lsn(0),
        }
    }
 }

+impl Default for SafeKeeperState {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 // protocol messages

 /// Initial Proposer -> Acceptor message
@@ -134,7 +147,7 @@ pub struct VoteResponse {
    /// Safekeeper's log position, to let proposer choose the most advanced one
    epoch: Term,
    flush_lsn: Lsn,
-    restart_lsn: Lsn,
+    truncate_lsn: Lsn,
 }

 /// Request with WAL message sent from proposer to safekeeper. Along the way it
@@ -155,8 +168,8 @@ pub struct AppendRequestHeader {
    end_lsn: Lsn,
    /// LSN committed by quorum of safekeepers
    commit_lsn: Lsn,
-    /// restart LSN position  (minimal LSN which may be needed by proposer to perform recovery)
-    restart_lsn: Lsn,
+    /// minimal LSN which may be needed by proposer to perform recovery of some safekeeper
+    truncate_lsn: Lsn,
    // only for logging/debugging
    proposer_uuid: PgUuid,
 }
@@ -172,6 +185,9 @@ pub struct AppendResponse {
    // make much sense without taking epoch into account, as history can be
    // diverged.
    pub flush_lsn: Lsn,
+    // We report back our awareness about which WAL is committed, as this is
+    // a criterion for walproposer --sync mode exit
+    pub commit_lsn: Lsn,
    pub hs_feedback: HotStandbyFeedback,
 }

@@ -205,7 +221,7 @@ impl ProposerAcceptorMessage {
                let rec_size = hdr
                    .end_lsn
                    .checked_sub(hdr.begin_lsn)
-                    .ok_or(anyhow!("begin_lsn > end_lsn in AppendRequest"))?
+                    .ok_or_else(|| anyhow!("begin_lsn > end_lsn in AppendRequest"))?
                    .0 as usize;
                if rec_size > MAX_SEND_SIZE {
                    bail!(
@@ -217,10 +233,7 @@ impl ProposerAcceptorMessage {
                let mut wal_data_vec: Vec<u8> = vec![0; rec_size];
                stream.read_exact(&mut wal_data_vec)?;
                let wal_data = Bytes::from(wal_data_vec);
-                let msg = AppendRequest {
-                    h: hdr,
-                    wal_data: wal_data,
-                };
+                let msg = AppendRequest { h: hdr, wal_data };

                Ok(ProposerAcceptorMessage::AppendRequest(msg))
            }
@@ -268,16 +281,18 @@ pub trait Storage {

 /// SafeKeeper which consumes events (messages from compute) and provides
 /// replies.
-#[derive(Debug)]
 pub struct SafeKeeper<ST: Storage> {
-    /// Locally flushed part of WAL (end_lsn of last record). Established by
-    /// reading wal.
+    /// Locally flushed part of WAL with full records (end_lsn of last record).
+    /// Established by reading wal.
    pub flush_lsn: Lsn,
    pub tli: u32,
-    pub flushed_truncate_lsn: Lsn,
+    /// not-yet-flushed pairs of same named fields in s.*
+    pub commit_lsn: Lsn,
+    pub truncate_lsn: Lsn,
    pub storage: ST,
    pub s: SafeKeeperState,          // persistent part
    pub elected_proposer_term: Term, // for monitoring/debugging
+    decoder: WalStreamDecoder,
 }

 impl<ST> SafeKeeper<ST>
@@ -289,10 +304,12 @@ where
        SafeKeeper {
            flush_lsn,
            tli,
-            flushed_truncate_lsn: Lsn(0),
+            commit_lsn: state.commit_lsn,
+            truncate_lsn: state.truncate_lsn,
            storage,
            s: state,
            elected_proposer_term: 0,
+            decoder: WalStreamDecoder::new(Lsn(0)),
        }
    }

@@ -320,13 +337,6 @@ where
                SK_PROTOCOL_VERSION
            );
        }
-        if self.s.server.system_id != 0 && self.s.server.system_id != msg.system_id {
-            bail!(
-                "system identifier changed: got {}, expected {}",
-                msg.system_id,
-                self.s.server.system_id,
-            );
-        }
        /* Postgres upgrade is not treated as fatal error */
        if msg.pg_version != self.s.server.pg_version
            && self.s.server.pg_version != UNKNOWN_SERVER_VERSION
@@ -339,10 +349,10 @@ where

        // set basic info about server, if not yet
        self.s.server.system_id = msg.system_id;
+        self.s.server.tenant_id = msg.tenant_id;
        self.s.server.ztli = msg.ztli;
        self.s.server.tli = msg.tli;
        self.s.server.wal_seg_size = msg.wal_seg_size;
-        self.s.proposer_uuid = msg.proposer_id;
        self.storage.persist(&self.s, true)?;

        info!(
@@ -362,7 +372,7 @@ where
            vote_given: false as u64,
            epoch: 0,
            flush_lsn: Lsn(0),
-            restart_lsn: Lsn(0),
+            truncate_lsn: Lsn(0),
        };
        if self.s.acceptor_state.term < msg.term {
            self.s.acceptor_state.term = msg.term;
@@ -371,19 +381,20 @@ where
            resp.vote_given = true as u64;
            resp.epoch = self.s.acceptor_state.epoch;
            resp.flush_lsn = self.flush_lsn;
-            resp.restart_lsn = self.s.truncate_lsn;
+            resp.truncate_lsn = self.s.truncate_lsn;
        }
        info!("processed VoteRequest for term {}: {:?}", msg.term, &resp);
        Ok(AcceptorProposerMessage::VoteResponse(resp))
    }

    /// Handle request to append WAL.
+    #[allow(clippy::comparison_chain)]
    fn handle_append_request(&mut self, msg: &AppendRequest) -> Result<AcceptorProposerMessage> {
        // log first AppendRequest from this proposer
        if self.elected_proposer_term < msg.h.term {
            info!(
-                "start receiving WAL from timeline {} term {}",
-                self.s.server.ztli, msg.h.term,
+                "start accepting WAL from timeline {}, tenant {}, term {}, epochStartLsn {:?}",
+                self.s.server.ztli, self.s.server.tenant_id, msg.h.term, msg.h.epoch_start_lsn,
            );
            self.elected_proposer_term = msg.h.term;
        }
@@ -398,62 +409,122 @@ where
            let resp = AppendResponse {
                term: self.s.acceptor_state.term,
                epoch: self.s.acceptor_state.epoch,
+                commit_lsn: Lsn(0),
                flush_lsn: Lsn(0),
                hs_feedback: HotStandbyFeedback::empty(),
            };
            return Ok(AcceptorProposerMessage::AppendResponse(resp));
        }

-        // do the job
-        self.storage
-            .write_wal(&self.s, msg.h.begin_lsn, &msg.wal_data)?;
+        self.s.proposer_uuid = msg.h.proposer_uuid;
        let mut sync_control_file = false;
+
+        // do the job
+        let mut last_rec_lsn = Lsn(0);
+        if !msg.wal_data.is_empty() {
+            self.storage
+                .write_wal(&self.s, msg.h.begin_lsn, &msg.wal_data)?;
+
+            // figure out last record's end lsn for reporting (if we got the
+            // whole record)
+            if self.decoder.available() != msg.h.begin_lsn {
+                info!(
+                    "restart decoder from {} to {}",
+                    self.decoder.available(),
+                    msg.h.begin_lsn,
+                );
+                self.decoder = WalStreamDecoder::new(msg.h.begin_lsn);
+            }
+            self.decoder.feed_bytes(&msg.wal_data);
+            loop {
+                match self.decoder.poll_decode()? {
+                    None => break, // no full record yet
+                    Some((lsn, _rec)) => {
+                        last_rec_lsn = lsn;
+                    }
+                }
+            }
+
+            // If this was the first record we ever receieved, remember LSN to help
+            // find_end_of_wal skip the hole in the beginning.
+            if self.s.wal_start_lsn == Lsn(0) {
+                self.s.wal_start_lsn = msg.h.begin_lsn;
+                sync_control_file = true;
+            }
+        }
+
        /*
         * Epoch switch happen when written WAL record cross the boundary.
         * The boundary is maximum of last WAL position at this node (FlushLSN) and global
         * maximum (vcl) determined by WAL proposer during handshake.
         * Switching epoch means that node completes recovery and start writing in the WAL new data.
         * XXX: this is wrong, we must actively truncate not matching part of log.
+         *
+         * The non-strict inequality is important for us, as proposer in --sync mode doesn't
+         * generate new records, but to advance commit_lsn epoch switch must happen on majority.
+         * We can regard this as commit of empty entry in new epoch, this should be safe.
         */
        if self.s.acceptor_state.epoch < msg.h.term
-            && msg.h.end_lsn > max(self.flush_lsn, msg.h.epoch_start_lsn)
+            && msg.h.end_lsn >= max(self.flush_lsn, msg.h.epoch_start_lsn)
        {
-            info!("switched to new epoch {}", msg.h.term);
+            info!(
+                "switched to new epoch {} on receival of request end_lsn={:?}, len={:?}",
+                msg.h.term,
+                msg.h.end_lsn,
+                msg.wal_data.len(),
+            );
            self.s.acceptor_state.epoch = msg.h.term; /* bump epoch */
            sync_control_file = true;
        }
-        if msg.h.end_lsn > self.flush_lsn {
-            self.flush_lsn = msg.h.end_lsn;
+        if last_rec_lsn > self.flush_lsn {
+            self.flush_lsn = last_rec_lsn;
        }

-        self.s.proposer_uuid = msg.h.proposer_uuid;
-        self.s.commit_lsn = msg.h.commit_lsn;
-        self.s.truncate_lsn = msg.h.restart_lsn;
+        // Advance commit_lsn taking into account what we have locally. xxx this
+        // is wrapped into epoch check because we overwrite wal instead of
+        // truncating it, so without it commit_lsn might include wrong part.
+        // Anyway, nobody is much interested in our commit_lsn while epoch
+        // switch hasn't happened, right?
+        //
+        // commit_lsn can be 0, being unknown to new walproposer while he hasn't
+        // collected majority of its epoch acks yet, ignore it in this case.
+        if self.s.acceptor_state.epoch == msg.h.term && msg.h.commit_lsn != Lsn(0) {
+            let commit_lsn = min(msg.h.commit_lsn, self.flush_lsn);
+            // If new commit_lsn reached epoch switch, force sync of control file:
+            // walproposer in sync mode is very interested when this happens.
+            sync_control_file |=
+                commit_lsn >= msg.h.epoch_start_lsn && self.s.commit_lsn < msg.h.epoch_start_lsn;
+            self.commit_lsn = commit_lsn;
+        }

+        self.truncate_lsn = msg.h.truncate_lsn;
        /*
-         * Update restart LSN in control file.
+         * Update truncate and commit LSN in control file.
         * To avoid negative impact on performance of extra fsync, do it only
         * when restart_lsn delta exceeds WAL segment size.
         */
        sync_control_file |=
-            self.flushed_truncate_lsn + (self.s.server.wal_seg_size as u64) < self.s.truncate_lsn;
-        self.storage.persist(&self.s, sync_control_file)?;
+            self.s.truncate_lsn + (self.s.server.wal_seg_size as u64) < self.truncate_lsn;
        if sync_control_file {
-            self.flushed_truncate_lsn = self.s.truncate_lsn;
+            self.s.commit_lsn = self.commit_lsn;
+            self.s.truncate_lsn = self.truncate_lsn;
        }
+        self.storage.persist(&self.s, sync_control_file)?;

        let resp = AppendResponse {
            term: self.s.acceptor_state.term,
            epoch: self.s.acceptor_state.epoch,
            flush_lsn: self.flush_lsn,
+            commit_lsn: self.s.commit_lsn,
            // will be filled by caller code to avoid bothering safekeeper
            hs_feedback: HotStandbyFeedback::empty(),
        };
-        trace!(
-            "processed AppendRequest of len {}, flush_lsn={:X}/{:>08X}, resp {:?}",
+        info!(
+            "processed AppendRequest of len {}, end_lsn={:?}, commit_lsn={:?}, truncate_lsn={:?}, resp {:?}",
            msg.wal_data.len(),
-            (self.flush_lsn.0 >> 32) as u32,
-            self.flush_lsn.0 as u32,
+            msg.h.end_lsn,
+            msg.h.commit_lsn,
+            msg.h.truncate_lsn,
            &resp,
        );
        Ok(AcceptorProposerMessage::AppendResponse(resp))
@@ -492,7 +563,7 @@ mod tests {
        let mut vote_resp = sk.process_msg(&vote_request);
        match vote_resp.unwrap() {
            AcceptorProposerMessage::VoteResponse(resp) => assert!(resp.vote_given != 0),
-            _ => assert!(false),
+            r => panic!("unexpected response: {:?}", r),
        }

        // reboot...
@@ -506,7 +577,7 @@ mod tests {
        vote_resp = sk.process_msg(&vote_request);
        match vote_resp.unwrap() {
            AcceptorProposerMessage::VoteResponse(resp) => assert!(resp.vote_given == 0),
-            _ => assert!(false),
+            r => panic!("unexpected response: {:?}", r),
        }
    }

@@ -519,11 +590,11 @@ mod tests {

        let mut ar_hdr = AppendRequestHeader {
            term: 1,
-            epoch_start_lsn: Lsn(2),
+            epoch_start_lsn: Lsn(3),
            begin_lsn: Lsn(1),
            end_lsn: Lsn(2),
            commit_lsn: Lsn(0),
-            restart_lsn: Lsn(0),
+            truncate_lsn: Lsn(0),
            proposer_uuid: [0; 16],
        };
        let mut append_request = AppendRequest {
@@ -531,20 +602,20 @@ mod tests {
            wal_data: Bytes::from_static(b"b"),
        };

-        // check that AppendRequest before VCL doesn't switch epoch
+        // check that AppendRequest before epochStartLsn doesn't switch epoch
        let resp = sk.process_msg(&ProposerAcceptorMessage::AppendRequest(append_request));
        assert!(resp.is_ok());
-        assert!(sk.storage.persisted_state.acceptor_state.epoch == 0);
+        assert_eq!(sk.storage.persisted_state.acceptor_state.epoch, 0);

-        // but record after VCL does the switch
+        // but record at epochStartLsn does the switch
        ar_hdr.begin_lsn = Lsn(2);
        ar_hdr.end_lsn = Lsn(3);
        append_request = AppendRequest {
-            h: ar_hdr.clone(),
+            h: ar_hdr,
            wal_data: Bytes::from_static(b"b"),
        };
        let resp = sk.process_msg(&ProposerAcceptorMessage::AppendRequest(append_request));
        assert!(resp.is_ok());
-        assert!(sk.storage.persisted_state.acceptor_state.epoch == 1);
+        assert_eq!(sk.storage.persisted_state.acceptor_state.epoch, 1);
    }
 }
--- a/walkeeper/src/send_wal.rs
+++ b/walkeeper/src/send_wal.rs
@@ -33,13 +33,13 @@ impl postgres_backend::Handler for SendWalHandler {
        let ztimelineid = sm
            .params
            .get("ztimelineid")
-            .ok_or(anyhow!("timelineid is required"))?;
+            .ok_or_else(|| anyhow!("timelineid is required"))?;
        self.timelineid = Some(ZTimelineId::from_str(ztimelineid)?);

        let ztenantid = sm
            .params
            .get("ztenantid")
-            .ok_or(anyhow!("tenantid is required"))?;
+            .ok_or_else(|| anyhow!("tenantid is required"))?;
        self.tenantid = Some(ZTenantId::from_str(ztenantid)?);

        if let Some(app_name) = sm.params.get("application_name") {
--- a/walkeeper/src/timeline.rs
+++ b/walkeeper/src/timeline.rs
@@ -27,12 +27,9 @@ use postgres_ffi::xlog_utils::{XLogFileName, XLOG_BLCKSZ};
 const CONTROL_FILE_NAME: &str = "safekeeper.control";

 /// Shared state associated with database instance (tenant)
-#[derive(Debug)]
 struct SharedState {
    /// Safekeeper object
    sk: SafeKeeper<FileStorage>,
-    /// opened file control file handle (needed to hold exlusive file lock)
-    control_file: File,
    /// For receiving-sending wal cooperation
    /// quorum commit LSN we've notified walsenders about
    commit_lsn: Lsn,
@@ -59,12 +56,17 @@ impl SharedState {
    ) -> Result<Self> {
        let (cf, state) = SharedState::load_control_file(conf, timelineid, create)?;
        let storage = FileStorage {
-            control_file: cf.try_clone()?,
+            control_file: cf,
            conf: conf.clone(),
        };
        let (flush_lsn, tli) = if state.server.wal_seg_size != 0 {
            let wal_dir = conf.data_dir.join(format!("{}", timelineid));
-            find_end_of_wal(&wal_dir, state.server.wal_seg_size as usize, true)
+            find_end_of_wal(
+                &wal_dir,
+                state.server.wal_seg_size as usize,
+                true,
+                state.wal_start_lsn,
+            )?
        } else {
            (0, 0)
        };
@@ -72,7 +74,6 @@ impl SharedState {
        Ok(Self {
            commit_lsn: Lsn(0),
            sk: SafeKeeper::new(Lsn(flush_lsn), tli, storage, state),
-            control_file: cf,
            hs_feedback: HotStandbyFeedback {
                ts: 0,
                xmin: u64::MAX,
@@ -127,7 +128,7 @@ impl SharedState {
                    if let CreateControlFile::False = create {
                        bail!("control file is empty");
                    }
-                    return Ok((file, SafeKeeperState::new()));
+                    Ok((file, SafeKeeperState::new()))
                } else {
                    match SafeKeeperState::des_from(&mut file) {
                        Err(e) => {
@@ -144,7 +145,7 @@ impl SharedState {
                                    SK_FORMAT_VERSION
                                );
                            }
-                            return Ok((file, s));
+                            Ok((file, s))
                        }
                    }
                }
@@ -161,7 +162,6 @@ impl SharedState {
 }

 /// Database instance (tenant)
-#[derive(Debug)]
 pub struct Timeline {
    pub timelineid: ZTimelineId,
    mutex: Mutex<SharedState>,
@@ -217,14 +217,11 @@ impl Timeline {
            rmsg = shared_state.sk.process_msg(msg)?;
            // locally available commit lsn. flush_lsn can be smaller than
            // commit_lsn if we are catching up safekeeper.
-            commit_lsn = min(shared_state.sk.flush_lsn, shared_state.sk.s.commit_lsn);
+            commit_lsn = shared_state.sk.commit_lsn;

            // if this is AppendResponse, fill in proper hot standby feedback
-            match rmsg {
-                AcceptorProposerMessage::AppendResponse(ref mut resp) => {
-                    resp.hs_feedback = shared_state.hs_feedback.clone();
-                }
-                _ => (),
+            if let AcceptorProposerMessage::AppendResponse(ref mut resp) = rmsg {
+                resp.hs_feedback = shared_state.hs_feedback.clone();
            }
        }
        // Ping wal sender that new data might be available.
@@ -401,7 +398,7 @@ impl Storage for FileStorage {
                    {
                        Ok(mut file) => {
                            for _ in 0..(wal_seg_size / XLOG_BLCKSZ) {
-                                file.write_all(&ZERO_BLOCK)?;
+                                file.write_all(ZERO_BLOCK)?;
                            }
                            wal_file = file;
                        }
--- a/zenith/src/main.rs
+++ b/zenith/src/main.rs
@@ -1,10 +1,10 @@
-use anyhow::{anyhow, bail};
+use anyhow::anyhow;
 use anyhow::{Context, Result};
 use clap::{App, AppSettings, Arg, ArgMatches, SubCommand};
 use control_plane::compute::ComputeControlPlane;
-use control_plane::local_env::{self, LocalEnv};
+use control_plane::local_env;
 use control_plane::storage::PageServerNode;
-use std::collections::btree_map::Entry;
+use pageserver::defaults::{DEFAULT_HTTP_LISTEN_PORT, DEFAULT_PG_LISTEN_PORT};
 use std::collections::HashMap;
 use std::process::exit;
 use std::str::FromStr;
@@ -13,7 +13,6 @@ use zenith_utils::postgres_backend::AuthType;
 use zenith_utils::zid::{ZTenantId, ZTimelineId};

 use pageserver::branches::BranchInfo;
-use zenith_utils::lsn::Lsn;

 ///
 /// Branches tree element used as a value in the HashMap.
@@ -30,7 +29,7 @@ struct BranchTreeEl {
 // This utility helps to manage zenith installation. That includes following:
 //   * Management of local postgres installations running on top of the
 //     pageserver.
-//   * Providing CLI api to the pageserver (local or remote)
+//   * Providing CLI api to the pageserver
 //   * TODO: export/import to/from usual postgres
 fn main() -> Result<()> {
    let timeline_arg = Arg::with_name("timeline")
@@ -45,16 +44,27 @@ fn main() -> Result<()> {
        .takes_value(true)
        .required(false);

+    let port_arg = Arg::with_name("port")
+        .long("port")
+        .required(false)
+        .value_name("port");
+
    let matches = App::new("Zenith CLI")
        .setting(AppSettings::ArgRequiredElseHelp)
        .subcommand(
            SubCommand::with_name("init")
                .about("Initialize a new Zenith repository")
                .arg(
-                    Arg::with_name("remote-pageserver")
-                        .long("remote-pageserver")
+                    Arg::with_name("pageserver-pg-port")
+                        .long("pageserver-pg-port")
                        .required(false)
-                        .value_name("pageserver-url"),
+                        .value_name("pageserver-pg-port"),
+                )
+                .arg(
+                    Arg::with_name("pageserver-http-port")
+                        .long("pageserver-http-port")
+                        .required(false)
+                        .value_name("pageserver-http-port"),
                )
                .arg(
                    Arg::with_name("enable-auth")
@@ -87,7 +97,7 @@ fn main() -> Result<()> {
                .subcommand(SubCommand::with_name("list").arg(tenantid_arg.clone()))
                .subcommand(SubCommand::with_name("create")
                    .about("Create a postgres compute node")
-                    .arg(timeline_arg.clone()).arg(tenantid_arg.clone())
+                    .arg(timeline_arg.clone()).arg(tenantid_arg.clone()).arg(port_arg.clone())
                    .arg(
                        Arg::with_name("config-only")
                            .help("Don't do basebackup, create compute node with only config files")
@@ -95,8 +105,12 @@ fn main() -> Result<()> {
                            .required(false)
                    ))
                .subcommand(SubCommand::with_name("start")
-                    .about("Start a postrges compute node.\n This command actually creates new node from scrath, but preserves existing config files")
-                    .arg(timeline_arg.clone()).arg(tenantid_arg.clone()))
+                    .about("Start a postgres compute node.\n This command actually creates new node from scratch, but preserves existing config files")
+                    .arg(
+                        timeline_arg.clone()
+                    ).arg(
+                        tenantid_arg.clone()
+                    ).arg(port_arg.clone()))
                .subcommand(
                    SubCommand::with_name("stop")
                        .arg(timeline_arg.clone())
@@ -107,36 +121,36 @@ fn main() -> Result<()> {
                                .long("destroy")
                                .required(false)
                        )
-                )
-        )
-        .subcommand(
-            SubCommand::with_name("remote")
-                .setting(AppSettings::ArgRequiredElseHelp)
-                .about("Manage remote pagerservers")
-                .subcommand(
-                    SubCommand::with_name("add")
-                        .about("Add a new remote pageserver")
-                        .arg(Arg::with_name("name").required(true))
-                        .arg(
-                            Arg::with_name("url")
-                                .help("PostgreSQL connection URI")
-                                .required(true),
-                        ),
-                ),
+                    )
+
        )
        .get_matches();

    // Create config file
    if let ("init", Some(init_match)) = matches.subcommand() {
        let tenantid = ZTenantId::generate();
-        let pageserver_uri = init_match.value_of("pageserver-url");
+        let pageserver_pg_port = match init_match.value_of("pageserver-pg-port") {
+            Some(v) => v.parse()?,
+            None => DEFAULT_PG_LISTEN_PORT,
+        };
+        let pageserver_http_port = match init_match.value_of("pageserver-http-port") {
+            Some(v) => v.parse()?,
+            None => DEFAULT_HTTP_LISTEN_PORT,
+        };
+
        let auth_type = if init_match.is_present("enable-auth") {
            AuthType::ZenithJWT
        } else {
            AuthType::Trust
        };
-        local_env::init(pageserver_uri, tenantid, auth_type)
-            .with_context(|| "Failed to create config file")?;
+
+        local_env::init(
+            pageserver_pg_port,
+            pageserver_http_port,
+            tenantid,
+            auth_type,
+        )
+        .with_context(|| "Failed to create config file")?;
    }

    // all other commands would need config
@@ -214,13 +228,6 @@ fn main() -> Result<()> {
            }
        }

-        ("remote", Some(remote_match)) => {
-            if let Err(e) = handle_remote(remote_match, &env) {
-                eprintln!("remote operation failed: {}", e);
-                exit(1);
-            }
-        }
-
        _ => {}
    };

@@ -359,7 +366,7 @@ fn get_branch_infos(
 }

 fn handle_tenant(tenant_match: &ArgMatches, env: &local_env::LocalEnv) -> Result<()> {
-    let pageserver = PageServerNode::from_env(&env);
+    let pageserver = PageServerNode::from_env(env);
    match tenant_match.subcommand() {
        ("list", Some(_)) => {
            for tenant in pageserver.tenant_list()? {
@@ -381,21 +388,19 @@ fn handle_tenant(tenant_match: &ArgMatches, env: &local_env::LocalEnv) -> Result
 }

 fn handle_branch(branch_match: &ArgMatches, env: &local_env::LocalEnv) -> Result<()> {
-    let pageserver = PageServerNode::from_env(&env);
+    let pageserver = PageServerNode::from_env(env);

    if let Some(branchname) = branch_match.value_of("branchname") {
        let startpoint_str = branch_match
            .value_of("start-point")
-            .ok_or(anyhow!("Missing start-point"))?;
+            .ok_or_else(|| anyhow!("Missing start-point"))?;
        let tenantid: ZTenantId = branch_match
            .value_of("tenantid")
            .map_or(Ok(env.tenantid), |value| value.parse())?;
        let branch = pageserver.branch_create(branchname, startpoint_str, &tenantid)?;
        println!(
            "Created branch '{}' at {:?} for tenant: {}",
-            branch.name,
-            branch.latest_valid_lsn.unwrap_or(Lsn(0)),
-            tenantid,
+            branch.name, branch.latest_valid_lsn, tenantid,
        );
    } else {
        let tenantid: ZTenantId = branch_match
@@ -434,9 +439,7 @@ fn handle_pg(pg_match: &ArgMatches, env: &local_env::LocalEnv) -> Result<()> {
                    node.address,
                    branch_infos
                        .get(&node.timelineid)
-                        .map(|bi| bi
-                            .latest_valid_lsn
-                            .map_or("?".to_string(), |lsn| lsn.to_string()))
+                        .map(|bi| bi.latest_valid_lsn.to_string())
                        .unwrap_or_else(|| "?".to_string()),
                    node.status(),
                );
@@ -447,9 +450,12 @@ fn handle_pg(pg_match: &ArgMatches, env: &local_env::LocalEnv) -> Result<()> {
                .value_of("tenantid")
                .map_or(Ok(env.tenantid), |value| value.parse())?;
            let timeline_name = create_match.value_of("timeline").unwrap_or("main");
-            let config_only = create_match.is_present("config-only");

-            cplane.new_node(tenantid, timeline_name, config_only)?;
+            let port: Option<u16> = match create_match.value_of("port") {
+                Some(p) => Some(p.parse()?),
+                None => None,
+            };
+            cplane.new_node(tenantid, timeline_name, port)?;
        }
        ("start", Some(start_match)) => {
            let tenantid: ZTenantId = start_match
@@ -457,6 +463,11 @@ fn handle_pg(pg_match: &ArgMatches, env: &local_env::LocalEnv) -> Result<()> {
                .map_or(Ok(env.tenantid), |value| value.parse())?;
            let timeline_name = start_match.value_of("timeline").unwrap_or("main");

+            let port: Option<u16> = match start_match.value_of("port") {
+                Some(p) => Some(p.parse()?),
+                None => None,
+            };
+
            let node = cplane.nodes.get(&(tenantid, timeline_name.to_owned()));

            let auth_token = if matches!(env.auth_type, AuthType::ZenithJWT) {
@@ -466,11 +477,20 @@ fn handle_pg(pg_match: &ArgMatches, env: &local_env::LocalEnv) -> Result<()> {
                None
            };

-            println!("Starting postgres on timeline {}...", timeline_name);
+            println!(
+                "Starting {} postgres on timeline {}...",
+                if node.is_some() { "existing" } else { "new" },
+                timeline_name
+            );
            if let Some(node) = node {
                node.start(&auth_token)?;
            } else {
-                let node = cplane.new_node(tenantid, timeline_name, false)?;
+                // when used with custom port this results in non obvious behaviour
+                // port is remembered from first start command, i e
+                // start --port X
+                // stop
+                // start <-- will also use port X even without explicit port argument
+                let node = cplane.new_node(tenantid, timeline_name, port)?;
                node.start(&auth_token)?;
            }
        }
@@ -493,29 +513,3 @@ fn handle_pg(pg_match: &ArgMatches, env: &local_env::LocalEnv) -> Result<()> {

    Ok(())
 }
-
-fn handle_remote(remote_match: &ArgMatches, local_env: &LocalEnv) -> Result<()> {
-    match remote_match.subcommand() {
-        ("add", Some(args)) => {
-            let name = args.value_of("name").unwrap();
-            let url = args.value_of("url").unwrap();
-
-            // validate the URL
-            postgres::Config::from_str(url)?;
-
-            let mut new_local_env = local_env.clone();
-
-            match new_local_env.remotes.entry(name.to_string()) {
-                Entry::Vacant(vacant) => {
-                    vacant.insert(url.to_string());
-                }
-                Entry::Occupied(_) => bail!("origin '{}' already exists", name),
-            }
-
-            local_env::save_config(&new_local_env)?;
-        }
-        _ => bail!("unknown command"),
-    }
-
-    Ok(())
-}
--- a/zenith_metrics/Cargo.toml
+++ b/zenith_metrics/Cargo.toml
@@ -4,6 +4,6 @@ version = "0.1.0"
 edition = "2018"

 [dependencies]
-prometheus = "0.12"
+prometheus = {version = "0.12", default_features=false} # removes protobuf dependency
 libc = "0.2"
 lazy_static = "1.4"
--- a/zenith_metrics/src/lib.rs
+++ b/zenith_metrics/src/lib.rs
@@ -13,7 +13,6 @@ pub use prometheus::{register_int_gauge_vec, IntGaugeVec};
 pub use prometheus::{Encoder, TextEncoder};

 mod wrappers;
-use libc::{c_long, getrusage, rusage, suseconds_t, time_t, timeval, RUSAGE_SELF};
 pub use wrappers::{CountedReader, CountedWriter};

 /// Gathers all Prometheus metrics and records the I/O stats just before that.
@@ -35,47 +34,33 @@ lazy_static! {
 }

 // Records I/O stats in a "cross-platform" way.
-// Compiles both on macOs and Linux, but current macOs implementation always returns 0 as values for I/O stats.
-// An alternative is to read procfs (`/proc/[pid]/io`) which does not work under macOs at all, hence abandoned.
+// Compiles both on macOS and Linux, but current macOS implementation always returns 0 as values for I/O stats.
+// An alternative is to read procfs (`/proc/[pid]/io`) which does not work under macOS at all, hence abandoned.
 //
 // Uses https://www.freebsd.org/cgi/man.cgi?query=getrusage to retrieve the number of block operations
 // performed by the process.
-// We know the the size of the block, so we can determine the I/O bytes out of it.
+// We know the size of the block, so we can determine the I/O bytes out of it.
 // The value might be not 100% exact, but should be fine for Prometheus metrics in this case.
+#[allow(clippy::unnecessary_cast)]
 fn update_io_metrics() {
-    let mut usage = rusage {
-        ru_utime: timeval {
-            tv_sec: 0 as time_t,
-            tv_usec: 0 as suseconds_t,
-        },
-        ru_stime: timeval {
-            tv_sec: 0 as time_t,
-            tv_usec: 0 as suseconds_t,
-        },
-        ru_maxrss: 0 as c_long,
-        ru_ixrss: 0 as c_long,
-        ru_idrss: 0 as c_long,
-        ru_isrss: 0 as c_long,
-        ru_minflt: 0 as c_long,
-        ru_majflt: 0 as c_long,
-        ru_nswap: 0 as c_long,
-        ru_inblock: 0 as c_long,
-        ru_oublock: 0 as c_long,
-        ru_msgsnd: 0 as c_long,
-        ru_msgrcv: 0 as c_long,
-        ru_nsignals: 0 as c_long,
-        ru_nvcsw: 0 as c_long,
-        ru_nivcsw: 0 as c_long,
-    };
-    unsafe {
-        getrusage(RUSAGE_SELF, (&mut usage) as *mut rusage);
-    }
+    let rusage_stats = get_rusage_stats();

    const BYTES_IN_BLOCK: i64 = 512;
    DISK_IO_BYTES
        .with_label_values(&["read"])
-        .set(usage.ru_inblock * BYTES_IN_BLOCK);
+        .set(rusage_stats.ru_inblock * BYTES_IN_BLOCK);
    DISK_IO_BYTES
        .with_label_values(&["write"])
-        .set(usage.ru_oublock * BYTES_IN_BLOCK);
+        .set(rusage_stats.ru_oublock * BYTES_IN_BLOCK);
+}
+
+fn get_rusage_stats() -> libc::rusage {
+    let mut rusage = std::mem::MaybeUninit::uninit();
+
+    // SAFETY: kernel will initialize the struct for us
+    unsafe {
+        let ret = libc::getrusage(libc::RUSAGE_SELF, rusage.as_mut_ptr());
+        assert!(ret == 0, "getrusage failed: bad args");
+        rusage.assume_init()
+    }
 }
--- a/zenith_metrics/src/wrappers.rs
+++ b/zenith_metrics/src/wrappers.rs
@@ -186,7 +186,7 @@ mod tests {
        assert_eq!(total, stream.len());
    }

-    // This mimicks the constraints of std::thread::spawn
+    // This mimics the constraints of std::thread::spawn
    fn assert_send_sync(_x: impl Sync + Send + 'static) {}

    #[test]
--- a/zenith_utils/Cargo.toml
+++ b/zenith_utils/Cargo.toml
@@ -17,7 +17,13 @@ routerify = "2"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1"
 thiserror = "1.0"
-tokio = { version = "1.5.0", features = ["full"] }
+tokio = "1.11"
+
+slog-async = "2.6.0"
+slog-stdlog = "4.1.0"
+slog-scope = "4.4.0"
+slog-term = "2.8.0"
+slog = "2.7.0"

 zenith_metrics = { path = "../zenith_metrics" }
 workspace_hack = { path = "../workspace_hack" }
--- a/zenith_utils/src/auth.rs
+++ b/zenith_utils/src/auth.rs
@@ -1,6 +1,6 @@
 // For details about authentication see docs/authentication.md
 // TODO there are two issues for our use case in jsonwebtoken library which will be resolved in next release
-// The fisrt one is that there is no way to disable expiration claim, but it can be excluded from validation, so use this as a workaround for now.
+// The first one is that there is no way to disable expiration claim, but it can be excluded from validation, so use this as a workaround for now.
 // Relevant issue: https://github.com/Keats/jsonwebtoken/issues/190
 // The second one is that we wanted to use ed25519 keys, but they are also not supported until next version. So we go with RSA keys for now.
 // Relevant issue: https://github.com/Keats/jsonwebtoken/issues/162
@@ -8,7 +8,8 @@
 use hex::{self, FromHex};
 use serde::de::Error;
 use serde::{self, Deserializer, Serializer};
-use std::{fs, path::PathBuf};
+use std::fs;
+use std::path::Path;

 use anyhow::{bail, Result};
 use jsonwebtoken::{
@@ -43,8 +44,8 @@ where
 {
    let opt: Option<String> = Option::deserialize(deserializer)?;
    match opt {
-        Some(tid) => return Ok(Some(ZTenantId::from_hex(tid).map_err(Error::custom)?)),
-        None => return Ok(None),
+        Some(tid) => Ok(Some(ZTenantId::from_hex(tid).map_err(Error::custom)?)),
+        None => Ok(None),
    }
 }

@@ -91,7 +92,7 @@ pub struct JwtAuth {
 }

 impl JwtAuth {
-    pub fn new<'a>(decoding_key: DecodingKey<'a>) -> Self {
+    pub fn new(decoding_key: DecodingKey<'_>) -> Self {
        Self {
            decoding_key: decoding_key.into_static(),
            validation: Validation {
@@ -102,7 +103,7 @@ impl JwtAuth {
        }
    }

-    pub fn from_key_path(key_path: &PathBuf) -> Result<Self> {
+    pub fn from_key_path(key_path: &Path) -> Result<Self> {
        let public_key = fs::read_to_string(key_path)?;
        Ok(Self::new(DecodingKey::from_rsa_pem(public_key.as_bytes())?))
    }
@@ -113,8 +114,8 @@ impl JwtAuth {
 }

 // this function is used only for testing purposes in CLI e g generate tokens during init
-pub fn encode_from_key_path(claims: &Claims, key_path: &PathBuf) -> Result<String> {
+pub fn encode_from_key_path(claims: &Claims, key_path: &Path) -> Result<String> {
    let key_data = fs::read_to_string(key_path)?;
-    let key = EncodingKey::from_rsa_pem(&key_data.as_bytes())?;
+    let key = EncodingKey::from_rsa_pem(key_data.as_bytes())?;
    Ok(encode(&Header::new(JWT_ALGORITHM), claims, &key)?)
 }
--- a/zenith_utils/src/bin_ser.rs
+++ b/zenith_utils/src/bin_ser.rs
@@ -6,7 +6,7 @@
 //!
 //! The [`LeSer`] trait does the same thing, in little-endian form.
 //!
-//! Note: you will get a compile error if you try to `use` both trais
+//! Note: you will get a compile error if you try to `use` both traits
 //! in the same module or scope. This is intended to be a safety
 //! mechanism: mixing big-endian and little-endian encoding in the same file
 //! is error-prone.
@@ -69,14 +69,13 @@ impl From<bincode::Error> for SerializeError {
 /// Properties:
 /// - Big endian
 /// - Fixed integer encoding (i.e. 1u32 is 00000001 not 01)
-/// - Allow trailing bytes: this means we don't throw an error
-///   if the deserializer is passed a buffer with more data
-///   past the end.
+///
+/// Does not allow trailing bytes in deserialization. If this is desired, you
+/// may set [`Options::allow_trailing_bytes`] to explicitly accomodate this.
 pub fn be_coder() -> impl Options {
    bincode::DefaultOptions::new()
        .with_big_endian()
        .with_fixint_encoding()
-        .allow_trailing_bytes()
 }

 /// A shortcut that configures little-ending binary serialization
@@ -84,14 +83,13 @@ pub fn be_coder() -> impl Options {
 /// Properties:
 /// - Little endian
 /// - Fixed integer encoding (i.e. 1u32 is 00000001 not 01)
-/// - Allow trailing bytes: this means we don't throw an error
-///   if the deserializer is passed a buffer with more data
-///   past the end.
+///
+/// Does not allow trailing bytes in deserialization. If this is desired, you
+/// may set [`Options::allow_trailing_bytes`] to explicitly accomodate this.
 pub fn le_coder() -> impl Options {
    bincode::DefaultOptions::new()
        .with_little_endian()
        .with_fixint_encoding()
-        .allow_trailing_bytes()
 }

 /// Binary serialize/deserialize helper functions (Big Endian)
@@ -118,13 +116,28 @@ pub trait BeSer: Serialize + DeserializeOwned {
        be_coder().serialize(&self).map_err(|e| e.into())
    }

-    /// Deserialize from a byte slice
+    /// Deserialize from the full contents of a byte slice
+    ///
+    /// See also: [`BeSer::des_prefix`]
    fn des(buf: &[u8]) -> Result<Self, DeserializeError> {
        be_coder()
            .deserialize(buf)
            .or(Err(DeserializeError::BadInput))
    }

+    /// Deserialize from a prefix of the byte slice
+    ///
+    /// Uses as much of the byte slice as is necessary to deserialize the
+    /// type, but does not guarantee that the entire slice is used.
+    ///
+    /// See also: [`BeSer::des`]
+    fn des_prefix(buf: &[u8]) -> Result<Self, DeserializeError> {
+        be_coder()
+            .allow_trailing_bytes()
+            .deserialize(buf)
+            .or(Err(DeserializeError::BadInput))
+    }
+
    /// Deserialize from a reader
    fn des_from<R: Read>(r: &mut R) -> Result<Self, DeserializeError> {
        be_coder().deserialize_from(r).map_err(|e| e.into())
@@ -163,13 +176,28 @@ pub trait LeSer: Serialize + DeserializeOwned {
        le_coder().serialize(&self).map_err(|e| e.into())
    }

-    /// Deserialize from a byte slice
+    /// Deserialize from the full contents of a byte slice
+    ///
+    /// See also: [`LeSer::des_prefix`]
    fn des(buf: &[u8]) -> Result<Self, DeserializeError> {
        le_coder()
            .deserialize(buf)
            .or(Err(DeserializeError::BadInput))
    }

+    /// Deserialize from a prefix of the byte slice
+    ///
+    /// Uses as much of the byte slice as is necessary to deserialize the
+    /// type, but does not guarantee that the entire slice is used.
+    ///
+    /// See also: [`LeSer::des`]
+    fn des_prefix(buf: &[u8]) -> Result<Self, DeserializeError> {
+        le_coder()
+            .allow_trailing_bytes()
+            .deserialize(buf)
+            .or(Err(DeserializeError::BadInput))
+    }
+
    /// Deserialize from a reader
    fn des_from<R: Read>(r: &mut R) -> Result<Self, DeserializeError> {
        le_coder().deserialize_from(r).map_err(|e| e.into())
@@ -247,8 +275,10 @@ mod tests {
        assert_eq!(decoded, SHORT2);

        // with trailing data
-        let decoded = ShortStruct::des(SHORT2_ENC_BE_TRAILING).unwrap();
+        let decoded = ShortStruct::des_prefix(SHORT2_ENC_BE_TRAILING).unwrap();
        assert_eq!(decoded, SHORT2);
+        let err = ShortStruct::des(SHORT2_ENC_BE_TRAILING).unwrap_err();
+        assert!(matches!(err, DeserializeError::BadInput));

        // serialize into a `Write` sink.
        let mut buf = Cursor::new(vec![0xFF; 8]);
@@ -279,8 +309,10 @@ mod tests {
        assert_eq!(decoded, SHORT2);

        // with trailing data
-        let decoded = ShortStruct::des(SHORT2_ENC_LE_TRAILING).unwrap();
+        let decoded = ShortStruct::des_prefix(SHORT2_ENC_LE_TRAILING).unwrap();
        assert_eq!(decoded, SHORT2);
+        let err = ShortStruct::des(SHORT2_ENC_LE_TRAILING).unwrap_err();
+        assert!(matches!(err, DeserializeError::BadInput));

        // serialize into a `Write` sink.
        let mut buf = Cursor::new(vec![0xFF; 8]);
--- a/zenith_utils/src/http/endpoint.rs
+++ b/zenith_utils/src/http/endpoint.rs
@@ -8,6 +8,7 @@ use lazy_static::lazy_static;
 use routerify::ext::RequestExt;
 use routerify::RequestInfo;
 use routerify::{Middleware, Router, RouterBuilder, RouterService};
+use std::net::TcpListener;
 use zenith_metrics::{register_int_counter, IntCounter};
 use zenith_metrics::{Encoder, TextEncoder};

@@ -95,13 +96,13 @@ pub fn attach_openapi_ui(

 fn parse_token(header_value: &str) -> Result<&str, ApiError> {
    // header must be in form Bearer <token>
-    let (prefix, token) = header_value.split_once(' ').ok_or(ApiError::Unauthorized(
-        "malformed authorization header".to_string(),
-    ))?;
+    let (prefix, token) = header_value
+        .split_once(' ')
+        .ok_or_else(|| ApiError::Unauthorized("malformed authorization header".to_string()))?;
    if prefix != "Bearer" {
-        Err(ApiError::Unauthorized(
+        return Err(ApiError::Unauthorized(
            "malformed authorization header".to_string(),
-        ))?
+        ));
    }
    Ok(token)
 }
@@ -123,9 +124,11 @@ pub fn auth_middleware<B: hyper::body::HttpBody + Send + Sync + 'static>(
                        .map_err(|_| ApiError::Unauthorized("malformed jwt token".to_string()))?;
                    req.set_context(data.claims);
                }
-                None => Err(ApiError::Unauthorized(
-                    "missing authorization header".to_string(),
-                ))?,
+                None => {
+                    return Err(ApiError::Unauthorized(
+                        "missing authorization header".to_string(),
+                    ))
+                }
            }
        }
        Ok(req)
@@ -142,10 +145,9 @@ pub fn check_permission(req: &Request<Body>, tenantid: Option<ZTenantId>) -> Res

 pub fn serve_thread_main(
    router_builder: RouterBuilder<hyper::Body, ApiError>,
-    addr: String,
+    listener: TcpListener,
 ) -> anyhow::Result<()> {
-    let addr = addr.parse()?;
-    log::info!("Starting a http endoint at {}", addr);
+    log::info!("Starting a http endoint at {}", listener.local_addr()?);

    // Create a Service from the router above to handle incoming requests.
    let service = RouterService::new(router_builder.build().map_err(|err| anyhow!(err))?).unwrap();
@@ -157,7 +159,7 @@ pub fn serve_thread_main(

    let _guard = runtime.enter();

-    let server = Server::bind(&addr).serve(service);
+    let server = Server::from_tcp(listener)?.serve(service);

    runtime.block_on(server)?;

--- a/zenith_utils/src/http/error.rs
+++ b/zenith_utils/src/http/error.rs
@@ -1,7 +1,6 @@
 use anyhow::anyhow;
 use hyper::{header, Body, Response, StatusCode};
-use serde::Serialize;
-use serde_json;
+use serde::{Deserialize, Serialize};
 use thiserror::Error;

 #[derive(Debug, Error)]
@@ -45,7 +44,7 @@ impl ApiError {
    }
 }

-#[derive(Serialize)]
+#[derive(Serialize, Deserialize)]
 pub struct HttpErrorBody {
    pub msg: String,
 }
@@ -56,10 +55,10 @@ impl HttpErrorBody {
    }

    pub fn response_from_msg_and_status(msg: String, status: StatusCode) -> Response<Body> {
-        HttpErrorBody { msg }.into_response(status)
+        HttpErrorBody { msg }.to_response(status)
    }

-    pub fn into_response(&self, status: StatusCode) -> Response<Body> {
+    pub fn to_response(&self, status: StatusCode) -> Response<Body> {
        Response::builder()
            .status(status)
            .header(header::CONTENT_TYPE, "application/json")
--- a/zenith_utils/src/http/json.rs
+++ b/zenith_utils/src/http/json.rs
@@ -1,7 +1,6 @@
 use bytes::Buf;
 use hyper::{header, Body, Request, Response, StatusCode};
 use serde::{Deserialize, Serialize};
-use serde_json;

 use super::error::ApiError;

--- a/zenith_utils/src/lib.rs
+++ b/zenith_utils/src/lib.rs
@@ -1,6 +1,8 @@
 //! zenith_utils is intended to be a place to put code that is shared
 //! between other crates in this repository.

+#![allow(clippy::manual_range_contains)]
+
 /// `Lsn` type implements common tasks on Log Sequence Numbers
 pub mod lsn;
 /// SeqWait allows waiting for a future sequence number to arrive
@@ -26,3 +28,6 @@ pub mod http;

 // socket splitting utils
 pub mod sock_split;
+
+// common log initialisation routine
+pub mod logging;
--- a/zenith_utils/src/logging.rs
+++ b/zenith_utils/src/logging.rs
@@ -0,0 +1,47 @@
+use slog::{Drain, Level};
+use std::{
+    fs::{File, OpenOptions},
+    path::Path,
+};
+
+use anyhow::{Context, Result};
+
+pub fn init(
+    log_filename: impl AsRef<Path>,
+    daemonize: bool,
+) -> Result<(slog_scope::GlobalLoggerGuard, File)> {
+    // Don't open the same file for output multiple times;
+    // the different fds could overwrite each other's output.
+    let log_file = OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(&log_filename)
+        .with_context(|| format!("failed to open {:?}", log_filename.as_ref()))?;
+
+    // we are cloning and returning log file in order to allow redirecting daemonized stdout and stderr to it
+    // if we do not use daemonization (e.g. in docker) it is better to log to stdout directly
+    // for example to be in line with docker log command which expects logs comimg from stdout
+    let guard = if daemonize {
+        let decorator = slog_term::PlainSyncDecorator::new(log_file.try_clone()?);
+        let drain = slog_term::FullFormat::new(decorator)
+            .build()
+            .filter_level(Level::Info)
+            .fuse();
+        let logger = slog::Logger::root(drain, slog::o!());
+        slog_scope::set_global_logger(logger)
+    } else {
+        let decorator = slog_term::TermDecorator::new().build();
+        let drain = slog_term::FullFormat::new(decorator)
+            .build()
+            .filter_level(Level::Info)
+            .fuse();
+        let drain = slog_async::Async::new(drain).chan_size(1000).build().fuse();
+        let logger = slog::Logger::root(drain, slog::o!());
+        slog_scope::set_global_logger(logger)
+    };
+
+    // initialise forwarding of std log calls
+    slog_stdlog::init()?;
+
+    Ok((guard, log_file))
+}
--- a/zenith_utils/src/postgres_backend.rs
+++ b/zenith_utils/src/postgres_backend.rs
@@ -377,7 +377,11 @@ impl PostgresBackend {
                // xxx distinguish fatal and recoverable errors?
                if let Err(e) = handler.process_query(self, m.body.clone()) {
                    let errmsg = format!("{}", e);
-                    warn!("query handler for {:?} failed: {}", m.body, errmsg);
+                    // ":#" uses the alternate formatting style, which makes anyhow display the
+                    // full cause of the error, not just the top-level context. We don't want to
+                    // send that in the ErrorResponse though, because it's not relevant to the
+                    // compute node logs.
+                    warn!("query handler for {:?} failed: {:#}", m.body, e);
                    self.write_message_noflush(&BeMessage::ErrorResponse(errmsg))?;
                }
                self.write_message(&BeMessage::ReadyForQuery)?;
--- a/zenith_utils/src/pq_proto.rs
+++ b/zenith_utils/src/pq_proto.rs
@@ -337,7 +337,6 @@ pub enum BeMessage<'a> {
    AuthenticationCleartextPassword,
    BindComplete,
    CommandComplete(&'a [u8]),
-    ControlFile,
    CopyData(&'a [u8]),
    CopyDone,
    CopyFail,
@@ -530,11 +529,6 @@ impl<'a> BeMessage<'a> {
                })?;
            }

-            BeMessage::ControlFile => {
-                // TODO pass checkpoint and xid info in this message
-                BeMessage::write(buf, &BeMessage::DataRow(&[Some(b"hello pg_control")]))?;
-            }
-
            BeMessage::CopyData(data) => {
                buf.put_u8(b'd');
                write_body(buf, |buf| {
--- a/zenith_utils/src/sock_split.rs
+++ b/zenith_utils/src/sock_split.rs
@@ -107,12 +107,21 @@ impl io::Write for WriteStream {
    }
 }

+pub struct TlsBoxed {
+    stream: BufStream,
+    session: rustls::ServerSession,
+}
+
+impl TlsBoxed {
+    fn rustls_stream(&mut self) -> rustls::Stream<rustls::ServerSession, BufStream> {
+        rustls::Stream::new(&mut self.session, &mut self.stream)
+    }
+}
+
 pub enum BidiStream {
    Tcp(BufStream),
-    Tls {
-        stream: BufStream,
-        session: rustls::ServerSession,
-    },
+    /// This variant is boxed, because [`rustls::ServerSession`] is quite larger than [`BufStream`].
+    Tls(Box<TlsBoxed>),
 }

 impl BidiStream {
@@ -123,17 +132,13 @@ impl BidiStream {
    pub fn shutdown(&mut self, how: Shutdown) -> io::Result<()> {
        match self {
            Self::Tcp(stream) => stream.get_ref().shutdown(how),
-            Self::Tls {
-                stream: reader,
-                session,
-            } => {
+            Self::Tls(tls_boxed) => {
                if how == Shutdown::Read {
-                    reader.get_ref().shutdown(how)
+                    tls_boxed.stream.get_ref().shutdown(how)
                } else {
-                    session.send_close_notify();
-                    let mut stream = rustls::Stream::new(session, reader);
-                    let res = stream.flush();
-                    reader.get_ref().shutdown(how)?;
+                    tls_boxed.session.send_close_notify();
+                    let res = tls_boxed.rustls_stream().flush();
+                    tls_boxed.stream.get_ref().shutdown(how)?;
                    res
                }
            }
@@ -149,8 +154,8 @@ impl BidiStream {

                (ReadStream::Tcp(reader), WriteStream::Tcp(stream))
            }
-            Self::Tls { stream, session } => {
-                let reader = stream.into_reader();
+            Self::Tls(tls_boxed) => {
+                let reader = tls_boxed.stream.into_reader();
                let buffer_data = reader.buffer().to_owned();
                let read_buf_cfg = rustls_split::BufCfg::with_data(buffer_data, 8192);
                let write_buf_cfg = rustls_split::BufCfg::with_capacity(8192);
@@ -159,7 +164,7 @@ impl BidiStream {
                let socket = Arc::try_unwrap(reader.into_inner().0).unwrap();

                let (read_half, write_half) =
-                    rustls_split::split(socket, session, read_buf_cfg, write_buf_cfg);
+                    rustls_split::split(socket, tls_boxed.session, read_buf_cfg, write_buf_cfg);
                (ReadStream::Tls(read_half), WriteStream::Tls(write_half))
            }
        }
@@ -170,7 +175,7 @@ impl BidiStream {
            Self::Tcp(mut stream) => {
                session.complete_io(&mut stream)?;
                assert!(!session.is_handshaking());
-                Ok(Self::Tls { stream, session })
+                Ok(Self::Tls(Box::new(TlsBoxed { stream, session })))
            }
            Self::Tls { .. } => Err(io::Error::new(
                io::ErrorKind::InvalidInput,
@@ -184,7 +189,7 @@ impl io::Read for BidiStream {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        match self {
            Self::Tcp(stream) => stream.read(buf),
-            Self::Tls { stream, session } => rustls::Stream::new(session, stream).read(buf),
+            Self::Tls(tls_boxed) => tls_boxed.rustls_stream().read(buf),
        }
    }
 }
@@ -193,14 +198,14 @@ impl io::Write for BidiStream {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        match self {
            Self::Tcp(stream) => stream.write(buf),
-            Self::Tls { stream, session } => rustls::Stream::new(session, stream).write(buf),
+            Self::Tls(tls_boxed) => tls_boxed.rustls_stream().write(buf),
        }
    }

    fn flush(&mut self) -> io::Result<()> {
        match self {
            Self::Tcp(stream) => stream.flush(),
-            Self::Tls { stream, session } => rustls::Stream::new(session, stream).flush(),
+            Self::Tls(tls_boxed) => tls_boxed.rustls_stream().flush(),
        }
    }
 }
--- a/zenith_utils/src/zid.rs
+++ b/zenith_utils/src/zid.rs
@@ -6,7 +6,6 @@ use serde::{Deserialize, Serialize};

 // Zenith ID is a 128-bit random ID.
 // Used to represent various identifiers. Provides handy utility methods and impls.
-// TODO (LizardWizzard) figure out best way to remove boiler plate with trait impls caused by newtype pattern
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize, PartialOrd, Ord)]
 struct ZId([u8; 16]);