Use the 'bookfile' crate for the snapshot files.

2026-07-03 20:20:38 +00:00 · 2021-07-11 10:59:58 +03:00
parent 3b84975ca9
commit 8f81ac064e
3 changed files with 98 additions and 29 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -80,6 +80,30 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"

+[[package]]
+name = "aversion"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "25b49482974b90e9f36c5adcc50acde2e27e806ac269ff32758d700432782bc0"
+dependencies = [
+ "aversion-macros",
+ "byteorder",
+ "serde",
+ "serde_cbor",
+ "thiserror",
+]
+
+[[package]]
+name = "aversion-macros"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed3009cf133dbd82459e96cf46bb24c8e6ad5c02c387ddb21d0f2c4c781a5394"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "aws-creds"
 version = "0.26.0"
@@ -158,6 +182,18 @@ dependencies = [
 "generic-array",
 ]

+[[package]]
+name = "bookfile"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7db391acd99b8bdce5d5a66ca28530761affec9a407df91aee668fc318e3db71"
+dependencies = [
+ "aversion",
+ "byteorder",
+ "serde",
+ "thiserror",
+]
+
 [[package]]
 name = "boxfnonce"
 version = "0.1.1"
@@ -638,6 +674,12 @@ dependencies = [
 "tracing",
 ]

+[[package]]
+name = "half"
+version = "1.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62aca2aba2d62b4a7f5b33f3712cb1b0692779a56fb510499d5c0aa594daeaf3"
+
 [[package]]
 name = "hashbrown"
 version = "0.9.1"
@@ -1106,6 +1148,7 @@ name = "pageserver"
 version = "0.1.0"
 dependencies = [
 "anyhow",
+ "bookfile",
 "byteorder",
 "bytes",
 "chrono",
@@ -1652,6 +1695,16 @@ dependencies = [
 "xml-rs",
 ]

+[[package]]
+name = "serde_cbor"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e18acfa2f90e8b735b2836ab8d538de304cbb6729a7360729ea5a895d15a622"
+dependencies = [
+ "half",
+ "serde",
+]
+
 [[package]]
 name = "serde_derive"
 version = "1.0.126"
--- a/pageserver/Cargo.toml
+++ b/pageserver/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

 [dependencies]
+bookfile = "^0.2"
 chrono = "0.4.19"
 rand = "0.8.3"
 regex = "1.4.5"
--- a/pageserver/src/layered_repository/snapshot_layer.rs
+++ b/pageserver/src/layered_repository/snapshot_layer.rs
@@ -17,29 +17,25 @@
 //! When a snapshot file needs to be accessed, we slurp the whole file into memory, into
 //! a SnapshotLayer struct.
 //!
-//! On disk, a snapshot file is actually two files: one containing all the page versions,
-//! and another containing the relation size information. That's just for the convenience
-//! of serializing the two objects.
-//!
-//! The files are stored in .zenith/timelines/<timelineid> directory.
+//! On disk, the snapshot files are stored in .zenith/timelines/<timelineid> directory.
 //! Currently, there are no subdirectories, and each snapshot file is named like this:
 //!
 //!    <spcnode>_<dbnode>_<relnode>_<forknum>_<start LSN>_<end LSN>
 //!
-//! And the corresponding file containing the relation size information has _relsizes
-//! suffix. For example:
+//! For example:
 //!
 //!    1663_13990_2609_0_000000000169C348_000000000169C349
-//!    1663_13990_2609_0_000000000169C348_000000000169C349_relsizes
 //!
-
+//! A snapshot file is constructed using the 'bookfile' crate. Each file consists of two
+//! parts: the page versions and the relation sizes. They are stored as separate chapters.
+//!
 use crate::layered_repository::storage_layer::Layer;
 use crate::layered_repository::storage_layer::PageVersion;
 use crate::repository::{RelTag, WALRecord};
 use crate::walredo::WalRedoManager;
 use crate::PageServerConf;
 use crate::ZTimelineId;
-use anyhow::{bail, Result};
+use anyhow::{anyhow, bail, Result};
 use bytes::Bytes;
 use log::*;
 use std::collections::{BTreeMap, HashSet};
@@ -47,14 +43,22 @@ use std::fs;
 use std::fs::File;
 use std::io::Write;
 use std::ops::Bound::Included;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
 use std::sync::Mutex;

+use bookfile::{Book, BookWriter};
+
 use zenith_utils::bin_ser::BeSer;
 use zenith_utils::lsn::Lsn;

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

+// Magic constant to identify a Zenith snapshot file
+static SNAPSHOT_FILE_MAGIC: u32 = 0x5A616E01;
+
+static PAGE_VERSIONS_CHAPTER: u64 = 1;
+static REL_SIZES_CHAPTER: u64 = 2;
+
 ///
 /// SnapshotLayer is the in-memory data structure associated with an on-disk snapshot file.
 /// It is also used to accumulate new changes at the tip of a branch; end_lsn is u64::MAX
@@ -297,13 +301,6 @@ impl SnapshotLayer {
        conf.timeline_path(timelineid).join(&fname)
    }

-    fn relsizes_path(path: &Path) -> PathBuf {
-        let mut fname = path.file_name().unwrap().to_os_string();
-        fname.push("_relsizes");
-
-        path.with_file_name(fname)
-    }
-
    /// Create a new snapshot file, using the given btreemaps containing the page versions and
    /// relsizes.
    ///
@@ -343,15 +340,22 @@ impl SnapshotLayer {
        // Note: This overwrites any existing file. There shouldn't be any.
        // FIXME: throw an error instead?

-        // Write out page versions
-        let mut file = File::create(&path)?;
-        let buf = BTreeMap::ser(&page_versions)?;
-        file.write_all(&buf)?;
+        let file = File::create(&path)?;
+        let book = BookWriter::new(file, SNAPSHOT_FILE_MAGIC)?;

-        // and relsizes to separate file
-        let mut file = File::create(Self::relsizes_path(&path))?;
+        // Write out page versions
+        let mut chapter = book.new_chapter(PAGE_VERSIONS_CHAPTER);
+        let buf = BTreeMap::ser(&page_versions)?;
+        chapter.write_all(&buf)?;
+        let book = chapter.close()?;
+
+        // and relsizes to separate chapter
+        let mut chapter = book.new_chapter(REL_SIZES_CHAPTER);
        let buf = BTreeMap::ser(&relsizes)?;
-        file.write_all(&buf)?;
+        chapter.write_all(&buf)?;
+        let book = chapter.close()?;
+
+        book.close()?;

        debug!("saved {}", &path.display());

@@ -421,12 +425,23 @@ impl SnapshotLayer {
    ) -> Result<SnapshotLayer> {
        let path = Self::path_for(conf, timelineid, tag, start_lsn, end_lsn);

-        let content = std::fs::read(&path)?;
-        let page_versions = BTreeMap::des(&content)?;
+        let file = File::open(&path)?;
+        let mut book = Book::new(file)?;
+
+        let chapter_index = book
+            .find_chapter(PAGE_VERSIONS_CHAPTER)
+            .ok_or_else(|| anyhow!("could not find page versions chapter in {}", path.display()))?;
+        let chapter = book.read_chapter(chapter_index)?;
+        let page_versions = BTreeMap::des(&chapter)?;
+
+        let chapter_index = book
+            .find_chapter(REL_SIZES_CHAPTER)
+            .ok_or_else(|| anyhow!("could not find relsizes chapter in {}", path.display()))?;
+        let chapter = book.read_chapter(chapter_index)?;
+        let relsizes = BTreeMap::des(&chapter)?;
+
        debug!("loaded from {}", &path.display());

-        let content = std::fs::read(Self::relsizes_path(&path))?;
-        let relsizes = BTreeMap::des(&content)?;
        Ok(SnapshotLayer {
            conf,
            timelineid,