8060e17b50
SeqWait adds a way to .await the arrival of some sequence number. It provides wait_for(num) which is an async fn, and advance(num) which is synchronous. This should be useful in solving the page cache deadlocks, and may be useful in other areas too. This implementation still uses a Mutex internally, but only for a brief critical section. If we find this code broadly useful and start to care more about executor stalls due to unfair thread scheduling, there might be ways to make it lock-free.
Zenith
Zenith substitutes PostgreSQL storage layer and redistributes data across a cluster of nodes
Running local installation
- Build zenith and patched postgres
git clone --recursive https://github.com/libzenith/zenith.git
cd zenith
./pgbuild.sh # builds postgres and installs it to ./tmp_install
cargo build
- Start pageserver and postggres on top of it (should be called from repo root):
# Create ~/.zenith with proper paths to binaries and data
# Later that would be responsibility of a package install script
>./target/debug/zenith init
# start pageserver
> ./target/debug/zenith pageserver start
Starting pageserver at '127.0.0.1:64000'
# create and configure postgres data dir
> ./target/debug/zenith pg create
Creating new postgres: path=/Users/user/code/zenith/tmp_check_cli/compute/pg1 port=55432
Database initialized
# start it
> ./target/debug/zenith pg start pg1
# look up status and connection info
> ./target/debug/zenith pg list
NODE ADDRESS STATUS
pg1 127.0.0.1:55432 running
- Now it is possible to connect to postgres and run some queries:
> psql -p55432 -h 127.0.0.1 postgres
postgres=# CREATE TABLE t(key int primary key, value text);
CREATE TABLE
postgres=# insert into t values(1,1);
INSERT 0 1
postgres=# select * from t;
key | value
-----+-------
1 | 1
(1 row)
Running tests
git clone --recursive https://github.com/libzenith/zenith.git
./pgbuild.sh # builds postgres and installs it to ./tmp_install
cargo test -- --test-threads=1
Source tree layout
/walkeeper:
WAL safekeeper. Written in Rust.
/pageserver:
Page Server. Written in Rust.
Depends on the modified 'postgres' binary for WAL redo.
/integration_tests:
Tests with different combinations of a Postgres compute node, WAL safekeeper and Page Server.
/mgmt-console:
Web UI to launch (modified) Postgres servers, using S3 as the backing store. Written in Python. This is somewhat outdated, as it doesn't use the WAL safekeeper or Page Servers.
/vendor/postgres:
PostgreSQL source tree, with the modifications needed for Zenith.
/vendor/postgres/src/bin/safekeeper:
Extension (safekeeper_proxy) that runs in the compute node, and connects to the WAL safekeepers and streams the WAL