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neon/compute_tools/README.md
2022-05-30 11:11:01 +03:00

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# Compute node tools
Postgres wrapper (`compute_ctl`) is intended to be run as a Docker entrypoint or as a `systemd`
`ExecStart` option. It will handle all the `Neon` specifics during compute node
initialization:
- `compute_ctl` accepts cluster (compute node) specification as a JSON file.
- Every start is a fresh start, so the data directory is removed and
initialized again on each run.
- Next it will put configuration files into the `PGDATA` directory.
- Sync safekeepers and get commit LSN.
- Get `basebackup` from pageserver using the returned on the previous step LSN.
- Try to start `postgres` and wait until it is ready to accept connections.
- Check and alter/drop/create roles and databases.
- Hang waiting on the `postmaster` process to exit.
Also `compute_ctl` spawns two separate service threads:
- `compute-monitor` checks the last Postgres activity timestamp and saves it
into the shared `ComputeNode`;
- `http-endpoint` runs a Hyper HTTP API server, which serves readiness and the
last activity requests.
Usage example:
```sh
compute_ctl -D /var/db/postgres/compute \
-C 'postgresql://cloud_admin@localhost/postgres' \
-S /var/db/postgres/specs/current.json \
-b /usr/local/bin/postgres
```
## Tests
Cargo formatter:
```sh
cargo fmt
```
Run tests:
```sh
cargo test
```
Clippy linter:
```sh
cargo clippy --all --all-targets -- -Dwarnings -Drust-2018-idioms
```
## Cross-platform compilation
Imaging that you are on macOS (x86) and you want a Linux GNU (`x86_64-unknown-linux-gnu` platform in `rust` terminology) executable.
### Using docker
You can use a throw-away Docker container ([rustlang/rust](https://hub.docker.com/r/rustlang/rust/) image) for doing that:
```sh
docker run --rm \
-v $(pwd):/compute_tools \
-w /compute_tools \
-t rustlang/rust:nightly cargo build --release --target=x86_64-unknown-linux-gnu
```
or one-line:
```sh
docker run --rm -v $(pwd):/compute_tools -w /compute_tools -t rust:latest cargo build --release --target=x86_64-unknown-linux-gnu
```
### Using rust native cross-compilation
Another way is to add `x86_64-unknown-linux-gnu` target on your host system:
```sh
rustup target add x86_64-unknown-linux-gnu
```
Install macOS cross-compiler toolchain:
```sh
brew tap SergioBenitez/osxct
brew install x86_64-unknown-linux-gnu
```
And finally run `cargo build`:
```sh
CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=x86_64-unknown-linux-gnu-gcc cargo build --target=x86_64-unknown-linux-gnu --release
```