pg-pool

Generic async connection pool for any connection type that implements the Poolable trait. Ships with a first-class pg-wired integration behind the default wire feature, but the core pool is protocol-agnostic.

What's in the box

• Checkout / checkin with configurable min and max connections.
• Six lifecycle hooks covering create, acquire, checkout, checkin, release, and destroy. Connection-aware where applicable, so you can e.g. RESET ALL at checkin or SET application_name at checkout.
• Idle timeout with a background reaper.
• Optional health-probe task that pings idle connections and evicts ones the server has torn down.
• Metrics snapshot (active, idle, waiters, creates, destroys, timeouts) for Prometheus scraping or ad-hoc logging.
• Graceful drain: stop accepting new waiters and return once all in-flight checkouts return.

Minimal example

use pg_pool::{ConnPool, ConnPoolConfig, LifecycleHooks};
use pg_pool::wire::WirePoolable;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut config = ConnPoolConfig::default();
    config.addr = "127.0.0.1:5432".into();
    config.user = "postgres".into();
    config.password = "postgres".into();
    config.database = "mydb".into();

    let pool = ConnPool::<WirePoolable>::new(config, LifecycleHooks::default()).await?;

    let guard = pool.get().await?;
    // use `guard.conn()` / `guard.conn_mut()` ...
    drop(guard); // returns to the pool
    Ok(())
}

Features

Architecture

See ARCHITECTURE.md for the internals: the Poolable trait, data layout (atomics + mutexed deques), the acquire and release paths, the six lifecycle hooks, the drain protocol, and hook safety rules.

License

Dual licensed under Apache 2.0 or MIT. See the workspace root for the broader project.