Crate r2d2

source · []
Expand description

A generic connection pool.

Opening a new database connection every time one is needed is both inefficient and can lead to resource exhaustion under high traffic conditions. A connection pool maintains a set of open connections to a database, handing them out for repeated use.

r2d2 is agnostic to the connection type it is managing. Implementors of the ManageConnection trait provide the database-specific logic to create and check the health of connections.


Using an imaginary “foodb” database.

use std::thread;

extern crate r2d2;
extern crate r2d2_foodb;

fn main() {
    let manager = r2d2_foodb::FooConnectionManager::new("localhost:1234");
    let pool = r2d2::Pool::builder()

    for _ in 0..20 {
        let pool = pool.clone();
        thread::spawn(move || {
            let conn = pool.get().unwrap();
            // use the connection
            // it will be returned to the pool when it falls out of scope.


pub use crate::event::HandleEvent;
pub use crate::event::NopEventHandler;


Event subscriptions.


A builder for a connection pool.

The error type returned by methods in this crate.

A “type map” used to associate data with pooled connections.

A HandleError implementation which logs at the error level.

A CustomizeConnection which does nothing.

A HandleError implementation which does nothing.

A generic connection pool.

A smart pointer wrapping a connection.

Information about the state of a Pool.


A trait which allows for customization of connections.

A trait which handles errors reported by the ManageConnection.

A trait which provides connection-specific functionality.