README.md

tourniquet

Easily round-robin between servers providing the same service, automatically reconnecting to the next server should an error happen.

This library facilitates resiliency to multiple service providers (e.g. servers) by connecting to the first available service from a list in a round-robin manner. If for some reason any provider goes down, any attempt to interact with it will reconnect to the next one, automatically.

Disclaimer: this library is not for load-balancing between a set of providers! It will connect to one provider, and only use this one provider as long as it is up. Tourniquet is meant for resiliency and not for load balancing.

Example

use async_trait::async_trait;
use std::{io::Error, net::IpAddr};
use tokio::{io::AsyncReadExt, net::TcpStream, sync::Mutex};
use tourniquet::{Connector, RoundRobin};

struct Conn(u16);

#[async_trait]
impl Connector<IpAddr, Mutex<TcpStream>, Error> for Conn {
    async fn connect(&self, src: &IpAddr) -> Result<Mutex<TcpStream>, Error> {
        let Conn(ref port) = self;
        TcpStream::connect((*src, *port)).await.map(Mutex::new)
    }
}

#[tokio::main]
async fn main() {
    let rr = RoundRobin::new(
        vec!["46.16.175.175".parse().unwrap(), "51.161.82.214".parse().unwrap()],
        Conn(6667),
    );

    let hello = rr.run(|sock| async move {
        let mut sock = sock.lock().await;
        let mut buf = [0; 50];
        sock.read_exact(&mut buf).await.map(|_| String::from_utf8(buf.to_vec()).unwrap())
    }).await.unwrap();

    assert!(hello.contains("libera.chat"));
}

Integrations

Tourniquet provides some integrations with existing crates, which shorthand functions to reduce boilerplate, as the raw run function may not be the most wieldy to use. It currently integrates with the following crates:

• celery with tourniquet-celery: provides a near drop-in replacement for the regular send_task function from celery
• tonic with tourniquet-tonic: provides a shorthand chan function with a cloned channel rather than an Arc-ed one

License: MIT