dannygale/tokio-pubsub

A simple publish/subscribe event bus built on tokio's broadcast channels

tokio-pubsub

An extensible pub/sub message passing implementation built on top of tokio's broadcast and mpsc channels

Features

• Publish/subscribe semantics (topics)
• Dynamically created and pruned topics
• Struct-based publishers and subscribers that wrap broadcast channels
• "bound publish" -- topic assigned at publisher creation time
• Preprocess events
• Dynamically add/remove subscribers
• out-of-band subscribe/unsubscribe
• In-band subscribe/unsubscribe
• add support for serde
• Transform events - apply to topic, subscriber, or by closure
• Filter events per subscriber by closure
• Chain Filters and Transformations
• Reimplement as a new type of channel instead of on top of broadcast channels

Getting Started

#[tokio::main]
fn main() -> Result<(), Box<dyn std::error::Error>> {
    #[derive(Debug, Clone, Eq, PartialEq)]
    enum ApolloEvent {
        Ignition,
        Liftoff,
        EagleHasLanded,
        HoustonWeHaveAProblem,
    }

    let (shutdown_tx, shutdown_rx) = broadcast::channel(1);
    let mut bus = PubSub::new(16, shutdown_rx);

    let apollo11 = bus.channel();
    let apollo13 = bus.channel();

    let mut houston1 = bus.subscribe("apollo11");
    let mut houston2 = bus.subscribe("apollo13");

    tokio::spawn(async move { bus.run().await });

    apollo11.send(("apollo11".into(), ApolloEvent::Ignition));
    apollo11.send(("apollo11".into(), ApolloEvent::Liftoff));
    apollo11.send(("apollo11".into(), ApolloEvent::EagleHasLanded));

    apollo13.send(("apollo13".into(), ApolloEvent::Ignition));
    apollo13.send(("apollo13".into(), ApolloEvent::Liftoff));
    apollo13.send(("apollo13".into(), ApolloEvent::HoustonWeHaveAProblem));

    let mut srx = shutdown_tx.subscribe();
    let apollo_future = tokio::spawn(async move {
        let mut apollo11_events = vec![];
        let mut apollo13_events = vec![];
        loop {
            tokio::select! {
                _ = srx.recv() => return (apollo11_events, apollo13_events),
                res = houston1.recv() => apollo11_events.push(res.unwrap()),
                res = houston2.recv() => apollo13_events.push(res.unwrap()),
            }
        }
    });
    sleep(Duration::from_millis(100)).await;
    shutdown_tx.send(());

    let (apollo11_events, apollo13_events) = apollo_future.await.unwrap();

    assert_eq!(
        apollo11_events,
        vec![
            ApolloEvent::Ignition,
            ApolloEvent::Liftoff,
            ApolloEvent::EagleHasLanded
        ]
    );
    assert_eq!(
        apollo13_events,
        vec![
            ApolloEvent::Ignition,
            ApolloEvent::Liftoff,
            ApolloEvent::HoustonWeHaveAProblem
        ]
    );

}

User Guide

TODO: User Guide