stan

NATS Streaming client wrapper built on top of NATS.rs

Examples

use nats;
use std::{io, str::from_utf8, time};

fn main() -> io::Result<()> {
    let nats_url = "nats://127.0.0.1:4222";
    let nc = nats::connect(nats_url)?;
    let sc = stan::connect(nc, "test-cluster", "rust-client-1")?;

    sc.publish("foo", "hello from rust 1")?;

    sc.subscribe("foo", Default::default())?
        .with_handler(|msg| {
            println!("sub 1 got {:?}", from_utf8(&msg.data));
            Ok(())
        });

    let sub = sc
        .subscribe(
            "foo",
            stan::SubscriptionConfig {
                queue_group: Some("queue-group-name"),
                durable_name: Some("my-durable-queue"),
                start: stan::SubscriptionStart::AllAvailable,
                ..Default::default()
            },
        )?
        .with_handler(|msg| {
            println!("sub 2 got {:?}", from_utf8(&msg.data));
            msg.ack()?;
            println!("manually acked!");
            Ok(())
        });

    for msg in sc.subscribe("foo", Default::default())?.messages() {
        println!("sub 3 got {:?}", from_utf8(&msg.data));
        msg.ack()?;
        break; // just break for the example to run
    }

    for msg in sc
        .subscribe("foo", Default::default())?
        .timeout_iter(time::Duration::from_secs(1))
    {
        println!("sub 4 got {:?}", from_utf8(&msg.data));
        msg.ack()?;
        break; // just break for the example to run
    }

    sc.publish("foo", "hello from rust 2")?;
    sc.publish("foo", "hello from rust 3")?;

    sub.unsubscribe()?;

    sc.publish("foo", "hello from rust 4")?;
    Ok(())
}

Rationale

We were interested in at-least-once delivery with NATS, and the options here today are NATS Streaming, Lightbridge or Jetstream.

Jetstream is the future of at-least-once delivery on NATS, but is still in development, while NATS Streaming has been battle tested in production.

At the same time, the NATS team is providing an awesome rust client that also has support for Jetstream, but they are not planning on supporting NATS Streaming (reasonable since Jetstream is their main focus).

Since NATS Streaming is just a layer on top of NATS, this library was written to just wrap the nats.rs client to handle the NATS Streaming protocol, for those like us stuck with NATS Streaming.

Installation

[dependencies]
nats = "0.9.7"
stan = "0.0.16"

Development

To start a local nats streaming server:

docker run -p 4222:4222 -p 8222:8222 nats-streaming

Running tests require docker. To run the tests:

cargo test