Correct way for measure connections counter

[dayvejones]

Summary

I have a need to measure the number of open connections (http1) and If I understand correctly, axum/hyper don't have built-in tools for measuring the number of connections.

I took this example - https://github.com/tokio-rs/axum/blob/main/examples/serve-with-hyper/src/main.rs
and added gauge! increment/decrement

async fn serve_plain() {
    let app = Router::new().route("/", get(|| async { "Hello!" }));

    let listener = TcpListener::bind("0.0.0.0:3000").await.unwrap();

    loop {
        let (socket, _remote_addr) = listener.accept().await.unwrap();

        let tower_service = app.clone();

        tokio::spawn(async move {
            let socket = TokioIo::new(socket);

            //increase connection counter
            gauge!("connections_counter").increment(1);

            let hyper_service = hyper::service::service_fn(move |request: Request<Incoming>| {
                tower_service.clone().call(request)
            });

            let result = server::conn::auto::Builder::new(TokioExecutor::new())
                .http1() 
                .serve_connection(socket, hyper_service)
                .await;

            //decrease connection counter
            gauge!("connections_counter").decrement(1);

            if let Err(err) = result {
                eprintln!("failed to serve connection: {err:#}");
            }
        });
    }
}

Next I read these metrics along with the other prometheus metrics for Grafana, like this - https://github.com/tokio-rs/axum/blob/main/examples/prometheus-metrics/src/main.rs

Is this approximately the correct way to measure? And is there still a way to determine which connections have the "idle" state?

axum version

0.8.4

[jplatte]

That looks correct to me. Don't know about the idle state.