Add Timeout middleware

[davidpdrsn]

tower::timeout::Timeout doesn't work well with axum since it changes the error type to BoxError. That requires doing this:

let app = Router::new()
    .route("/", get(|| async {}))
    .layer(
        ServiceBuilder::new()
            .layer(HandleErrorLayer::new(handle_timeout_error))
            .timeout(Duration::from_secs(30))
    );

async fn handle_timeout_error(err: BoxError) -> (StatusCode, String) {
    if err.is::<tower::timeout::error::Elapsed>() {
        (
            StatusCode::REQUEST_TIMEOUT,
            "Request took too long".to_string(),
        )
    } else {
        (
            StatusCode::INTERNAL_SERVER_ERROR,
            format!("Unhandled internal error: {}", err),
        )
    }
}

Thats quite a mouthful. With this middleware that becomes:

let app = Router::new()
    .route("/", get(|| async {}))
    .layer(TimeoutLayer::new(Duration::from_secs(30));

This works because it doesn't change the service's error type and thus keeps Infallible which axum requires.

[jplatte]

LGTM, except one somewhat clunky sentence in the docs.

[LucioFranco]

I wonder if this should just either 1) wrap the main tower timeout and just map the error (with a way to customize it, 2) we should just make tower timeout more flexible.

Also, this rases a question can you use other regular tower services or are you limited to ones just in tower-http because of the error shape?

[davidpdrsn]

I wonder if this should just either 1) wrap the main tower timeout and just map the error (with a way to customize it, 2) we should just make tower timeout more flexible.

I think its okay for tower-http to provide its own without wrapping tower's, since timeouts are so simple. For more complex middleware it might be better to wrap tower's.

Also, this rases a question can you use other regular tower services or are you limited to ones just in tower-http because of the error shape?

For axum there are no limits thanks to HandleErrorLayer and MethodRouter::handle_error so its mostly a question of ergonomics.

I haven't don't often use other middleware from tower (except timeout) that changes the error type.