Function warp::filters::sse::keep_alive

pub fn keep_alive() -> KeepAlive

Keeps event source connection alive when no events sent over a some time.

Some proxy servers may drop HTTP connection after a some timeout of inactivity. This function helps to prevent such behavior by sending comment events every keep_interval of inactivity.

By default the comment is : (an empty comment) and the time interval between events is 15 seconds. Both may be customized using the builder pattern as shown below.

use std::time::Duration;
use std::convert::Infallible;
use futures::StreamExt;
use tokio::time::interval;
use tokio_stream::wrappers::IntervalStream;
use warp::{Filter, Stream, sse::Event};

// create server-sent event
fn sse_counter(counter: u64) ->  Result<Event, Infallible> {
    Ok(Event::default().data(counter.to_string()))
}

fn main() {
    let routes = warp::path("ticks")
        .and(warp::get())
        .map(|| {
            let mut counter: u64 = 0;
            let interval = interval(Duration::from_secs(15));
            let stream = IntervalStream::new(interval);
            let event_stream = stream.map(move |_| {
                counter += 1;
                sse_counter(counter)
            });
            // reply using server-sent events
            let stream = warp::sse::keep_alive()
                .interval(Duration::from_secs(5))
                .text("thump".to_string())
                .stream(event_stream);
            warp::sse::reply(stream)
        });
}

See notes.

Examples found in repository

examples/sse_chat.rs (line 43)

↕

async fn main() {
    pretty_env_logger::init();

    // Keep track of all connected users, key is usize, value
    // is an event stream sender.
    let users = Arc::new(Mutex::new(HashMap::new()));
    // Turn our "state" into a new Filter...
    let users = warp::any().map(move || users.clone());

    // POST /chat -> send message
    let chat_send = warp::path("chat")
        .and(warp::post())
        .and(warp::path::param::<usize>())
        .and(warp::body::content_length_limit(500))
        .and(
            warp::body::bytes().and_then(|body: bytes::Bytes| async move {
                std::str::from_utf8(&body)
                    .map(String::from)
                    .map_err(|_e| warp::reject::custom(NotUtf8))
            }),
        )
        .and(users.clone())
        .map(|my_id, msg, users| {
            user_message(my_id, msg, &users);
            warp::reply()
        });

    // GET /chat -> messages stream
    let chat_recv = warp::path("chat").and(warp::get()).and(users).map(|users| {
        // reply using server-sent events
        let stream = user_connected(users);
        warp::sse::reply(warp::sse::keep_alive().stream(stream))
    });

    // GET / -> index html
    let index = warp::path::end().map(|| {
        warp::http::Response::builder()
            .header("content-type", "text/html; charset=utf-8")
            .body(INDEX_HTML)
    });

    let routes = index.or(chat_recv).or(chat_send);

    warp::serve(routes).run(([127, 0, 0, 1], 3030)).await;
}