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_util::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.