send explicit pings to client

src/main.rs

@@ -1,12 +1,14 @@
 use std::convert::Infallible;
 use std::sync::{Arc, Mutex};
+use std::time::Duration;
 
-use futures_util::StreamExt;
+use futures_util::{stream, StreamExt};
 #[allow(unused_imports)] use log::{debug, error, info, trace};
 use rppal::gpio::{Gpio, Level, Trigger};
 use smallvec::SmallVec;
-use tokio::sync::mpsc;
-use warp::{Filter, sse};
+use tokio::{ sync::mpsc,
+             time::interval };
+use warp::{Filter, sse, sse::ServerSentEvent};
 
 
 const BUTTON_PIN: u8 = 26;
@@ -51,11 +53,16 @@ async fn main() {
       let (tx, rx) = mpsc::channel(1);
       clients.lock().unwrap().push(tx);
 
-      let stream = rx.map(|()| {
-        debug!("sending sse");
-        Ok::<_, Infallible>((sse::event("ring"),
-                             sse::data("")))
-      });
+      let stream = stream::select(
+        interval(Duration::from_secs(5)).map(move |_| {
+          Ok::<_, Infallible>((sse::event("ping"), sse::data("")).into_a())
+        }),
+
+        rx.map(|()| {
+          debug!("sending ring sse");
+          Ok::<_, Infallible>((sse::event("ring"), sse::data("")).into_b())
+        })
+      );
       sse::reply(stream)
    });
 

static/main.html

@@ -8,12 +8,19 @@
     <section id="log">
       <h1>Incoming Events</h1>
     </section>
+    <template id="logline">
+      <p>Ping
+    </template>
     <template id="ring">
       <p>Ring!
     </template>
     <script>
       "use strict";
       let sse = new EventSource('events');
+      sse.addEventListener('ping', msg => {
+        const template = document.querySelector('#logline').content.cloneNode(true);
+        document.querySelector('#log').appendChild(template);
+      });
       sse.addEventListener('ring', msg => {
         const template = document.querySelector('#ring').content.cloneNode(true);
         document.querySelector('#log').appendChild(template);