Chrome on Android : connection become dead after 30 minutes

Question

We are building a chatroom with our own notification system without depending on GCM but with service worker + SSE. On desktop it is fine , but on mobile android app (which uses cordova-crosswalk , chromium 53 ) . The long running notification connection become stuck after 20-30 minutes and it is in foreground activity. It dosen't die with an error , just not reciving data. No error at all which is very weird. No way to reconnect since we do not know if the connection is dead at all.

What would be the cleanest way? Restarting connection every 5 minutes is one idea but it is not clean. code

  runEvtSource(url, fn) {
if (this.get('session.content.isAuthenticated') === true) {
  var evtSource = new EventSource(url, {
    withCredentials: true
  });
}}

Agressive reconnect code

var evtSource = this.runEvtSource(url, fn)
var evtSourceErrorHandler = (event) => {
  var txt;
  switch (event.target.readyState) {
    case EventSource.CONNECTING:
      txt = 'Reconnecting...';
      evtSource.onerror = evtSourceErrorHandler;
      break;
    case EventSource.CLOSED:
      txt = 'Reinitializing...';
      evtSource = this.runEvtSource(url, fn)
      evtSource.onerror = evtSourceErrorHandler;
      break;
  }
  console.log(txt);
evtSource.onerror = evtSourceErrorHandler

Answer 1

I normally add a keep-alive layer on top of the the SSE connection. It doesn't happen that often, but sockets can die without dying properly, so your connection just goes quiet and you don't get an error.

So, one way is, inside your get data function:

if(timer)clearTimeout(timer);
timer = setTimeout(reconnect, 30 * 1000);
...process the data

In other words, if it is over 30 seconds since you last got data, reconnect. Choose a value based on the frequency of the data you send: if 10% of the time there is a 60 second gap between data events, but never a 120 second gap, then setting the time-out to something higher than 120 seconds makes sense.

You might also want to keep things alive by pushing regular messages from the server to client. This is a good idea if the frequency of messages from the server is very irregular. E.g. I might have the server send the current timestamp every 30 seconds, and use a keep-alive time-out of 45 seconds on the client.

As an aside, if this is a mobile app, bear in mind if the user will appreciate the benefit of reduced latency of receiving chat messages against the downside of reduced battery life.