title: Push notifications arrive after a long time on some devices
body: <p>On Android, I have been experiencing long push delay in some devices (minutes, half an hour). Seems like the device is asleep (but not for WhatsApp). Even on Pre-Marshmallow devices.</p>
  
  <p><strong>After a while they don't respond to push</strong>.</p>
  
  <p>I have created a simple app (copied <a href="https://firebase.google.com/docs/cloud-messaging/android/client" rel="nofollow noreferrer">Google's Cloud Messaging client sample</a>). </p>
  
  <p>Tried to send push via The Firebase Console, setting priority to HIGH and made sure it works.</p>
  
  <ul>
  <li><p>Experiment 1: After a while - tried to send. The device is not responding. </p></li>
  <li><p>Experiment 2: Tried to use Telegram and WhatsApp. Message passes immediately on both.</p></li>
  <li><p>Experiment 3: Tried the my test app again. Not working.</p></li>
  <li><p>Experiment 4: Tried to downgrade from FCM to GCM and all the way to C2DM. Same thing, not working.</p></li>
  </ul>
  
  <p>Any ideas?</p>
  
  <p>To make it clear:</p>
  
  <ul>
  <li>The token is okay. In most cases it works. It just falls asleep after a while.</li>
  <li>It's a Lollipop device so <strong>no Power Saving exempts here or battery saving</strong>.</li>
  <li>I use <code>priority:high</code> on the payload.</li>
  <li>It is no server issue because I use FCM composer and it's just the same.</li>
  <li>Waking the device does not necessarily fix it. It just begins to receive notifications minutes later and then all ok.</li>
  <li>Other apps such as WhatsApp work without problem whatsoever, always.</li>
  <li>I tried C2DM, GCM, FCM. I am using a printout on the C2DM receiver. They all behave the same.</li>
  <li>I log everything. Every event, broadcast I get. I don't get push when I should.</li>
  </ul>
  
  <p><em>Possible clue:</em> some of my customers are using VMWare AirWatch. anybody know about any issues related to AirWatch and Push?</p>