title: GCM and App update: how re-register if app is not open after update?
body: <p>I have an app that receives <code>GCM</code> notifications and updates local data in background through a <code>Service</code> (classic pattern).</p>
  
  <p>Documentation says that, if an app update occurs, the registration id may become useless and a check for a new registration id is needed.
  The sample provided by Google (<a href="http://code.google.com/p/gcm/source/browse/gcm-client/src/com/google/android/gcm/demo/app/DemoActivity.java" rel="nofollow"><code>DemoActivity</code></a>) shows that, soon, in the OnCreate (or <code>OnResume</code>) of the main activity the check should be done.</p>
  
  <p>But, what if the user updates app through Play Store and <strong>doesn't open the app soon after</strong>?
  In this case, is there a risk that, after the update, the registration id becomes invalid and notifications stop to be received (and my background Service stops to update local data)?</p>
  
  <p>Or maybe this case is managed by the <code>Google</code> GCM server with the "canonical IDs" mechanism?</p>
  
  <p>Thank you,<br>
  Max</p>