Today, I received duplicate FCM push notifications over a period of ~30 mins. These push notifications are identical in terms of content, and the push notification was sent ONCE. Here's a snippet of the timeline of when I was receiving these push notifications:
1 01-15 10:41:30.349+0200 MyPushListenerService onMessageReceived
1 01-15 10:43:30.004+0200 MyPushListenerService onMessageReceived
1 01-15 10:47:31.665+0200 MyPushListenerService onMessageReceived
1 01-15 10:55:32.062+0200 MyPushListenerService onMessageReceived
Why does this happen?
How does Firebase confirm that a push notification was delivered? Are there retry mechanism?