Firebase Cloud Messaging onDeletedMessages() not called

Issue

My Android app uses Firebase Cloud Messaging to send data messages, and it's been working fine. Now I'm implementing onDeletedMessages(), but I can't get my test case to call it. The message being sent is:

{
  "priority": "high",
  "to": "/topics/test",
  "time_to_live": 0,
  "data": {
    "sites": [
      {
        "plusMD5": "959d4d57d19a2047a2e75fccfb9a1512",
        "plus": [
          "abcderf:r"
        ],
        "site": "computers"
      }
    ],
    "time": 1500660817
  }
}

To test:

1. Set the device to Airplane Mode
2. Send the data message
3. Wait a bit (15 seconds or so)
4. Turn off Airplane Mode

Now that the device has a network connection again, I'd expect onDeletedMessages() to be called, but it's not. Am I misunderstanding how FCM handles deleted and missed messages, or could something else be going on? Thanks!

Rob

Solution

Interesting..

The docs here : https://firebase.google.com/docs/cloud-messaging/android/receive#override-ondeletedmessages

said that In some situations, FCM may not deliver a message. This occurs when there are too many messages (>100) pending for your app on a particular device at the time it connects or if the device hasn't connected to FCM in more than one month. In these cases, you may receive a callback to FirebaseMessagingService.onDeletedMessages()

So you need to fullfill these 2 conditions :

1. Need to send (>100) notification where the device is offline
2. Turn on Airplane Mode for more than one month

Answered By - faruk