Sometimes even with a valid Firebase token, the notification is not sent to our users. Also often there is a delay when a notification is scheduled to all our users. In many cases this delay is more than 30 min. I have thoroughly checked our logs and there are no error responses when we send requests to FCM
2 Answers
Firebase does not guarantee notification delivery. If you dig deep you will find many reported scenarios where this issue has been reported:
Main scenarios could be:
- If the internet is not available.
- Differences in devices, how the code is written to handle notifications in different android versions.
- Background / foreground status.
I faced the same issue tonight. Here's a great answer from similar question that i found.
From what I understood, the FCM attempts reconnecting the socket from device after intervals of 15 - 28 minuites depending on the network it is connected to. While doing so, it opens the app in background and fetches pending notifications if any. It just so happens that sometimes it misses to fetch these pending notifications.
Conclusion - FCM is not very reliable[read 'sucks'] in timely delivery of our notifications.
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