问题
I was running through FCM documentation and
- I would like to understand about what would happen when the subscribers come online after a longer offline period.
- Will FCM store all the push notifications received during the offline period
- Will FCM deliver all the messages once the subscribers have come online
回答1:
If the device is not connected to FCM, the message is stored until a connection is established (again respecting the collapse key rules). When a connection is established, FCM delivers all pending messages to the device. If the device never gets connected again (for instance, if it was factory reset), the message eventually times out and is discarded from FCM storage. The default timeout is four weeks, unless the
time_to_liveflag is set.
- Lifetime of a message
来源：https://stackoverflow.com/questions/61606697/fcm-push-notification-when-subscribers-offline