Comment by greysonp
19 hours ago
Signal developer here. Not entirely sure what you're saying. I'm only an Android guy, but FCM messages are certainly one trigger that can allow an app process to run, but it's not the only trigger. You can schedule system alarms, jobs, etc. And the notification does not need to be provided by the FCM message. In our case, the server just sends empty FCM messages to wake up the app, we fetch the messages ourselves from the server, decrypt them, and build the notification ourselves. No data, encrypted or otherwise, is ever put into the FCM payloads.
Sure but it needs to go through Firebase regardless of the content of the notification message, I do not believe there is a way to use a third party notification service which does not depend on Firebase.
It doesn't. The API for displaying a notification is purely local.
Receiving a ping from Firebase Cloud Messaging triggers the app to whatever it does in order to display its notification. In the case of Signal, that probably means something like fetching the user's latest messages from the server, then deciding what to show in the notification based on the user's settings, metadata, and message content.
Here's example code for using FCM to show a notification. In this case, the notification content also passes through FCM, but Signal does not do that. https://www.geeksforgeeks.org/android/how-to-push-notificati...
Sorry I should clarify, by "it" I meant any sort of ping must go through Firebase Cloud Messaging, not that the message content itself goes through Firebase.
Looks like there is a way to bypass Firebase by using something like UnifiedPush which runs a perpetual background process that acts similar to Google Play Services to pick up notifications from the server and calls the local notification API.
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When running Signal without google play services, Signal reliably received push notifications and with minimal battery drain.
Do you have microG? That provides a compatibility layer for FCM.
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Any application can send notifications without going through a server.
How? I'm not talking about an application backend server but a notification server which Google and Apple have for all apps. I'm not sure besides polling or having a persistent connection to send notifications to an app while that app is not running.