How to determine if token needs to be refreshed in

Question

My application is receiving the push notification from 2 firebase project. I am getting the tokens for each sender id by calling "getToken(String authorizedEntity, String scope)" separately.

String token1 = FirebaseInstanceId.getInstance().getToken("authorizedEntity1", "FCM");
String token2 = FirebaseInstanceId.getInstance().getToken("authorizedEntity2", "FCM");

As per the onTokenRefresh documentation

Called when the system determines that the tokens need to be refreshed. The application should call getToken() and send the tokens to all application servers.This will not be called very frequently, it is needed for key rotation and to handle Instance ID changes due to:

App deletes Instance ID

App is restored on a new device

User uninstalls/reinstall the app

User clears app data

As onTokenRefresh has been deprecated, I have checked the onNewToken, As per the documentation

Called when a new token for the default Firebase project is generated. This is invoked after app install when a token is first generated, and again if the token changes.

Q1. How to know which is the default Firebase project in case of multiple sender id ?

Q2. Suppose if "authorizedEntity1" is associated with the default firebase project then does it mean onNewToken will be invoked only when token1 will be changed ? or it will be also invoked when token2 will be changed? If it doesn't work for token2 then how to know that token2 need to be refreshed?

Q3. With reference of this my understanding is onTokenRefresh will be invoked whenever any of the token needs to be refreshed(not only for default project). Is this understanding correct ?

I want to send the updated token to the server whenever system determines that the token1 or token2 need to be refreshed.

Note: I am initializing the firebase in my application class as I am dealing with multiple sender ids.

Answer 1

Depending on @sNash comment who contaced Firebase Support, you should manage tokens for all sender ids other than the default sender id.

How? One simple solution is through storing all sender ids with their tokens in SharedPreferences or in db. When app starts, check if the token changed for each sender by comparing the stored token with the token returned by

FirebaseInstanceId.getInstance().getToken(SENDER_ID, "FCM");

Moreover, do the same check in onNewToken method. There is a chance that tokens other than the default may be changed when the default token is changed.

The default sender is the one related to your Firebase project that the app is connected to and it can be found in google-services.json

Answer 2

After some test, I found out that only default project's token will be delivered to onNewToken. onNewToken will not be called when new token created for other sender ids by calling getToken.

Tokens retrieved by calling getToken API are consist of different string data than default token.

And these other sender id's tokens are not refreshed when default token changes. It look like they last until you explicitly call deleteToken API. (Token value didn't changed when I repeatedly call getToken.)