Messages not received when registration is done after first app launch

[pfrischmuth]

Environment

• Xcode version: 8.3.3 (8E3004b)
• Firebase SDK version: 4.1.1 (happens starting from 4.0.0)
• Library version: FirebaseMessaging 2.0.2
• Firebase Product: messaging

Describe the problem

Steps to reproduce:

When I register for push notifications directly when the app starts for the first time (after install), the registration process works and I can send a notification to my device via the Firebase console.

However when I do not register on first app launch (i.e. launching the app for the first time, stopping it and register on second launch), the registration process seems to succeed (I can access the FCM token), but when I send a message via the Firebase console to that token, I will not receive the message.

When I use (almost) the same code (changes only in the commented out lines, due to changes to the API) with a Firebase version <4.0.0 (e.g. Firebase 3.15.0), both cases work fine.

Relevant Code:

I created a very simple project that reproduces the problem. I comment out the code for the first launch and then do the registration on the second launch, which produces the issue.

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    FirebaseApp.configure()
    // use the following line for Firebase < 4.0.0
    //FIRApp.configure()

    // START: comment out the following block on first app launch
    UNUserNotificationCenter.current().delegate = self

    let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]
    UNUserNotificationCenter.current().requestAuthorization(
        options: authOptions,
        completionHandler: {_, _ in })

    application.registerForRemoteNotifications()

    let token = Messaging.messaging().fcmToken
    // use the following line for Firebase < 4.0.0
    //let token = FIRInstanceID.instanceID().token()
    print("FCM token: \(token ?? "")")
    // END

    return true
}

[katowulf]

@pfrischmuth thanks for this. Can you note your iOS version and whether you've disabled method swizzling, since those are related to setup and may be needed for a repro?

[pfrischmuth]

I tested on iOS 10.3.

In the above example I did not disable method swizzling, but I also tried it with method swizzling disabled and the issue still occurs.

[rsattar]

Hmm this could be related to a bug I'm fixing in Instance ID that was introduced in the last release, where a race condition is created on first launch. (This is being fixed for the next release)

Hmm, to confirm what you're saying:
First Launch

• Don't register for push notifications
• Retrieve FCM token anyway
• Attempt to send push notification fails (expected behavior)

Second Launch

• Register for push notifications
• Retrieve FCM token
• Attempt to push notifications succeeds (expected behavior)

I think I'm misunderstanding the issue, then. However, I want to clarify:

However when I do not register on first app launch (i.e. launching the app for the first time, stopping it and register on second launch), the registration process seems to succeed (I can access the FCM token), but when I send a message via the Firebase console to that token, I will not receive the message.

FCM / IID creates an FCM token whether or not you register for remote notifications, it's just that there is no APNs device token associated with that FCM token yet. When an APNs token is provided, the FCM token is updated on the backend to be associated with that APNs token, and notifications can now be sent via APNs using that FCM token.

[pfrischmuth]

I tried with Firebase 3.15.0, 4.0.0 and 4.1.1. With both 4.x releases I can produce the issue, with the 3.x release it works as expected (although the API is slightly different).

I don't even access the FCM token on first launch. I only call FirebaseApp.configure() on first launch, since I need this call for other Firebase features (remote config). So I do nothing cloud messaging related on first launch and of course I can not receive notifications then (as expected).

I do all the registration steps on the second launch (or later) and would expect that I can receive notifications afterwards, but this does not work for me (not with a 4.x SDK, with a 3.x SDK it works fine).

However when I complete the registration process on first launch, I can receive notifications (with all tested versions of the SDK).

I hope this clarifies my issue.

[rsattar]

Thanks @pfrischmuth for the detailed info. Yes, it sounds like the issue that is being fixed in Instance ID for the next release of Firebase.

As a workaround for now, you should be able to call application.registerForRemoteNotifications() on first launch of your app. This is safe to do, and will not show a permissions dialog to the developer. It will provide an APNs token to you (and FCM) even on first launch. For example:

FirebaseApp.configure()
application.registerForRemoteNotifications()

Later on (in your second launch), you can always request permissions for user notifications as you have done before (i.e. UNUserNotificationCenter.current().requestAuthorization(...)).

Hope that makes sense!

[pfrischmuth]

OK, thanks for the response.

I will consider the workaround and look forward for a fix in the next release.

[ChrisRicca]

Hi @pfrischmuth I'm trying to determine if the issue I'm seeing is the same as yours. Would it be possible to clarify: when you say "when I send a message via the Firebase console to that token, I will not receive the message.", did you see an error message in the console? (I am seeing "Unregistered Registration Token").

[pfrischmuth]

Hi @ChrisRicca No, I do not receive an error message in the Firebase Console. I see the usual "Done" state there, but the message is never received on the device.

[paulb777]

Fixed in Firebase 4.2.0 FirebaseInstanceID 2.0.3 released today.

[pfrischmuth]

Unfortunately this fix does not solve my problem.

I think I can narrow the issue down to an issue in FirebaseInstanceID, since when I try it with FirebaseInstanceID 2.0.0 it works fine. I tried the following versions:

FirebaseInstanceID Version	Status
2.0.0	working fine
2.0.1	not working
2.0.2	not working
2.0.3	not working

I have a very simple app that just executes the following code on first launch (fresh install of the app):

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    FirebaseApp.configure()

    return true
}

On second launch of the app I execute the following code:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    FirebaseApp.configure()

    UNUserNotificationCenter.current().delegate = self

    let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]
    UNUserNotificationCenter.current().requestAuthorization(
        options: authOptions,
        completionHandler: {_, _ in })

    application.registerForRemoteNotifications()

    let token = Messaging.messaging().fcmToken
    print("FCM token: \(token ?? "")")

    return true
}

I think I can narrow it down to that calling application.registerForRemoteNotifications() needs to be done on first launch always. However this is not an option in my real application where I need to use Firebase Messaging.

[ChrisRicca]

I have reproduced this issue as well in our application using the latest release (Firebase 4.2.0 FirebaseInstanceID 2.0.3). At first, the push notifications silently fail as @pfrischmuth described. (I suspect over time they get cleaned up by the firebase system and start returning the "Unregistered Registration Token" error that I was seeing later.)

We can probably call application.registerForRemoteNotifications() as suggested in didFinishLaunchingWithOptions to try to avoid this situation on installation (I am testing this now), but that won't fix the users who are currently in the "broken" state, who keep getting the same (apparently inactive) token back from Messaging.messaging().fcmToken.

Relying on the initial application.registerForRemoteNotifications() call also makes me nervous for this reason. If for whatever reason the notifications aren't setup correctly on first launch (a crash, for example), the user will be stuck in a broken state with no option but to uninstall and reinstall to fix the notifications.