Fix crash in Messaging on Android when Terminate is called while tasks are still pending.

[TBarendt]

When firebase::messaging::Terminate is called while there are still pending tasks left a null pointer exception is causing an ANR on Andriod.

FutureData is destroyed before calling util::Terminate which in turn will try to cancel all pending callbacks. This will call cancel() in JniResultCallback.java which will lock a mutex and callback into C++ using the JniResultCallback_nativeResult function. Depending on the task canceled it will call into different callbacks in messaging.cc and some of them as for example CompleteStringCallback are using FutureData which has already been destroyed. This will cause the thread to stop and the mutex in JniResultCallbak.java to remain locked. The next message that either completes or fails will now end up in a dead lock causing an ANR.

The proposed fix is to not destroy FutureData until after the tasks have been canceled.

Description

Provide details of the change, and generalize the change in the PR title above.

---

Testing

Describe how you've tested these changes. Link any manually triggered Integration tests or CPP binary SDK Packaging Github Action workflows, if applicable.

---

Type of Change

Place an x the applicable box:

• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

---

Notes

• Bug fixes and feature changes require an update to the Release Notes section of release_build_files/readme.md.
• Read the contribution guidelines CONTRIBUTING.md.
• Changes to the public API require an internal API review. If you'd like to help us make Firebase APIs better, please propose your change in a feature request so that we can discuss it together.

[ktaylor86]

Resolves a common ANR event in firebase when shutting down Messaging on Android

[github-actions]

❌  Integration test FAILED

Requested by @jonsimantov on commit refs/pull/739/merge
Last updated: Fri Nov 5 18:32 PDT 2021
View integration test log & download artifacts

Failures	Configs
firestore	[TEST] [ERROR] [Android] [ubuntu, windows] [android_target]
functions	[TEST] [ERROR] [Android] [ubuntu] [android_target]
messaging	[TEST] [ERROR] [Android] [All os] [android_target]

Add flaky tests to go/fpl-cpp-flake-tracker

[jonsimantov]

Nice find! I kicked off an integration test run and will approve the PR after that finishes.

Because we currently have some flaky tests, don't worry if the integration test fails - I'll manually remove the failure tag as long as the failure isn't caused by this change.

Oh, also, could you please add a note to the "Next Release" section of release_build_files/readme.md? (You may need to merge from main if you don't see that section, I just added it in a recent PR.)

Thanks for your contribution!

🍞 Dismissed stale approval on external PR.