Improve Resource Cleanup

[apuig]

This PR addresses critical problems caused by the use of JVM shutdownHooks in environments where analytics-kotlin is loaded via isolated class loaders (e.g., plugin systems). Relying on shutdownHooks in these scenarios leads to failures and class-loading errors during system shutdown, especially when plugins and their class loaders are retired before the JVM executes any registered hooks using classes not previously loaded.

No More Runtime.addShutdownHook

All references to shutdownHooks in EventStream and EventPipeline are gone. Cleanup and shutdown are now handled directly via the shutdown() call instead.

Plugin & Coroutine Cleanup:

All EventPipeline plugins get stopped before coroutines are shut down.

• Once shutdown starts, no new analytics work gets accepted.
• The global coroutine scope (analyticsScope) gets canceled, and shutdown can (optionally) wait for all analytics work to finish up.
  • The shutdown() method now has a waitForTasks parameter (defaults to false). If you set it to true, shutdown will block until all ongoing analytics tasks finish.
  • Java API compatibility is kept with @JvmOverloads so nothing breaks on the Java side.
• Custom coroutine dispatchers are closed properly; The default Kotlin dispatchers will still stick around, though.

Potential issue

Now, shutdown needs to be called directly when you want cleanup. If for some reason this is not a good idea on Android, I recommend adding a shutdownHook in the android module.

Disclaimer 1

Didn’t get a chance to add a test for this, our integration tests seem to be working fine, but I’m not experienced with writing Kotlin tests or handling the analytics object lifecycle. I did give it a shot, just didn’t have much luck. If anyone can point me in the right direction, I’m happy to try again!

[apuig]

Merging with main has resulted in some test failures on my end.

> Task :core:test

WaitingTests > test timeout force resume on DestinationPlugin() FAILED
    org.opentest4j.AssertionFailedError at WaitingTests.kt:162

WaitingTests > test timeout force resume() FAILED
    org.opentest4j.AssertionFailedError at WaitingTests.kt:97

346 tests completed, 2 failed, 10 skipped

UPDATE: These seem like flaky tests, I see them failing roughly 1 out of every 3 runs

[apuig]

Hi @wenxi-zeng, could you please take a look at this?
This issue is still affecting us and we are force to to maintain a list of 39 exotic Kotlin classes as a workaround, which is quite fragile and can easily break with any kotlin or kotlinx updates.
I’d appreciate your consideration on this.

[wenxi-zeng]

hi @apuig, thanks for the pr. this is great stuff. would you mind to address my feedback before I got it merged? I can do it on my end too, but just don't want to steal your idea.

[wenxi-zeng]

maybe add a shutdown method with empty body to the Plugin interface, so we can just call it.shutdown without knowing the existence of EventPipeline? then in SegmentDestination override the shutdown method to close EventPipeline

[wenxi-zeng]

we can also add a close method with empty body to Storage and in StorageImpl override it to close the eventStream. so we could just call storage.close without the check