Crash with kotlinx.coroutines.JobCancellationException

[frist008]

Hello.
Migrated my project from RxJava to Kotlin coroutines.
My project has up to 2000-3000 online per day and 20_000 per month.

I started getting all sorts of errors on Crashlitics with JobCancellationException.

Full log:
Fatal Exception: kotlinx.coroutines.JobCancellationException: Job was cancelled.

However, there are 30-50 other streams. I'm worried that I don't have a Stacktrace where the error occurred? and I cannot fix the problem.

Furthermore. I cannot reproduce it myself. This error occurs with real users, but not me. For real users, the error does not repeat itself for a month. The sample for all users is very small - 0.23%. And the chance of repetition is even less.

The error header can be quite different on Crashlitics:

AndroidLeakFixes.java line 400
leakcanary.AndroidLeakFixes$Companion$backgroundExecutor$1$thread$1.run

bn.java line 1
bn.a

bn.java line 1
bn.b

bf.java line 1
bf.b

rw.java line 2
rw.run

zj.java line 2
zj.a

bt.java line 1
bt.a

DpmTcmClient.java line 149
com.qti.tcmclient.DpmTcmClient$TcmReceiver.run

GlideExecutor.java line 393
com.bumptech.glide.load.engine.executor.GlideExecutor$DefaultThreadFactory$1.run

You may also have noticed that I have listed 2 sides of the library that are thrown with JobCancellationException.

It's funny, but I don't use coroutines explicitly in them. It's just magic.

implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.3.72"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.8"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.8"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-play-services:1.3.8"

I am using a wrapper to run coroutines.

fun CoroutineScope.launchSafe(
    context: CoroutineContext = EmptyCoroutineContext,
    start: CoroutineStart = CoroutineStart.DEFAULT,
    launchSafe: LaunchSafe = object : LaunchSafe {
        override fun onCancellation(e: CancellationException) {
            Timber.v(e)
        }

        override fun onFailure(t: Throwable) {
            Timber.e(t)
        }
    },
    onStart: (suspend CoroutineScope.() -> Unit)? = null,
    block: suspend CoroutineScope.() -> Unit
) = launch(context, start) {
    try {
        onStart?.invoke(this)
        block()
    } catch (e: CancellationException) {
        try {
            launchSafe.onCancellation(e)
        } catch (t: Throwable) {
            Timber.e(t)
        }
    } catch (t: Throwable) {
        try {
            launchSafe.onFailure(t)
        } catch (t: Throwable) {
            Timber.e(t)
        }
    }
}

interface LaunchSafe {

    @WorkerThread
    fun onCancellation(e: CancellationException)

    @WorkerThread
    fun onFailure(t: Throwable)
}

abstract class BaseViewModel : ViewModel(), CoroutineScope, LaunchSafe {

    override var coroutineContext =
        Dispatchers.Default + SupervisorJob() + CoroutineName("ViewModel") + SafeCoroutineExceptionHandler()

    val errorLiveEvent = LiveEvent<Throwable>()

    override fun onFailure(t: Throwable) {
        errorLiveEvent.postValue(t)
    }

    override fun onCancellation(e: CancellationException) {
        // none
    }

    override fun onCleared() {
        coroutineContext.cancel()
        super.onCleared()
    }
}

@Suppress("FunctionName", "NOTHING_TO_INLINE")
inline fun SafeCoroutineExceptionHandler() = CoroutineExceptionHandler { _, throwable ->
    if (BuildConfig.DEBUG) {
        Thread.currentThread()
            .uncaughtExceptionHandler
            ?.uncaughtException(Thread.currentThread(), throwable)
    } else {
        Timber.e(throwable, "Error ExceptionHandler")
    }
}

[frist008]

All logs usually contain Unsafe.park.

glide-source-thread-3
       at java.lang.Object.wait(Object.java)
       at java.lang.Thread.parkFor$(Thread.java:2161)
       at sun.misc.Unsafe.park(Unsafe.java:358)
       at java.util.concurrent.locks.LockSupport.park(LockSupport.java:190)
       at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2059)
       at java.util.concurrent.PriorityBlockingQueue.take(PriorityBlockingQueue.java:548)
       at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1087)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1147)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
       at java.lang.Thread.run(Thread.java:784)
       at com.bumptech.glide.load.engine.executor.GlideExecutor$DefaultThreadFactory$1.run(GlideExecutor.java:393)

sun.misc.Unsafe.park (Unsafe.java)
java.util.concurrent.locks.LockSupport.park (LockSupport.java:190)
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await (AbstractQueuedSynchronizer.java:2067)
java.util.concurrent.PriorityBlockingQueue.take (PriorityBlockingQueue.java:548)
bn.a (bn.java:1)
bn.run (bn.java:2)

[qwwdfsad]

Hi,

I'm worried that I don't have a Stacktrace where the error occurred

Please try to enable debug mode: https://github.com/Kotlin/kotlinx.coroutines/blob/master/docs/debugging.md#debug-mode to have stacktraces in JobCancellationException

It's hard to tell what exactly is wrong without actual stacktraces, but as a wild guess, please ensure that you do not invoke channel.offer from non-suspending methods as it can unexpectedly throw CancellationException (#974).
Also, it is worth to add SafeCoroutineExceptionHandler to your launchSafe to handle exceptions from coroutine children as well

[torresmi]

My team encountered this as well and unfortunately, we haven't identified the root cause.

But we did make the following changes in a release and haven't seen it since. Maybe these will be helpful:

1. Replaced our Observable.asFlow() usages to Observable.toFlowable(BackPressureStrategy.LATEST).asFlow(), like this comment from ChildCancelledException when using Rx Observable.asFlow() extension within combine() #2104.
2. Replaced our Flow.asObservable() usages to Flow.asFlowable().toObservable()
3. A lot of our exceptions involved OkHttp usage. So we updated from v3.14.9 to v4.7.2.
4. Updated Coroutines from v1.3.7 to v1.3.8

Other things to note:

• We weren't using channel.offer explicitly in our source code.
• Crashlytics reports would often point to lines of library code that were existing issues for us before we introduced coroutines. Those issues did not have stack traces that lead back to our source code. After using coroutines more, we would get the same reports but started happening much more often and the stacktrace became Fatal Exception: kotlinx.coroutines.JobCancellationException: Job was cancelled.
  • This has more information on those stacktraces https://github.com/gildor/kotlin-coroutines-okhttp#debugging

[frist008]

Hi,

I'm worried that I don't have a Stacktrace where the error occurred

Please try to enable debug mode: https://github.com/Kotlin/kotlinx.coroutines/blob/master/docs/debugging.md#debug-mode to have stacktraces in JobCancellationException

It's hard to tell what exactly is wrong without actual stacktraces, but as a wild guess, please ensure that you do not invoke channel.offer from non-suspending methods as it can unexpectedly throw CancellationException (#974).
Also, it is worth to add SafeCoroutineExceptionHandler to your launchSafe to handle exceptions from coroutine children as well

We weren't using channel.offer or RX explicitly in our source code.

I already add SafeCoroutineExceptionHandler in coroutineContext for BaseViewModel : ViewModel(), CoroutineScope.
If I add it again to launchSafe, won't it be a duplicate?

[frist008]

I am not using experimental or deprecated functions in the project at all.

I have set in Application
System.setProperty (DEBUG_PROPERTY_NAME, DEBUG_PROPERTY_VALUE_ON)

I think it will be necessary to wait a few days. Before I get any results from users in beta testing.

[qwwdfsad]

Replaced our Observable.asFlow() usages to Observable.toFlowable(BackPressureStrategy.LATEST).asFlow()

Thanks, that's a great place to start looking!

I already add SafeCoroutineExceptionHandler in coroutineContext for BaseViewModel : ViewModel(), CoroutineScope.
If I add it again to launchSafe, won't it be a duplicate?

If the scope of BaseViewModel is used for launchSafe, then it's indeed not necessary

[frist008]

I found a bug. It consisted in the fact that I used in one place in my code the suspend function in the catch (e: CancellationException) block.

Helped me:

class Application : Application {

    override fun onCreate() {
        super.onCreate()

        System.setProperty(DEBUG_PROPERTY_NAME, DEBUG_PROPERTY_VALUE_ON)
    }
}

I continue to observe. If no new issues are found by the end of the month, I will close the discussion.

[frist008]

Perhaps this problem is somehow related to a Google bug.
https://issuetracker.google.com/issues/164317567

[frist008]

After switching to Kotlin 1.4, no new error messages appeared. Thanks to all.

[mhernand40]

@frist008 have you by any chance switched back to Observable.asFlow() now that you have switched to Kotlin 1.4? How about Flow.asObservable()?

[frist008]

@frist008 have you by any chance switched back to Observable.asFlow() now that you have switched to Kotlin 1.4? How about Flow.asObservable()?

We weren't using RX explicitly in our source code.