3

I am seeing the following crash on Crashlytics:

Fatal Exception: io.reactivex.exceptions.UndeliverableException: java.net.SocketTimeoutException: connect timed out
       at io.reactivex.plugins.RxJavaPlugins.onError(RxJavaPlugins.java:366)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.disposeAll(FlowableFlatMap.java:590)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.cancel(FlowableFlatMap.java:354)
       at io.reactivex.internal.subscriptions.SubscriptionHelper.cancel(SubscriptionHelper.java:189)
       at io.reactivex.internal.operators.flowable.FlowableSubscribeOn$SubscribeOnSubscriber.cancel(FlowableSubscribeOn.java:141)
       at io.reactivex.internal.subscriptions.SubscriptionHelper.cancel(SubscriptionHelper.java:189)
       at io.reactivex.internal.operators.flowable.FlowableCombineLatest$CombineLatestInnerSubscriber.cancel(FlowableCombineLatest.java:540)
       at io.reactivex.internal.operators.flowable.FlowableCombineLatest$CombineLatestCoordinator.cancelAll(FlowableCombineLatest.java:454)
       at io.reactivex.internal.operators.flowable.FlowableCombineLatest$CombineLatestCoordinator.cancel(FlowableCombineLatest.java:209)
       at io.reactivex.internal.subscriptions.SubscriptionHelper.cancel(SubscriptionHelper.java:189)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$InnerSubscriber.dispose(FlowableFlatMap.java:690)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.innerError(FlowableFlatMap.java:602)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$InnerSubscriber.onError(FlowableFlatMap.java:668)
       at io.reactivex.internal.subscribers.BasicFuseableSubscriber.onError(BasicFuseableSubscriber.java:101)
       at io.reactivex.internal.operators.flowable.FlowableSubscribeOn$SubscribeOnSubscriber.onError(FlowableSubscribeOn.java:102)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.checkTerminate(FlowableFlatMap.java:566)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.drainLoop(FlowableFlatMap.java:374)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.drain(FlowableFlatMap.java:366)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.innerError(FlowableFlatMap.java:605)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$InnerSubscriber.onError(FlowableFlatMap.java:668)
       at io.reactivex.internal.operators.single.SingleToFlowable$SingleToFlowableObserver.onError(SingleToFlowable.java:68)
       at io.reactivex.internal.operators.observable.ObservableElementAtSingle$ElementAtObserver.onError(ObservableElementAtSingle.java:104)
       at io.reactivex.internal.util.HalfSerializer.onError(HalfSerializer.java:133)
       at io.reactivex.internal.operators.observable.ObservableRetryWhen$RepeatWhenObserver.innerError(ObservableRetryWhen.java:132)
       at io.reactivex.internal.operators.observable.ObservableRetryWhen$RepeatWhenObserver$InnerRepeatObserver.onError(ObservableRetryWhen.java:172)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.checkTerminate(ObservableFlatMap.java:495)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.drainLoop(ObservableFlatMap.java:331)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.drain(ObservableFlatMap.java:323)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$InnerObserver.onError(ObservableFlatMap.java:571)
       at io.reactivex.internal.disposables.EmptyDisposable.error(EmptyDisposable.java:63)
       at io.reactivex.internal.operators.observable.ObservableError.subscribeActual(ObservableError.java:37)
       at io.reactivex.Observable.subscribe(Observable.java:11194)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.subscribeInner(ObservableFlatMap.java:162)
       at io.reactivex.internal.operators.observable.ObservableFlatMap$MergeObserver.onNext(ObservableFlatMap.java:139)
       at io.reactivex.internal.operators.observable.ObservableZip$ZipCoordinator.drain(ObservableZip.java:205)
       at io.reactivex.internal.operators.observable.ObservableZip$ZipObserver.onNext(ObservableZip.java:276)
       at io.reactivex.subjects.PublishSubject$PublishDisposable.onNext(PublishSubject.java:309)
       at io.reactivex.subjects.PublishSubject.onNext(PublishSubject.java:230)
       at io.reactivex.subjects.SerializedSubject.onNext(SerializedSubject.java:104)
       at io.reactivex.internal.operators.observable.ObservableRetryWhen$RepeatWhenObserver.onError(ObservableRetryWhen.java:106)
       at io.reactivex.internal.operators.single.SingleToObservable$SingleToObservableObserver.onError(SingleToObservable.java:65)
       at io.reactivex.internal.operators.single.SingleDoOnSuccess$DoOnSuccess.onError(SingleDoOnSuccess.java:64)
       at io.reactivex.internal.operators.single.SingleMap$MapSingleObserver.onError(SingleMap.java:69)
       at io.reactivex.internal.operators.observable.ObservableSingleSingle$SingleElementObserver.onError(ObservableSingleSingle.java:95)
       at retrofit2.adapter.rxjava2.BodyObservable$BodyObserver.onError(BodyObservable.java:72)
       at retrofit2.adapter.rxjava2.CallExecuteObservable.subscribeActual(CallExecuteObservable.java:56)
       at io.reactivex.Observable.subscribe(Observable.java:11194)
       at retrofit2.adapter.rxjava2.BodyObservable.subscribeActual(BodyObservable.java:34)
       at io.reactivex.Observable.subscribe(Observable.java:11194)
       at io.reactivex.internal.operators.observable.ObservableSingleSingle.subscribeActual(ObservableSingleSingle.java:35)
       at io.reactivex.Single.subscribe(Single.java:3096)
       at io.reactivex.internal.operators.single.SingleMap.subscribeActual(SingleMap.java:34)
       at io.reactivex.Single.subscribe(Single.java:3096)
       at io.reactivex.internal.operators.single.SingleDoOnSuccess.subscribeActual(SingleDoOnSuccess.java:35)
       at io.reactivex.Single.subscribe(Single.java:3096)
       at io.reactivex.internal.operators.single.SingleToObservable.subscribeActual(SingleToObservable.java:34)
       at io.reactivex.Observable.subscribe(Observable.java:11194)
       at io.reactivex.internal.operators.observable.ObservableRetryWhen$RepeatWhenObserver.subscribeNext(ObservableRetryWhen.java:150)
       at io.reactivex.internal.operators.observable.ObservableRetryWhen.subscribeActual(ObservableRetryWhen.java:60)
       at io.reactivex.Observable.subscribe(Observable.java:11194)
       at io.reactivex.internal.operators.observable.ObservableElementAtSingle.subscribeActual(ObservableElementAtSingle.java:37)
       at io.reactivex.Single.subscribe(Single.java:3096)
       at io.reactivex.internal.operators.single.SingleToFlowable.subscribeActual(SingleToFlowable.java:37)
       at io.reactivex.Flowable.subscribe(Flowable.java:13234)
       at io.reactivex.Flowable.subscribe(Flowable.java:13180)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.onNext(FlowableFlatMap.java:163)
       at io.reactivex.internal.operators.flowable.FlowableFromArray$ArraySubscription.slowPath(FlowableFromArray.java:164)
       at io.reactivex.internal.operators.flowable.FlowableFromArray$BaseArraySubscription.request(FlowableFromArray.java:89)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.onSubscribe(FlowableFlatMap.java:117)
       at io.reactivex.internal.operators.flowable.FlowableFromArray.subscribeActual(FlowableFromArray.java:37)
       at io.reactivex.Flowable.subscribe(Flowable.java:13234)
       at io.reactivex.internal.operators.flowable.FlowableFlatMap.subscribeActual(FlowableFlatMap.java:53)
       at io.reactivex.Flowable.subscribe(Flowable.java:13234)
       at io.reactivex.Flowable.subscribe(Flowable.java:13180)
       at io.reactivex.internal.operators.flowable.FlowableSubscribeOn$SubscribeOnSubscriber.run(FlowableSubscribeOn.java:82)
       at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:66)
       at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:57)
       at java.util.concurrent.FutureTask.run(FutureTask.java:237)
       at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:272)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
       at java.lang.Thread.run(Thread.java:761)

Now according to the official documentation this is because somewhere in some rx chain the exception cannot be delivered and thus rather than hiding it Rx handles it by causing a crash.

I know I could just avoid this behavior by using 

RxJavaPlugins.setErrorHandler(e -> { });

but I'd rather find the source of the problem. However nowhere in the exception log can I see the actual api request or method call that is causing this, only the stack trace from Rx and Okhttp/retrofit.

My app is quite big so I'd have to go through all my repositories to see where I might have missed an onError handling.

Is there a better way to debug this issue?

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2
  • We had a similar issue. Network calls were taking too long, the users would send our app to the background, forcing us to dispose. When the socket timeout happened we add no one to process the error and saw the above exception. We ended up changing the global error handler to ignore socket timeouts. If you want I can provide an example. Commented Mar 22, 2019 at 11:35
  • @Fred that would be great! Commented Mar 25, 2019 at 8:34

1 Answer 1

Reset to default
4

As stated in the question comments, I had to deal with a similar issue. Our problem was in our Android app. The network calls would take too long and the users would send the app to the background. When this happens, we dispose of the subscriptions. When the socket timeout happens there's no one listening for the exception and this causes an UndeliverableException.

We've replaced the default error handler with (it's in kotlin, I hope this is ok):

private object DefaultErrorHandler : Consumer<Throwable> {
  override fun accept(t: Throwable) {
    when (t) {
        is UndeliverableException -> accept(t.cause!!)
        is NullPointerException,
        is IllegalArgumentException -> Thread.currentThread().run {
            uncaughtExceptionHandler.uncaughtException(this, t)
        }
        else -> // Swallow the exception here. We logged it to Crashlytics...
    }
  }
}

val defaultErrorHandler: Consumer<Throwable> = DefaultErrorHandler

// Then on application start we would replace the error handler
RxJavaPlugins.setErrorHandler(defaultErrorHandler)

I'm pretty sure defaultErrorHandler is a horrible name. Sorry about that.

A bit of explanation. The exceptions we don't swallow are NullPointerException and IllegalArgumentException. These get forwarded to the current thread's uncaught exceptions handler. We did this because these are usually related to programming errors.

We check for UndeliverableExceptions and unwrap them to rerun again through the same consumer. This is just to make sure we run the correct logic on the exception that couldn't be delivered.

All other exceptions are swallowed and logged into crashlytics for further assessment.

One key thing, this works for our use cases. It might be that you need to adapt it to yours. I'm not saying this is the best way to do it. It's an example. Perhaps for you, you want to just ignore socket timeouts.

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9 Comments

your explanation sounds like my issue as well. thanks
About this line else -> // Swallow the exception here. We logged it to Crashlytics..., should we really do anything here you mean? or it'd redirect the exception automatically to the producer?
For accept(t.cause!!) is it possible to with this approach we get stuck in a loop?
accept(t.cause!!) never actually got us in a loop. I must confess I don't know of any case where the exception causes circle back to an old one in the stack trace.
@Dr.jacky yes you should definitely do something there. It won't do any redirection as far as I know.
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