RxJava: Stack trace is opaque for IllegalStateException: Exception thrown on Scheduler.Worker thread. Add `onError` handling.

This occurs when using RxAndroid 0.23.0/RxJava 1.0.0, please redirect me if this is not the most appropriate place for this.

There seem to be a several ways to cause the following exception, notably using observeOn() on a when there exists overproducing or underconsuming, and there is no clear association with client code:

java.lang.IllegalStateException: Exception thrown on Scheduler.Worker thread. Add `onError` handling.
       at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:50)
       at android.os.Handler.handleCallback(Handler.java:733)
       at android.os.Handler.dispatchMessage(Handler.java:95)
       at android.os.Looper.loop(Looper.java:146)
       at android.app.ActivityThread.main(ActivityThread.java:5598)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:515)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
       at dalvik.system.NativeStart.main(NativeStart.java)
Caused by: rx.exceptions.OnErrorNotImplementedException
       at rx.Observable$31.onError(Observable.java:7204)
       at rx.observers.SafeSubscriber._onError(SafeSubscriber.java:127)
       at rx.observers.SafeSubscriber.onError(SafeSubscriber.java:96)
       at rx.internal.operators.NotificationLite.accept(NotificationLite.java:147)
       at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:177)
       at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.access$000(OperatorObserveOn.java:65)
       at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:153)
       at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:45)
       at android.os.Handler.handleCallback(Handler.java:733)
       at android.os.Handler.dispatchMessage(Handler.java:95)
       at android.os.Looper.loop(Looper.java:146)
       at android.app.ActivityThread.main(ActivityThread.java:5598)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:515)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
       at dalvik.system.NativeStart.main(NativeStart.java)
Caused by: rx.exceptions.MissingBackpressureException
       at rx.internal.util.RxRingBuffer.onNext(RxRingBuffer.java:222)
       at rx.internal.operators.OnSubscribeCombineLatest$MultiSourceProducer.onNext(OnSubscribeCombineLatest.java:201)
       at rx.internal.operators.OnSubscribeCombineLatest$MultiSourceRequestableSubscriber.onNext(OnSubscribeCombineLatest.java:252)
       at rx.internal.operators.OnSubscribeTimerPeriodically$1.call(OnSubscribeTimerPeriodically.java:51)
       at rx.Scheduler$Worker$1.call(Scheduler.java:118)
       at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:45)
       at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
       at java.util.concurrent.FutureTask.run(FutureTask.java:237)
       at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:152)
       at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:265)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
       at java.lang.Thread.run(Thread.java:841)

I’d like to strike up a discussion highlighting common causes on these backpressure exceptions, how to determine the source of them in client code, and finally how to improve the stacktrace.

About this issue

Original URL
State: closed
Created 10 years ago
Comments: 21 (10 by maintainers)

Most upvoted comments

The problem is this:

.subscribe( action );

You have to handle exception by consuming it via subscribe:

.subscribe( action, error -> errorHandler(error) );

akarnokd on Nov 28, 2016

I am toying with RxJava and I had this issue as well. I think ReactiveX should be very careful to explain the difference between Observable.doOnError (side effect, will still blow up) and Subscriber.onError (last consumer, if handled here your error won’t pop anymore. At least that was my problem. https://twitter.com/Corlaez/status/782023068793339904

corlaez on Oct 1, 2016

Right, but given I have hundreds of places that I could add that onError handler to, and decoupled stacktrace, I have no obvious place to start.

jondwillis on Dec 30, 2014

but rx.plugins.RxJavaPlugins.getInstance().registerErrorHandler( rxJavaErrorHandler ); was my error handler.

if i put .doOnError( Action1<Throwable>… ) after .observeOn, it gets called but the chain continues on to call the plugin errorhandler, then it calls the actual Subscriber that Observable creates to wrap the Action, and this then throws OnErrorNotImplementedException.

(if i subscribe on a SafeSubscriber, i.e. new rx.Observer<>… then there is not the problem … problem is with subscribing with an Action1)

gubo on Nov 28, 2016

You can register a global error handler if you don’t have specific error handlers. We use it at Netflix to track unhandled errors.

Take a look at http://reactivex.io/RxJava/javadoc/rx/plugins/RxJavaPlugins.html#registerErrorHandler(rx.plugins.RxJavaErrorHandler)

benjchristensen on Dec 30, 2014