Find missing onError in the project

Question

I am trying to locate a missing onError() in a project. It means that the app crashes because a subscription does not handle the throwables so I want to locate that subcription and add the onError method.

Unfortunatelly the stacktrace is not really helpful here and it only shows the line of the throw new IOException but nothing more:

 FATAL EXCEPTION: main
    Process: my.app.example.dev, PID: 20309
    java.lang.IllegalStateException: Fatal Exception thrown on Scheduler.Worker thread.
            at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:54)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: rx.exceptions.OnErrorFailedException: Error occurred when trying to propagate error to Observer.onError
            at rx.observers.SafeSubscriber._onError(SafeSubscriber.java:201)
            at rx.observers.SafeSubscriber.onError(SafeSubscriber.java:111)
            at rx.android.app.OperatorConditionalBinding$1.onError(OperatorConditionalBinding.java:69)
            at rx.internal.operators.NotificationLite.accept(NotificationLite.java:147)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:177)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.access$000(OperatorObserveOn.java:65)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:153)
            at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:47)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: rx.exceptions.CompositeException: 2 exceptions occurred.
            at rx.observers.SafeSubscriber._onError(SafeSubscriber.java:201)
            at rx.observers.SafeSubscriber.onError(SafeSubscriber.java:111)
            at rx.android.app.OperatorConditionalBinding$1.onError(OperatorConditionalBinding.java:69)
            at rx.internal.operators.NotificationLite.accept(NotificationLite.java:147)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:177)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.access$000(OperatorObserveOn.java:65)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:153)
            at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:47)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: rx.exceptions.CompositeException$CompositeExceptionCausalChain: Chain of Causes for CompositeException In Order Received =>
            at com.splunk.mint.ExceptionHandler.uncaughtException(ExceptionHandler.java:42)
            at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:693)
            at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:690)
            at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:58)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: retrofit.RetrofitError: java.io.IOException: No connectivity
            at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:385)
            at retrofit.RestAdapter$RestHandler.access$100(RestAdapter.java:221)
            at retrofit.RestAdapter$RestHandler$1.call(RestAdapter.java:271)
            at retrofit.RestAdapter$RestHandler$1.call(RestAdapter.java:269)
            at retrofit.RxSupport$2.run(RxSupport.java:46)
            at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:818)
     Caused by: java.io.IOException: No connectivity
            at my.app.example.manager.ApiManager$NetworkAwareOKClient.execute(ApiManager.java:1071)
            at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:322)
            at retrofit.RestAdapter$RestHandler.access$100(RestAdapter.java:221)
            at retrofit.RestAdapter$RestHandler$1.call(RestAdapter.java:271)
            at retrofit.RestAdapter$RestHandler$1.call(RestAdapter.java:269)
            at retrofit.RxSupport$2.run(RxSupport.java:46)
            at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)
            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:818)

Any ideas to locate the subscription (line in code) that does not have the onError() ?

Answer 1

This can be a pain to debug. Funnily enough I had an error inside the Action1<Throwable> [facepalm].

The best was to debug this is to register a global error handler. This will saw you the truth in your code:

RxJavaPlugins.getInstance().registerErrorHandler(new RxJavaErrorHandler() {
        @Override
        public void handleError(Throwable e) {
            Log.w("Error",e);
        }
});    

A discussion on github: https://github.com/ReactiveX/RxJava/issues/2293