RX Java Exception - UndeliverableException

[talbigelbinah]

Platform on which you observed the bug:

• Android
• iOS
• Other
• Platform is not relevant for this bug

Device on which you observed the bug:

• Polar OH1
• Polar Verity Sense
• Polar H10
• Polar H9
• Other
• Device is not relevant for this bug

Describe the bug
SDK version: 5.1.0
We had a crash/error report from Sentry:

ProtocolViolationException

io.reactivex.rxjava3.exceptions.UndeliverableException in

com.polar.androidcommunications.api.ble.exceptions.BleAttributeError: Failed to set characteristic notification or indication  failed with error: 133
    at com.polar.androidcommunications.api.ble.model.gatt.BleGattBase.lambda$waitNotificationEnabled$1
    at com.google.firebase.messaging.FcmBroadcastProcessor$$ExternalSyntheticLambda1.subscribe(FcmBroadcastProcessor:0)
    at io.reactivex.rxjava3.internal.operators.completable.CompletableCreate.subscribeActual(CompletableCreate.java:40)
    at io.reactivex.rxjava3.core.Completable.subscribe(Completable.java:2860)
    at io.reactivex.rxjava3.internal.operators.completable.CompletableSubscribeOn$SubscribeOnObserver.run(CompletableSubscribeOn.java:64)
    at io.reactivex.rxjava3.core.Scheduler$DisposeTask.run(Scheduler.java:644)
    at io.reactivex.rxjava3.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:65)
    at io.reactivex.rxjava3.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:56)
    at java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:307)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:644)
    at java.lang.Thread.run(Thread.java:1012)
io.reactivex.rxjava3.exceptions.ProtocolViolationException: The exception could not be delivered to the consumer because it has already canceled/disposed the flow or the exception has nowhere to go to begin with. Further reading: https://github.com/ReactiveX/RxJava/wiki/What's-different-in-2.0#error-handling | com.biosensesignal.sdk.zn: Failed to set characteristic notification or indication  failed with error: 133
    at io.reactivex.rxjava3.exceptions.UndeliverableException.<init>
    at io.reactivex.rxjava3.plugins.RxJavaPlugins.onError(RxJavaPlugins.java:372)
    at io.reactivex.rxjava3.internal.util.AtomicThrowable.tryAddThrowableOrReport(AtomicThrowable.java:52)
    at io.reactivex.rxjava3.internal.operators.flowable.FlowableFlatMap$MergeSubscriber.innerError
    at io.reactivex.rxjava3.internal.operators.flowable.FlowableFlatMap$InnerSubscriber.onError(FlowableFlatMap.java:636)
    at io.reactivex.rxjava3.internal.operators.flowable.FlowableFromCompletable$FromCompletableObserver.onError(FlowableFromCompletable.java:83)
    at io.reactivex.rxjava3.internal.operators.completable.CompletablePeek$CompletableObserverImplementation.onError(CompletablePeek.java:95)
    at io.reactivex.rxjava3.internal.operators.completable.CompletableObserveOn$ObserveOnCompletableObserver.run(CompletableObserveOn.java:87)
    at io.reactivex.rxjava3.android.schedulers.HandlerScheduler$ScheduledRunnable.run(HandlerScheduler.java:123)
    at android.os.Handler.handleCallback(Handler.java:959)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loopOnce(Looper.java:232)
    at android.os.Looper.loop(Looper.java:317)
    at android.app.ActivityThread.main(ActivityThread.java:8705)
    at java.lang.reflect.Method.invoke(Method.java)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:886)

How to Reproduce
We don't know how to reproduce. This is a sentry issue we received. It looks like something in the Polar lib

[TeemuLauPolar]

FLOW-61107

[orestesgaolin]

To avoid crashes in the meantime you can use following code (see more here):

RxJavaPlugins.setErrorHandler {
  Logger.error(TAG, "Error from RxJavaPlugins.setErrorHandler", it)
  // send error to Sentry etc.
}