Fatal Exception thrown on Scheduler.Worker thread with Retrofit 2 and Rx

Question

This is the code I use to make Http call. I can't reproduce the error, but Bugsnag tells me that some users are getting this error : java.lang.IllegalStateException StrictMode.java

public class ApiManager {
    public interface Callback<T> {
        void onError(Throwable e);

        void onSuccess(T result);
    }

    private ApiService _apiService;

    public ApiManager() {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(BuildConfig.BASE_URL)
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .client(ew OkHttpClient())
                .build();
        _apiService = retrofit.create(ApiService.class);
    }

    private <T> void execute(Observable<T> observable, final Callback<T> callback) {
        observable.subscribeOn(Schedulers.computation())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Subscriber<T>() {
                    @Override
                    public void onCompleted() {
                    }

                    @Override
                    public void onError(Throwable e) {
                        callback.onError(e);
                    }

                    @Override
                    public void onNext(T result) {
                        callback.onSuccess(result);
                    }
                });
    }

    public void createUser(Callback<Void> callback) {
        execute(_apiService.createUser(new User()), callback);
    }

    // Retrofit Service
    public interface ApiService {
        @POST("users")
        Observable<Void> createUser(@Body User user);
    }
}

Here is the full trace :

java.lang.IllegalStateException: Fatal Exception thrown on Scheduler.Worker thread.
        at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:62)
        at android.os.Handler.handleCallback(Handler.java:725)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:153)
        at android.app.ActivityThread.main(ActivityThread.java:5340)
        at java.lang.reflect.Method.invokeNative(Method.java:-2)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
        at dalvik.system.NativeStart.main(NativeStart.java:-2)
Caused by: rx.exceptions.UnsubscribeFailedException
        at rx.observers.SafeSubscriber.onCompleted(SafeSubscriber.java:98)
        at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:195)
        at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:162)
        at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
        at android.os.Handler.handleCallback(Handler.java:725)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:153)
        at android.app.ActivityThread.main(ActivityThread.java:5340)
        at java.lang.reflect.Method.invokeNative(Method.java:-2)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
        at dalvik.system.NativeStart.main(NativeStart.java:-2)
Caused by: android.os.NetworkOnMainThreadException
        at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1128)
        at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.close(OpenSSLSocketImpl.java:906)
        at com.squareup.okhttp.Connection.closeIfOwnedBy(Connection.java:148)
        at com.squareup.okhttp.OkHttpClient$1.closeIfOwnedBy(OkHttpClient.java:75)
        at com.squareup.okhttp.internal.http.HttpConnection.closeIfOwnedBy(HttpConnection.java:137)
        at com.squareup.okhttp.internal.http.HttpTransport.disconnect(HttpTransport.java:135)
        at com.squareup.okhttp.internal.http.HttpEngine.disconnect(HttpEngine.java:573)
        at com.squareup.okhttp.Call.cancel(Call.java:122)
        at retrofit.OkHttpCall.cancel(OkHttpCall.java:162)
        at retrofit.RxJavaCallAdapterFactory$CallOnSubscribe$1.call(RxJavaCallAdapterFactory.java:102)
        at rx.subscriptions.BooleanSubscription.unsubscribe(BooleanSubscription.java:71)
        at rx.internal.util.SubscriptionList.unsubscribeFromAll(SubscriptionList.java:124)
        at rx.internal.util.SubscriptionList.unsubscribe(SubscriptionList.java:113)
        at rx.Subscriber.unsubscribe(Subscriber.java:98)
        at rx.internal.util.SubscriptionList.unsubscribeFromAll(SubscriptionList.java:124)
        at rx.internal.util.SubscriptionList.unsubscribe(SubscriptionList.java:113)
        at rx.Subscriber.unsubscribe(Subscriber.java:98)
        at rx.internal.util.SubscriptionList.unsubscribeFromAll(SubscriptionList.java:124)
        at rx.internal.util.SubscriptionList.unsubscribe(SubscriptionList.java:113)
        at rx.Subscriber.unsubscribe(Subscriber.java:98)
        at rx.observers.SafeSubscriber.onCompleted(SafeSubscriber.java:95)
        at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:195)
        at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:162)
        at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
        at android.os.Handler.handleCallback(Handler.java:725)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:153)
        at android.app.ActivityThread.main(ActivityThread.java:5340)
        at java.lang.reflect.Method.invokeNative(Method.java:-2)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
        at dalvik.system.NativeStart.main(NativeStart.java:-2)

I also tried to subscribe on Sheduler.io() and Scheduler.newThread(), but I get the same error.

Answer 1

Note this isn't a permanent fix, but it helped me and might help you. It's too long to put in a comment.

While I was using the specific version of retrofit you've mentioned I noticed there was a bug (already being addressed) with the okhttp library and the rx integration with retrofit.

I don't know the state of the fix, but I have a quick fix which was adding to the rx stream unsubscribeOn(Schedulers.io()), like so:

observable.subscribeOn(Schedulers.computation())
            .observeOn(AndroidSchedulers.mainThread())
            .unsubscribeOn(Schedulers.io())
            .subscribe(new Subscriber<T>() {
                @Override
                public void onCompleted() {
                }

                @Override
                public void onError(Throwable e) {
                    callback.onError(e);
                }

                @Override
                public void onNext(T result) {
                    callback.onSuccess(result);
                }
            });