那些遇到过的问题

长链中的rxjava StackOverflowError异常

Dmi*_*try 1 stack-overflow android rx-java retrofit jack-compiler

我使用许多运算符构建了很长的rxjava链（带有改装请求）：doOnNext，doOnError，switchIfEmpty，onErrorResumeNext，flatMap在某些设备（例如Android 4.1）上，当链沿最长路线走时，它会引发StackOverflowError异常。

是否有一些方法或最佳实践来优化链或防止StackOverflowError？

现在，我只看到一种方法-断开链，并从第一个onComplete（OnNext）调用第二部分，但我认为这不是被动方式。

另一种方法-使用.subscribeOn（Schedulers.newThread（））;更改线程 操作员。似乎也不是最好的解决方案。

我的代码：1）订阅代码

fastSearch(keyphrase)
    .onErrorResumeNext(throwable -> {
        return correctKeyphraseAndSearch(keyphrase);
    })
    .doOnNext(resultsDao -> {...})
    .subscribe(...)
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2）辅助方法

public static Observable<SearchResultsDao> fastSearch(final String keyphrase) {
    String SRD = "true";
    final HttpQueryParams params = new HttpQueryParams();
    //read from cache chain
    Observable<SearchResultsDao> cacheChain = getCache().fastSearch(keyphrase, SRD)
            .doOnNext(...)
            .doOnError(...)
            .onErrorResumeNext(new HandleNoCacheEntry<SearchResultsDao>(params)); //save some data to "params", and return Observable.empty
    //network request chain
    Observable<SearchResultsDao> networkChain = getApi().fastSearch(keyphrase, SRD)
            .retryWhen(new OnNewSessionRequired())
            .doOnNext(new WriteToCacheAction<SearchResultsDao>(params)); //save to cache
    //combine cache+network chains
    return cacheChain
            .switchIfEmpty(networkChain)
            .doOnNext(resultsDao -> resultsDao.setKeyphrase(keyphrase));
}

public static Observable<SearchResultsDao> correctKeyphraseAndSearch(final String keyphrase) {
    return mainDiv()
            .flatMap(str -> syntax(str, keyphrase, true))
            .flatMap(syntaxDao -> {
                //get corrected keyphrase from server
                StringBuilder newKeyphrase = ... ;
                //repeat search request with new keyphrase
                return fastSearch(newKeyphrase.toString());
            });
}
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3）一些评论：

mainDiv（）和语法（）方法与fastSearch（）方法相同，但是对服务器进行了另一个请求

getCache（）。fastSearch（）-创建可观察到的从其自身的缓存中读取数据（类似retrofit的方法：getCache（）实现改造的Api方法接口）

堆栈跟踪：

Uncaught Exception
java.lang.IllegalStateException: Fatal Exception thrown on Scheduler.Worker thread.
at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:62)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:442)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
at java.util.concurrent.FutureTask.run(FutureTask.java:137)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:150)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:264)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
at java.lang.Thread.run(Thread.java:856)
Caused by: java.lang.StackOverflowError
okhttp3.HttpUrl.newBuilder (HttpUrl.java:633)
retrofit2.RequestBuilder.addQueryParam (RequestBuilder.java:144)
retrofit2.ParameterHandler$Query.apply (ParameterHandler.java:109)
retrofit2.ServiceMethod.toRequest (ServiceMethod.java:108)
retrofit2.OkHttpCall.createRawCall (OkHttpCall.java:178)
retrofit2.OkHttpCall.execute (OkHttpCall.java:162)
retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$RequestArbiter.request (RxJavaCallAdapterFactory.java:171)
rx.internal.producers.ProducerArbiter.setProducer (ProducerArbiter.java:126)
rx.internal.operators.OnSubscribeRedo$2$1.setProducer (OnSubscribeRedo.java:272)
rx.Subscriber.setProducer (Subscriber.java:205)
retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$CallOnSubscribe.call (RxJavaCallAdapterFactory.java:152)
retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$CallOnSubscribe.call (RxJavaCallAdapterFactory.java:138)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OnSubscribeRedo$2.call (OnSubscribeRedo.java:278)
rx.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.enqueue (TrampolineScheduler.java:80)
rx.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.schedule (TrampolineScheduler.java:59)
rx.internal.operators.OnSubscribeRedo$5.request (OnSubscribeRedo.java:366)
rx.internal.producers.ProducerArbiter.setProducer (ProducerArbiter.java:126)
rx.internal.operators.OperatorSwitchIfEmpty$AlternateSubscriber.setProducer (OperatorSwitchIfEmpty.java:106)
rx.Subscriber.setProducer (Subscriber.java:205)
rx.internal.operators.OnSubscribeRedo.call (OnSubscribeRedo.java:358)
rx.internal.operators.OnSubscribeRedo.call (OnSubscribeRedo.java:55)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorSwitchIfEmpty$ParentSubscriber.subscribeToAlternate (OperatorSwitchIfEmpty.java:78)
rx.internal.operators.OperatorSwitchIfEmpty$ParentSubscriber.onCompleted (OperatorSwitchIfEmpty.java:71)
rx.internal.operators.OperatorOnErrorResumeNextViaFunction$4$1.onCompleted (OperatorOnErrorResumeNextViaFunction.java:125)
rx.Observable$EmptyHolder$1.call (Observable.java:1123)
rx.Observable$EmptyHolder$1.call (Observable.java:1120)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorOnErrorResumeNextViaFunction$4.onError (OperatorOnErrorResumeNextViaFunction.java:141)
rx.internal.operators.OperatorDoOnEach$1.onError (OperatorDoOnEach.java:71)
rx.internal.operators.OperatorDoOnEach$1.onError (OperatorDoOnEach.java:71)
com.testrx.app.retrofit.api.CacheHelper$1.call (CacheHelper.java:56)
com.testrx.app.retrofit.api.CacheHelper$1.call (CacheHelper.java:46)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorMerge$MergeSubscriber.onNext (OperatorMerge.java:235)
rx.internal.operators.OperatorMerge$MergeSubscriber.onNext (OperatorMerge.java:145)
rx.internal.operators.OperatorMap$1.onNext (OperatorMap.java:54)
rx.internal.operators.OperatorMerge$MergeSubscriber.emitScalar (OperatorMerge.java:368)
rx.internal.operators.OperatorMerge$MergeSubscriber.tryEmit (OperatorMerge.java:330)
rx.internal.operators.OperatorMerge$InnerSubscriber.onNext (OperatorMerge.java:807)
rx.internal.operators.OperatorSwitchIfEmpty$ParentSubscriber.onNext (OperatorSwitchIfEmpty.java:89)
rx.internal.operators.OperatorOnErrorResumeNextViaFunction$4.onNext (OperatorOnErrorResumeNextViaFunction.java:153)
rx.internal.operators.OperatorDoOnEach$1.onNext (OperatorDoOnEach.java:85)
rx.internal.operators.OperatorDoOnEach$1.onNext (OperatorDoOnEach.java:85)
com.testrx.app.retrofit.api.CacheHelper$1.call (CacheHelper.java:53)
com.testrx.retrofit.api.CacheHelper$1.call (CacheHelper.java:46)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorMerge$MergeSubscriber.onNext (OperatorMerge.java:235)
rx.internal.operators.OperatorMerge$MergeSubscriber.onNext (OperatorMerge.java:145)
rx.internal.operators.OperatorMap$1.onNext (OperatorMap.java:54)
rx.internal.operators.OperatorSwitchIfEmpty$ParentSubscriber.onNext (OperatorSwitchIfEmpty.java:89)
rx.internal.operators.OperatorOnErrorResumeNextViaFunction$4.onNext (OperatorOnErrorResumeNextViaFunction.java:153)
rx.internal.operators.OperatorDoOnEach$1.onNext (OperatorDoOnEach.java:85)
rx.internal.operators.OperatorDoOnEach$1.onNext (OperatorDoOnEach.java:85)
com.testrx.app.retrofit.api.CacheHelper$1.call (CacheHelper.java:53)
com.testrx.app.retrofit.api.CacheHelper$1.call (CacheHelper.java:46)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorOnErrorResumeNextViaFunction$4.onError (OperatorOnErrorResumeNextViaFunction.java:141)
rx.internal.operators.OperatorDoOnEach$1.onError (OperatorDoOnEach.java:71)
rx.internal.operators.OperatorSwitchIfEmpty$AlternateSubscriber.onError (OperatorSwitchIfEmpty.java:116)
rx.internal.operators.OperatorDoOnEach$1.onError (OperatorDoOnEach.java:71)
rx.internal.operators.OnSubscribeRedo$4$1.onError (OnSubscribeRedo.java:331)
rx.internal.operators.OperatorMerge$MergeSubscriber.reportError (OperatorMerge.java:243)
rx.internal.operators.OperatorMerge$MergeSubscriber.checkTerminate (OperatorMerge.java:779)
rx.internal.operators.OperatorMerge$MergeSubscriber.emitLoop (OperatorMerge.java:540)
rx.internal.operators.OperatorMerge$MergeSubscriber.emit (OperatorMerge.java:529)
rx.internal.operators.OperatorMerge$InnerSubscriber.onError (OperatorMerge.java:813)
rx.Observable$ThrowObservable$1.call (Observable.java:10200)
rx.Observable$ThrowObservable$1.call (Observable.java:10190)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorMerge$MergeSubscriber.onNext (OperatorMerge.java:235)
rx.internal.operators.OperatorMerge$MergeSubscriber.onNext (OperatorMerge.java:145)
rx.internal.operators.OperatorMap$1.onNext (OperatorMap.java:54)
rx.internal.operators.OperatorMap$1.onNext (OperatorMap.java:54)
rx.internal.operators.OnSubscribeRedo$3$1.onNext (OnSubscribeRedo.java:307)
rx.internal.operators.OnSubscribeRedo$3$1.onNext (OnSubscribeRedo.java:289)
rx.internal.operators.NotificationLite.accept (NotificationLite.java:150)
rx.subjects.SubjectSubscriptionManager$SubjectObserver.emitNext (SubjectSubscriptionManager.java:253)
rx.subjects.BehaviorSubject.onNext (BehaviorSubject.java:160)
rx.internal.operators.OnSubscribeRedo$2$1.onError (OnSubscribeRedo.java:242)
retrofit2.adapter.rxjava.OperatorMapResponseToBodyOrError$1.onNext (OperatorMapResponseToBodyOrError.java:43)
retrofit2.adapter.rxjava.OperatorMapResponseToBodyOrError$1.onNext (OperatorMapResponseToBodyOrError.java:38)
retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$RequestArbiter.request (RxJavaCallAdapterFactory.java:173)
rx.internal.producers.ProducerArbiter.setProducer (ProducerArbiter.java:126)
rx.internal.operators.OnSubscribeRedo$2$1.setProducer (OnSubscribeRedo.java:272)
rx.Subscriber.setProducer (Subscriber.java:205)
retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$CallOnSubscribe.call (RxJavaCallAdapterFactory.java:152)
retrofit2.adapter.rxjava.RxJavaCallAdapterFactory$CallOnSubscribe.call (RxJavaCallAdapterFactory.java:138)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OnSubscribeRedo$2.call (OnSubscribeRedo.java:278)
rx.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.enqueue (TrampolineScheduler.java:80)
rx.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.schedule (TrampolineScheduler.java:59)
rx.internal.operators.OnSubscribeRedo$5.request (OnSubscribeRedo.java:366)
rx.internal.producers.ProducerArbiter.setProducer (ProducerArbiter.java:126)
rx.internal.operators.OperatorSwitchIfEmpty$AlternateSubscriber.setProducer (OperatorSwitchIfEmpty.java:106)
rx.Subscriber.setProducer (Subscriber.java:205)
rx.internal.operators.OnSubscribeRedo.call (OnSubscribeRedo.java:358)
rx.internal.operators.OnSubscribeRedo.call (OnSubscribeRedo.java:55)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorSwitchIfEmpty$ParentSubscriber.subscribeToAlternate (OperatorSwitchIfEmpty.java:78)
rx.internal.operators.OperatorSwitchIfEmpty$ParentSubscriber.onCompleted (OperatorSwitchIfEmpty.java:71)
rx.internal.operators.OperatorOnErrorResumeNextViaFunction$4$1.onCompleted (OperatorOnErrorResumeNextViaFunction.java:125)
rx.Observable$EmptyHolder$1.call (Observable.java:1123)
rx.Observable$EmptyHolder$1.call (Observable.java:1120)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorOnErrorResumeNextViaFunction$4.onError (OperatorOnErrorResumeNextViaFunction.java:141)
rx.internal.operators.OperatorDoOnEach$1.onError (OperatorDoOnEach.java:71)
rx.internal.operators.OperatorDoOnEach$1.onError (OperatorDoOnEach.java:71)
com.testrx.app.retrofit.api.CacheHelper$1.call (CacheHelper.java:56)
com.testrx.app.retrofit.api.CacheHelper$1.call (CacheHelper.java:46)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable$2.call (Observable.java:162)
rx.Observable$2.call (Observable.java:154)
rx.Observable.unsafeSubscribe (Observable.java:8314)
rx.internal.operators.OperatorSubscribeOn$1.call (OperatorSubscribeOn.java:94)
rx.internal.schedulers.ScheduledAction.run (ScheduledAction.java:55)
java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:442)
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aka*_*okd 5

典型的流很少发生Stackoverflow。没有代码，我不确定是怎么回事。

在早期版本的RxJava中，某些运算符中存在重入问题，可能会导致StackOverflows，但现在一段时间以来我们还没有收到任何类似的错误报告。请确保您使用的是1.x版本中的最新RxJava（RxAndroid插件的依赖项可能需要覆盖，因为这方面的更新很少）。

您可以做几件事：

  • 压缩后续doOnNext并doOnError调用doOnEach
  • observeOn(Schedulers.computation())偶尔添加
  • 避免链接太多mergeWith，将源收集到一个List并使用merge(Iterable)
  • 升级到应该具有较小堆栈深度的RxJava 2.x（尚未验证）

编辑：

基于堆栈跟踪，我无法理解的是您有太多的空序列，并且switchIfEmpty在从一个空序列切换到下一个空序列时会不断加深堆栈。如您所知，subscribeOn有助于“重新启动”堆栈。我将研究RxJava本身内部可能的解决方案。

  • 这是[PR]（https://github.com/ReactiveX/RxJava/pull/5125），可能会对您有帮助。 (2认同)
  • 是。它有助于。例如：.subscribeOn（Schedulers.from（Executors.newFixedThreadPool（1，new ThreadFactory（）{ ） (2认同)

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