1.3.0

Maven

Summary

Version 1.3.0 is the next minor release of the 1.x series of RxJava containing many formerly experimental API components promoted to standard. Most notably the Completable base reactive type is now standard as well.

Note that the experimental rx.Observable.fromEmitter() has been removed in favor for the now also standard Observable.create(Action1<Emitter<T>> emitter, Emitter.BackpressureMode backpressure)

The planned lifecycle of the 1.x line is as follows:

Date	Remark
June 1, 2017	Feature freeze, only bugfixes from this on.
September 1, 2017	Release 1.4.0 finalizing the remaining API components.
March 31, 2018	End of development.

The following components have been promoted to standard:

Classes, interfaces

• classes: AssemblyStackTraceException, RxJavaCompletableExecutionHook, RxJavaHooks, UnicastSubject, BlockingSingle, Completable, AssertableSubscriber, AsyncCompletableSubscriber, SafeCompletableSubscriber
• interfaces: Cancellable, Emitter, SingleEmitter, CompletableEmitter, CompletableSubscriber, BackpressureOverflow.Strategy

Operators

• Observable: create, unsafeCreate, to, zip(Observable[], FuncN), flatMapCompletable, flatMapSingle, groupby(Func1, Func1, Func1<Action1<K>, Map<K, Object>>), onTerminateDetach, rebatchRequests, subscribeOn(Scheduler, boolean), sorted, withLatestFrom, test, toCompletable, concatDelayError, mergeDelayError, switchOnNextDelayError, using(Func0, Func1, Action1, boolean), concatMapDelayError, delaySubscription(Observable), distinctUntilChanged(Func2), concatEager, concatMapEager, onBackpressureBuffer(long, Action0, BackpressureOverflow.Strategy), switchMapDelayError, toSortedList(int), toSortedList(Func2, int)
• Completable: fromEmitter, test
• Single: fromEmitter, merge, mergeDelayError, cache, to, doOnEach, doOnSuccess, test, onErrorResumeNext, toCompletable, doOnError, doOnSubscribe, delay, defer, doOnUnsubscribe, doAfterTerminate, flatMapCompletable, lift, toBlocking, using, delaySubscription(Observable)
• TestSubscriber: getCompletions, awaitValueCount, assertValuesAndClear
• SyncOnSubscriber: createSingleState, createStateful, createStateless

Other

• Schedulers.reset
• CompositeException(Throwable...) constructor
• Exceptions.throwOrReport (4 overloads)
• BlockingObservable.subscribe (6 overloads)
• RxJavaSchedulersHook: createComputationScheduler, createIoScheduler, createNewThreadScheduler
• internal: AssertableSubscriberObservable, FlatMapCompletable, FlatMapSingle, SchedulerWhen, BackpressureDrainManager, BlockingUtils.
• RxJavaPlugins: reset, getCompletableExecutionHook, registerCompletableExecutionHook
• RxJavaErrorHandler: handleOnNextValueRendering, render

In addition, the class AsyncOnsubscribe with its 7 factory methods and Observable.create(AsyncOnSubscribe<S, T>) have been promoted to beta.

Acknowledgements

Thanks to all who contributed to the 1.x line in the past 6 months (in order they appear on the commit page):

@mtiidla, @dhendry, @mostroverkhov, @yshrsmz, @BraisGabin, @cesar1000, @Jawnnypoo, @chanx2, @abersnaze, @davidmoten, @ortex, @marwinxxii, @ekchang, @pyricau, @JakeWharton, @VictorAlbertos

2.1.0

Maven

Summary

Version 2.1.0 is the next minor release of the 2.x era and contains the standardization of many experimental API additions from the past half a year since version 2.0.0. Therefore, the following components are now considered stable and will be supported throughout the rest of the life of RxJava 2.x.

Classes, Enums, Annotations

• Annotation: CheckReturnValue
• Subjects: CompletableSubject, MaybeSubject, SingleSubject
• Enum: TestWaitStrategy

Operators

• Flowable: doAfterNext, doFinally, sample (emitLast)
• Observable: doAfterNext, doFinally, sample (emitLast)
• Single: doAfterSuccess, doAfterTerminate, doFinally
• Maybe: doAfterSuccess, doFinally, flatMapSingleElement
• Completable: cache, doFinally, hide
• Test{Observer, Subscriber}: assertNever, assertTimeout, assertNoTimeout, awaitCount, clearTimeout, isTimeout, withTag
• RxJavaPlugins: createComputationScheduler, createIoScheduler, createNewThreadScheduler, createSingleScheduler, getOnBeforeBlocking, setOnBeforeBlocking, isFailOnBlockingScheduler, setFailOnBlockingScheduler.
• Other: Scheduler.when, TestSubscriber.requestMore

(For the complete list and details on the promotions, see issue 5243.)

Release 2.1.0 is functionally identical to 2.0.9 except the removal of now unnecessary Flowable.strict() operator. To clarify, just like with previous minor version increments with RxJava, there won't be any further development or updates on the version 2.0.x (patch) level.

Beta promotions

Some of the enhancements of RxJava 2.0.x were added recently which often represent complex additions to RxJava itself (such as the whole ParallelFlowable). We are confident their functionality adds value to the library but not enough time elapsed since their introduction for the community to try it out and provide feedback on them (i.e., naming, encompassed functionality, etc.). To indicate we are willing to support them and eventually standardize them in the next minor release, the following components have been promoted to the status of Beta:

• Classes: OnErrorNotImplementedException, ProtocolViolationException, UndeliverableException,
  ParallelFlowable
• Interface: FlowableSubscriber
• Methods
  • Flowable: parallel, subscribe(FlowableSubscriber)
  • RxJavaPlugins: getOnParallelAssembly, onAssembly(ParallelFlowable), setOnParallelAssembly

Non-functional changes between 2.0.9 and 2.1

• Pull 5306: Change ObservableSource.defer to Observable.defer in Observable.scan() documentation.
• Pull 5309: Fix Javadoc of Flowable.toObservable referring to Publisher instead of Observable.

Project statistics

• Unique contributors: 41
• Issues closed: 315
• Bugs reported: 43
  • by community: 40 (93%)
• Commits: 193
• PRs: 225
  • PRs accepted: 198 (88%)
  • Community PRs: 76 (38.4% of all accepted)
• Bugs fixed: 58
  • by community: 8 (13.9%)
• Documentation enhancements: 46
  • by community: 22 (52.2%)
• Cleanup: 40
  • by community: 22 (55%)
• Lines
  • added: 44,931
  • removed: 7,405

Acknowledgements

The project would like to thank the following contributors for their work on various code and documentation improvements (in the order they appear on the commit page):

@vanniktech, @veyndan, @Mauin, @smartbeng, @ImangazalievM, @bloderxd, @mibac138, @ggikko, @mostroverkhov, @sadegh, @nmorioka, @SleimanJneidi, @davidmoten, @hkurokawa, @jbarr21, @alexandre-dubois, @VeskoI, @Stephan202, @PaulWoitaschek, @soulkeykim, @stevepeak, @jschneider, @JakeWharton, @tonycosentini, @hzsweers, @passsy, @sergiomarquesmoura, @ikesyo, @benjchristensen, @zsavely, @DDesideria, @gaemi, @Jawnnypoo, @artem-zinnatullin, @mkobit, @abersnaze, @tbcs, @gengjiawen, @qwert2603, @DmitriyZaitsev

(40 contributors)

The project would also thank its tireless reviewers, @JakeWharton and @vanniktech for all their efforts on verifying and providing feedback on the many PRs from the project lead himself. 👍

1.2.10

Maven

Bugfixes

• Pull 5225: Fix Completable.onErrorResumeNext unsubscribe not propagated.

Other

• Pull 5250: Defer creation of the TimeoutException when using the Single.timeout() operator.
• Pull 5258: Use IntelliJ IDE friendly assertion failure message.

2.0.9

Maven

API enhancements

• Pull 5302: Add Single.unsubscribeOn().

Bugfixes

• Pull 5247: Fix Flowable.toList() onNext/cancel race.
• Pull 5256: Fix flatMapIterable appearing to be empty when fused.
• Pull 5277: Fix Single.subscribe(BiConsumer) to be consistent with isDisposed.
• Pull 5281: Fix BehaviorProcessor & BehaviorSubject terminate-subscribe race.
• Pull 5287: Fix Flowable.flatMapMaybe/Flowable.flatMapSingle maxConcurrency not requesting more.

Documentation

• Pull 5271: enable link to external JDK, fix Schedulers style.
• Pull 5286: Cleanup for text and Javadoc 04/15.
• Commit 7c95808: Fix DisposableX copy-paste error in Javadoc.
• Pull 5296: Improve doOnDispose JavaDoc.
• Pull 5297: Fix JavaDoc image for Single.flatMapObservable().
• Pull 5304: Correct documented return type of Single.flatMapObservable()'s function argument.

Other

• Pull 5255: Add NullPointerException comments and ObjectHelper test code.
• Pull 5251: More nullability annotations.
• Pull 5257: Remove @NonNull annotations from BiConsumer.
• Pull 5268: Remove commented out code from IoScheduler.
• Pull 5301: More detailed no-multi-subscribe error message with the standard consumer types (such as DisposableObserver).

2.0.8

Maven

API enhancements

• Pull 5161: Add Observable.switchMapSingle()
• Pull 5184: Add offer() method to PublishProcessor & BehaviorProcessor.
• Pull 5197: Add ParallelTransformer interface.
• Pull 5217: UnicastSubject fail-fast support.
• Pull 5202: Add resilient versions of parallel map(), filter() and doOnNext().
• Pull 5226: UnicastProcessor fail-fast support.

Bugfixes

• Pull 5163: Single.subscribe() to report isDisposed() true on success/error.
• Pull 5170: Fix LambdaObserver not cancelling the upstream.
• Pull 5182: Fix replay().refCount() leaking items between connections.
• Pull 5188: Fix flatMap emitting the terminal exception indicator on cancel.
• Pull 5207: Prevent tasks to self interrupt on the standard schedulers.
• Pull 5213: Fix window() with time+size emission problems.
• Pull 5240: fix CallbackCompletableObserver calling onError.

Documentation

• Pull 5189: Declare concatMapEager requires positive prefetch amount.
• Pull 5191: Correct java doc for refCount() return type.
• Pull 5208: Fix images of firstElement, flattenAsX, flatMapIterable, UnicastSubject and UnicastProcessor.
• Pull 5210: Better documentation on the abstract consumer classes (such as DisposableSubscriber).
• Pull 5223: Improve the documentation of Schedulers utility class.
• Pull 5230: Fix wrong comments in Functions “Function3” -> “BiFunction, Function3”

Other

• Remove anonymous inner classes.
  • Pull 5174
  • Pull 5177
• Pull 5183: Test to disallow anonymous inner classes.
• Pull 5187: Reflection-based parameter validator & fixes.
• Pull 5196: Add a few more @Nullable & @NonNull annotations to public interfaces.

1.2.9

Maven

API enhancements

• Pull 5146: Add Single.unsubscribeOn.
• Pull 5195: Enhance UnicastSubject with optional delay error behavior.

Bugfixes

• Pull 5141: Fix timed replay() not terminating when all items timeout.
• Pull 5181: replay().refCount() avoid leaking items between connections.

1.2.8

Accidental release of the wrong branch. Please ignore this.

2.0.7

Maven

Reactive-Streams compliance

Related issue 5110, related pull 5112.

RxJava 2's Flowable was designed with Reactive-Streams compliance in mind but didn't follow all rules to the letter. A temporary workaround was the introduction of the strict() operator to enable full compliance. Unfortunately, according to the clarified stance from the specification leads, implementors of Publisher must honor the specification (despite its shortcomings) without excuses or workarounds.

Honoring the specification adds a per-item cost of two atomic increments, manifesting in between the Flowable and an arbitrary Reactive-Streams compliant org.reactivestreams.Subscriber. See Pull 5115 for the benchmark comparison.

Starting from 2.0.7, the Flowable.subscribe(org.reactivestreams.Subscriber) now follows the spec by wrapping via the StrictSubscriber of the strict() operator unless the consuming instance implements a new interface specific to RxJava 2: FlowableSubscriber.

The FlowableSubscriber extends org.reactivestreams.Subscriber but doesn't add any new methods and only overrides four of the textual rules of the specification to enable a relaxed operation within RxJava 2. All internal operators have been converted to use this new interface and thus don't have suffer the per-item overhead required by the specification, including the standard DisposableSubscriber, TestSubscriber and ResourceSubscriber. The lambda-based subscribe() operators were also retrofitted.

If you were implementing a Subscriber (directly or anonymously), you may want to change the interface to FlowableSubscriber. In order to avoid some of the runtime checks when subscribing to Flowable the new subscribe(FlowableSubscriber) has been introduced.

Note that the other reactive base types, Observable, Single, Maybe and Completable are not affected as these were never intended to implement the Reactive-Streams specification (they were only inspired by the spec and are RxJava 2 only to begin with).

API enhancements

• Pull 5117: Add ParallelFlowable.sequentialDelayError.
• Pull 5137: Add TestSubscriber.withTag.
• Pull 5140: Fix timed replay-like components replaying outdated items.
• Pull 5155: Add TestSubscriber.awaitCount, assertTimeout & assertNoTimeout, improve assertion error message

API deprecations

• Pull 5112: Flowable.strict() deprecated and will be removed in 2.1.0 - the default Flowable behavior is now strict.

Bugfixes

• Pull 5101: Fix Maybe.concat() subscribe-after-cancel, verify others.
• Pull 5103: Fix doOnSubscribe signalling UndeliverableException instead of onError.
• Pull 5106: Fix window(time, size) not completing windows on timeout.
• Pull 5114: Fix Observable.combineLatest to dispose eagerly.
• Pull 5121: Fix Observable.zip to dispose eagerly.
• Pull 5133: Fix flatMap not cancelling the upstream eagerly.
• Pull 5136: Fix repeatWhen and retryWhen signatures.

Other

• Pull 5102: Added missing @NonNull attribute to Function7.
• Pull 5112: Flowable as a Publisher to be fully RS compliant.
• Pull 5127: Update javadoc of flatMap() overloads.
• Pull 5153: Java 9 compatibility fixes
• Pull 5156: Add @NonNull to the methods of Emitter

1.2.7

Maven

Deprecation of create(OnSubscribe)

The method started out in RxJava 0.x as a simple and direct way for implementing custom operators because 0.x had a much simpler protocol requirements. Over the years, as the Observable protocol evolved and create became a powerful and complicated extension point of RxJava that required users to implement the Observable protocol, including cancellation and backpressure manually.

Unfortunately, guides, blogs, StackOverflow answers and mere typical user behavior still leads to this create method and lots of confusion, unstoppable sequences and MissingBackpressureException. We tried remedying the situation by introducing fromEmitter with limited discoverability success.

Therefore, as of 1.2.7 the create() method is now deprecated (but won't be removed due to binary compatibility requirements). In addition fromEmitter has been deprecate-renamed to create(Action1, BackpressureMode) and the experimental-marked fromEmitter itself will be removed in 1.3.0.

Since the functionality of create() was useful for writing (custom) operators inside and outside of RxJava, the new unsafeCreate(OnSubscribe) method was introduced as the replacement.

The new create() and unsafeCreate() methods will be fast-tracked to become standard in 1.3.0.

API enhancements

• Pull 5086: Deprecate create(), add alternatives
• Pull 5092: Add Single.merge(Observable<Single<T>>), Observable.flatMapSingle() & Observable.flatMapCompletable.
• Pull 5091: Add subscribeOn(Scheduler, boolean) avoid same-pool deadlock.

API deprecations

• Pull 5086:
  • Deprecate Observable.create(OnSubscribe),
  • Deprecate fromEmitter in favor of Observable.create(Action1, BackpressureMode).

Bugfixes

• Pull 5091: create(Action1, BackpressureMode)+subscribeOn avoid same-pool deadlock.
• Pull 5123: throttleFirst detecting clock-drift backwards to open the gate

Other

• Pull 5125: reduce stack depth with switchIfEmpty

2.0.6

Maven

Undeliverable exceptions

One of the design goals of 2.x was that no errors can be lost. Sometimes, the sequence ends or gets cancelled before the source could emit an onError which has nowhere to go at that point and gets routed to the RxJavaPlugins.onError.

Unlike 1.x, 2.x by default calls Thread.currentThread().getUncaughtExceptionHandler().uncaughtException() which crashes an Android app. Many developers have noticed the increased number of app crashes when porting to 2.x due to this behavior change. Note that this doesn't mean RxJava 2 is unstable but it means you likely had these exceptions all along but they were silently dropped.

Unfortunately, RxJava can't tell which of these out-of-lifecycle, undeliverable exceptions should or shouldn't crash your app. Identifying the source and reason for these exceptions can be tiresome, especially if they originate from a source and get routed to RxJavaPlugins.onError somewhere lower the chain.

Therefore, 2.0.6 introduces specific exception wrappers to help distinguish and track down what was happening the time of the error:

• OnErrorNotImplementedException: reintroduced to detect when the user forgot to add error handling to subscribe().
• ProtocolViolationException: indicates a bug in an operator
• UndeliverableException: wraps the original exception that can't be delivered due to lifecycle restrictions on a Subscriber/Observer. It is automatically applied by RxJavaPlugins.onError with intact stacktrace that may help find which exact operator rerouted the original error.

If an undeliverable exception is an instance/descendant of NullPointerException, IllegalStateException (UndeliverableException and ProtocolViolationException extend this), IllegalArgumentException, CompositeException, MissingBackpressureException or OnErrorNotImplementedException, the UndeliverableException wrapping doesn't happen.

In addition, some 3rd party libraries/code throw when they get interrupted by a cancel/dispose call which leads to an undeliverable exception most of the time. Internal changes in 2.0.6 now consistently cancel or dispose a Subscription/Disposable before cancelling/disposing a task or worker (which causes the interrupt on the target thread).

// in some library
try {
   doSomethingBlockingly()
} catch (InterruptedException ex) {
   // check if the interrupt is due to cancellation
   // if so, no need to signal the InterruptedException
   if (!disposable.isDisposed()) {
      observer.onError(ex);
   }
}

If the library/code already did this, the undeliverable InterruptedExceptions should stop now. If this pattern was not employed before, we encourage updating the code/library in question.

API enhancements

• Pull 5036: Reintroduce OnErrorNotImplementedException for 0-1 arg subscribe.
• Pull 5043: Add parallel hooks to RxJavaPlugins, add missing params validation
• Pull 5080: Wrap undeliverable errors.
• Pull 5093: Add Single.doAfterTerminate

Bugfixes

• Pull 5064: Fix replay() cancel/dispose NullPointerException.
• Pull 5090: fix scan(seed, f) to emit accumulated values without delay.

Other

• Pull 5027: Dedicated Single.zip implementation, no dispose on all-success.
• Pull 5023: Annotate function interfaces.
• Pull 5047: Document and test amb subscription ordering.
• Pull 5051: More @Nonnull annotations.
• Pull 5054: Add @Nullable annotation to SimpleQueue.
• Pull 5055: More null checks.
• Pull 5049: Use bounded wildcards for errorHandler.
• Pull 5075: Cancel upstream first, dispose worker last.
• Pull 5058: More generics in RxJavaPlugins.
• Pull 5076: Removed documentation leftover of Completable.subscribe.
• Pull 5087: Correct marble diagram dimensions.