ObserveOn Operator with Backpressure

rxjava-core/src/main/java/rx/Observable.java

@@ -49,7 +49,6 @@
 import rx.operators.OperationDematerialize;
 import rx.operators.OperationDistinct;
 import rx.operators.OperationDistinctUntilChanged;
-import rx.operators.OperatorDoOnEach;
 import rx.operators.OperationElementAt;
 import rx.operators.OperationFilter;
 import rx.operators.OperationFinally;
@@ -63,13 +62,11 @@
 import rx.operators.OperationMergeDelayError;
 import rx.operators.OperationMinMax;
 import rx.operators.OperationMulticast;
-import rx.operators.OperationObserveOn;
 import rx.operators.OperationOnErrorResumeNextViaFunction;
 import rx.operators.OperationOnErrorResumeNextViaObservable;
 import rx.operators.OperationOnErrorReturn;
 import rx.operators.OperationOnExceptionResumeNextViaObservable;
 import rx.operators.OperationParallelMerge;
-import rx.operators.OperatorRepeat;
 import rx.operators.OperationReplay;
 import rx.operators.OperationRetry;
 import rx.operators.OperationSample;
@@ -96,18 +93,21 @@
 import rx.operators.OperationToObservableFuture;
 import rx.operators.OperationUsing;
 import rx.operators.OperationWindow;
-import rx.operators.OperatorSubscribeOn;
-import rx.operators.OperatorZip;
 import rx.operators.OperatorCast;
+import rx.operators.OperatorDoOnEach;
 import rx.operators.OperatorFromIterable;
 import rx.operators.OperatorGroupBy;
 import rx.operators.OperatorMap;
 import rx.operators.OperatorMerge;
+import rx.operators.OperatorObserveOn;
 import rx.operators.OperatorParallel;
+import rx.operators.OperatorRepeat;
+import rx.operators.OperatorSubscribeOn;
 import rx.operators.OperatorTake;
 import rx.operators.OperatorTimestamp;
 import rx.operators.OperatorToObservableList;
 import rx.operators.OperatorToObservableSortedList;
+import rx.operators.OperatorZip;
 import rx.operators.OperatorZipIterable;
 import rx.plugins.RxJavaObservableExecutionHook;
 import rx.plugins.RxJavaPlugins;
@@ -5139,8 +5139,7 @@ public final <R> ConnectableObservable<R> multicast(Subject<? super T, ? extends
     }
 
     /**
-     * Modify the source Observable so that it asynchronously notifies {@link Observer}s on the
-     * specified {@link Scheduler}.
+     * Move notifications to the specified {@link Scheduler} one `onNext` at a time.
      * <p>
      * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/observeOn.png">
      * 
@@ -5151,9 +5150,26 @@ public final <R> ConnectableObservable<R> multicast(Subject<? super T, ? extends
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Observable-Utility-Operators#wiki-observeon">RxJava Wiki: observeOn()</a>
      */
     public final Observable<T> observeOn(Scheduler scheduler) {
-        return create(OperationObserveOn.observeOn(this, scheduler));
+        return lift(new OperatorObserveOn<T>(scheduler));
     }
 
+    /**
+     * Move notifications to the specified {@link Scheduler} asynchronously with a buffer of the given size.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/observeOn.png">
+     * 
+     * @param scheduler
+     *            the {@link Scheduler} to notify {@link Observer}s on
+     * @param bufferSize
+     *            that will be rounded up to the next power of 2
+     * @return the source Observable modified so that its {@link Observer}s are notified on the
+     *         specified {@link Scheduler}
+     * @see <a href="https://github.com/Netflix/RxJava/wiki/Observable-Utility-Operators#wiki-observeon">RxJava Wiki: observeOn()</a>
+     */
+    public final Observable<T> observeOn(Scheduler scheduler, int bufferSize) {
+        return lift(new OperatorObserveOn<T>(scheduler, bufferSize));
+    }
+
     /**
      * Filters the items emitted by an Observable, only emitting those of the specified type.
      * <p>
@@ -5296,7 +5312,9 @@ public final Observable<T> onExceptionResumeNext(final Observable<? extends T> r
      * @see <a href="https://github.com/Netflix/RxJava/wiki/Observable-Utility-Operators#wiki-parallel">RxJava Wiki: parallel()</a>
      */
     public final <R> Observable<R> parallel(Func1<Observable<T>, Observable<R>> f) {
-        return lift(new OperatorParallel<T, R>(f, Schedulers.computation()));
+        // TODO move this back to Schedulers.computation() again once that is properly using eventloops
+        // see https://github.com/Netflix/RxJava/issues/713 for why this was changed
+        return lift(new OperatorParallel<T, R>(f, Schedulers.newThread()));
     }
 
     /**