Merge pull request ReactiveX#238 from benjchristensen/pull-234-merge-ObserveOn

ScheduledObserver/ObserveOn - Manual Merge of Pull 234

Author: benjchristensen

rxjava-core/src/main/java/rx/operators/OperationObserveOn.java

@@ -15,17 +15,22 @@
  */
 package rx.operators;
 
-import static org.mockito.Matchers.*;
+import static org.junit.Assert.*;
 import static org.mockito.Mockito.*;
 
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
 import org.junit.Test;
+import org.mockito.InOrder;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
 
 import rx.Observable;
 import rx.Observer;
 import rx.Scheduler;
 import rx.Subscription;
 import rx.concurrency.Schedulers;
-import rx.util.functions.Action0;
 import rx.util.functions.Func1;
 
 public class OperationObserveOn {
@@ -60,15 +65,46 @@ public void testObserveOn() {
             Observer<Integer> observer = mock(Observer.class);
             Observable.create(observeOn(Observable.toObservable(1, 2, 3), scheduler)).subscribe(observer);
 
-            verify(scheduler, times(4)).schedule(any(Action0.class));
-            verifyNoMoreInteractions(scheduler);
-
             verify(observer, times(1)).onNext(1);
             verify(observer, times(1)).onNext(2);
             verify(observer, times(1)).onNext(3);
             verify(observer, times(1)).onCompleted();
         }
 
+        @Test
+        @SuppressWarnings("unchecked")
+        public void testOrdering() throws InterruptedException {
+            Observable<String> obs = Observable.from("one", null, "two", "three", "four");
+
+            Observer<String> observer = mock(Observer.class);
+
+            InOrder inOrder = inOrder(observer);
+
+            final CountDownLatch completedLatch = new CountDownLatch(1);
+            doAnswer(new Answer<Void>() {
+
+                @Override
+                public Void answer(InvocationOnMock invocation) throws Throwable {
+                    completedLatch.countDown();
+                    return null;
+                }
+            }).when(observer).onCompleted();
+
+            obs.observeOn(Schedulers.threadPoolForComputation()).subscribe(observer);
+
+            if (!completedLatch.await(1000, TimeUnit.MILLISECONDS)) {
+                fail("timed out waiting");
+            }
+
+            inOrder.verify(observer, times(1)).onNext("one");
+            inOrder.verify(observer, times(1)).onNext(null);
+            inOrder.verify(observer, times(1)).onNext("two");
+            inOrder.verify(observer, times(1)).onNext("three");
+            inOrder.verify(observer, times(1)).onNext("four");
+            inOrder.verify(observer, times(1)).onCompleted();
+            inOrder.verifyNoMoreInteractions();
+        }
+
     }
 
 }

rxjava-core/src/main/java/rx/operators/ScheduledObserver.java

@@ -1,12 +1,12 @@
 /**
  * Copyright 2013 Netflix, Inc.
- * 
+ *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  * http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -15,45 +15,77 @@
  */
 package rx.operators;
 
+import rx.Notification;
 import rx.Observer;
 import rx.Scheduler;
 import rx.util.functions.Action0;
 
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+
 /* package */class ScheduledObserver<T> implements Observer<T> {
     private final Observer<T> underlying;
     private final Scheduler scheduler;
 
+    private final ConcurrentLinkedQueue<Notification<T>> queue = new ConcurrentLinkedQueue<Notification<T>>();
+    private final AtomicInteger counter = new AtomicInteger(0);
+
     public ScheduledObserver(Observer<T> underlying, Scheduler scheduler) {
         this.underlying = underlying;
         this.scheduler = scheduler;
     }
 
     @Override
     public void onCompleted() {
-        scheduler.schedule(new Action0() {
-            @Override
-            public void call() {
-                underlying.onCompleted();
-            }
-        });
+        enqueue(new Notification<T>());
     }
 
     @Override
     public void onError(final Exception e) {
-        scheduler.schedule(new Action0() {
-            @Override
-            public void call() {
-                underlying.onError(e);
-            }
-        });
+        enqueue(new Notification<T>(e));
     }
 
     @Override
     public void onNext(final T args) {
+        enqueue(new Notification<T>(args));
+    }
+
+    private void enqueue(Notification<T> notification) {
+        int count = counter.getAndIncrement();
+
+        queue.offer(notification);
+
+        if (count == 0) {
+            processQueue();
+        }
+    }
+
+    private void processQueue() {
         scheduler.schedule(new Action0() {
             @Override
             public void call() {
-                underlying.onNext(args);
+                Notification<T> not = queue.poll();
+
+                switch (not.getKind()) {
+                    case OnNext:
+                        underlying.onNext(not.getValue());
+                        break;
+                    case OnError:
+                        underlying.onError(not.getException());
+                        break;
+                    case OnCompleted:
+                        underlying.onCompleted();
+                        break;
+                    default:
+                        throw new IllegalStateException("Unknown kind of notification " + not);
+
+                }
+
+                int count = counter.decrementAndGet();
+                if (count > 0) {
+                    scheduler.schedule(this);
+                }
+
             }
         });
     }

rxjava-core/src/test/java/rx/concurrency/TestSchedulers.java

@@ -23,6 +23,7 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 
 import org.junit.Test;
 
@@ -395,4 +396,137 @@ public Subscription call(Scheduler scheduler, String state) {
         }
     }
 
+    @Test
+    public void testConcurrentOnNextFailsValidation() throws InterruptedException {
+
+        final int count = 10;
+        final CountDownLatch latch = new CountDownLatch(count);
+        Observable<String> o = Observable.create(new Func1<Observer<String>, Subscription>() {
+
+            @Override
+            public Subscription call(final Observer<String> observer) {
+                for (int i = 0; i < count; i++) {
+                    final int v = i;
+                    new Thread(new Runnable() {
+
+                        @Override
+                        public void run() {
+                            observer.onNext("v: " + v);
+
+                            latch.countDown();
+                        }
+                    }).start();
+                }
+                return Subscriptions.empty();
+            }
+        });
+
+        ConcurrentObserverValidator<String> observer = new ConcurrentObserverValidator<String>();
+        // this should call onNext concurrently
+        o.subscribe(observer);
+
+        if (!observer.completed.await(3000, TimeUnit.MILLISECONDS)) {
+            fail("timed out");
+        }
+
+        if (observer.error.get() == null) {
+            fail("We expected error messages due to concurrency");
+        }
+    }
+
+    @Test
+    public void testObserveOn() throws InterruptedException {
+
+        Observable<String> o = Observable.from("one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten");
+
+        ConcurrentObserverValidator<String> observer = new ConcurrentObserverValidator<String>();
+
+        o.observeOn(Schedulers.threadPoolForComputation()).subscribe(observer);
+
+        if (!observer.completed.await(3000, TimeUnit.MILLISECONDS)) {
+            fail("timed out");
+        }
+
+        if (observer.error.get() != null) {
+            observer.error.get().printStackTrace();
+            fail("Error: " + observer.error.get().getMessage());
+        }
+    }
+
+    @Test
+    public void testSubscribeOnNestedConcurrency() throws InterruptedException {
+
+        Observable<String> o = Observable.from("one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten")
+                .mapMany(new Func1<String, Observable<String>>() {
+
+                    @Override
+                    public Observable<String> call(final String v) {
+                        return Observable.create(new Func1<Observer<String>, Subscription>() {
+
+                            @Override
+                            public Subscription call(final Observer<String> observer) {
+                                observer.onNext("value_after_map-" + v);
+                                observer.onCompleted();
+                                return Subscriptions.empty();
+                            }
+                        }).subscribeOn(Schedulers.newThread()); // subscribe on a new thread
+                    }
+                });
+
+        ConcurrentObserverValidator<String> observer = new ConcurrentObserverValidator<String>();
+
+        o.subscribe(observer);
+
+        if (!observer.completed.await(3000, TimeUnit.MILLISECONDS)) {
+            fail("timed out");
+        }
+
+        if (observer.error.get() != null) {
+            observer.error.get().printStackTrace();
+            fail("Error: " + observer.error.get().getMessage());
+        }
+    }
+
+    /**
+     * Used to determine if onNext is being invoked concurrently.
+     * 
+     * @param <T>
+     */
+    private static class ConcurrentObserverValidator<T> implements Observer<T> {
+
+        final AtomicInteger concurrentCounter = new AtomicInteger();
+        final AtomicReference<Exception> error = new AtomicReference<Exception>();
+        final CountDownLatch completed = new CountDownLatch(1);
+
+        @Override
+        public void onCompleted() {
+            completed.countDown();
+        }
+
+        @Override
+        public void onError(Exception e) {
+            completed.countDown();
+            error.set(e);
+        }
+
+        @Override
+        public void onNext(T args) {
+            int count = concurrentCounter.incrementAndGet();
+            System.out.println("ConcurrentObserverValidator.onNext: " + args);
+            if (count > 1) {
+                onError(new RuntimeException("we should not have concurrent execution of onNext"));
+            }
+            try {
+                try {
+                    // take some time so other onNext calls could pile up (I haven't yet thought of a way to do this without sleeping)
+                    Thread.sleep(50);
+                } catch (InterruptedException e) {
+                    // ignore
+                }
+            } finally {
+                concurrentCounter.decrementAndGet();
+            }
+        }
+
+    }
 }