1.x: PublishSubject fail-fast when backpressured (#4225)

* 1.x: PublishSubject fail-fast when backpressured

* Inline get(), use smaller error array at first.

Author: akarnokd

src/main/java/rx/subjects/PublishSubject.java

@@ -16,13 +16,13 @@
 package rx.subjects;
 
 import java.util.*;
+import java.util.concurrent.atomic.*;
 
+import rx.*;
 import rx.Observer;
 import rx.annotations.Beta;
-import rx.exceptions.Exceptions;
-import rx.functions.Action1;
-import rx.internal.operators.NotificationLite;
-import rx.subjects.SubjectSubscriptionManager.SubjectObserver;
+import rx.exceptions.*;
+import rx.internal.operators.BackpressureUtils;
 
 /**
  * Subject that, once an {@link Observer} has subscribed, emits all subsequently observed items to the
@@ -50,8 +50,8 @@
  *          the type of items observed and emitted by the Subject
  */
 public final class PublishSubject<T> extends Subject<T, T> {
-    final SubjectSubscriptionManager<T> state;
-    private final NotificationLite<T> nl = NotificationLite.instance();
+
+    final PublishSubjectState<T> state;
 
     /**
      * Creates and returns a new {@code PublishSubject}.
@@ -60,63 +60,33 @@ public final class PublishSubject<T> extends Subject<T, T> {
      * @return the new {@code PublishSubject}
      */
     public static <T> PublishSubject<T> create() {
-        final SubjectSubscriptionManager<T> state = new SubjectSubscriptionManager<T>();
-        state.onTerminated = new Action1<SubjectObserver<T>>() {
-
-            @Override
-            public void call(SubjectObserver<T> o) {
-                o.emitFirst(state.getLatest(), state.nl);
-            }
-            
-        };
-        return new PublishSubject<T>(state, state);
+        return new PublishSubject<T>(new PublishSubjectState<T>());
     }
-
-    protected PublishSubject(OnSubscribe<T> onSubscribe, SubjectSubscriptionManager<T> state) {
-        super(onSubscribe);
+    
+    protected PublishSubject(PublishSubjectState<T> state) {
+        super(state);
         this.state = state;
     }
 
     @Override
-    public void onCompleted() {
-        if (state.active) {
-            Object n = nl.completed();
-            for (SubjectObserver<T> bo : state.terminate(n)) {
-                bo.emitNext(n, state.nl);
-            }
-        }
-
+    public void onNext(T v) {
+        state.onNext(v);
     }
 
     @Override
-    public void onError(final Throwable e) {
-        if (state.active) {
-            Object n = nl.error(e);
-            List<Throwable> errors = null;
-            for (SubjectObserver<T> bo : state.terminate(n)) {
-                try {
-                    bo.emitNext(n, state.nl);
-                } catch (Throwable e2) {
-                    if (errors == null) {
-                        errors = new ArrayList<Throwable>();
-                    }
-                    errors.add(e2);
-                }
-            }
-            Exceptions.throwIfAny(errors);
-        }
+    public void onError(Throwable e) {
+        state.onError(e);
     }
 
     @Override
-    public void onNext(T v) {
-        for (SubjectObserver<T> bo : state.observers()) {
-            bo.onNext(v);
-        }
+    public void onCompleted() {
+        state.onCompleted();
     }
 
+
     @Override
     public boolean hasObservers() {
-        return state.observers().length > 0;
+        return state.get().length != 0;
     }
 
     /**
@@ -125,17 +95,15 @@ public boolean hasObservers() {
      */
     @Beta
     public boolean hasThrowable() {
-        Object o = state.getLatest();
-        return nl.isError(o);
+        return state.get() == PublishSubjectState.TERMINATED && state.error != null;
     }
     /**
      * Check if the Subject has terminated normally.
      * @return true if the subject completed normally via {@code onCompleted}
      */
     @Beta
     public boolean hasCompleted() {
-        Object o = state.getLatest();
-        return o != null && !nl.isError(o);
+        return state.get() == PublishSubjectState.TERMINATED && state.error == null;
     }
     /**
      * Returns the Throwable that terminated the Subject.
@@ -144,10 +112,216 @@ public boolean hasCompleted() {
      */
     @Beta
     public Throwable getThrowable() {
-        Object o = state.getLatest();
-        if (nl.isError(o)) {
-            return nl.getError(o);
+        if (state.get() == PublishSubjectState.TERMINATED) {
+            return state.error;
         }
         return null;
     }
+    
+    static final class PublishSubjectState<T> 
+    extends AtomicReference<PublishSubjectProducer<T>[]>
+    implements OnSubscribe<T>, Observer<T> {
+
+        /** */
+        private static final long serialVersionUID = -7568940796666027140L;
+        
+        @SuppressWarnings("rawtypes")
+        static final PublishSubjectProducer[] EMPTY = new PublishSubjectProducer[0]; 
+        @SuppressWarnings("rawtypes")
+        static final PublishSubjectProducer[] TERMINATED = new PublishSubjectProducer[0]; 
+        
+        Throwable error;
+        
+        @SuppressWarnings("unchecked")
+        public PublishSubjectState() {
+            lazySet(EMPTY);
+        }
+        
+        @Override
+        public void call(Subscriber<? super T> t) {
+            PublishSubjectProducer<T> pp = new PublishSubjectProducer<T>(this, t);
+            t.add(pp);
+            t.setProducer(pp);
+            
+            if (add(pp)) {
+                if (pp.isUnsubscribed()) {
+                    remove(pp);
+                }
+            } else {
+                Throwable ex = error;
+                if (ex != null) {
+                    t.onError(ex);
+                } else {
+                    t.onCompleted();
+                }
+            }
+        }
+        
+        
+        boolean add(PublishSubjectProducer<T> inner) {
+            for (;;) {
+                PublishSubjectProducer<T>[] curr = get();
+                if (curr == TERMINATED) {
+                    return false;
+                }
+                
+                int n = curr.length;
+                
+                @SuppressWarnings("unchecked")
+                PublishSubjectProducer<T>[] next = new PublishSubjectProducer[n + 1];
+                System.arraycopy(curr, 0, next, 0, n);
+                
+                next[n] = inner;
+                if (compareAndSet(curr, next)) {
+                    return true;
+                }
+            }
+        }
+        
+        @SuppressWarnings("unchecked")
+        void remove(PublishSubjectProducer<T> inner) {
+            for (;;) {
+                PublishSubjectProducer<T>[] curr = get();
+                if (curr == TERMINATED || curr == EMPTY) {
+                    return;
+                }
+                
+                int n = curr.length;
+                int j = -1;
+                for (int i = 0; i < n; i++) {
+                    if (curr[i] == inner) {
+                        j = i;
+                        break;
+                    }
+                }
+                
+                if (j < 0) {
+                    return;
+                }
+                
+                PublishSubjectProducer<T>[] next;
+                if (n == 1) {
+                    next = EMPTY;
+                } else {
+                    next = new PublishSubjectProducer[n - 1];
+                    System.arraycopy(curr, 0, next, 0, j);
+                    System.arraycopy(curr, j + 1, next, j, n - j - 1);
+                }
+                
+                if (compareAndSet(curr, next)) {
+                    return;
+                }
+            }
+        }
+
+        @Override
+        public void onNext(T t) {
+            for (PublishSubjectProducer<T> pp : get()) {
+                pp.onNext(t);
+            }
+        }
+
+        @SuppressWarnings("unchecked")
+        @Override
+        public void onError(Throwable e) {
+            error = e;
+            List<Throwable> errors = null;
+            for (PublishSubjectProducer<T> pp : getAndSet(TERMINATED)) {
+                try {
+                    pp.onError(e);
+                } catch (Throwable ex) {
+                    if (errors == null) {
+                        errors = new ArrayList<Throwable>(1);
+                    }
+                    errors.add(ex);
+                }
+            }
+            
+            Exceptions.throwIfAny(errors);
+        }
+
+        @SuppressWarnings("unchecked")
+        @Override
+        public void onCompleted() {
+            for (PublishSubjectProducer<T> pp : getAndSet(TERMINATED)) {
+                pp.onCompleted();
+            }
+        }
+
+    }
+    
+    static final class PublishSubjectProducer<T> 
+    extends AtomicLong
+    implements Producer, Subscription, Observer<T> {
+        /** */
+        private static final long serialVersionUID = 6451806817170721536L;
+
+        final PublishSubjectState<T> parent;
+        
+        final Subscriber<? super T> actual;
+        
+        long produced;
+        
+        public PublishSubjectProducer(PublishSubjectState<T> parent, Subscriber<? super T> actual) {
+            this.parent = parent;
+            this.actual = actual;
+        }
+        
+        @Override
+        public void request(long n) {
+            if (BackpressureUtils.validate(n)) {
+                for (;;) {
+                    long r = get();
+                    if (r == Long.MIN_VALUE) {
+                        return;
+                    }
+                    long u = BackpressureUtils.addCap(r, n);
+                    if (compareAndSet(r, u)) {
+                        return;
+                    }
+                }
+            }
+        }
+        
+        @Override
+        public boolean isUnsubscribed() {
+            return get() == Long.MIN_VALUE;
+        }
+        
+        @Override
+        public void unsubscribe() {
+            if (getAndSet(Long.MIN_VALUE) != Long.MIN_VALUE) {
+                parent.remove(this);
+            }
+        }
+        
+        @Override
+        public void onNext(T t) {
+            long r = get();
+            if (r != Long.MIN_VALUE) {
+                long p = produced;
+                if (r != p) {
+                    produced = p + 1;
+                    actual.onNext(t);
+                } else {
+                    unsubscribe();
+                    actual.onError(new MissingBackpressureException("PublishSubject: could not emit value due to lack of requests"));
+                }
+            }
+        }
+        
+        @Override
+        public void onError(Throwable e) {
+            if (get() != Long.MIN_VALUE) {
+                actual.onError(e);
+            }
+        }
+        
+        @Override
+        public void onCompleted() {
+            if (get() != Long.MIN_VALUE) {
+                actual.onCompleted();
+            }
+        }
+    }
 }

src/test/java/rx/internal/operators/OperatorMapNotificationTest.java

@@ -132,9 +132,16 @@ public Integer call() {
         ps.onNext(3);
         ps.onCompleted();
 
-        ts.assertValues(2, 3, 4, 5);
+        ts.assertNoValues();
+        ts.assertNoErrors();
+        ts.assertNotCompleted();
+        
+        ts.requestMore(1);
+        
+        ts.assertValue(0);
         ts.assertNoErrors();
         ts.assertCompleted();
+        
     }
 
 }

src/test/java/rx/internal/operators/OperatorPublishFunctionTest.java

@@ -222,7 +222,7 @@ public Observable<Integer> call(Observable<Integer> o) {
         ts.assertError(MissingBackpressureException.class);
         ts.assertNotCompleted();
 
-        Assert.assertEquals("Queue full?!", ts.getOnErrorEvents().get(0).getMessage());
+        Assert.assertEquals("PublishSubject: could not emit value due to lack of requests", ts.getOnErrorEvents().get(0).getMessage());
         Assert.assertFalse("Source has subscribers?", ps.hasObservers());
     }
 
@@ -249,7 +249,7 @@ public Observable<Integer> call(Observable<Integer> o) {
         ts.assertError(MissingBackpressureException.class);
         ts.assertNotCompleted();
 
-        Assert.assertEquals("Queue full?!", ts.getOnErrorEvents().get(0).getMessage());
+        Assert.assertEquals("PublishSubject: could not emit value due to lack of requests", ts.getOnErrorEvents().get(0).getMessage());
         Assert.assertFalse("Source has subscribers?", ps.hasObservers());
     }
 }

src/test/java/rx/internal/operators/OperatorTakeTest.java

@@ -425,7 +425,9 @@ public void testReentrantTake() {
 
         TestSubscriber<Integer> ts = new TestSubscriber<Integer>();
 
-        source.take(1).doOnNext(new Action1<Integer>() {
+        source
+        .rebatchRequests(2) // take(1) requests 1
+        .take(1).doOnNext(new Action1<Integer>() {
             @Override
             public void call(Integer v) {
                 source.onNext(2);