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Publish: fixed incorrect subscriber requested accounting #2552

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Jan 31, 2015
Merged

Publish: fixed incorrect subscriber requested accounting #2552

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77c5643
Publish: fixed incorrect subscriber requested accounting
akarnokd Jan 28, 2015
aeb879a
Handle concurrent unsubscription in drain (avoid NPE).
akarnokd Jan 29, 2015
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81 changes: 43 additions & 38 deletions src/main/java/rx/internal/operators/OperatorPublish.java
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Original file line number Diff line number Diff line change
Expand Up @@ -206,7 +206,6 @@ public void onNext(T t) {
*/
private static class State<T> {
private long outstandingRequests = -1;
private long emittedSinceRequest = 0;
private OriginSubscriber<T> origin;
// using AtomicLong to simplify mutating it, not for thread-safety since we're synchronizing access to this class
// using LinkedHashMap so the order of Subscribers having onNext invoked is deterministic (same each time the code is run)
Expand All @@ -225,15 +224,13 @@ public synchronized void setOrigin(OriginSubscriber<T> o) {
public synchronized boolean canEmitWithDecrement() {
if (outstandingRequests > 0) {
outstandingRequests--;
emittedSinceRequest++;
return true;
}
return false;
}

public synchronized void incrementOutstandingAfterFailedEmit() {
outstandingRequests++;
emittedSinceRequest--;
}

public synchronized Subscriber<? super T>[] getSubscribers() {
Expand All @@ -243,50 +240,55 @@ public synchronized Subscriber<? super T>[] getSubscribers() {
/**
* @return long outstandingRequests
*/
public synchronized long requestFromSubscriber(Subscriber<? super T> subscriber, Long request) {
AtomicLong r = ss.get(subscriber);
public synchronized long requestFromSubscriber(Subscriber<? super T> subscriber, long request) {
Map<Subscriber<? super T>, AtomicLong> subs = ss;
AtomicLong r = subs.get(subscriber);
if (r == null) {
ss.put(subscriber, new AtomicLong(request));
subs.put(subscriber, new AtomicLong(request));
} else {
if (r.get() != Long.MAX_VALUE) {
if (request == Long.MAX_VALUE) {
r.set(Long.MAX_VALUE);
} else {
r.addAndGet(request.longValue());
do {
long current = r.get();
if (current == Long.MAX_VALUE) {
break;
}
}
long u = current + request;
if (u < 0) {
u = Long.MAX_VALUE;
}
if (r.compareAndSet(current, u)) {
break;
}
} while (true);
}

return resetAfterSubscriberUpdate();
return resetAfterSubscriberUpdate(subs);
}

public synchronized void removeSubscriber(Subscriber<? super T> subscriber) {
ss.remove(subscriber);
resetAfterSubscriberUpdate();
Map<Subscriber<? super T>, AtomicLong> subs = ss;
subs.remove(subscriber);
resetAfterSubscriberUpdate(subs);
}

@SuppressWarnings("unchecked")
private long resetAfterSubscriberUpdate() {
subscribers = new Subscriber[ss.size()];
private long resetAfterSubscriberUpdate(Map<Subscriber<? super T>, AtomicLong> subs) {
Subscriber<? super T>[] subscriberArray = new Subscriber[subs.size()];
int i = 0;
for (Subscriber<? super T> s : ss.keySet()) {
subscribers[i++] = s;
}

long lowest = -1;
for (AtomicLong l : ss.values()) {
// decrement all we have emitted since last request
long c = l.addAndGet(-emittedSinceRequest);
for (Map.Entry<Subscriber<? super T>, AtomicLong> e : subs.entrySet()) {
subscriberArray[i++] = e.getKey();
AtomicLong l = e.getValue();
long c = l.get();
if (lowest == -1 || c < lowest) {
lowest = c;
}
}
this.subscribers = subscriberArray;
/*
* when receiving a request from a subscriber we reset 'outstanding' to the lowest of all subscribers
*/
outstandingRequests = lowest;
emittedSinceRequest = 0;
return outstandingRequests;
return lowest;
}
}

Expand All @@ -299,7 +301,7 @@ private static class RequestHandler<T> {
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater<RequestHandler> WIP = AtomicLongFieldUpdater.newUpdater(RequestHandler.class, "wip");

public void requestFromChildSubscriber(Subscriber<? super T> subscriber, Long request) {
public void requestFromChildSubscriber(Subscriber<? super T> subscriber, long request) {
state.requestFromSubscriber(subscriber, request);
OriginSubscriber<T> originSubscriber = state.getOrigin();
if(originSubscriber != null) {
Expand Down Expand Up @@ -333,6 +335,11 @@ private void requestMoreAfterEmission(int emitted) {

public void drainQueue(OriginSubscriber<T> originSubscriber) {
if (WIP.getAndIncrement(this) == 0) {
State<T> localState = state;
Map<Subscriber<? super T>, AtomicLong> localMap = localState.ss;
RxRingBuffer localBuffer = originSubscriber.buffer;
NotificationLite<T> nl = notifier;

int emitted = 0;
do {
/*
Expand All @@ -345,26 +352,24 @@ public void drainQueue(OriginSubscriber<T> originSubscriber) {
* If we want to batch this then we need to account for new subscribers arriving with a lower request count
* concurrently while iterating the batch ... or accept that they won't
*/

while (true) {
boolean shouldEmit = state.canEmitWithDecrement();
boolean shouldEmit = localState.canEmitWithDecrement();
if (!shouldEmit) {
break;
}
Object o = originSubscriber.buffer.poll();
Object o = localBuffer.poll();
if (o == null) {
// nothing in buffer so increment outstanding back again
state.incrementOutstandingAfterFailedEmit();
localState.incrementOutstandingAfterFailedEmit();
break;
}

if (notifier.isCompleted(o)) {
for (Subscriber<? super T> s : state.getSubscribers()) {
notifier.accept(s, o);
}

} else {
for (Subscriber<? super T> s : state.getSubscribers()) {
notifier.accept(s, o);
for (Subscriber<? super T> s : localState.getSubscribers()) {
AtomicLong req = localMap.get(s);
if (req != null) { // null req indicates a concurrent unsubscription happened
nl.accept(s, o);
req.decrementAndGet();
}
}
emitted++;
Expand Down
77 changes: 66 additions & 11 deletions src/test/java/rx/internal/operators/OperatorPublishTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,23 +15,17 @@
*/
package rx.internal.operators;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.fail;
import static org.junit.Assert.*;

import java.util.Arrays;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;

import org.junit.Test;

import rx.Observable;
import rx.*;
import rx.Observable.OnSubscribe;
import rx.Subscriber;
import rx.Subscription;
import rx.functions.Action0;
import rx.functions.Action1;
import rx.functions.Func1;
import rx.functions.*;
import rx.internal.util.RxRingBuffer;
import rx.observables.ConnectableObservable;
import rx.observers.TestSubscriber;
Expand Down Expand Up @@ -187,4 +181,65 @@ public Boolean call(Integer i) {
System.out.println(ts.getOnNextEvents());
}

@Test(timeout = 10000)
public void testBackpressureTwoConsumers() {
final AtomicInteger sourceEmission = new AtomicInteger();
final AtomicBoolean sourceUnsubscribed = new AtomicBoolean();
final Observable<Integer> source = Observable.range(1, 100)
.doOnNext(new Action1<Integer>() {
@Override
public void call(Integer t1) {
sourceEmission.incrementAndGet();
}
})
.doOnUnsubscribe(new Action0() {
@Override
public void call() {
sourceUnsubscribed.set(true);
}
}).share();
;

final AtomicBoolean child1Unsubscribed = new AtomicBoolean();
final AtomicBoolean child2Unsubscribed = new AtomicBoolean();

final TestSubscriber<Integer> ts2 = new TestSubscriber<Integer>();

final TestSubscriber<Integer> ts1 = new TestSubscriber<Integer>() {
@Override
public void onNext(Integer t) {
if (getOnNextEvents().size() == 2) {
source.doOnUnsubscribe(new Action0() {
@Override
public void call() {
child2Unsubscribed.set(true);
}
}).take(5).subscribe(ts2);
}
super.onNext(t);
}
};

source.doOnUnsubscribe(new Action0() {
@Override
public void call() {
child1Unsubscribed.set(true);
}
}).take(5).subscribe(ts1);

ts1.awaitTerminalEvent();
ts2.awaitTerminalEvent();

ts1.assertNoErrors();
ts2.assertNoErrors();

assertTrue(sourceUnsubscribed.get());
assertTrue(child1Unsubscribed.get());
assertTrue(child2Unsubscribed.get());

ts1.assertReceivedOnNext(Arrays.asList(1, 2, 3, 4, 5));
ts2.assertReceivedOnNext(Arrays.asList(4, 5, 6, 7, 8));

assertEquals(8, sourceEmission.get());
}
}