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fix OperatorConcat race condition where request lost #2960

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Merged
merged 1 commit into from
May 27, 2015
Merged

fix OperatorConcat race condition where request lost #2960

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60 changes: 31 additions & 29 deletions src/main/java/rx/internal/operators/OperatorConcat.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
import rx.Producer;
import rx.Subscriber;
import rx.functions.Action0;
import rx.internal.producers.ProducerArbiter;
import rx.observers.SerializedSubscriber;
import rx.subscriptions.SerialSubscription;
import rx.subscriptions.Subscriptions;
Expand Down Expand Up @@ -85,17 +86,19 @@ static final class ConcatSubscriber<T> extends Subscriber<Observable<? extends T

volatile int wip;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater<ConcatSubscriber> WIP_UPDATER = AtomicIntegerFieldUpdater.newUpdater(ConcatSubscriber.class, "wip");
static final AtomicIntegerFieldUpdater<ConcatSubscriber> WIP = AtomicIntegerFieldUpdater.newUpdater(ConcatSubscriber.class, "wip");

// accessed by REQUESTED_UPDATER
// accessed by REQUESTED
private volatile long requested;
@SuppressWarnings("rawtypes")
private static final AtomicLongFieldUpdater<ConcatSubscriber> REQUESTED_UPDATER = AtomicLongFieldUpdater.newUpdater(ConcatSubscriber.class, "requested");
private static final AtomicLongFieldUpdater<ConcatSubscriber> REQUESTED = AtomicLongFieldUpdater.newUpdater(ConcatSubscriber.class, "requested");
private final ProducerArbiter arbiter;

public ConcatSubscriber(Subscriber<T> s, SerialSubscription current) {
super(s);
this.child = s;
this.current = current;
this.arbiter = new ProducerArbiter();
this.queue = new ConcurrentLinkedQueue<Object>();
add(Subscriptions.create(new Action0() {
@Override
Expand All @@ -113,32 +116,27 @@ public void onStart() {
}

private void requestFromChild(long n) {
if (n <=0) return;
// we track 'requested' so we know whether we should subscribe the next or not
ConcatInnerSubscriber<T> actualSubscriber = currentSubscriber;
if (n > 0 && BackpressureUtils.getAndAddRequest(REQUESTED_UPDATER, this, n) == 0) {
if (actualSubscriber == null && wip > 0) {
long previous = BackpressureUtils.getAndAddRequest(REQUESTED, this, n);
arbiter.request(n);
if (previous == 0) {
if (currentSubscriber == null && wip > 0) {
// this means we may be moving from one subscriber to another after having stopped processing
// so need to kick off the subscribe via this request notification
subscribeNext();
// return here as we don't want to do the requestMore logic below (which would double request)
return;
}
}

if (actualSubscriber != null) {
// otherwise we are just passing it through to the currentSubscriber
actualSubscriber.requestMore(n);
}
}

private void decrementRequested() {
REQUESTED_UPDATER.decrementAndGet(this);
REQUESTED.decrementAndGet(this);
}

@Override
public void onNext(Observable<? extends T> t) {
queue.add(nl.next(t));
if (WIP_UPDATER.getAndIncrement(this) == 0) {
if (WIP.getAndIncrement(this) == 0) {
subscribeNext();
}
}
Expand All @@ -152,14 +150,15 @@ public void onError(Throwable e) {
@Override
public void onCompleted() {
queue.add(nl.completed());
if (WIP_UPDATER.getAndIncrement(this) == 0) {
if (WIP.getAndIncrement(this) == 0) {
subscribeNext();
}
}


void completeInner() {
currentSubscriber = null;
if (WIP_UPDATER.decrementAndGet(this) > 0) {
if (WIP.decrementAndGet(this) > 0) {
subscribeNext();
}
request(1);
Expand All @@ -172,7 +171,7 @@ void subscribeNext() {
child.onCompleted();
} else if (o != null) {
Observable<? extends T> obs = nl.getValue(o);
currentSubscriber = new ConcatInnerSubscriber<T>(this, child, requested);
currentSubscriber = new ConcatInnerSubscriber<T>(this, child, arbiter);
current.set(currentSubscriber);
obs.unsafeSubscribe(currentSubscriber);
}
Expand All @@ -193,39 +192,42 @@ static class ConcatInnerSubscriber<T> extends Subscriber<T> {
@SuppressWarnings("unused")
private volatile int once = 0;
@SuppressWarnings("rawtypes")
private final static AtomicIntegerFieldUpdater<ConcatInnerSubscriber> ONCE_UPDATER = AtomicIntegerFieldUpdater.newUpdater(ConcatInnerSubscriber.class, "once");
private final static AtomicIntegerFieldUpdater<ConcatInnerSubscriber> ONCE = AtomicIntegerFieldUpdater.newUpdater(ConcatInnerSubscriber.class, "once");
private final ProducerArbiter arbiter;

public ConcatInnerSubscriber(ConcatSubscriber<T> parent, Subscriber<T> child, long initialRequest) {
public ConcatInnerSubscriber(ConcatSubscriber<T> parent, Subscriber<T> child, ProducerArbiter arbiter) {
this.parent = parent;
this.child = child;
request(initialRequest);
}

void requestMore(long n) {
request(n);
this.arbiter = arbiter;
}

@Override
public void onNext(T t) {
parent.decrementRequested();
child.onNext(t);
parent.decrementRequested();
arbiter.produced(1);
}

@Override
public void onError(Throwable e) {
if (ONCE_UPDATER.compareAndSet(this, 0, 1)) {
if (ONCE.compareAndSet(this, 0, 1)) {
// terminal error through parent so everything gets cleaned up, including this inner
parent.onError(e);
}
}

@Override
public void onCompleted() {
if (ONCE_UPDATER.compareAndSet(this, 0, 1)) {
if (ONCE.compareAndSet(this, 0, 1)) {
// terminal completion to parent so it continues to the next
parent.completeInner();
}
}

@Override
public void setProducer(Producer producer) {
arbiter.setProducer(producer);
}

};
}
2 changes: 1 addition & 1 deletion src/main/java/rx/internal/producers/ProducerArbiter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -95,7 +95,7 @@ public void produced(long n) {
if (r != Long.MAX_VALUE) {
long u = r - n;
if (u < 0) {
throw new IllegalStateException();
throw new IllegalStateException("more items arrived than were requested");
}
requested = u;
}
Expand Down
31 changes: 29 additions & 2 deletions src/test/java/rx/internal/operators/OperatorConcatTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -36,9 +36,7 @@
import org.mockito.InOrder;

import rx.Observable.OnSubscribe;
import rx.Scheduler.Worker;
import rx.*;
import rx.functions.Action0;
import rx.functions.Func1;
import rx.internal.util.RxRingBuffer;
import rx.observers.TestSubscriber;
Expand Down Expand Up @@ -795,4 +793,33 @@ public void onNext(Integer t) {
assertTrue(completed.get());
}

@Test//(timeout = 100000)
public void concatMapRangeAsyncLoopIssue2876() {
final long durationSeconds = 2;
final long startTime = System.currentTimeMillis();
for (int i = 0;; i++) {
//only run this for a max of ten seconds
if (System.currentTimeMillis()-startTime > TimeUnit.SECONDS.toMillis(durationSeconds))
return;
if (i % 1000 == 0) {
System.out.println("concatMapRangeAsyncLoop > " + i);
}
TestSubscriber<Integer> ts = new TestSubscriber<Integer>();
Observable.range(0, 1000)
.concatMap(new Func1<Integer, Observable<Integer>>() {
@Override
public Observable<Integer> call(Integer t) {
return Observable.from(Arrays.asList(t));
}
})
.observeOn(Schedulers.computation()).subscribe(ts);

ts.awaitTerminalEvent(2500, TimeUnit.MILLISECONDS);
ts.assertTerminalEvent();
ts.assertNoErrors();
assertEquals(1000, ts.getOnNextEvents().size());
assertEquals((Integer)999, ts.getOnNextEvents().get(999));
}
}

}