src/main/java/rx/internal/operators/OnSubscribeRedo.java
/**
* Copyright 2014 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.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package rx.internal.operators;
/**
* Copyright 2014 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.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import static rx.Observable.unsafeCreate; // NOPMD
import java.util.concurrent.atomic.*;
import rx.*;
import rx.Observable.*;
import rx.functions.*;
import rx.internal.producers.ProducerArbiter;
import rx.observers.Subscribers;
import rx.schedulers.Schedulers;
import rx.subjects.*;
import rx.subscriptions.SerialSubscription;
public final class OnSubscribeRedo<T> implements OnSubscribe<T> {
final Observable<T> source;
private final Func1<? super Observable<? extends Notification<?>>, ? extends Observable<?>> controlHandlerFunction;
final boolean stopOnComplete;
final boolean stopOnError;
private final Scheduler scheduler;
static final Func1<Observable<? extends Notification<?>>, Observable<?>> REDO_INFINITE = new Func1<Observable<? extends Notification<?>>, Observable<?>>() {
@Override
public Observable<?> call(Observable<? extends Notification<?>> ts) {
return ts.map(new Func1<Notification<?>, Notification<?>>() {
@Override
public Notification<?> call(Notification<?> terminal) {
return Notification.createOnNext(null);
}
});
}
};
public static final class RedoFinite implements Func1<Observable<? extends Notification<?>>, Observable<?>> {
final long count;
public RedoFinite(long count) {
this.count = count;
}
@Override
public Observable<?> call(Observable<? extends Notification<?>> ts) {
return ts.map(new Func1<Notification<?>, Notification<?>>() {
int num;
@Override
public Notification<?> call(Notification<?> terminalNotification) {
if (count == 0) {
return terminalNotification;
}
num++;
if (num <= count) {
return Notification.createOnNext(num);
} else {
return terminalNotification;
}
}
}).dematerialize();
}
}
public static final class RetryWithPredicate implements Func1<Observable<? extends Notification<?>>, Observable<? extends Notification<?>>> {
final Func2<Integer, Throwable, Boolean> predicate;
public RetryWithPredicate(Func2<Integer, Throwable, Boolean> predicate) {
this.predicate = predicate;
}
@Override
public Observable<? extends Notification<?>> call(Observable<? extends Notification<?>> ts) {
return ts.scan(Notification.createOnNext(0), new Func2<Notification<Integer>, Notification<?>, Notification<Integer>>() {
@SuppressWarnings("unchecked")
@Override
public Notification<Integer> call(Notification<Integer> n, Notification<?> term) {
final int value = n.getValue();
if (predicate.call(value, term.getThrowable())) {
return Notification.createOnNext(value + 1);
} else {
return (Notification<Integer>) term;
}
}
});
}
}
public static <T> Observable<T> retry(Observable<T> source) {
return retry(source, REDO_INFINITE);
}
public static <T> Observable<T> retry(Observable<T> source, final long count) {
if (count < 0) {
throw new IllegalArgumentException("count >= 0 expected");
}
if (count == 0) {
return source;
}
return retry(source, new RedoFinite(count));
}
public static <T> Observable<T> retry(Observable<T> source, Func1<? super Observable<? extends Notification<?>>, ? extends Observable<?>> notificationHandler) {
return unsafeCreate(new OnSubscribeRedo<T>(source, notificationHandler, true, false, Schedulers.trampoline()));
}
public static <T> Observable<T> retry(Observable<T> source, Func1<? super Observable<? extends Notification<?>>, ? extends Observable<?>> notificationHandler, Scheduler scheduler) {
return unsafeCreate(new OnSubscribeRedo<T>(source, notificationHandler, true, false, scheduler));
}
public static <T> Observable<T> repeat(Observable<T> source) {
return repeat(source, Schedulers.trampoline());
}
public static <T> Observable<T> repeat(Observable<T> source, Scheduler scheduler) {
return repeat(source, REDO_INFINITE, scheduler);
}
public static <T> Observable<T> repeat(Observable<T> source, final long count) {
return repeat(source, count, Schedulers.trampoline());
}
public static <T> Observable<T> repeat(Observable<T> source, final long count, Scheduler scheduler) {
if (count == 0) {
return Observable.empty();
}
if (count < 0) {
throw new IllegalArgumentException("count >= 0 expected");
}
return repeat(source, new RedoFinite(count - 1), scheduler);
}
public static <T> Observable<T> repeat(Observable<T> source, Func1<? super Observable<? extends Notification<?>>, ? extends Observable<?>> notificationHandler) {
return unsafeCreate(new OnSubscribeRedo<T>(source, notificationHandler, false, true, Schedulers.trampoline()));
}
public static <T> Observable<T> repeat(Observable<T> source, Func1<? super Observable<? extends Notification<?>>, ? extends Observable<?>> notificationHandler, Scheduler scheduler) {
return unsafeCreate(new OnSubscribeRedo<T>(source, notificationHandler, false, true, scheduler));
}
public static <T> Observable<T> redo(Observable<T> source, Func1<? super Observable<? extends Notification<?>>, ? extends Observable<?>> notificationHandler, Scheduler scheduler) {
return unsafeCreate(new OnSubscribeRedo<T>(source, notificationHandler, false, false, scheduler));
}
private OnSubscribeRedo(Observable<T> source, Func1<? super Observable<? extends Notification<?>>, ? extends Observable<?>> f, boolean stopOnComplete, boolean stopOnError,
Scheduler scheduler) {
this.source = source;
this.controlHandlerFunction = f;
this.stopOnComplete = stopOnComplete;
this.stopOnError = stopOnError;
this.scheduler = scheduler;
}
@Override
public void call(final Subscriber<? super T> child) {
// when true is a marker to say we are ready to resubscribe to source
final AtomicBoolean resumeBoundary = new AtomicBoolean(true);
// incremented when requests are made, decremented when requests are fulfilled
final AtomicLong consumerCapacity = new AtomicLong();
final Scheduler.Worker worker = scheduler.createWorker();
child.add(worker);
final SerialSubscription sourceSubscriptions = new SerialSubscription();
child.add(sourceSubscriptions);
// use a subject to receive terminals (onCompleted and onError signals) from
// the source observable. We use a BehaviorSubject because subscribeToSource
// may emit a terminal before the restarts observable (transformed terminals)
// is subscribed
final Subject<Notification<?>, Notification<?>> terminals = BehaviorSubject.<Notification<?>>create().toSerialized();
final Subscriber<Notification<?>> dummySubscriber = Subscribers.empty();
// subscribe immediately so the last emission will be replayed to the next
// subscriber (which is the one we care about)
terminals.subscribe(dummySubscriber);
final ProducerArbiter arbiter = new ProducerArbiter();
final Action0 subscribeToSource = new Action0() {
@Override
public void call() {
if (child.isUnsubscribed()) {
return;
}
Subscriber<T> terminalDelegatingSubscriber = new Subscriber<T>() {
boolean done;
@Override
public void onCompleted() {
if (!done) {
done = true;
unsubscribe();
terminals.onNext(Notification.createOnCompleted());
}
}
@Override
public void onError(Throwable e) {
if (!done) {
done = true;
unsubscribe();
terminals.onNext(Notification.createOnError(e));
}
}
@Override
public void onNext(T v) {
if (!done) {
child.onNext(v);
decrementConsumerCapacity();
arbiter.produced(1);
}
}
private void decrementConsumerCapacity() {
// use a CAS loop because we don't want to decrement the
// value if it is Long.MAX_VALUE
while (true) {
long cc = consumerCapacity.get();
if (cc != Long.MAX_VALUE) {
if (consumerCapacity.compareAndSet(cc, cc - 1)) {
break;
}
} else {
break;
}
}
}
@Override
public void setProducer(Producer producer) {
arbiter.setProducer(producer);
}
};
// new subscription each time so if it unsubscribes itself it does not prevent retries
// by unsubscribing the child subscription
sourceSubscriptions.set(terminalDelegatingSubscriber);
source.unsafeSubscribe(terminalDelegatingSubscriber);
}
};
// the observable received by the control handler function will receive notifications of onCompleted in the case of 'repeat'
// type operators or notifications of onError for 'retry' this is done by lifting in a custom operator to selectively divert
// the retry/repeat relevant values to the control handler
final Observable<?> restarts = controlHandlerFunction.call(
terminals.lift(new Operator<Notification<?>, Notification<?>>() {
@Override
public Subscriber<? super Notification<?>> call(final Subscriber<? super Notification<?>> filteredTerminals) {
return new Subscriber<Notification<?>>(filteredTerminals) {
@Override
public void onCompleted() {
filteredTerminals.onCompleted();
}
@Override
public void onError(Throwable e) {
filteredTerminals.onError(e);
}
@Override
public void onNext(Notification<?> t) {
if (t.isOnCompleted() && stopOnComplete) {
filteredTerminals.onCompleted();
} else if (t.isOnError() && stopOnError) {
filteredTerminals.onError(t.getThrowable());
} else {
filteredTerminals.onNext(t);
}
}
@Override
public void setProducer(Producer producer) {
producer.request(Long.MAX_VALUE);
}
};
}
}));
// subscribe to the restarts observable to know when to schedule the next redo.
worker.schedule(new Action0() {
@Override
public void call() {
restarts.unsafeSubscribe(new Subscriber<Object>(child) {
@Override
public void onCompleted() {
child.onCompleted();
}
@Override
public void onError(Throwable e) {
child.onError(e);
}
@Override
public void onNext(Object t) {
if (!child.isUnsubscribed()) {
// perform a best endeavours check on consumerCapacity
// with the intent of only resubscribing immediately
// if there is outstanding capacity
if (consumerCapacity.get() > 0) {
worker.schedule(subscribeToSource);
} else {
// set this to true so that on next request
// subscribeToSource will be scheduled
resumeBoundary.compareAndSet(false, true);
}
}
}
@Override
public void setProducer(Producer producer) {
producer.request(Long.MAX_VALUE);
}
});
}
});
child.setProducer(new Producer() {
@Override
public void request(final long n) {
if (n > 0) {
BackpressureUtils.getAndAddRequest(consumerCapacity, n);
arbiter.request(n);
if (resumeBoundary.compareAndSet(true, false)) {
worker.schedule(subscribeToSource);
}
}
}
});
}
}