io.reactivex.netty.protocol.http.UnicastContentSubject Maven / Gradle / Ivy
/*
* Copyright 2015 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 io.reactivex.netty.protocol.http;
import io.netty.buffer.ByteBuf;
import io.netty.util.ReferenceCountUtil;
import io.reactivex.netty.protocol.http.client.HttpClientResponse;
import io.reactivex.netty.protocol.http.server.HttpServerRequest;
import rx.Observable;
import rx.Observer;
import rx.Scheduler;
import rx.Subscriber;
import rx.Subscription;
import rx.functions.Action0;
import rx.functions.Action1;
import rx.internal.operators.BufferUntilSubscriber;
import rx.observers.Subscribers;
import rx.schedulers.Schedulers;
import rx.subjects.Subject;
import rx.subscriptions.Subscriptions;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
/**
* A {@link Subject} implementation to be used by {@link HttpClientResponse} and {@link HttpServerRequest}.
*
* Unicast
* This implementation allows a single subscription as this buffers the content till subscription to solve the issue
* described in this github issue.
* If we allow multiple subscription and still maintain it as a cold observable i.e. which re-runs the stream on every
* subscription, we loose the control on the scope of this {@link Observable} as any code can hold the reference to
* this {@link Observable} at any point in time and hence subscribe to it at any time. This will eventually increase
* memory consumption as we will hold on to the content buffers for more time than required.
*
* Multicast option
* If at all it is required to allow multiple subscriptions to this {@link Subject} one should use a
* {@link Observable#publish()} operator.
*
* Buffering
* This subject will buffer all content till the first (one and only) subscriber arrives.
* In cases, when there are no subscriptions, this buffer may be held till infinity and hence can cause a memory leak in
* case of netty's {@link ByteBuf} which needs to be released explicitly.
* In order to avoid this leak, this subject provides a "no subscription timeout" which disposes this subject (calling
* {@link #disposeIfNotSubscribed()} if it does not get a subscription in the configured timeout duration.
*
* The buffer is only utilized if there are any items emitted to this subject before a subscription arrives. After a
* subscription arrives, this subject becomes a pass through i.e. it does not buffer before sending the notifications.
*
* @author Nitesh Kant
*/
public final class UnicastContentSubject extends Subject {
private final State state;
private volatile Observable timeoutScheduler;
private UnicastContentSubject(State state) {
super(new OnSubscribeAction(state));
this.state = state;
timeoutScheduler = Observable.empty(); // No timeout.
}
private UnicastContentSubject(final State state, long noSubscriptionTimeout, TimeUnit timeUnit,
Scheduler scheduler) {
super(new OnSubscribeAction(state));
this.state = state;
timeoutScheduler = Observable.interval(noSubscriptionTimeout, timeUnit, scheduler).take(1); // Started when content arrives.
}
/**
* Creates a new {@link UnicastContentSubject} without a no subscription timeout.
* This can cause a memory leak in case no one ever subscribes to this subject. See
* {@link UnicastContentSubject} for details.
*
* @param onUnsubscribe An action to be invoked when the sole subscriber to this {@link Subject} unsubscribes.
* @param The type emitted and received by this subject.
*
* @return The new instance of {@link UnicastContentSubject}
*/
public static UnicastContentSubject createWithoutNoSubscriptionTimeout(Action0 onUnsubscribe) {
State state = new State(onUnsubscribe);
return new UnicastContentSubject(state);
}
/**
* Creates a new {@link UnicastContentSubject} without a no subscription timeout.
* This can cause a memory leak in case no one ever subscribes to this subject. See
* {@link UnicastContentSubject} for details.
*
* @param The type emitted and received by this subject.
*
* @return The new instance of {@link UnicastContentSubject}
*/
public static UnicastContentSubject createWithoutNoSubscriptionTimeout() {
return createWithoutNoSubscriptionTimeout(null);
}
public static UnicastContentSubject create(long noSubscriptionTimeout, TimeUnit timeUnit) {
return create(noSubscriptionTimeout, timeUnit, (Action0)null);
}
public static UnicastContentSubject create(long noSubscriptionTimeout, TimeUnit timeUnit,
Action0 onUnsubscribe) {
return create(noSubscriptionTimeout, timeUnit, Schedulers.computation(), onUnsubscribe);
}
public static UnicastContentSubject create(long noSubscriptionTimeout, TimeUnit timeUnit,
Scheduler timeoutScheduler) {
return create(noSubscriptionTimeout, timeUnit, timeoutScheduler, null);
}
public static UnicastContentSubject create(long noSubscriptionTimeout, TimeUnit timeUnit,
Scheduler timeoutScheduler, Action0 onUnsubscribe) {
State state = new State(onUnsubscribe);
return new UnicastContentSubject(state, noSubscriptionTimeout, timeUnit, timeoutScheduler);
}
/**
* This will eagerly dispose this {@link Subject} without waiting for the no subscription timeout period,
* if configured.
*
* This must be invoked when the caller is sure that no one will subscribe to this subject. Any subscriber after
* this call will receive an error that the subject is disposed.
*
* @return {@code true} if the subject was disposed by this call (if and only if there was no subscription).
*/
public boolean disposeIfNotSubscribed() {
if (state.casState(State.STATES.UNSUBSCRIBED, State.STATES.DISPOSED)) {
state.bufferedObservable.subscribe(Subscribers.empty()); // Drain all items so that ByteBuf gets released.
return true;
}
return false;
}
public void updateTimeoutIfNotScheduled(long noSubscriptionTimeout, TimeUnit timeUnit) {
if (0 == state.timeoutScheduled) {
timeoutScheduler = Observable.interval(noSubscriptionTimeout, timeUnit).take(1);
}
}
/** The common state. */
private static final class State {
private final Action0 onUnsubscribe;
private volatile Subscription releaseSubscription;
private State(Action0 onUnsubscribe) {
this.onUnsubscribe = onUnsubscribe;
final BufferUntilSubscriber bufferedSubject = BufferUntilSubscriber.create();
bufferedObservable = bufferedSubject.lift(new AutoReleaseByteBufOperator()); // Always auto-release
bufferedObserver = bufferedSubject;
}
/**
* Following are the only possible state transitions:
* UNSUBSCRIBED -> SUBSCRIBED
* UNSUBSCRIBED -> DISPOSED
*/
private enum STATES {
UNSUBSCRIBED /*Initial*/, SUBSCRIBED /*Terminal state*/, DISPOSED/*Terminal state*/
}
private volatile int state = STATES.UNSUBSCRIBED.ordinal(); /*Values are the ordinals of STATES enum*/
private final Observer bufferedObserver;
private final Observable bufferedObservable;
@SuppressWarnings("unused")private volatile int timeoutScheduled; // Boolean
/** Field updater for state. */
@SuppressWarnings("rawtypes")
private static final AtomicIntegerFieldUpdater STATE_UPDATER
= AtomicIntegerFieldUpdater.newUpdater(State.class, "state");
/** Field updater for timeoutScheduled. */
@SuppressWarnings("rawtypes")
private static final AtomicIntegerFieldUpdater TIMEOUT_SCHEDULED_UPDATER
= AtomicIntegerFieldUpdater.newUpdater(State.class, "timeoutScheduled");
public boolean casState(STATES expected, STATES next) {
return STATE_UPDATER.compareAndSet(this, expected.ordinal(), next.ordinal());
}
public boolean casTimeoutScheduled() {
return TIMEOUT_SCHEDULED_UPDATER.compareAndSet(this, 0, 1);
}
public void setReleaseSubscription(final Subscription releaseSubscription) {
this.releaseSubscription = releaseSubscription;
}
public void unsubscribeReleaseSubscription() {
if(releaseSubscription != null) {
releaseSubscription.unsubscribe();
}
}
}
private static final class OnSubscribeAction implements OnSubscribe {
private final State state;
public OnSubscribeAction(State state) {
this.state = state;
}
@Override
public void call(final Subscriber subscriber) {
if (state.casState(State.STATES.UNSUBSCRIBED, State.STATES.SUBSCRIBED)) {
subscriber.add(Subscriptions.create(new Action0() {
@Override
public void call() {
if (null != state.onUnsubscribe) {
state.onUnsubscribe.call();
}
}
}));
state.bufferedObservable.unsafeSubscribe(subscriber);
state.unsubscribeReleaseSubscription();
} else if(State.STATES.SUBSCRIBED.ordinal() == state.state) {
subscriber.onError(new IllegalStateException("Content can only have one subscription. Use Observable.publish() if you want to multicast."));
} else if(State.STATES.DISPOSED.ordinal() == state.state) {
subscriber.onError(new IllegalStateException("Content stream is already disposed."));
}
}
}
private static class AutoReleaseByteBufOperator implements Operator {
@Override
public Subscriber call(final Subscriber subscriber) {
return new Subscriber() {
@Override
public void onCompleted() {
subscriber.onCompleted();
}
@Override
public void onError(Throwable e) {
subscriber.onError(e);
}
@Override
public void onNext(I t) {
try {
subscriber.onNext(t);
} finally {
ReferenceCountUtil.release(t);
}
}
};
}
}
@Override
public void onCompleted() {
state.bufferedObserver.onCompleted();
}
@Override
public void onError(Throwable e) {
state.bufferedObserver.onError(e);
}
@Override
public void onNext(T t) {
// Retain so that post-buffer, the ByteBuf does not get released.
// Release will be done after reading from the subject.
ReferenceCountUtil.retain(t);
state.bufferedObserver.onNext(t);
// Schedule timeout once and when not subscribed yet.
if (state.casTimeoutScheduled() && state.state == State.STATES.UNSUBSCRIBED.ordinal()) {
// Schedule timeout after the first content arrives.
state.setReleaseSubscription(timeoutScheduler.subscribe(new Action1() {
@Override
public void call(Long aLong) {
disposeIfNotSubscribed();
}
}));
}
}
@Override
public boolean hasObservers() {
return state.state == State.STATES.SUBSCRIBED.ordinal();
}
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy