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io.reactivx.mantis.operators.BufferOnBackPressureOperator Maven / Gradle / Ivy
/*
* Copyright 2019 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.reactivx.mantis.operators;
import io.mantisrx.common.metrics.Counter;
import io.mantisrx.common.metrics.Gauge;
import io.mantisrx.common.metrics.Metrics;
import io.mantisrx.common.metrics.MetricsRegistry;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import rx.Observable.Operator;
import rx.Observer;
import rx.Producer;
import rx.Subscriber;
import rx.functions.Action0;
import rx.internal.operators.NotificationLite;
import rx.subscriptions.Subscriptions;
@SuppressWarnings("unchecked")
public class BufferOnBackPressureOperator implements Operator {
public static final String METRICS_NAME_PREFIX = "DropOperator_";
private static final Logger logger = LoggerFactory.getLogger(BufferOnBackPressureOperator.class);
private static final int DEFAULT_SIZE = 4096;
private final int size;
private final ArrayBlockingQueue queue;
private final Counter next;
private final Counter error;
private final Counter complete;
private final Gauge subscribe;
private final Gauge requestedGauge;
private final Counter dropped;
private final Gauge bufferedGauge;
private String name;
public BufferOnBackPressureOperator(String name) {
this(name, DEFAULT_SIZE);
}
public BufferOnBackPressureOperator(final Metrics m, int size) {
this.size = size;
this.queue = new ArrayBlockingQueue(size);
next = m.getCounter("" + Counters.onNext);
error = m.getCounter("" + Counters.onError);
complete = m.getCounter("" + Counters.onComplete);
subscribe = m.getGauge("" + Gauges.subscribe);
dropped = m.getCounter("" + Counters.dropped);
requestedGauge = m.getGauge("" + Gauges.requested);
bufferedGauge = m.getGauge("" + Gauges.bufferedGauge);
}
public BufferOnBackPressureOperator(String name, int size) {
this.size = size;
this.name = METRICS_NAME_PREFIX + name;
this.queue = new ArrayBlockingQueue(size);
Metrics m = new Metrics.Builder()
.name(this.name)
.addCounter("" + Counters.onNext)
.addCounter("" + Counters.onError)
.addCounter("" + Counters.onComplete)
.addGauge("" + Gauges.subscribe)
.addCounter("" + Counters.dropped)
.addGauge("" + Gauges.requested)
.addGauge("" + Gauges.bufferedGauge)
.build();
m = MetricsRegistry.getInstance().registerAndGet(m);
next = m.getCounter("" + Counters.onNext);
error = m.getCounter("" + Counters.onError);
complete = m.getCounter("" + Counters.onComplete);
subscribe = m.getGauge("" + Gauges.subscribe);
dropped = m.getCounter("" + Counters.dropped);
requestedGauge = m.getGauge("" + Gauges.requested);
bufferedGauge = m.getGauge("" + Gauges.bufferedGauge);
}
@Override
public Subscriber call(final Subscriber child) {
subscribe.increment();
final AtomicLong requested = new AtomicLong();
final AtomicInteger completionEmitted = new AtomicInteger();
final AtomicInteger terminated = new AtomicInteger();
final AtomicInteger bufferedCount = new AtomicInteger();
final AtomicBoolean onCompleteReceived = new AtomicBoolean();
final AtomicInteger wip = new AtomicInteger();
child.add(Subscriptions.create(new Action0() {
@Override
public void call() {
subscribe.decrement();
}
}));
child.setProducer(new Producer() {
@Override
public void request(long n) {
requested.getAndAdd(n);
requestedGauge.increment(n);
// System.out.println("request: " + requested.get());
pollQueue(child,
requested,
bufferedCount,
onCompleteReceived,
completionEmitted,
wip);
}
});
Subscriber parent = new Subscriber() {
@Override
public void onStart() {
request(Long.MAX_VALUE);
}
@Override
public void onCompleted() {
if (terminated.compareAndSet(0, 1)) {
complete.increment();
onCompleteReceived.set(true);
pollQueue(child,
requested,
bufferedCount,
onCompleteReceived,
completionEmitted,
wip);
}
}
@Override
public void onError(Throwable e) {
if (terminated.compareAndSet(0, 1)) {
child.onError(e);
error.increment();
queue.clear();
}
}
@Override
public void onNext(T t) {
emitItem(NotificationLite.next(t));
}
private void emitItem(Object item) {
// short circuit buffering
if (requested.get() > 0 && queue.isEmpty()) {
NotificationLite.accept((Observer) child, item);
requested.decrementAndGet();
requestedGauge.decrement();
next.increment();
// System.out.println("next count: " + next.value());
} else {
boolean success = queue.offer(item);
if (success) {
bufferedCount.incrementAndGet();
bufferedGauge.increment();
// System.out.println("buffered count: " + bufferedGauge.value());
drainIfPossible(child, requested, bufferedCount, onCompleteReceived, completionEmitted);
} else {
dropped.increment();
// System.out.println("dropped count: " + dropped.value());
// dropped
}
}
}
};
// if child unsubscribes it should unsubscribe the parent, but not the other way around
child.add(parent);
return parent;
}
private void drainIfPossible(final Subscriber child,
AtomicLong requested,
AtomicInteger bufferedCount,
AtomicBoolean onCompleteReceived,
AtomicInteger completionEmitted
) {
while (requested.get() > 0) {
Object t = queue.poll();
if (t != null) {
NotificationLite.accept((Observer) child, t);
requested.decrementAndGet();
requestedGauge.decrement();
bufferedCount.decrementAndGet();
bufferedGauge.decrement();
// System.out.println("buffered count: " + bufferedGauge.value() + " next " + next.value()) ;
} else {
if (onCompleteReceived.get()) {
if (completionEmitted.compareAndSet(0, 1)) {
child.onCompleted();
queue.clear();
bufferedGauge.set(0);
}
}
// queue is empty break
break;
}
}
}
private void pollQueue(final Subscriber child,
AtomicLong requested,
AtomicInteger bufferedCount,
AtomicBoolean onCompleteReceived,
AtomicInteger completionEmitted,
AtomicInteger wip) {
do {
drainIfPossible(child, requested, bufferedCount, onCompleteReceived, completionEmitted);
long c = wip.decrementAndGet();
if (c > 1) {
/*
* Set down to 1 and then iterate again.
* we lower it to 1 otherwise it could have grown very large while in the last poll loop
* and then we can end up looping all those times again here before existing even once we've drained
*/
wip.set(1);
// we now loop again, and if anything tries scheduling again after this it will increment and cause us to loop again after
}
} while (wip.get() > 0);
}
public enum Counters {
onNext,
onError,
onComplete,
dropped
}
public enum Gauges {
subscribe,
requested,
bufferedGauge
}
}
