/*
* Copyright DataStax, 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 com.datastax.oss.driver.internal.core.util.concurrent;
import edu.umd.cs.findbugs.annotations.NonNull;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.GenericFutureListener;
import io.netty.util.concurrent.Promise;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import net.jcip.annotations.ThreadSafe;
A thread-safe version of Netty's PromiseCombiner
that uses proper synchronization to trigger the completion of the aggregate promise. /**
* A thread-safe version of Netty's {@link io.netty.util.concurrent.PromiseCombiner} that uses
* proper synchronization to trigger the completion of the aggregate promise.
*/
@ThreadSafe
public class PromiseCombiner {
Combines the given futures into the given promise, that is, ties the completion of the latter
to that of the formers.
Params: - aggregatePromise – The promise that will complete when all parents complete.
- parents – The parent futures.
/**
* Combines the given futures into the given promise, that is, ties the completion of the latter
* to that of the formers.
*
* @param aggregatePromise The promise that will complete when all parents complete.
* @param parents The parent futures.
*/
public static void combine(
@NonNull Promise<Void> aggregatePromise, @NonNull Future<?>... parents) {
PromiseCombinerListener listener =
new PromiseCombinerListener(aggregatePromise, parents.length);
for (Future<?> parent : parents) {
parent.addListener(listener);
}
}
private static class PromiseCombinerListener implements GenericFutureListener<Future<Object>> {
private final Promise<Void> aggregatePromise;
private final AtomicInteger remainingCount;
private final AtomicReference<Throwable> aggregateFailureRef = new AtomicReference<>();
private PromiseCombinerListener(Promise<Void> aggregatePromise, int numberOfParents) {
this.aggregatePromise = aggregatePromise;
remainingCount = new AtomicInteger(numberOfParents);
}
@Override
public void operationComplete(Future<Object> future) {
if (!future.isSuccess()) {
aggregateFailureRef.updateAndGet(
aggregateFailure -> {
if (aggregateFailure == null) {
aggregateFailure = future.cause();
} else {
aggregateFailure.addSuppressed(future.cause());
}
return aggregateFailure;
});
}
if (remainingCount.decrementAndGet() == 0) {
Throwable aggregateFailure = aggregateFailureRef.get();
if (aggregateFailure != null) {
aggregatePromise.tryFailure(aggregateFailure);
} else {
aggregatePromise.trySuccess(null);
}
}
}
}
}