/*
* Copyright (c) 2014 Brocade Communications Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.yangtools.util.concurrent;
import com.google.common.base.MoreObjects;
import com.google.common.base.MoreObjects.ToStringHelper;
import com.google.common.base.Preconditions;
import com.google.common.util.concurrent.AbstractListeningExecutorService;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
/**
* An {@link com.google.common.util.concurrent.ListeningExecutorService}
* implementation that also allows for an {@link Executor} to be specified on
* construction that is used to execute {@link ListenableFuture} callback
* Runnables, registered via
* {@link com.google.common.util.concurrent.Futures#addCallback} or
* {@link ListenableFuture#addListener} directly, asynchronously when a task
* that is run on this executor completes. This is useful when you want to
* guarantee listener callback executions are off-loaded onto another thread to
* avoid blocking the thread that completed the task, as a common use case is to
* pass an executor that runs tasks in the same thread as the caller (ie
* <code>MoreExecutors#sameThreadExecutor</code>}) to
* {@link ListenableFuture#addListener}.
*
* <p>
* Most commonly, this class would be used in lieu of
* <code>MoreExecutors#listeningDecorator</code> when the underlying delegate
* Executor is single-threaded, in which case, you may not want ListenableFuture
* callbacks to block the single thread.
*
* <p>
* Note: the Executor specified on construction does not replace the Executor
* specified in {@link ListenableFuture#addListener}. The latter Executor is
* still used however, if it is detected that the listener Runnable would
* execute in the thread that completed the task, the listener is executed on
* Executor specified on construction.
*
* @author Thomas Pantelis
* @see AsyncNotifyingListenableFutureTask
*/
public class AsyncNotifyingListeningExecutorService extends AbstractListeningExecutorService {
private final ExecutorService delegate;
private final Executor listenableFutureExecutor;
/**
* Constructor.
*
* @param delegate the back-end ExecutorService.
* @param listenableFutureExecutor the executor used to run listener callbacks asynchronously.
* If null, no executor is used.
*/
public AsyncNotifyingListeningExecutorService( final ExecutorService delegate,
@Nullable final Executor listenableFutureExecutor ) {
this.delegate = Preconditions.checkNotNull( delegate );
this.listenableFutureExecutor = listenableFutureExecutor;
}
/**
* Creates an {@link AsyncNotifyingListenableFutureTask} instance with the listener Executor.
*
* @param task the Callable to execute
*/
private <T> AsyncNotifyingListenableFutureTask<T> newFutureTask( final Callable<T> task ) {
return AsyncNotifyingListenableFutureTask.create( task, listenableFutureExecutor );
}
/**
* Creates an {@link AsyncNotifyingListenableFutureTask} instance with the listener Executor.
*
* @param task the Runnable to execute
*/
private <T> AsyncNotifyingListenableFutureTask<T> newFutureTask( final Runnable task, final T result ) {
return AsyncNotifyingListenableFutureTask.create( task, result, listenableFutureExecutor );
}
/**
* Returns the delegate ExecutorService.
*/
protected ExecutorService getDelegate() {
return delegate;
}
@Override
public boolean awaitTermination( final long timeout, @Nonnull final TimeUnit unit ) throws InterruptedException {
return delegate.awaitTermination( timeout, unit );
}
@Override
public boolean isShutdown() {
return delegate.isShutdown();
}
@Override
public boolean isTerminated() {
return delegate.isTerminated();
}
@Override
public void shutdown() {
delegate.shutdown();
}
@Nonnull
@Override
public List<Runnable> shutdownNow() {
return delegate.shutdownNow();
}
@Override
public void execute( @Nonnull final Runnable command ) {
delegate.execute( command );
}
@Nonnull
@Override
public <T> ListenableFuture<T> submit( final Callable<T> task ) {
AsyncNotifyingListenableFutureTask<T> futureTask = newFutureTask( task );
delegate.execute( futureTask );
return futureTask;
}
@Nonnull
@Override
public ListenableFuture<?> submit( final Runnable task ) {
AsyncNotifyingListenableFutureTask<Void> futureTask = newFutureTask( task, null );
delegate.execute( futureTask );
return futureTask;
}
@Nonnull
@Override
public <T> ListenableFuture<T> submit( final Runnable task, final T result ) {
AsyncNotifyingListenableFutureTask<T> futureTask = newFutureTask( task, result );
delegate.execute( futureTask );
return futureTask;
}
protected ToStringHelper addToStringAttributes( final ToStringHelper toStringHelper ) {
return toStringHelper;
}
@Override
public final String toString() {
return addToStringAttributes( MoreObjects.toStringHelper( this )
.add( "delegate", delegate ) ).toString();
}
}