org.eclipse.jetty.util.thread.SerializedExecutor Maven / Gradle / Ivy
//
// ========================================================================
// Copyright (c) 1995-2022 Mort Bay Consulting Pty Ltd and others.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.util.thread;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
import org.eclipse.jetty.util.log.Log;
/**
* An executor than ensurers serial execution of submitted tasks.
*
* Callers of this execute will never block in the executor, but they may
* be required to either execute the task they submit or tasks submitted
* by other threads whilst they are executing tasks.
*
*
* This class was inspired by the public domain class
* NonBlockingMutexExecutor
*
*/
public class SerializedExecutor implements Executor
{
private final AtomicReference _tail = new AtomicReference<>();
@Override
public void execute(Runnable task)
{
Link link = new Link(task);
Link lastButOne = _tail.getAndSet(link);
if (lastButOne == null)
run(link);
else
lastButOne._next.lazySet(link);
}
protected void onError(Runnable task, Throwable t)
{
if (task instanceof ErrorHandlingTask)
((ErrorHandlingTask)task).accept(t);
Log.getLogger(task.getClass()).warn(t);
}
private void run(Link link)
{
while (link != null)
{
try
{
link._task.run();
}
catch (Throwable t)
{
onError(link._task, t);
}
finally
{
// Are we the current the last Link?
if (_tail.compareAndSet(link, null))
link = null;
else
{
// not the last task, so its next link will eventually be set
Link next = link._next.get();
while (next == null)
{
Thread.yield(); // Thread.onSpinWait();
next = link._next.get();
}
link = next;
}
}
}
}
private class Link
{
private final Runnable _task;
private final AtomicReference _next = new AtomicReference<>();
public Link(Runnable task)
{
_task = task;
}
}
/**
* Error handling task
* If a submitted task implements this interface, it will be passed
* any exceptions thrown when running the task.
*/
public interface ErrorHandlingTask extends Runnable, Consumer
{}
}