org.jboss.threads.OrderedExecutor Maven / Gradle / Ivy
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* JBoss, Home of Professional Open Source
* Copyright 2008, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.threads;
import java.util.ArrayDeque;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.Condition;
/**
* An executor that always runs all tasks in queue order, using a delegate executor to run the tasks.
*
* More specifically, if a FIFO queue type is used, any call B to the {@link #execute(Runnable)} method that
* happens-after another call A to the same method, will result in B's task running after A's.
*/
public final class OrderedExecutor extends AbstractExecutorService implements BlockingExecutorService {
private final Executor parent;
private final Runnable runner = new Runner();
private final Lock lock = new ReentrantLock();
private final Condition removeCondition = lock.newCondition();
// @protectedby lock
private final Queue queue;
// @protectedby lock
private boolean running;
// @protectedby lock
private boolean blocking;
// @protectedby lock
private Executor handoffExecutor;
/**
* Construct a new instance using an unbounded FIFO queue. Since the queue is unbounded, tasks are never
* rejected.
*
* @param parent the parent to delegate tasks to
*/
public OrderedExecutor(final Executor parent) {
this(parent, new ArrayDeque());
}
/**
* Construct a new instance using the given queue and a blocking reject policy.
*
* @param parent the parent to delegate tasks to
* @param queue the queue to use to hold tasks
*/
public OrderedExecutor(final Executor parent, final Queue queue) {
this(parent, queue, true, null);
}
/**
* Construct a new instance using a bounded FIFO queue of the given size and a blocking reject policy.
*
* @param parent the parent to delegate tasks to
* @param queueLength the fixed length of the queue to use to hold tasks
*/
public OrderedExecutor(final Executor parent, final int queueLength) {
this(parent, new ArrayQueue(queueLength), true, null);
}
/**
* Construct a new instance using a bounded FIFO queue of the given size and a handoff reject policy.
*
* @param parent the parent executor
* @param queueLength the fixed length of the queue to use to hold tasks
* @param handoffExecutor the executor to hand tasks to if the queue is full
*/
public OrderedExecutor(final Executor parent, final int queueLength, final Executor handoffExecutor) {
this(parent, new ArrayQueue(queueLength), false, handoffExecutor);
}
/**
* Construct a new instance.
*
* @param parent the parent executor
* @param queue the task queue to use
* @param blocking {@code true} if rejected tasks should block, {@code false} if rejected tasks should be handed off
* @param handoffExecutor the executor to hand tasks to if the queue is full
*/
public OrderedExecutor(final Executor parent, final Queue queue, final boolean blocking, final Executor handoffExecutor) {
if (parent == null) {
throw new NullPointerException("parent is null");
}
if (queue == null) {
throw new NullPointerException("queue is null");
}
this.queue = queue;
this.parent = parent;
this.blocking = blocking;
this.handoffExecutor = handoffExecutor;
}
/**
* Construct a new instance using a bounded FIFO queue of the given size and a handoff reject policy.
*
* @param parent the parent executor
* @param queueLength the fixed length of the queue to use to hold tasks
* @param blocking {@code true} if rejected tasks should block, {@code false} if rejected tasks should be handed off
* @param handoffExecutor the executor to hand tasks to if the queue is full
*/
public OrderedExecutor(final Executor parent, final int queueLength, final boolean blocking, final Executor handoffExecutor) {
this(parent, new ArrayQueue(queueLength), blocking, handoffExecutor);
}
/**
* Run a task.
*
* @param task the task to run.
*/
public void execute(Runnable task) {
if (task == null) {
throw new NullPointerException("task is null");
}
Executor executor;
OUT: for (;;) {
lock.lock();
try {
if (! running) {
running = true;
boolean ok = false;
try {
parent.execute(runner);
ok = true;
} finally {
if (! ok) {
running = false;
}
}
}
if (! queue.offer(task)) {
if (blocking) {
try {
removeCondition.await();
continue;
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new ExecutionInterruptedException();
}
} else {
executor = handoffExecutor;
break;
}
}
return;
} finally {
lock.unlock();
}
}
if (executor != null) {
executor.execute(task);
}
}
public void executeBlocking(final Runnable task) throws RejectedExecutionException, InterruptedException {
if (task == null) {
throw new NullPointerException("task is null");
}
OUT: for (;;) {
lock.lock();
try {
if (! running) {
running = true;
boolean ok = false;
try {
parent.execute(runner);
ok = true;
} finally {
if (! ok) {
running = false;
}
}
}
if (! queue.offer(task)) {
removeCondition.await();
continue;
}
return;
} finally {
lock.unlock();
}
}
}
public void executeBlocking(final Runnable task, final long timeout, final TimeUnit unit) throws RejectedExecutionException, InterruptedException {
if (task == null) {
throw new NullPointerException("task is null");
}
long now = System.currentTimeMillis();
final long deadline = now + unit.toMillis(timeout);
if (deadline < 0L) {
executeBlocking(task);
return;
}
OUT: for (;;) {
lock.lock();
try {
if (! running) {
running = true;
boolean ok = false;
try {
parent.execute(runner);
ok = true;
} finally {
if (! ok) {
running = false;
}
}
}
if (! queue.offer(task)) {
final long remaining = deadline - now;
if (remaining <= 0L) {
throw new ExecutionTimedOutException();
}
removeCondition.await(remaining, TimeUnit.MILLISECONDS);
now = System.currentTimeMillis();
continue;
}
return;
} finally {
lock.unlock();
}
}
}
public void executeNonBlocking(final Runnable task) throws RejectedExecutionException {
if (task == null) {
throw new NullPointerException("task is null");
}
Executor executor;
OUT: for (;;) {
lock.lock();
try {
if (! running) {
running = true;
boolean ok = false;
try {
parent.execute(runner);
ok = true;
} finally {
if (! ok) {
running = false;
}
}
}
if (! queue.offer(task)) {
executor = handoffExecutor;
break;
}
return;
} finally {
lock.unlock();
}
}
if (executor != null) {
executor.execute(task);
}
}
public boolean isShutdown() {
// container managed executors are never shut down from the application's perspective
return false;
}
public boolean isTerminated() {
// container managed executors are never shut down from the application's perspective
return false;
}
public boolean awaitTermination(final long timeout, final TimeUnit unit) throws InterruptedException {
return false;
}
public void shutdown() {
throw new SecurityException("shutdown() not allowed on container-managed executor");
}
public List shutdownNow() {
throw new SecurityException("shutdownNow() not allowed on container-managed executor");
}
private class Runner implements Runnable {
public void run() {
for (;;) {
final Runnable task;
lock.lock();
try {
task = queue.poll();
removeCondition.signal();
if (task == null) {
running = false;
return;
}
} finally {
lock.unlock();
}
try {
task.run();
} catch (Throwable t) {
// todo log?
}
}
}
}
}
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