/*
* (C) Copyright 2013 Nuxeo SA (http://nuxeo.com/) and contributors.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the GNU Lesser General Public License
* (LGPL) version 2.1 which accompanies this distribution, and is available at
* http://www.gnu.org/licenses/lgpl-2.1.html
*
* This library 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.
*
* Contributors:
* Florent Guillaume
*/
package org.nuxeo.ecm.core.work;
import java.util.AbstractQueue;
import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
/**
* An abstract {@link BlockingQueue} suitable for a fixed-sized
* {@link java.util.concurrent.ThreadPoolExecutor ThreadPoolExecutor}, that can
* be implemented in terms of a few methods.
*
* {@link #offer} always succeeds.
*
* @since 5.8
*/
public abstract class NuxeoBlockingQueue extends AbstractQueue<Runnable>
implements BlockingQueue<Runnable> {
/*
* ThreadPoolExecutor uses a BlockingQueue but the Java 7 implementation
* only calls these methods on it:
*
* - isEmpty()
*
* - size()
*
* - poll(timeout, unit): not used, as core pool size = max size and no core
* thread timeout
*
* - take()
*
* - offer(e)
*
* - remove(e)
*
* - toArray(), toArray(a): for purge and shutdown
*
* - drainTo(c)
*
* - iterator() : hasNext(), next(), remove() (called by toArray)
*/
protected final ReentrantLock activationLock = new ReentrantLock();
protected final Condition activation = activationLock.newCondition();
protected volatile boolean active = true;
/**
* Sets the queue active or inactive.
*
* When deactivated, taking an element from the queue (take, poll, peek)
* behaves as if the queue was empty. Elements can still be added when the
* queue is deactivated. When reactivated, all elements are again available.
*
* @param active {@code true} to make the queue active, or {@code false} to
* deactivate it
*/
public void setActive(boolean active) {
this.active = active;
activationLock.lock();
try {
activation.signalAll();
} finally {
activationLock.unlock();
}
}
@Override
public boolean offer(Runnable r) {
try {
put(r);
} catch (InterruptedException e) {
Thread.currentThread().interrupt(); // restore interrupt status
throw new RuntimeException("interrupted", e);
}
return true;
}
@Override
public boolean offer(Runnable r, long timeout, TimeUnit unit)
throws InterruptedException {
// not needed for ThreadPoolExecutor
put(r);
return true;
}
@Override
public void put(Runnable r) throws InterruptedException {
putElement(r);
}
@Override
public Runnable peek() {
// not needed for ThreadPoolExecutor
throw new UnsupportedOperationException("not supported");
}
@Override
public Runnable poll() {
if (!active) {
return null;
}
return pollElement();
}
protected long timeUntil(long end) {
long timeout = end - System.currentTimeMillis();
if (timeout < 0) {
timeout = 0;
}
return timeout;
}
protected long awaitActivation(long nanos) throws InterruptedException {
activationLock.lock();
try {
while (nanos > 0 && !active) {
nanos = activation.awaitNanos(nanos);
}
} finally {
activationLock.unlock();
}
return nanos;
}
@Override
public boolean contains(Object o) {
// TODO Auto-generated method stub
throw new UnsupportedOperationException();
}
@Override
public int size() {
return getQueueSize();
}
@Override
public int remainingCapacity() {
return Integer.MAX_VALUE;
}
@Override
public Iterator<Runnable> iterator() {
return new Iter();
}
/*
* Used by drainQueue/purge methods of ThreadPoolExector through toArray.
*/
private class Iter implements Iterator<Runnable> {
public Iter() {
throw new UnsupportedOperationException();
}
@Override
public boolean hasNext() {
// TODO Auto-generated method stub
throw new UnsupportedOperationException();
}
@Override
public Runnable next() {
// TODO Auto-generated method stub
throw new UnsupportedOperationException();
}
@Override
public void remove() {
// TODO Auto-generated method stub
throw new UnsupportedOperationException();
}
}
@Override
public int drainTo(Collection<? super Runnable> c) {
return drainTo(c, Integer.MAX_VALUE);
}
@Override
public int drainTo(Collection<? super Runnable> c, int maxElements) {
for (int i = 0; i < maxElements; i++) {
Runnable r = poll();
if (r == null) {
return i;
}
c.add(r);
}
return maxElements;
}
/**
* Gets the size of the queue.
*/
public abstract int getQueueSize();
/**
* Adds an element into this queue, waiting if necessary for space to become
* available.
*/
public abstract void putElement(Runnable r) throws InterruptedException;
/**
* Retrieves and removes an element from the queue, or returns null if the
* queue is empty.
*/
public abstract Runnable pollElement();
}