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* JBoss, Home of Professional Open Source
*
* Copyright 2009, Red Hat Middleware LLC, and individual contributors
* by the @author tags. 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.netty.util;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.jboss.netty.logging.InternalLogger;
import org.jboss.netty.logging.InternalLoggerFactory;
import org.jboss.netty.util.internal.ConcurrentIdentityHashMap;
import org.jboss.netty.util.internal.MapBackedSet;
import org.jboss.netty.util.internal.ReusableIterator;
import org.jboss.netty.util.internal.ThreadRenamingRunnable;
/**
* @author The Netty Project (netty-dev@lists.jboss.org)
* @author Trustin Lee (tlee@redhat.com)
* @version $Rev: 1130 $, $Date: 2009-04-04 02:37:49 +0900 (Sat, 04 Apr 2009) $
*/
public class HashedWheelTimer implements Timer {
static final InternalLogger logger =
InternalLoggerFactory.getInstance(HashedWheelTimer.class);
private static final AtomicInteger id = new AtomicInteger();
// I'd say 64 active timer threads are obvious misuse.
private static final int MISUSE_WARNING_THRESHOLD = 64;
private static final AtomicInteger activeInstances = new AtomicInteger();
private static final AtomicBoolean loggedMisuseWarning = new AtomicBoolean();
private final Worker worker = new Worker();
final Thread workerThread;
final AtomicBoolean shutdown = new AtomicBoolean();
private final long roundDuration;
final long tickDuration;
final Set<HashedWheelTimeout>[] wheel;
final ReusableIterator<HashedWheelTimeout>[] iterators;
final int mask;
final ReadWriteLock lock = new ReentrantReadWriteLock();
volatile int wheelCursor;
public HashedWheelTimer() {
this(Executors.defaultThreadFactory());
}
public HashedWheelTimer(long tickDuration, TimeUnit unit) {
this(Executors.defaultThreadFactory(), tickDuration, unit);
}
public HashedWheelTimer(long tickDuration, TimeUnit unit, int ticksPerWheel) {
this(Executors.defaultThreadFactory(), tickDuration, unit, ticksPerWheel);
}
public HashedWheelTimer(ThreadFactory threadFactory) {
this(threadFactory, 100, TimeUnit.MILLISECONDS);
}
public HashedWheelTimer(
ThreadFactory threadFactory, long tickDuration, TimeUnit unit) {
this(threadFactory, tickDuration, unit, 512);
}
public HashedWheelTimer(
ThreadFactory threadFactory,
long tickDuration, TimeUnit unit, int ticksPerWheel) {
if (threadFactory == null) {
throw new NullPointerException("threadFactory");
}
if (unit == null) {
throw new NullPointerException("unit");
}
if (tickDuration <= 0) {
throw new IllegalArgumentException(
"tickDuration must be greater than 0: " + tickDuration);
}
if (ticksPerWheel <= 0) {
throw new IllegalArgumentException(
"ticksPerWheel must be greater than 0: " + ticksPerWheel);
}
// Normalize ticksPerWheel to power of two and initialize the wheel.
wheel = createWheel(ticksPerWheel);
iterators = createIterators(wheel);
mask = wheel.length - 1;
// Convert tickDuration to milliseconds.
this.tickDuration = tickDuration = unit.toMillis(tickDuration);
// Prevent overflow.
if (tickDuration == Long.MAX_VALUE ||
tickDuration >= Long.MAX_VALUE / wheel.length) {
throw new IllegalArgumentException(
"tickDuration is too long: " +
tickDuration + ' ' + unit);
}
roundDuration = tickDuration * wheel.length;
workerThread = threadFactory.newThread(new ThreadRenamingRunnable(
worker, "Hashed wheel timer #" + id.incrementAndGet()));
// Misuse check
int activeInstances = HashedWheelTimer.activeInstances.incrementAndGet();
if (activeInstances >= MISUSE_WARNING_THRESHOLD &&
loggedMisuseWarning.compareAndSet(false, true)) {
logger.debug(
"There are too many active " +
HashedWheelTimer.class.getSimpleName() + " instances (" +
activeInstances + ") - you should share the small number " +
"of instances to avoid excessive resource consumption.");
}
}
@SuppressWarnings("unchecked")
private static Set<HashedWheelTimeout>[] createWheel(int ticksPerWheel) {
if (ticksPerWheel <= 0) {
throw new IllegalArgumentException(
"ticksPerWheel must be greater than 0: " + ticksPerWheel);
}
if (ticksPerWheel > 1073741824) {
throw new IllegalArgumentException(
"ticksPerWheel may not be greater than 2^30: " + ticksPerWheel);
}
ticksPerWheel = normalizeTicksPerWheel(ticksPerWheel);
Set<HashedWheelTimeout>[] wheel = new Set[ticksPerWheel];
for (int i = 0; i < wheel.length; i ++) {
wheel[i] = new MapBackedSet<HashedWheelTimeout>(
new ConcurrentIdentityHashMap<HashedWheelTimeout, Boolean>(16, 0.95f, 4));
}
return wheel;
}
@SuppressWarnings("unchecked")
private static ReusableIterator<HashedWheelTimeout>[] createIterators(Set<HashedWheelTimeout>[] wheel) {
ReusableIterator<HashedWheelTimeout>[] iterators = new ReusableIterator[wheel.length];
for (int i = 0; i < wheel.length; i ++) {
iterators[i] = (ReusableIterator<HashedWheelTimeout>) wheel[i].iterator();
}
return iterators;
}
private static int normalizeTicksPerWheel(int ticksPerWheel) {
int normalizedTicksPerWheel = 1;
while (normalizedTicksPerWheel < ticksPerWheel) {
normalizedTicksPerWheel <<= 1;
}
return normalizedTicksPerWheel;
}
public synchronized void start() {
if (shutdown.get()) {
throw new IllegalStateException("cannot be started once stopped");
}
if (!workerThread.isAlive()) {
workerThread.start();
}
}
public synchronized Set<Timeout> stop() {
if (!shutdown.compareAndSet(false, true)) {
return Collections.emptySet();
}
while (workerThread.isAlive()) {
workerThread.interrupt();
try {
workerThread.join(100);
} catch (InterruptedException e) {
// Ignore
}
}
activeInstances.decrementAndGet();
Set<Timeout> unprocessedTimeouts = new HashSet<Timeout>();
for (Set<HashedWheelTimeout> bucket: wheel) {
unprocessedTimeouts.addAll(bucket);
bucket.clear();
}
return Collections.unmodifiableSet(unprocessedTimeouts);
}
public Timeout newTimeout(TimerTask task, long delay, TimeUnit unit) {
final long currentTime = System.currentTimeMillis();
if (task == null) {
throw new NullPointerException("task");
}
if (unit == null) {
throw new NullPointerException("unit");
}
delay = unit.toMillis(delay);
if (delay < tickDuration) {
delay = tickDuration;
}
if (!workerThread.isAlive()) {
start();
}
// Prepare the required parameters to create the timeout object.
HashedWheelTimeout timeout;
final long lastRoundDelay = delay % roundDuration;
final long lastTickDelay = delay % tickDuration;
final long relativeIndex =
lastRoundDelay / tickDuration + (lastTickDelay != 0? 1 : 0);
final long deadline = currentTime + delay;
final long remainingRounds =
delay / roundDuration - (delay % roundDuration == 0? 1 : 0);
// Add the timeout to the wheel.
lock.readLock().lock();
try {
timeout =
new HashedWheelTimeout(
task, deadline,
(int) (wheelCursor + relativeIndex & mask),
remainingRounds);
wheel[timeout.stopIndex].add(timeout);
} finally {
lock.readLock().unlock();
}
return timeout;
}
private final class Worker implements Runnable {
private long startTime;
private long tick;
Worker() {
super();
}
public void run() {
List<HashedWheelTimeout> expiredTimeouts =
new ArrayList<HashedWheelTimeout>();
startTime = System.currentTimeMillis();
tick = 1;
while (!shutdown.get()) {
waitForNextTick();
fetchExpiredTimeouts(expiredTimeouts);
notifyExpiredTimeouts(expiredTimeouts);
}
}
private void fetchExpiredTimeouts(
List<HashedWheelTimeout> expiredTimeouts) {
// Find the expired timeouts and decrease the round counter
// if necessary. Note that we don't send the notification
// immediately to make sure the listeners are called without
// an exclusive lock.
lock.writeLock().lock();
try {
int oldBucketHead = wheelCursor;
int newBucketHead = oldBucketHead + 1 & mask;
wheelCursor = newBucketHead;
ReusableIterator<HashedWheelTimeout> i = iterators[oldBucketHead];
fetchExpiredTimeouts(expiredTimeouts, i);
} finally {
lock.writeLock().unlock();
}
}
private void fetchExpiredTimeouts(
List<HashedWheelTimeout> expiredTimeouts,
ReusableIterator<HashedWheelTimeout> i) {
long currentTime = System.currentTimeMillis();
i.rewind();
while (i.hasNext()) {
HashedWheelTimeout timeout = i.next();
if (timeout.remainingRounds <= 0) {
if (timeout.deadline <= currentTime) {
i.remove();
expiredTimeouts.add(timeout);
} else {
// A rare case where a timeout is put for the next
// round: just wait for the next round.
}
} else {
timeout.remainingRounds --;
}
}
}
private void notifyExpiredTimeouts(
List<HashedWheelTimeout> expiredTimeouts) {
// Notify the expired timeouts.
for (int i = expiredTimeouts.size() - 1; i >= 0; i --) {
expiredTimeouts.get(i).expire();
}
// Clean up the temporary list.
expiredTimeouts.clear();
}
private void waitForNextTick() {
for (;;) {
final long currentTime = System.currentTimeMillis();
final long sleepTime = tickDuration * tick - (currentTime - startTime);
if (sleepTime <= 0) {
break;
}
try {
Thread.sleep(sleepTime);
} catch (InterruptedException e) {
if (shutdown.get()) {
return;
}
}
}
// Reset the tick if overflow is expected.
if (tickDuration * tick > Long.MAX_VALUE - tickDuration) {
startTime = System.currentTimeMillis();
tick = 1;
} else {
// Increase the tick if overflow is not likely to happen.
tick ++;
}
}
}
private final class HashedWheelTimeout implements Timeout {
private final TimerTask task;
final int stopIndex;
final long deadline;
volatile long remainingRounds;
private volatile boolean cancelled;
HashedWheelTimeout(
TimerTask task, long deadline, int stopIndex, long remainingRounds) {
this.task = task;
this.deadline = deadline;
this.stopIndex = stopIndex;
this.remainingRounds = remainingRounds;
}
public TimerTask getTask() {
return task;
}
public void cancel() {
if (isExpired()) {
return;
}
cancelled = true;
// Might be called more than once, but doesn't matter.
wheel[stopIndex].remove(this);
}
public boolean isCancelled() {
return cancelled;
}
public boolean isExpired() {
return cancelled || System.currentTimeMillis() > deadline;
}
public void expire() {
if (cancelled) {
return;
}
try {
task.run(this);
} catch (Throwable t) {
logger.warn(
"An exception was thrown by " +
TimerTask.class.getSimpleName() + ".", t);
}
}
@Override
public String toString() {
long currentTime = System.currentTimeMillis();
long remaining = deadline - currentTime;
StringBuilder buf = new StringBuilder(192);
buf.append(getClass().getSimpleName());
buf.append('(');
buf.append("deadline: ");
if (remaining > 0) {
buf.append(remaining);
buf.append(" ms later, ");
} else if (remaining < 0) {
buf.append(-remaining);
buf.append(" ms ago, ");
} else {
buf.append("now, ");
}
if (isCancelled()) {
buf.append (", cancelled");
}
return buf.append(')').toString();
}
}
}