// ========================================================================
// Copyright 2004-2005 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ========================================================================
package org.mortbay.thread;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import org.mortbay.component.AbstractLifeCycle;
import org.mortbay.log.Log;
/* ------------------------------------------------------------ */
/** A pool of threads.
* <p>
* Avoids the expense of thread creation by pooling threads after
* their run methods exit for reuse.
* <p>
* If an idle thread is available a job is directly dispatched,
* otherwise the job is queued. After queuing a job, if the total
* number of threads is less than the maximum pool size, a new thread
* is spawned.
* <p>
*
* @author Greg Wilkins <gregw@mortbay.com>
*/
public class QueuedThreadPool extends AbstractLifeCycle implements Serializable, ThreadPool
{
private String _name;
private Set _threads;
private List _idle;
private Runnable[] _jobs;
private int _nextJob;
private int _nextJobSlot;
private int _queued;
private int _maxQueued;
private boolean _daemon;
private int _id;
private final Object _lock = new Lock();
private final Object _threadsLock = new Lock();
private final Object _joinLock = new Lock();
private long _lastShrink;
private int _maxIdleTimeMs=60000;
private int _maxThreads=250;
private int _minThreads=2;
private boolean _warned=false;
private int _lowThreads=0;
private int _priority= Thread.NORM_PRIORITY;
private int _spawnOrShrinkAt=0;
private int _maxStopTimeMs;
/* ------------------------------------------------------------------- */
/* Construct
*/
public QueuedThreadPool()
{
_name="qtp-"+hashCode();
}
/* ------------------------------------------------------------------- */
/* Construct
*/
public QueuedThreadPool(int maxThreads)
{
this();
setMaxThreads(maxThreads);
}
/* ------------------------------------------------------------ */
/** Run job.
* @return true
*/
public boolean dispatch(Runnable job)
{
if (!isRunning() || job==null)
return false;
PoolThread thread=null;
boolean spawn=false;
synchronized(_lock)
{
// Look for an idle thread
int idle=_idle.size();
if (idle>0)
thread=(PoolThread)_idle.remove(idle-1);
else
{
// queue the job
_queued++;
if (_queued>_maxQueued)
_maxQueued=_queued;
_jobs[_nextJobSlot++]=job;
if (_nextJobSlot==_jobs.length)
_nextJobSlot=0;
if (_nextJobSlot==_nextJob)
{
// Grow the job queue
Runnable[] jobs= new Runnable[_jobs.length+_maxThreads];
int split=_jobs.length-_nextJob;
if (split>0)
System.arraycopy(_jobs,_nextJob,jobs,0,split);
if (_nextJob!=0)
System.arraycopy(_jobs,0,jobs,split,_nextJobSlot);
_jobs=jobs;
_nextJob=0;
_nextJobSlot=_queued;
}
spawn=_queued>_spawnOrShrinkAt;
}
}
if (thread!=null)
{
thread.dispatch(job);
}
else if (spawn)
{
newThread();
}
return true;
}
/* ------------------------------------------------------------ */
/** Get the number of idle threads in the pool.
* @see #getThreads
* @return Number of threads
*/
public int getIdleThreads()
{
return _idle==null?0:_idle.size();
}
/* ------------------------------------------------------------ */
/**
* @return low resource threads threshhold
*/
public int getLowThreads()
{
return _lowThreads;
}
/* ------------------------------------------------------------ */
/**
* @return maximum queue size
*/
public int getMaxQueued()
{
return _maxQueued;
}
/* ------------------------------------------------------------ */
/** Get the maximum thread idle time.
* Delegated to the named or anonymous Pool.
* @see #setMaxIdleTimeMs
* @return Max idle time in ms.
*/
public int getMaxIdleTimeMs()
{
return _maxIdleTimeMs;
}
/* ------------------------------------------------------------ */
/** Set the maximum number of threads.
* Delegated to the named or anonymous Pool.
* @see #setMaxThreads
* @return maximum number of threads.
*/
public int getMaxThreads()
{
return _maxThreads;
}
/* ------------------------------------------------------------ */
/** Get the minimum number of threads.
* Delegated to the named or anonymous Pool.
* @see #setMinThreads
* @return minimum number of threads.
*/
public int getMinThreads()
{
return _minThreads;
}
/* ------------------------------------------------------------ */
/**
* @return The name of the BoundedThreadPool.
*/
public String getName()
{
return _name;
}
/* ------------------------------------------------------------ */
/** Get the number of threads in the pool.
* @see #getIdleThreads
* @return Number of threads
*/
public int getThreads()
{
return _threads.size();
}
/* ------------------------------------------------------------ */
/** Get the priority of the pool threads.
* @return the priority of the pool threads.
*/
public int getThreadsPriority()
{
return _priority;
}
/* ------------------------------------------------------------ */
public int getQueueSize()
{
return _queued;
}
/* ------------------------------------------------------------ */
/**
* @return the spawnOrShrinkAt The number of queued jobs (or idle threads) needed
* before the thread pool is grown (or shrunk)
*/
public int getSpawnOrShrinkAt()
{
return _spawnOrShrinkAt;
}
/* ------------------------------------------------------------ */
/**
* @param spawnOrShrinkAt The number of queued jobs (or idle threads) needed
* before the thread pool is grown (or shrunk)
*/
public void setSpawnOrShrinkAt(int spawnOrShrinkAt)
{
_spawnOrShrinkAt=spawnOrShrinkAt;
}
/* ------------------------------------------------------------ */
/**
* @return maximum total time that stop() will wait for threads to die.
*/
public int getMaxStopTimeMs()
{
return _maxStopTimeMs;
}
/* ------------------------------------------------------------ */
/**
* @param stopTimeMs maximum total time that stop() will wait for threads to die.
*/
public void setMaxStopTimeMs(int stopTimeMs)
{
_maxStopTimeMs = stopTimeMs;
}
/* ------------------------------------------------------------ */
/**
* Delegated to the named or anonymous Pool.
*/
public boolean isDaemon()
{
return _daemon;
}
/* ------------------------------------------------------------ */
public boolean isLowOnThreads()
{
return _queued>_lowThreads;
}
/* ------------------------------------------------------------ */
public void join() throws InterruptedException
{
synchronized (_joinLock)
{
while (isRunning())
_joinLock.wait();
}
// TODO remove this semi busy loop!
while (isStopping())
Thread.sleep(100);
}
/* ------------------------------------------------------------ */
/**
* Delegated to the named or anonymous Pool.
*/
public void setDaemon(boolean daemon)
{
_daemon=daemon;
}
/* ------------------------------------------------------------ */
/**
* @param lowThreads low resource threads threshhold
*/
public void setLowThreads(int lowThreads)
{
_lowThreads = lowThreads;
}
/* ------------------------------------------------------------ */
/** Set the maximum thread idle time.
* Threads that are idle for longer than this period may be
* stopped.
* Delegated to the named or anonymous Pool.
* @see #getMaxIdleTimeMs
* @param maxIdleTimeMs Max idle time in ms.
*/
public void setMaxIdleTimeMs(int maxIdleTimeMs)
{
_maxIdleTimeMs=maxIdleTimeMs;
}
/* ------------------------------------------------------------ */
/** Set the maximum number of threads.
* Delegated to the named or anonymous Pool.
* @see #getMaxThreads
* @param maxThreads maximum number of threads.
*/
public void setMaxThreads(int maxThreads)
{
if (isStarted() && maxThreads<_minThreads)
throw new IllegalArgumentException("!minThreads<maxThreads");
_maxThreads=maxThreads;
}
/* ------------------------------------------------------------ */
/** Set the minimum number of threads.
* Delegated to the named or anonymous Pool.
* @see #getMinThreads
* @param minThreads minimum number of threads
*/
public void setMinThreads(int minThreads)
{
if (isStarted() && (minThreads<=0 || minThreads>_maxThreads))
throw new IllegalArgumentException("!0<=minThreads<maxThreads");
_minThreads=minThreads;
synchronized (_threadsLock)
{
while (isStarted() && _threads.size()<_minThreads)
{
newThread();
}
}
}
/* ------------------------------------------------------------ */
/**
* @param name Name of the BoundedThreadPool to use when naming Threads.
*/
public void setName(String name)
{
_name= name;
}
/* ------------------------------------------------------------ */
/** Set the priority of the pool threads.
* @param priority the new thread priority.
*/
public void setThreadsPriority(int priority)
{
_priority=priority;
}
/* ------------------------------------------------------------ */
/* Start the BoundedThreadPool.
* Construct the minimum number of threads.
*/
protected void doStart() throws Exception
{
if (_maxThreads<_minThreads || _minThreads<=0)
throw new IllegalArgumentException("!0<minThreads<maxThreads");
_threads=new HashSet();
_idle=new ArrayList();
_jobs=new Runnable[_maxThreads];
for (int i=0;i<_minThreads;i++)
{
newThread();
}
}
/* ------------------------------------------------------------ */
/** Stop the BoundedThreadPool.
* New jobs are no longer accepted,idle threads are interrupted
* and stopJob is called on active threads.
* The method then waits
* min(getMaxStopTimeMs(),getMaxIdleTimeMs()), for all jobs to
* stop, at which time killJob is called.
*/
protected void doStop() throws Exception
{
super.doStop();
long start=System.currentTimeMillis();
for (int i=0;i<100;i++)
{
synchronized (_threadsLock)
{
Iterator iter = _threads.iterator();
while (iter.hasNext())
((Thread)iter.next()).interrupt();
}
Thread.yield();
if (_threads.size()==0 || (_maxStopTimeMs>0 && _maxStopTimeMs < (System.currentTimeMillis()-start)))
break;
try
{
Thread.sleep(i*100);
}
catch(InterruptedException e){}
}
// TODO perhaps force stops
if (_threads.size()>0)
Log.warn(_threads.size()+" threads could not be stopped");
synchronized (_joinLock)
{
_joinLock.notifyAll();
}
}
/* ------------------------------------------------------------ */
protected void newThread()
{
synchronized (_threadsLock)
{
if (_threads.size()<_maxThreads)
{
PoolThread thread =new PoolThread();
_threads.add(thread);
thread.setName(thread.hashCode()+"@"+_name+"-"+_id++);
thread.start();
}
else if (!_warned)
{
_warned=true;
Log.debug("Max threads for {}",this);
}
}
}
/* ------------------------------------------------------------ */
/** Stop a Job.
* This method is called by the Pool if a job needs to be stopped.
* The default implementation does nothing and should be extended by a
* derived thread pool class if special action is required.
* @param thread The thread allocated to the job, or null if no thread allocated.
* @param job The job object passed to run.
*/
protected void stopJob(Thread thread, Object job)
{
thread.interrupt();
}
/* ------------------------------------------------------------ */
public String dump()
{
StringBuffer buf = new StringBuffer();
synchronized (_threadsLock)
{
for (Iterator i=_threads.iterator();i.hasNext();)
{
Thread thread = (Thread)i.next();
buf.append(thread.getName()).append(" ").append(thread.toString()).append('\n');
}
}
return buf.toString();
}
/* ------------------------------------------------------------ */
/**
* @param name The thread name to stop.
* @return true if the thread was found and stopped.
* @Deprecated Use {@link #interruptThread(long)} in preference
*/
public boolean stopThread(String name)
{
synchronized (_threadsLock)
{
for (Iterator i=_threads.iterator();i.hasNext();)
{
Thread thread = (Thread)i.next();
if (name.equals(thread.getName()))
{
thread.stop();
return true;
}
}
}
return false;
}
/* ------------------------------------------------------------ */
/**
* @param name The thread name to interrupt.
* @return true if the thread was found and interrupted.
*/
public boolean interruptThread(String name)
{
synchronized (_threadsLock)
{
for (Iterator i=_threads.iterator();i.hasNext();)
{
Thread thread = (Thread)i.next();
if (name.equals(thread.getName()))
{
thread.interrupt();
return true;
}
}
}
return false;
}
/* ------------------------------------------------------------ */
/** Pool Thread class.
* The PoolThread allows the threads job to be
* retrieved and active status to be indicated.
*/
public class PoolThread extends Thread
{
Runnable _job=null;
/* ------------------------------------------------------------ */
PoolThread()
{
setDaemon(_daemon);
setPriority(_priority);
}
/* ------------------------------------------------------------ */
/** BoundedThreadPool run.
* Loop getting jobs and handling them until idle or stopped.
*/
public void run()
{
boolean idle=false;
Runnable job=null;
try
{
while (isRunning())
{
// Run any job that we have.
if (job!=null)
{
final Runnable todo=job;
job=null;
idle=false;
todo.run();
}
synchronized(_lock)
{
// is there a queued job?
if (_queued>0)
{
_queued--;
job=_jobs[_nextJob];
_jobs[_nextJob++]=null;
if (_nextJob==_jobs.length)
_nextJob=0;
continue;
}
// Should we shrink?
final int threads=_threads.size();
if (threads>_minThreads &&
(threads>_maxThreads ||
_idle.size()>_spawnOrShrinkAt))
{
long now = System.currentTimeMillis();
if ((now-_lastShrink)>getMaxIdleTimeMs())
{
_lastShrink=now;
_idle.remove(this);
return;
}
}
if (!idle)
{
// Add ourselves to the idle set.
_idle.add(this);
idle=true;
}
}
// We are idle
// wait for a dispatched job
synchronized (this)
{
if (_job==null)
this.wait(getMaxIdleTimeMs());
job=_job;
_job=null;
}
}
}
catch (InterruptedException e)
{
Log.ignore(e);
}
finally
{
synchronized (_lock)
{
_idle.remove(this);
}
synchronized (_threadsLock)
{
_threads.remove(this);
}
synchronized (this)
{
job=_job;
}
// we died with a job! reschedule it
if (job!=null)
{
QueuedThreadPool.this.dispatch(job);
}
}
}
/* ------------------------------------------------------------ */
void dispatch(Runnable job)
{
synchronized (this)
{
_job=job;
this.notify();
}
}
}
private class Lock{}
}