/*
* Distributed as part of c3p0 v.0.9.1-pre6
*
* Copyright (C) 2005 Machinery For Change, Inc.
*
* Author: Steve Waldman <swaldman@mchange.com>
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 2.1, as
* published by the Free Software Foundation.
*
* 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; see the file LICENSE. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307, USA.
*/
package com.mchange.v2.async;
import java.util.*;
import com.mchange.v2.log.*;
import com.mchange.v2.util.ResourceClosedException;
public final class ThreadPoolAsynchronousRunner implements AsynchronousRunner
{
final static MLogger logger = MLog.getLogger( ThreadPoolAsynchronousRunner.class );
final static int POLL_FOR_STOP_INTERVAL = 5000; //milliseconds
final static int DFLT_DEADLOCK_DETECTOR_INTERVAL = 10000; //milliseconds
final static int DFLT_INTERRUPT_DELAY_AFTER_APPARENT_DEADLOCK = 60000; //milliseconds
final static int DFLT_MAX_INDIVIDUAL_TASK_TIME = 0; //milliseconds, <= 0 means don't enforce a max task time
final static int DFLT_MAX_EMERGENCY_THREADS = 10;
int deadlock_detector_interval;
int interrupt_delay_after_apparent_deadlock;
int max_individual_task_time;
int num_threads;
boolean daemon;
HashSet managed;
HashSet available;
LinkedList pendingTasks;
Timer myTimer;
boolean should_cancel_timer;
TimerTask deadlockDetector = new DeadlockDetector();
TimerTask replacedThreadInterruptor = new ReplacedThreadInterruptor();
Map stoppedThreadsToStopDates = new HashMap();
private ThreadPoolAsynchronousRunner( int num_threads,
boolean daemon,
int max_individual_task_time,
int deadlock_detector_interval,
int interrupt_delay_after_apparent_deadlock,
Timer myTimer,
boolean should_cancel_timer )
{
this.num_threads = num_threads;
this.daemon = daemon;
this.max_individual_task_time = max_individual_task_time;
this.deadlock_detector_interval = deadlock_detector_interval;
this.interrupt_delay_after_apparent_deadlock = interrupt_delay_after_apparent_deadlock;
this.myTimer = myTimer;
this.should_cancel_timer = should_cancel_timer;
recreateThreadsAndTasks();
myTimer.schedule( deadlockDetector, deadlock_detector_interval, deadlock_detector_interval );
int replacedThreadProcessDelay = interrupt_delay_after_apparent_deadlock / 4;
myTimer.schedule( replacedThreadInterruptor, replacedThreadProcessDelay, replacedThreadProcessDelay );
}
public ThreadPoolAsynchronousRunner( int num_threads,
boolean daemon,
int max_individual_task_time,
int deadlock_detector_interval,
int interrupt_delay_after_apparent_deadlock,
Timer myTimer )
{
this( num_threads,
daemon,
max_individual_task_time,
deadlock_detector_interval,
interrupt_delay_after_apparent_deadlock,
myTimer,
false );
}
public ThreadPoolAsynchronousRunner( int num_threads,
boolean daemon,
int max_individual_task_time,
int deadlock_detector_interval,
int interrupt_delay_after_apparent_deadlock )
{
this( num_threads,
daemon,
max_individual_task_time,
deadlock_detector_interval,
interrupt_delay_after_apparent_deadlock,
new Timer( true ),
true );
}
public ThreadPoolAsynchronousRunner( int num_threads, boolean daemon, Timer sharedTimer )
{
this( num_threads,
daemon,
DFLT_MAX_INDIVIDUAL_TASK_TIME,
DFLT_DEADLOCK_DETECTOR_INTERVAL,
DFLT_INTERRUPT_DELAY_AFTER_APPARENT_DEADLOCK,
sharedTimer,
false );
}
public ThreadPoolAsynchronousRunner( int num_threads, boolean daemon )
{
this( num_threads,
daemon,
DFLT_MAX_INDIVIDUAL_TASK_TIME,
DFLT_DEADLOCK_DETECTOR_INTERVAL,
DFLT_INTERRUPT_DELAY_AFTER_APPARENT_DEADLOCK,
new Timer( true ),
true ); }
public synchronized void postRunnable(Runnable r)
{
try
{
pendingTasks.add( r );
this.notifyAll();
}
catch ( NullPointerException e )
{
//e.printStackTrace();
if ( Debug.DEBUG )
{
if ( logger.isLoggable( MLevel.FINE ) )
logger.log( MLevel.FINE, "NullPointerException while posting Runnable -- Probably we're closed.", e );
}
throw new ResourceClosedException("Attempted to use a ThreadPoolAsynchronousRunner in a closed or broken state.");
}
}
public void close( boolean skip_remaining_tasks )
{
synchronized ( this )
{
if (managed == null) return;
deadlockDetector.cancel();
replacedThreadInterruptor.cancel();
if (should_cancel_timer)
myTimer.cancel();
myTimer = null;
for (Iterator ii = managed.iterator(); ii.hasNext(); )
{
PoolThread stopMe = (PoolThread) ii.next();
stopMe.gentleStop();
if (skip_remaining_tasks)
stopMe.interrupt();
}
managed = null;
if (!skip_remaining_tasks)
{
for (Iterator ii = pendingTasks.iterator(); ii.hasNext(); )
{
Runnable r = (Runnable) ii.next();
new Thread(r).start();
ii.remove();
}
}
available = null;
pendingTasks = null;
}
}
public void close()
{ close( true ); }
public synchronized String getStatus()
{
StringBuffer sb = new StringBuffer( 512 );
sb.append( this.toString() );
sb.append( ' ' );
appendStatusString( sb );
return sb.toString();
}
// protected by ThreadPoolAsynchronousRunner.this' lock
// BE SURE CALLER OWNS ThreadPoolAsynchronousRunner.this' lock
private void appendStatusString( StringBuffer sb )
{
if (managed == null)
sb.append( "[closed]" );
else
{
HashSet active = (HashSet) managed.clone();
active.removeAll( available );
sb.append("[num_managed_threads: ");
sb.append( managed.size() );
sb.append(", num_active: ");
sb.append( active.size() );
sb.append("; activeTasks: ");
boolean first = true;
for (Iterator ii = active.iterator(); ii.hasNext(); )
{
if (first)
first = false;
else
sb.append(", ");
PoolThread pt = (PoolThread) ii.next();
sb.append( pt.getCurrentTask() );
sb.append( " (");
sb.append( pt.getName() );
sb.append(')');
}
sb.append("; pendingTasks: ");
for (int i = 0, len = pendingTasks.size(); i < len; ++i)
{
if (i != 0) sb.append(", ");
sb.append( pendingTasks.get( i ) );
}
sb.append(']');
}
}
// protected by ThreadPoolAsynchronousRunner.this' lock
// BE SURE CALLER OWNS ThreadPoolAsynchronousRunner.this' lock (or is ctor)
private void recreateThreadsAndTasks()
{
if ( this.managed != null)
{
Date aboutNow = new Date();
for (Iterator ii = managed.iterator(); ii.hasNext(); )
{
PoolThread pt = (PoolThread) ii.next();
pt.gentleStop();
stoppedThreadsToStopDates.put( pt, aboutNow );
}
}
this.managed = new HashSet();
this.available = new HashSet();
this.pendingTasks = new LinkedList();
for (int i = 0; i < num_threads; ++i)
{
Thread t = new PoolThread(i, daemon);
managed.add( t );
available.add( t );
t.start();
}
}
// protected by ThreadPoolAsynchronousRunner.this' lock
// BE SURE CALLER OWNS ThreadPoolAsynchronousRunner.this' lock
private void processReplacedThreads()
{
long about_now = System.currentTimeMillis();
for (Iterator ii = stoppedThreadsToStopDates.keySet().iterator(); ii.hasNext(); )
{
PoolThread pt = (PoolThread) ii.next();
if (! pt.isAlive())
ii.remove();
else
{
Date d = (Date) stoppedThreadsToStopDates.get( pt );
if ((about_now - d.getTime()) > interrupt_delay_after_apparent_deadlock)
{
if (logger.isLoggable(MLevel.WARNING))
logger.log(MLevel.WARNING,
"Task " + pt.getCurrentTask() + " (in deadlocked PoolThread) failed to complete in maximum time " +
interrupt_delay_after_apparent_deadlock + "ms. Trying interrupt().");
pt.interrupt();
ii.remove();
}
//else keep waiting...
}
}
}
// protected by ThreadPoolAsynchronousRunner.this' lock
// BE SURE CALLER OWNS ThreadPoolAsynchronousRunner.this' lock
private void shuttingDown( PoolThread pt )
{
if (managed != null && managed.contains( pt )) //we are not closed, and this was a thread in the current pool, not a replaced thread
{
managed.remove( pt );
available.remove( pt );
PoolThread replacement = new PoolThread( pt.getIndex(), daemon );
managed.add( replacement );
available.add( replacement );
replacement.start();
}
}
class PoolThread extends Thread
{
// protected by ThreadPoolAsynchronousRunner.this' lock
Runnable currentTask;
// protected by ThreadPoolAsynchronousRunner.this' lock
boolean should_stop;
// post ctor immutable
int index;
// post ctor immutable
TimerTask maxIndividualTaskTimeEnforcer;
PoolThread(int index, boolean daemon)
{
this.setName( this.getClass().getName() + "-#" + index);
this.setDaemon( daemon );
this.index = index;
if (max_individual_task_time > 0)
this.maxIndividualTaskTimeEnforcer = new TimerTask() { public void run() { interrupt(); } };
}
public int getIndex()
{ return index; }
// protected by ThreadPoolAsynchronousRunner.this' lock
// BE SURE CALLER OWNS ThreadPoolAsynchronousRunner.this' lock
void gentleStop()
{ should_stop = true; }
// protected by ThreadPoolAsynchronousRunner.this' lock
// BE SURE CALLER OWNS ThreadPoolAsynchronousRunner.this' lock
Runnable getCurrentTask()
{ return currentTask; }
public void run()
{
try
{
thread_loop:
while (true)
{
Runnable myTask;
synchronized ( ThreadPoolAsynchronousRunner.this )
{
while ( !should_stop && pendingTasks.size() == 0 )
ThreadPoolAsynchronousRunner.this.wait( POLL_FOR_STOP_INTERVAL );
if (should_stop)
break thread_loop;
if (! available.remove( this ) )
throw new InternalError("An unavailable PoolThread tried to check itself out!!!");
myTask = (Runnable) pendingTasks.remove(0);
currentTask = myTask;
}
try
{
if ( maxIndividualTaskTimeEnforcer != null )
myTimer.schedule( maxIndividualTaskTimeEnforcer, max_individual_task_time );
myTask.run();
}
catch ( RuntimeException e )
{
if ( logger.isLoggable( MLevel.WARNING ) )
logger.log(MLevel.WARNING, this + " -- caught unexpected Exception while executing posted task.", e);
//e.printStackTrace();
}
finally
{
if ( maxIndividualTaskTimeEnforcer != null )
maxIndividualTaskTimeEnforcer.cancel();
synchronized ( ThreadPoolAsynchronousRunner.this )
{
if (should_stop)
break thread_loop;
if ( available != null && ! available.add( this ) )
throw new InternalError("An apparently available PoolThread tried to check itself in!!!");
currentTask = null;
}
}
}
}
catch ( InterruptedException exc )
{
// if ( Debug.TRACE > Debug.TRACE_NONE )
// System.err.println(this + " interrupted. Shutting down.");
if ( Debug.TRACE > Debug.TRACE_NONE && logger.isLoggable( MLevel.FINE ) )
logger.fine(this + " interrupted. Shutting down.");
}
synchronized ( ThreadPoolAsynchronousRunner.this )
{ ThreadPoolAsynchronousRunner.this.shuttingDown( this ); }
}
}
class DeadlockDetector extends TimerTask
{
LinkedList last = null;
LinkedList current = null;
public void run()
{
boolean run_stray_tasks = false;
synchronized ( ThreadPoolAsynchronousRunner.this )
{
if (pendingTasks.size() == 0)
{
last = null;
return;
}
current = (LinkedList) pendingTasks.clone();
if ( current.equals( last ) )
{
//System.err.println(this + " -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!");
if ( logger.isLoggable( MLevel.WARNING ) )
{
logger.warning(this + " -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!");
StringBuffer sb = new StringBuffer( 512 );
sb.append( this );
sb.append( " -- APPARENT DEADLOCK!!! Complete Status: ");
appendStatusString( sb );
//System.err.println( sb.toString() );
logger.warning( sb.toString() );
}
recreateThreadsAndTasks();
run_stray_tasks = true;
}
}
if (run_stray_tasks)
{
AsynchronousRunner ar = new ThreadPerTaskAsynchronousRunner( DFLT_MAX_EMERGENCY_THREADS, max_individual_task_time );
for ( Iterator ii = current.iterator(); ii.hasNext(); )
ar.postRunnable( (Runnable) ii.next() );
ar.close( false ); //tell the emergency runner to close itself when its tasks are complete
last = null;
}
else
last = current;
// under some circumstances, these lists seem to hold onto a lot of memory... presumably this
// is when long pending task lists build up for some reason... nevertheless, let's dereference
// things as soon as possible. [Thanks to Venkatesh Seetharamaiah for calling attention to this
// issue, and for documenting the source of object retention.]
current = null;
}
}
//not currently used...
private void runInEmergencyThread( final Runnable r )
{
final Thread t = new Thread( r );
t.start();
if (max_individual_task_time > 0)
{
TimerTask maxIndividualTaskTimeEnforcer = new TimerTask()
{
public void run()
{
if (logger.isLoggable(MLevel.WARNING))
logger.log(MLevel.WARNING,
"Task " + t + " (in one-off task Thread created after deadlock) failed to complete in maximum time " +
max_individual_task_time + " ms. Trying interrupt().");
t.interrupt();
}
};
myTimer.schedule( maxIndividualTaskTimeEnforcer, max_individual_task_time );
}
}
class ReplacedThreadInterruptor extends TimerTask
{
public void run()
{
synchronized (ThreadPoolAsynchronousRunner.this)
{ processReplacedThreads(); }
}
}
}