net.timewalker.ffmq4.utils.watchdog.ActivityWatchdog Maven / Gradle / Ivy
/*
* This file is part of FFMQ.
*
* FFMQ 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 of the License, or
* (at your option) any later version.
*
* FFMQ 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 FFMQ; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package net.timewalker.ffmq4.utils.watchdog;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* Daemon thread watching a list of active objects.
*
* The watchdog will wake up every WAKE_UP_INTERVAL milliseconds
* and check the active objects last activity timestamps.
* If an active object has been inactive for too long, its associated
* timeout callback is called.
*
*
* The activity watchdog is a singleton.
*
* @see ActiveObject
*/
public class ActivityWatchdog extends Thread
{
private static final Log log = LogFactory.getLog(ActivityWatchdog.class);
// Singleton instance
private static ActivityWatchdog instance;
/**
* Get the singleton instance
* @return the singleton instance
*/
public static synchronized ActivityWatchdog getInstance()
{
if (instance == null)
{
instance = new ActivityWatchdog();
instance.start();
}
return instance;
}
//-------------------------------------------------------------
// Attributes
private static long WAKE_UP_INTERVAL = 2000;
// Runtime
private List> watchList = new ArrayList<>();
private boolean stop;
/**
* Constructor
*/
private ActivityWatchdog()
{
super("ActivityWatchdog");
setDaemon(true);
setPriority(MIN_PRIORITY);
}
/* (non-Javadoc)
* @see java.lang.Thread#run()
*/
@Override
public synchronized void run()
{
List inactiveList = new ArrayList<>();
try
{
log.debug("Starting activity watchdog (wakeUpInterval="+WAKE_UP_INTERVAL+"ms)");
while (!stop)
{
wait(WAKE_UP_INTERVAL);
if (stop)
return;
// Check watchlist
long now = System.currentTimeMillis();
synchronized (watchList)
{
for (int i = 0; i < watchList.size(); i++)
{
WeakReference weakRef = watchList.get(i);
ActiveObject obj = weakRef.get();
if (obj == null)
{
// Object was garbage collected, remove and continue
watchList.remove(i--);
continue;
}
// Check object activity
if ((now - obj.getLastActivity()) > obj.getTimeoutDelay())
{
log.trace("Marking object as inactive : "+obj);
inactiveList.add(obj);
}
}
}
// Process inactive objects
for (int n = 0; n < inactiveList.size(); n++)
{
ActiveObject obj = inactiveList.get(n);
try
{
if (!obj.onActivityTimeout())
inactiveList.remove(n--);
}
catch (Exception e)
{
log.error("Error notifying an inactive object",e);
}
}
// Remove expired objects
synchronized (watchList)
{
for(int n=0;n weakRef = watchList.get(i);
ActiveObject obj = weakRef.get();
if (obj == targetObj)
{
log.trace("Removing inactive object from watch list : "+targetObj);
watchList.remove(i--);
break;
}
}
}
}
// Clear inactive object list
inactiveList.clear();
}
log.debug("Activity watchdog stopped");
}
catch (Throwable e)
{
log.error("Activity watchdog failed",e);
}
}
/**
* Ask the watchdog thread to stop
*/
public synchronized void pleaseStop()
{
stop = true;
notify();
}
/**
* Register an active object to be monitored
* @param object the object to register
*/
public void register( ActiveObject object )
{
synchronized (watchList)
{
watchList.add(new WeakReference<>(object));
}
}
/**
* Unregister a monitored active object
* @param object the object to unregister
*/
public void unregister( ActiveObject object )
{
synchronized (watchList)
{
for (int i = 0; i < watchList.size(); i++)
{
WeakReference weakRef = watchList.get(i);
ActiveObject obj = weakRef.get();
if (obj == null)
{
// Object was garbage collected, remove and continue
watchList.remove(i--);
continue;
}
if (obj == object)
{
// Found it !
watchList.remove(i);
break;
}
}
}
}
}
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