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//
// Copyright 2001 iPlanet/ Sun Microsystems, Inc. All Rights Reserved.
//
// Author : darpan
// Module : Utils
//
package com.sun.enterprise.util.scheduler;
import com.sun.enterprise.util.ApproximateClock;
//Bug 4677074 begin
import java.util.logging.Logger;
import java.util.logging.Level;
import com.sun.logging.LogDomains;
//Bug 4677074 end
/**
* PeriodicEventScheduler manages tasks of the type PeriodicallyServicable. Such
* objects can be added to the manager and the time interval in these objects
* defines at what frequency the service() method of these tasks gets invoked by
* the manager.<br>
* It is critical that the service() operation be as brisk as possible for the
* manager to work effectively.<br>
* PeriodicEventScheduler is internally set as daemon.
* <BR> <I>$Source: /cvs/glassfish/appserv-commons/src/java/com/sun/enterprise/util/scheduler/PeriodicEventScheduler.java,v $</I>
* @author $Author: tcfujii $
* @version 1.0 $Revision: 1.4 $ $Date: 2007/05/05 05:32:17 $
* @see PeriodicallyServicable
*/
public class PeriodicEventScheduler
implements Runnable
{
//Bug 4677074 begin
static Logger _logger=LogDomains.getLogger(LogDomains.UTIL_LOGGER);
//Bug 4677074 end
// TODO: What the scheduler can also do, is to put these tasks at the top of
// the worker thread pool task queue, instead of executing the task on itself.
/** Internal Thread holder */
protected Thread _thread;
/** Scheduler instance holder */
private static PeriodicEventScheduler _instance = null;
/** Instance lock */
private static Object instanceLock = new Object();
/** Sorted task list */
protected TimedTaskList sortedList;
/** Thread runs while bRun is true (unless shutdown) */
protected boolean bRun;
/** Debug flag */
protected boolean bDebug=false;
/** Current time holder */
protected transient long counter=0;
/** Delay for time approximation */
protected long delay_time_approx = 100;
/** Approximate clock holder */
protected ApproximateClock clock = null;
static
{
_instance = new PeriodicEventScheduler();
}
/**
* Method to access the PeriodicEventScheduler singleton.
* @return singleton object.
*/
public static PeriodicEventScheduler getInstance()
{
return _instance;
}
/**
* Constructor invoked once for the singleton.
*/
private PeriodicEventScheduler()
{
super();
bRun = true;
sortedList = new TimedTaskList();
clock = new ApproximateClock (delay_time_approx);
counter = getTime();
_thread = new Thread (this, "PeriodicEventScheduler");
_thread.setDaemon(true);
_thread.start();
}
/**
* Get approximate or actual time.
* @return long current time.
*/
private long getTime()
{
return clock.getActualTime(); // TODO : change actual time to perhaps approx time
}
/**
* Add a PeriodicallyServicable object to the 'timed task execution queue'.
* @param seconds time in seconds after which the task will be invoked for
* the first time. <I>Do not confuse with the frequency period which is given
* by the getTimeIntervalForService() method on this object.</I>
* @param obj object that has to be serviced in timed interval fashion.
* @param startingTime start calling service() method in startingTime + frequency time.
* @return boolean true on success, false otherwise
*/
public synchronized boolean addTimeRepeatableTask(PeriodicallyServicable obj, int startingTime)
{
if(startingTime < 0 || obj.getFrequency() < 1)
{
//Bug 4677074 if(bDebug) System.out.println("PeriodicEventScheduler::addTimeRepeatableTask() rejected task" + obj.toString());
//Bug 4677074 begin
if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"PeriodicEventScheduler::addTimeRepeatableTask() rejected task" + obj.toString());
//Bug 4677074 end
return false;
}
boolean bool = sortedList.addTask(obj, startingTime, counter);
synchronized(instanceLock)
{
instanceLock.notify();
}
return bool;
}
/**
* Remove the servicable object from the task list.
* @param obj PeriodicallyServicable object to be removed from the task list.
* @return boolean true on success, false otherwise
*/
public synchronized boolean removeTimeRepeatableTask(PeriodicallyServicable obj)
{
if(executingTask.equals(obj))
{
removeExecutingTask=true;
return true;
}
else
return sortedList.removeTask(obj);
}
/**
* Insert the task object into the task list.
* @param taskObj task object to insert.
* @return boolean true on success, false otherwise
*/
protected synchronized boolean insertSorted(TaskData taskObj)
{
return sortedList.insertTask(taskObj);
}
/** Maintained by the run() method */
private PeriodicallyServicable executingTask=null;
/** On remove, a check is made if the executingTask is the one to be removed. This is the flag set. */
private boolean removeExecutingTask=false;
/**
* Start running the thread.
*/
public void run()
{
TaskData task=null;
while(bRun)
{
try
{
//if(bDebug) System.out.println("---run()" + sortedList.toString() + "---");
//Bug 4677074 begin
//if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"---run()" + sortedList.toString() + "---");
//Bug 4677074 end
task = sortedList.getFirstTask();
//if(bDebug) System.out.println("---run()" + sortedList.toString() + "+++");
//Bug 4677074 begin
//if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"---run()" + sortedList.toString() + "+++");
//Bug 4677074 end
if(null==task)
{
synchronized(instanceLock)
{
instanceLock.wait();
continue; // fetches a task
}
}
executingTask=task.obj;
// got the first task
counter = getTime();
long sleepingTime = task.abs_execute_time - counter;
if(sleepingTime > 0L)
{
try
{
//Bug 4677074 if(bDebug) System.out.println("Current time=" + (int)(counter/1000) + ", Sleeping for " + sleepingTime + " msec.");
//Bug 4677074 begin
if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"Current time=" + (int)(counter/1000) + ", Sleeping for " + sleepingTime + " msec.");
//Bug 4677074 end
Thread.sleep( sleepingTime );
}
catch(InterruptedException ieInner)
{
//Bug 4677074 if(bDebug) System.out.println("PeriodicEventScheduler::run() > " + ieInner);
//Bug 4677074 begin
if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"PeriodicEventScheduler::run() > " + ieInner);
//Bug 4677074 end
}
}else
{
// a decision has to be made immediately if we want to execute
// the task even if we missed the right time to execute it
if (!task.obj.getExecutionTolerance(Math.abs(sleepingTime)) )
{
//Bug 4677074 if(bDebug) System.out.println("Missed scheduling for " + task.obj.toString());
//Bug 4677074 begin
if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"Missed scheduling for " + task.obj.toString());
//Bug 4677074 end
continue;
} else
{
//Bug 4677074 if(bDebug) System.out.println("Executing after missing scheduling for " + task.obj.toString());
//Bug 4677074 begin
if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"Executing after missing scheduling for " + task.obj.toString());
//Bug 4677074 end
}
}
// now we can execute this task in multiple ways, one is on this thread,
// other is on other task queues (by putting this task on the front of the Q)
task.obj.service();
}catch(InterruptedException ieOuter)
{
//Bug 4677074 if(bDebug) System.out.println("PeriodicEventScheduler::run() > " + ieOuter);
//Bug 4677074 begin
if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"PeriodicEventScheduler::run() > " + ieOuter);
//Bug 4677074 end
}
catch(Exception e)
{
System.out.println("PeriodicEventScheduler::run() > " + e);
//Bug 4677074 begin
_logger.log(Level.WARNING,"iplanet_util.generic_exception",e);
//Bug 4677074 end
}
finally
{
if (null!=task)
{
counter = getTime();
// now put this task back into the Q
task.abs_execute_time = counter;
//if(bDebug) System.out.println("Adding in list " + task.obj.toString());
//Bug 4677074 begin
//if(com.sun.enterprise.util.logging.Debug.enabled) _logger.log(Level.FINE,"Adding in list " + task.obj.toString());
//Bug 4677074 end
if(!removeExecutingTask)
insertSorted(task);
else
removeExecutingTask=false;
executingTask=null;
}
}
} // while
}
public String toString()
{
return "[PeriodicEventScheduler: " + sortedList.toString() + "]";
}
}
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