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/*
* Filename: BoundedPool.java
*
* Copyright 2000-2001 by iPlanet/Sun Microsystems, Inc.,
* 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
* All rights reserved.
*
* This software is the confidential and proprietary information
* of iPlanet/Sun Microsystems, Inc. ("Confidential Information").
* You shall not disclose such Confidential Information and shall
* use it only in accordance with the terms of the license
* agreement you entered into with iPlanet/Sun Microsystems.
*/
/**
* <BR> <I>$Source: /cvs/glassfish/appserv-commons/src/java/com/sun/enterprise/util/pool/SoftObjectPool.java,v $</I>
* @author $Author: tcfujii $
* @version $Revision: 1.5 $ $Date: 2007/05/05 05:32:17 $
*/
package com.sun.enterprise.util.pool;
import java.util.List;
import java.util.Iterator;
import java.util.ArrayList;
import java.util.Collection;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import com.sun.enterprise.util.collection.DList;
import com.sun.enterprise.util.collection.DListNode;
import com.sun.enterprise.util.scheduler.PeriodicallyServicable;
import com.sun.enterprise.util.scheduler.PeriodicEventScheduler;
import com.sun.enterprise.util.ApproximateClock;
import com.sun.enterprise.util.collection.DListNode;
import com.sun.enterprise.util.collection.DListNodeFactory;
import com.sun.enterprise.util.collection.FastStack;
//Bug 4677074 begin
import java.util.logging.Logger;
import java.util.logging.Level;
import com.sun.logging.LogDomains;
//Bug 4677074 end
public class SoftObjectPool
extends com.sun.enterprise.util.pool.AbstractPool
implements PeriodicallyServicable
{
//Bug 4677074 begin
static Logger _logger=LogDomains.getLogger(LogDomains.UTIL_LOGGER);
//Bug 4677074 end
protected DList list;
protected int minSize;
protected int initialSize;
protected int maxLimit;
protected long maxIdleTime;
protected int maxStrongRefs;
protected Boolean isBounded;
/**
* Create an Unbounded pool.
* @param The ObjectFactory to create objects
* @param The minimum number of objects to be held in the pool (initial size)
* @param The initial size of the pool. If this is less than the minSize parameter then this is ignored.
* @param The maximum idle time after which the object may be removed from the pool.
* @param The pool limit (maximum number of objects in the pool).
*/
public SoftObjectPool(ObjectFactory factory, int minSize, int initialSize,
long maxIdleTime, int maxStrongRefs) {
super();
super.factory = factory;
this.minSize = minSize;
this.initialSize = initialSize;
this.maxIdleTime = maxIdleTime;
this.maxStrongRefs = maxStrongRefs;
setMaxLimit(-1);
initPool();
}
/**
* Create a Bounded pool.
* @param The ObjectFactory to create objects
* @param The minimum number of objects to be held in the pool (initial size)
* @param The pool limit (maximum number of objects in the pool).
* @param The maximum idle time after which the object may be removed from the pool.
* @param The initial size of the pool. If this is less than the minSize parameter then this is ignored.
*/
public SoftObjectPool(ObjectFactory factory, int minSize, int initialSize, int maxLimit,
long maxIdleTime, int maxStrongRefs)
{
super();
super.factory = factory;
this.minSize = minSize;
this.maxIdleTime = maxIdleTime;
this.initialSize = initialSize;
this.maxStrongRefs = maxStrongRefs;
setMaxLimit(maxLimit);
initPool();
}
public int getMaxLimit() {
return this.maxLimit;
}
public void setMaxLimit(int limit) {
if ((limit <= 0) || (limit >= Integer.MAX_VALUE-1)) {
this.isBounded = null;
} else {
this.isBounded = Boolean.valueOf(true);
this.maxLimit = limit;
}
}
private void initPool() {
list = new DList();
super.collection = list;
super.preload((minSize < initialSize) ? initialSize : minSize);
scheduler.addTimeRepeatableTask(this, (int) maxIdleTime);
}
/**
* Since this method would be called only if the pool is empty
*/
protected boolean canCreate() {
return (isBounded == null) ? true : (createdCount < maxLimit);
}
/**
* Notification when an object is put back into the pool (checkin).
* @param The object to be returned back to the pool.
* @return Any non null value can be returned to signal that the object
* was indeed added to the pool. This class always adds the object to the
* pool (at the end of the list), it returns non-null value.
* Subclasses can override this behaviour.
*/
protected Object checkin(Object object) {
int size = list.size();
long now = _clock.getTime();
if (size < maxStrongRefs) {
list.addAsLastNode(new TimeStampedSoftDListNode(object, now, object));
} else {
list.addAsLastNode(new TimeStampedSoftDListNode(new SoftReference(object), now, null));
}
return this;
}
private Object obtainObject(Object param) {
SoftReference ref;
Object object = null;
int notifyCount = 0;
for (int size = list.size(); size > 0; size--) {
TimeStampedSoftDListNode tsNode = (TimeStampedSoftDListNode) list.getDListNodeAt(0);
list.delink(tsNode);
if (tsNode.isSoftRef == null) {
ref = (SoftReference) tsNode.object;
if ((object = ref.get()) != null) {
break;
} else {
notifyCount++;
}
} else {
object = tsNode.object;
break;
}
}
if (object == null) {
try {
object = factory.create(param);
afterCreate(object);
} catch (PoolException poolEx) {
}
}
super.createdCount -= notifyCount;
if (notifyCount == 1) {
super.collection.notify();
} else if (notifyCount > 1) {
super.collection.notifyAll();
}
return object;
}
/**
* Notification when an object is given out from the pool (checout).
* @return The object that has to be returned to the application. A null
* value must be returned if no object can be returned to the application. Since this
* class always returns the last node from the list, it returns non-null value.
* Subclasses can override this behaviour.
*/
protected Object checkout(Object param) {
return obtainObject(param);
}
//Methods required for periodically schedulable task
public void prolog() {
}
public void service() {
int killedCount = 0;
long now = _clock.getTime();
long allowed = now - maxIdleTime;
TimeStampedSoftDListNode tsNode = null;
FastStack stack = new FastStack();
synchronized (super.collection) {
Object done = null;
while (done == null) {
tsNode = (TimeStampedSoftDListNode) list.getFirstDListNode();
if (tsNode == null) { //Empty list
done = new Object();
} else if (tsNode.timeStamp <= allowed) {
//Need to destroy the contained object
list.delink(tsNode);
stack.push(tsNode.object);
killedCount++;
} else {
//This node is not old enough
done = new Object();
}
} //End of for loop
super.createdCount -= killedCount;
int deficit = list.size() - minSize;
super.preload(0 - deficit);
if (killedCount == 0) {
} else if (killedCount == 1) {
collection.notify();
} else {
collection.notifyAll();
}
} // end of synchronized
//Now destroy all collected objects
while (! stack.isEmpty()) {
Object object = stack.pop();
beforeDestroy(object);
factory.destroy(object);
}
//Bug 4677074 System.out.println("Leaving service after killing " + killedCount + " (idle) objects. Now size: " + list.size());
//Bug 4677074 begin
_logger.log(Level.FINE,"Leaving service after killing " + killedCount + " (idle) objects. Now size: " + list.size());
//Bug 4677074 end
}
public void epilog() {
}
/**
* Get the frequency (time interval) at which service() method will be invoked.
* @return time in milli seconds.
*/
public long getFrequency() {
return this.maxIdleTime;
}
/**
* Determine to execute the service method of this object even if it has
* missed the right schedule.
*/
public boolean getExecuteIfMissed() {
return true;
}
/**
* Determine to execute the service method of this object when the
* schedule is delayed by 'missedByMillis' milli seconds.
*/
public boolean getExecutionTolerance(long missedByMillis) {
return true;
}
/**
* Print an identification for the object.
*/
public String toString() {
return "";
}
//Some helper classes
class TimeStampedSoftDListNode
extends DListNode
{
long timeStamp;
Object isSoftRef;
public TimeStampedSoftDListNode(Object object, long ts, Object isSoftRef) {
super(object);
this.timeStamp = ts;
this.isSoftRef = isSoftRef;
//Bug 4677074 System.out.println(this + ": created DListNode at: " + ts);
//Bug 4677074 begin
_logger.log(Level.FINE,this + ": created DListNode at: " + ts);
//Bug 4677074 end
}
public String toString() {
return "TSDListNode: " + object + "; isSoftRef: " + isSoftRef;
}
}
}