/*
// $Id: //open/mondrian-release/3.2/src/main/mondrian/util/NotificationMemoryMonitor.java#1 $
// This software is subject to the terms of the Eclipse Public License v1.0
// Agreement, available at the following URL:
// http://www.eclipse.org/legal/epl-v10.html.
// Copyright (C) 2007-2009 Julian Hyde and others
// All Rights Reserved.
// You must accept the terms of that agreement to use this software.
*/
package mondrian.util;
import java.lang.management.MemoryMXBean;
import java.lang.management.MemoryNotificationInfo;
import java.lang.management.MemoryUsage;
import java.lang.management.ManagementFactory;
import java.lang.management.MemoryPoolMXBean;
import java.lang.management.MemoryType;
import javax.management.Notification;
import javax.management.NotificationEmitter;
import javax.management.NotificationListener;
import org.apache.log4j.Logger;
/**
* The <code>NotificationMemoryMonitor</code> class uses the Java5
* memory management system to detect system low memory events.
* <p>
* This code is loosely based on the code taken from The Java
* Specialists' Newsletter,
* <a href="http://www.javaspecialists.co.za/archive/newsletter.do?issue=092"
* >issue 92</a> authored by Dr. Heinz M. Kabutz.
* As a note, his on-line newletters are a good source of Java information,
* take a look.
* <p>
* For more information one should review the Java5 classes in
* java.lang.management.
*
*
* @author <a>Richard M. Emberson</a>
* @since Feb 03 2007
* @version $Id: //open/mondrian-release/3.2/src/main/mondrian/util/NotificationMemoryMonitor.java#1 $
*/
public class NotificationMemoryMonitor extends AbstractMemoryMonitor {
private static final Logger LOGGER =
Logger.getLogger(NotificationMemoryMonitor.class);
protected static final MemoryPoolMXBean TENURED_POOL;
static {
TENURED_POOL = findTenuredGenPool();
}
private static MemoryPoolMXBean findTenuredGenPool() {
for (MemoryPoolMXBean pool : ManagementFactory.getMemoryPoolMXBeans()) {
// I don't know whether this approach is better, or whether
// we should rather check for the pool name "Tenured Gen"?
if (pool.getType() == MemoryType.HEAP
&& pool.isUsageThresholdSupported())
{
return pool;
}
}
throw new AssertionError("Could not find tenured space");
}
/**
* The <code>NotificationHandler</code> implements the Java memory
* notification listener, <code>NotificationListener</code>,
* and is used to take notifications from Java and pass them on
* to the <code>NotificationMemoryMonitor</code>'s
* <code>Listerner</code>s.
*/
private class NotificationHandler implements NotificationListener {
/**
* This method is called by the Java5 code to notify clients
* registered with the JVM that the JVM memory threshold
* has been exceeded.
*
* @param notification
* @param unused
*/
public void handleNotification(
final Notification notification,
final Object unused)
{
final String type = notification.getType();
if (type.equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {
final MemoryUsage usage = TENURED_POOL.getUsage();
notifyListeners(usage.getUsed(), usage.getMax());
}
}
}
/**
* Construct a <code>NotificationMemoryMonitor</code> instance and
* register it with the Java5 memory management system.
*/
NotificationMemoryMonitor() {
super();
final MemoryMXBean mbean = ManagementFactory.getMemoryMXBean();
final NotificationEmitter emitter = (NotificationEmitter) mbean;
// register with the Java5 memory management system.
emitter.addNotificationListener(new NotificationHandler(), null, null);
}
/**
* Get the <code>Logger</code>.
*
* @return the <code>Logger</code>.
*/
protected Logger getLogger() {
return LOGGER;
}
/**
* Notify the Java5 memory management system that there is a new
* low threshold.
*
* @param newLowThreshold the new threshold.
*/
protected void notifyNewLowThreshold(final long newLowThreshold) {
if (newLowThreshold == Long.MAX_VALUE) {
TENURED_POOL.setUsageThreshold(0);
} else {
TENURED_POOL.setUsageThreshold(newLowThreshold);
}
}
/**
* Get the maximum possible memory usage for this JVM instance.
*
* @return maximum memory that can be used.
*/
public long getMaxMemory() {
return TENURED_POOL.getUsage().getMax();
}
/**
* Get the current memory usage for this JVM instance.
*
* @return current memory used.
*/
public long getUsedMemory() {
return TENURED_POOL.getUsage().getUsed();
}
}
// End NotificationMemoryMonitor.java