001 /*
002 // $Id: //open/mondrian/src/main/mondrian/util/NotificationMemoryMonitor.java#5 $
003 // This software is subject to the terms of the Common Public License
004 // Agreement, available at the following URL:
005 // http://www.opensource.org/licenses/cpl.html.
006 // Copyright (C) 2007-2007 Julian Hyde and others
007 // All Rights Reserved.
008 // You must accept the terms of that agreement to use this software.
009 */
010 package mondrian.util;
011
012 import java.lang.management.MemoryMXBean;
013 import java.lang.management.MemoryNotificationInfo;
014 import java.lang.management.MemoryUsage;
015 import java.lang.management.ManagementFactory;
016 import java.lang.management.MemoryPoolMXBean;
017 import java.lang.management.MemoryType;
018 import javax.management.Notification;
019 import javax.management.NotificationEmitter;
020 import javax.management.NotificationListener;
021 import org.apache.log4j.Logger;
022
023 /**
024 * The <code>NotificationMemoryMonitor</code> class uses the Java5
025 * memory management system to detect system low memory events.
026 * <p>
027 * This code is loosely based on the code taken from The Java
028 * Specialists' Newsletter,
029 * <a href="http://www.javaspecialists.co.za/archive/newsletter.do?issue=092"
030 * >issue 92</a> authored by Dr. Heinz M. Kabutz.
031 * As a note, his on-line newletters are a good source of Java information,
032 * take a look.
033 * <p>
034 * For more information one should review the Java5 classes in
035 * java.lang.management.
036 *
037 *
038 * @author <a>Richard M. Emberson</a>
039 * @since Feb 03 2007
040 * @version $Id: //open/mondrian/src/main/mondrian/util/NotificationMemoryMonitor.java#5 $
041 */
042 public class NotificationMemoryMonitor extends AbstractMemoryMonitor {
043 private static final Logger LOGGER =
044 Logger.getLogger(NotificationMemoryMonitor.class);
045
046
047 protected static final MemoryPoolMXBean TENURED_POOL;
048
049 static {
050 TENURED_POOL = findTenuredGenPool();
051 }
052
053 private static MemoryPoolMXBean findTenuredGenPool() {
054 for (MemoryPoolMXBean pool : ManagementFactory.getMemoryPoolMXBeans()) {
055 // I don't know whether this approach is better, or whether
056 // we should rather check for the pool name "Tenured Gen"?
057 if (pool.getType() == MemoryType.HEAP &&
058 pool.isUsageThresholdSupported()) {
059 return pool;
060 }
061 }
062 throw new AssertionError("Could not find tenured space");
063 }
064
065 /**
066 * The <code>NotificationHandler</code> implements the Java memory
067 * notification listener, <code>NotificationListener</code>,
068 * and is used to take notifications from Java and pass them on
069 * to the <code>NotificationMemoryMonitor</code>'s
070 * <code>Listerner</code>s.
071 */
072 private class NotificationHandler implements NotificationListener {
073
074 /**
075 * This method is called by the Java5 code to notify clients
076 * registered with the JVM that the JVM memory threshold
077 * has been exceeded.
078 *
079 * @param notification
080 * @param unused
081 */
082 public void handleNotification(final Notification notification,
083 final Object unused) {
084 final String type = notification.getType();
085
086 if (type.equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {
087 final MemoryUsage usage = TENURED_POOL.getUsage();
088
089 notifyListeners(usage.getUsed(), usage.getMax());
090 }
091 }
092 }
093
094
095 /**
096 * Construct a <code>NotificationMemoryMonitor</code> instance and
097 * register it with the Java5 memory management system.
098 */
099 NotificationMemoryMonitor() {
100 super();
101 final MemoryMXBean mbean = ManagementFactory.getMemoryMXBean();
102 final NotificationEmitter emitter = (NotificationEmitter) mbean;
103
104 // register with the Java5 memory management system.
105 emitter.addNotificationListener(new NotificationHandler(), null, null);
106 }
107
108 /**
109 * Get the <code>Logger</code>.
110 *
111 * @return the <code>Logger</code>.
112 */
113 protected Logger getLogger() {
114 return LOGGER;
115 }
116
117 /**
118 * Notify the Java5 memory management system that there is a new
119 * low threshold.
120 *
121 * @param newLowThreshold the new threshold.
122 */
123 protected void notifyNewLowThreshold(final long newLowThreshold) {
124
125 if (newLowThreshold == Long.MAX_VALUE) {
126 TENURED_POOL.setUsageThreshold(0);
127 } else {
128 TENURED_POOL.setUsageThreshold(newLowThreshold);
129 }
130 }
131
132 /**
133 * Get the maximum possible memory usage for this JVM instance.
134 *
135 * @return maximum memory that can be used.
136 */
137 public long getMaxMemory() {
138 return TENURED_POOL.getUsage().getMax();
139 }
140 /**
141 * Get the current memory usage for this JVM instance.
142 *
143 * @return current memory used.
144 */
145 public long getUsedMemory() {
146 return TENURED_POOL.getUsage().getUsed();
147 }
148 }
149
150 // End NotificationMemoryMonitor.java