001    /**
002     * Copyright 2005-2013 The Kuali Foundation
003     *
004     * Licensed under the Educational Community License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.opensource.org/licenses/ecl2.php
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    package org.kuali.rice.krad.util;
017    
018    import java.lang.management.ManagementFactory;
019    import java.lang.management.MemoryMXBean;
020    import java.lang.management.MemoryNotificationInfo;
021    import java.lang.management.MemoryPoolMXBean;
022    import java.lang.management.MemoryType;
023    import java.util.ArrayList;
024    import java.util.Collection;
025    
026    import javax.management.Notification;
027    import javax.management.NotificationEmitter;
028    import javax.management.NotificationListener;
029    
030    import org.apache.log4j.Logger;
031    
032    public class MemoryMonitor {
033        private final Collection<Listener> listeners = new ArrayList<Listener>();
034        private static final Logger LOG = Logger.getLogger(MemoryMonitor.class);
035        private String springContextId;
036    
037        public interface Listener {
038            public void memoryUsageLow(String springContextId, long usedMemory, long maxMemory);
039        }
040    
041        public MemoryMonitor() {
042            LOG.info("initializing");
043            this.springContextId = "Unknown";
044            MemoryMXBean mbean = ManagementFactory.getMemoryMXBean();
045            NotificationEmitter emitter = (NotificationEmitter) mbean;
046            emitter.addNotificationListener(new NotificationListener() {
047                public void handleNotification(Notification n, Object hb) {
048                    if (n.getType().equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {
049                        long maxMemory = tenuredGenPool.getUsage().getMax();
050                        long usedMemory = tenuredGenPool.getUsage().getUsed();
051                        for (Listener listener : listeners) {
052                            listener.memoryUsageLow(springContextId, usedMemory, maxMemory);
053                        }
054                    }
055                }
056            }, null, null);
057        }
058    
059        public MemoryMonitor(String springContextId) {
060            this();
061            this.springContextId = springContextId;
062        }
063    
064        public boolean addListener(Listener listener) {
065            return listeners.add(listener);
066        }
067    
068        public boolean removeListener(Listener listener) {
069            return listeners.remove(listener);
070        }
071    
072        private static final MemoryPoolMXBean tenuredGenPool = findTenuredGenPool();
073    
074        public static void setPercentageUsageThreshold(double percentage) {
075            if (percentage <= 0.0 || percentage > 1.0) {
076                throw new IllegalArgumentException("percentage not in range");
077            }
078            long maxMemory = tenuredGenPool.getUsage().getMax();
079            long warningThreshold = (long) (maxMemory * percentage);
080            tenuredGenPool.setUsageThreshold(warningThreshold);
081        }
082    
083        private static MemoryPoolMXBean findTenuredGenPool() {
084            for (MemoryPoolMXBean pool : ManagementFactory.getMemoryPoolMXBeans()) {
085                if (pool.getType() == MemoryType.HEAP && pool.isUsageThresholdSupported()) {
086                    return pool;
087                }
088            }
089            throw new AssertionError("could not find tenured space");
090        }
091    }