/*

  * Copyright 2006-2008 The Kuali Foundation

  * 

  * Licensed under the Educational Community License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  * 

  * http://www.opensource.org/licenses/ecl2.php

  * 

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.kuali.rice.krad.util;

 import java.lang.management.ManagementFactory;

 import java.lang.management.MemoryMXBean;

 import java.lang.management.MemoryNotificationInfo;

 import java.lang.management.MemoryPoolMXBean;

 import java.lang.management.MemoryType;

 import java.util.ArrayList;

 import java.util.Collection;

 import javax.management.Notification;

 import javax.management.NotificationEmitter;

 import javax.management.NotificationListener;

 import org.apache.log4j.Logger;

 public class MemoryMonitor {

     private final Collection<Listener> listeners = new ArrayList<Listener>();

     private static final Logger LOG = Logger.getLogger(MemoryMonitor.class);

     private String springContextId;

     public interface Listener {

         public void memoryUsageLow(String springContextId, long usedMemory, long maxMemory);

     }

     public MemoryMonitor() {

         LOG.info("initializing");

         this.springContextId = "Unknown";

         MemoryMXBean mbean = ManagementFactory.getMemoryMXBean();

         NotificationEmitter emitter = (NotificationEmitter) mbean;

         emitter.addNotificationListener(new NotificationListener() {

             public void handleNotification(Notification n, Object hb) {

                 if (n.getType().equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {

                     long maxMemory = tenuredGenPool.getUsage().getMax();

                     long usedMemory = tenuredGenPool.getUsage().getUsed();

                     for (Listener listener : listeners) {

                         listener.memoryUsageLow(springContextId, usedMemory, maxMemory);

                     }

                 }

             }

         }, null, null);

     }

     public MemoryMonitor(String springContextId) {

         this();

         this.springContextId = springContextId;

     }

     public boolean addListener(Listener listener) {

         return listeners.add(listener);

     }

     public boolean removeListener(Listener listener) {

         return listeners.remove(listener);

     }

     private static final MemoryPoolMXBean tenuredGenPool = findTenuredGenPool();

     public static void setPercentageUsageThreshold(double percentage) {

         if (percentage <= 0.0 || percentage > 1.0) {

             throw new IllegalArgumentException("percentage not in range");

         }

         long maxMemory = tenuredGenPool.getUsage().getMax();

         long warningThreshold = (long) (maxMemory * percentage);

         tenuredGenPool.setUsageThreshold(warningThreshold);

     }

     private static MemoryPoolMXBean findTenuredGenPool() {

         for (MemoryPoolMXBean pool : ManagementFactory.getMemoryPoolMXBeans()) {

             if (pool.getType() == MemoryType.HEAP && pool.isUsageThresholdSupported()) {

                 return pool;

             }

         }

         throw new AssertionError("could not find tenured space");

     }

 }