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Java > Open Source Codes > org > apache > activemq > memory > CacheEvictionUsageListener


1 /**
2  *
3  * Licensed to the Apache Software Foundation (ASF) under one or more
4  * contributor license agreements. See the NOTICE file distributed with
5  * this work for additional information regarding copyright ownership.
6  * The ASF licenses this file to You under the Apache License, Version 2.0
7  * (the "License"); you may not use this file except in compliance with
8  * the License. You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18 package org.apache.activemq.memory;
19
20 import java.util.Iterator JavaDoc;
21 import java.util.LinkedList JavaDoc;
22
23 import org.apache.activemq.thread.Task;
24 import org.apache.activemq.thread.TaskRunner;
25 import org.apache.activemq.thread.TaskRunnerFactory;
26 import org.apache.commons.logging.Log;
27 import org.apache.commons.logging.LogFactory;
28
29 import java.util.concurrent.CopyOnWriteArrayList JavaDoc;
30
31 public class CacheEvictionUsageListener implements UsageListener {
32     
33     private final static Log log = LogFactory.getLog(CacheEvictionUsageListener.class);
34     
35     private final CopyOnWriteArrayList JavaDoc evictors = new CopyOnWriteArrayList JavaDoc();
36     private final int usageHighMark;
37     private final int usageLowMark;
38
39     private final TaskRunner evictionTask;
40     private final UsageManager usageManager;
41     
42     public CacheEvictionUsageListener(UsageManager usageManager, int usageHighMark, int usageLowMark, TaskRunnerFactory taskRunnerFactory) {
43         this.usageManager = usageManager;
44         this.usageHighMark = usageHighMark;
45         this.usageLowMark = usageLowMark;
46         evictionTask = taskRunnerFactory.createTaskRunner(new Task(){
47             public boolean iterate() {
48                 return evictMessages();
49             }
50         }, "Cache Evictor: "+System.identityHashCode(this));
51     }
52     
53     private boolean evictMessages() {
54         // Try to take the memory usage down below the low mark.
55 try {
56             log.debug("Evicting cache memory usage: "+usageManager.getPercentUsage());
57             
58             LinkedList JavaDoc list = new LinkedList JavaDoc(evictors);
59             while (list.size()>0 && usageManager.getPercentUsage() > usageLowMark) {
60                 
61                 // Evenly evict messages from all evictors
62 for (Iterator JavaDoc iter = list.iterator(); iter.hasNext();) {
63                     CacheEvictor evictor = (CacheEvictor) iter.next();
64                     if( evictor.evictCacheEntry() == null )
65                         iter.remove();
66                 }
67             }
68         } finally {
69         }
70         return false;
71     }
72     
73     public void onMemoryUseChanged(UsageManager memoryManager, int oldPercentUsage, int newPercentUsage) {
74         // Do we need to start evicting cache entries? Usage > than the
75 // high mark
76 if (oldPercentUsage < newPercentUsage && memoryManager.getPercentUsage() >= usageHighMark) {
77             try {
78                 evictionTask.wakeup();
79             } catch (InterruptedException JavaDoc e) {
80                 Thread.currentThread().interrupt();
81             }
82         }
83     }
84     
85     public void add(CacheEvictor evictor) {
86         evictors.add(evictor);
87     }
88     
89     public void remove(CacheEvictor evictor) {
90         evictors.remove(evictor);
91     }
92 }
93
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