alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

ActiveMQ example source code file (CacheEvictionUsageListener.java)

This example ActiveMQ source code file (CacheEvictionUsageListener.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - ActiveMQ tags/keywords

cacheevictionusagelistener, cacheevictionusagelistener, cacheevictor, copyonwritearraylist, evicting, evictor, interruptedexception, iterator, list, list, logger, task, taskrunnerfactory, threading, threads, usagelistener, util

The ActiveMQ CacheEvictionUsageListener.java source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache 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.apache.org/licenses/LICENSE-2.0
 *
 * 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.apache.activemq.memory;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

import org.apache.activemq.thread.Task;
import org.apache.activemq.thread.TaskRunner;
import org.apache.activemq.thread.TaskRunnerFactory;
import org.apache.activemq.usage.Usage;
import org.apache.activemq.usage.UsageListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class CacheEvictionUsageListener implements UsageListener {

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

    private final List<CacheEvictor> evictors = new CopyOnWriteArrayList();
    private final int usageHighMark;
    private final int usageLowMark;

    private final TaskRunner evictionTask;
    private final Usage usage;

    public CacheEvictionUsageListener(Usage usage, int usageHighMark, int usageLowMark, TaskRunnerFactory taskRunnerFactory) {
        this.usage = usage;
        this.usageHighMark = usageHighMark;
        this.usageLowMark = usageLowMark;
        evictionTask = taskRunnerFactory.createTaskRunner(new Task() {
            public boolean iterate() {
                return evictMessages();
            }
        }, "Cache Evictor: " + System.identityHashCode(this));
    }

    boolean evictMessages() {
        // Try to take the memory usage down below the low mark.
        LOG.debug("Evicting cache memory usage: " + usage.getPercentUsage());

        List<CacheEvictor> list = new LinkedList(evictors);
        while (list.size() > 0 && usage.getPercentUsage() > usageLowMark) {

            // Evenly evict messages from all evictors
            for (Iterator<CacheEvictor> iter = list.iterator(); iter.hasNext();) {
                CacheEvictor evictor = iter.next();
                if (evictor.evictCacheEntry() == null) {
                    iter.remove();
                }
            }
        }
        return false;
    }

    public void onUsageChanged(Usage usage, int oldPercentUsage, int newPercentUsage) {
        // Do we need to start evicting cache entries? Usage > than the
        // high mark
        if (oldPercentUsage < newPercentUsage && usage.getPercentUsage() >= usageHighMark) {
            try {
                evictionTask.wakeup();
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }

    public void add(CacheEvictor evictor) {
        evictors.add(evictor);
    }

    public void remove(CacheEvictor evictor) {
        evictors.remove(evictor);
    }
}

Other ActiveMQ examples (source code examples)

Here is a short list of links related to this ActiveMQ CacheEvictionUsageListener.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.