ActiveMQ example source code file (Usage.java)

This example ActiveMQ source code file (Usage.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

interruptedexception, iterator, list, object, runnable, runnable, string, string, t, t, threading, threadpoolexecutor, threads, usage, usage, usagecapacity, util

The ActiveMQ Usage.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.usage;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.activemq.Service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Used to keep track of how much of something is being used so that a
 * productive working set usage can be controlled. Main use case is manage
 * memory usage.
 * 
 * @org.apache.xbean.XBean
 * 
 */
public abstract class Usage<T extends Usage> implements Service {

    private static final Logger LOG = LoggerFactory.getLogger(Usage.class);
    protected final Object usageMutex = new Object();
    protected int percentUsage;
    protected T parent;
    private UsageCapacity limiter = new DefaultUsageCapacity();
    private int percentUsageMinDelta = 1;
    private final List<UsageListener> listeners = new CopyOnWriteArrayList();
    private final boolean debug = LOG.isDebugEnabled();
    private String name;
    private float usagePortion = 1.0f;
    private final List<T> children = new CopyOnWriteArrayList();
    private final List<Runnable> callbacks = new LinkedList();
    private int pollingTime = 100;
    private final AtomicBoolean started=new AtomicBoolean();
    private ThreadPoolExecutor executor;
    public Usage(T parent, String name, float portion) {
        this.parent = parent;
        this.usagePortion = portion;
        if (parent != null) {
            this.limiter.setLimit((long)(parent.getLimit() * portion));
            name = parent.name + ":" + name;
        }
        this.name = name;
    }

    protected abstract long retrieveUsage();

    /**
     * @throws InterruptedException
     */
    public void waitForSpace() throws InterruptedException {
        waitForSpace(0);
    }

    public boolean waitForSpace(long timeout) throws InterruptedException {
        return waitForSpace(timeout, 100);
    }
    
    /**
     * @param timeout
     * @throws InterruptedException
     * @return true if space
     */
    public boolean waitForSpace(long timeout, int highWaterMark) throws InterruptedException {
        if (parent != null) {
            if (!parent.waitForSpace(timeout, highWaterMark)) {
                return false;
            }
        }
        synchronized (usageMutex) {
            percentUsage=caclPercentUsage();
            if (percentUsage >= highWaterMark) {
                long deadline = timeout > 0 ? System.currentTimeMillis() + timeout : Long.MAX_VALUE;
                long timeleft = deadline;
                while (timeleft > 0) {
                    percentUsage=caclPercentUsage();
                    if (percentUsage >= highWaterMark) {
                        usageMutex.wait(pollingTime);
                        timeleft = deadline - System.currentTimeMillis();
                    } else {
                        break;
                    }
                }
            }
            return percentUsage < highWaterMark;
        }
    }

    public boolean isFull() {
        return isFull(100);
    }
    
    public boolean isFull(int highWaterMark) {
        if (parent != null && parent.isFull(highWaterMark)) {
            return true;
        }
        synchronized (usageMutex) {
            percentUsage=caclPercentUsage();
            return percentUsage >= highWaterMark;
        }
    }

    public void addUsageListener(UsageListener listener) {
        listeners.add(listener);
    }

    public void removeUsageListener(UsageListener listener) {
        listeners.remove(listener);
    }

    public long getLimit() {
        synchronized (usageMutex) {
            return limiter.getLimit();
        }
    }

    /**
     * Sets the memory limit in bytes. Setting the limit in bytes will set the
     * usagePortion to 0 since the UsageManager is not going to be portion based
     * off the parent.
     * When set using Xbean, values of the form "20 Mb", "1024kb", and "1g" can be used
     * 
     * @org.apache.xbean.Property propertyEditor="org.apache.activemq.util.MemoryPropertyEditor"
     */
    public void setLimit(long limit) {
        if (percentUsageMinDelta < 0) {
            throw new IllegalArgumentException("percentUsageMinDelta must be greater or equal to 0");
        }
        synchronized (usageMutex) {
            this.limiter.setLimit(limit);
            this.usagePortion = 0;
        }
        onLimitChange();
    }

    protected void onLimitChange() {
        // We may need to calculate the limit
        if (usagePortion > 0 && parent != null) {
            synchronized (usageMutex) {
                this.limiter.setLimit((long)(parent.getLimit() * usagePortion));
            }
        }
        // Reset the percent currently being used.
        int percentUsage;
        synchronized (usageMutex) {
            percentUsage = caclPercentUsage();
        }
        setPercentUsage(percentUsage);
        // Let the children know that the limit has changed. They may need to
        // set
        // their limits based on ours.
        for (T child : children) {
            child.onLimitChange();
        }
    }

    public float getUsagePortion() {
        synchronized (usageMutex) {
            return usagePortion;
        }
    }

    public void setUsagePortion(float usagePortion) {
        synchronized (usageMutex) {
            this.usagePortion = usagePortion;
        }
        onLimitChange();
    }

    public int getPercentUsage() {
        synchronized (usageMutex) {
            return percentUsage;
        }
    }

    public int getPercentUsageMinDelta() {
        synchronized (usageMutex) {
            return percentUsageMinDelta;
        }
    }

    /**
     * Sets the minimum number of percentage points the usage has to change
     * before a UsageListener event is fired by the manager.
     * 
     * @param percentUsageMinDelta
     * @org.apache.xbean.Property propertyEditor="org.apache.activemq.util.MemoryPropertyEditor"
     */
    public void setPercentUsageMinDelta(int percentUsageMinDelta) {
        if (percentUsageMinDelta < 1) {
            throw new IllegalArgumentException("percentUsageMinDelta must be greater than 0");
        }
        int percentUsage;
        synchronized (usageMutex) {
            this.percentUsageMinDelta = percentUsageMinDelta;
            percentUsage = caclPercentUsage();
        }
        setPercentUsage(percentUsage);
    }

    public long getUsage() {
        synchronized (usageMutex) {
            return retrieveUsage();
        }
    }

    protected void setPercentUsage(int value) {
        synchronized (usageMutex) {
            int oldValue = percentUsage;
            percentUsage = value;
            if (oldValue != value) {
                fireEvent(oldValue, value);
            }
        }
    }

    protected int caclPercentUsage() {
        if (limiter.getLimit() == 0) {
            return 0;
        }
        return (int)((((retrieveUsage() * 100) / limiter.getLimit()) / percentUsageMinDelta) * percentUsageMinDelta);
    }

    private void fireEvent(final int oldPercentUsage, final int newPercentUsage) {
        if (debug) {
            LOG.debug(getName() + ": usage change from: " + oldPercentUsage + "% of available memory, to: " 
                + newPercentUsage + "% of available memory");
        }   
        if (started.get()) {
            // Switching from being full to not being full..
            if (oldPercentUsage >= 100 && newPercentUsage < 100) {
                synchronized (usageMutex) {
                    usageMutex.notifyAll();
                    if (!callbacks.isEmpty()) {
                        for (Iterator<Runnable> iter = new ArrayList(callbacks).iterator(); iter.hasNext();) {
                            Runnable callback = iter.next();
                            getExecutor().execute(callback);
                        }
                        callbacks.clear();
                    }
                }
            }
            if (!listeners.isEmpty()) {
                // Let the listeners know on a separate thread
                Runnable listenerNotifier = new Runnable() {
                    public void run() {
                        for (Iterator<UsageListener> iter = listeners.iterator(); iter.hasNext();) {
                            UsageListener l = iter.next();
                            l.onUsageChanged(Usage.this, oldPercentUsage, newPercentUsage);
                        }
                    }
                };
                if (started.get()) {
                    getExecutor().execute(listenerNotifier);
                } else {
                    LOG.warn("Not notifying memory usage change to listeners on shutdown");
                }
            }
        }
    }

    public String getName() {
        return name;
    }

    @Override
    public String toString() {
        return "Usage(" + getName() + ") percentUsage=" + percentUsage + "%, usage=" + retrieveUsage() + " limit=" + limiter.getLimit() + " percentUsageMinDelta=" + percentUsageMinDelta + "%";
    }

    @SuppressWarnings("unchecked")
    public void start() {
        if (started.compareAndSet(false, true)){
            if (parent != null) {
                parent.addChild(this);
            }
            for (T t:children) {
                t.start();
            }
        }
    }

    @SuppressWarnings("unchecked")
    public void stop() {
        if (started.compareAndSet(true, false)){
            if (parent != null) {
                parent.removeChild(this);
            }
            
            //clear down any callbacks
            synchronized (usageMutex) {
                usageMutex.notifyAll();
                for (Iterator<Runnable> iter = new ArrayList(this.callbacks).iterator(); iter.hasNext();) {
                    Runnable callback = iter.next();
                    callback.run();
                }
                this.callbacks.clear();
            }
            for (T t:children) {
                t.stop();
            }
        }
    }

    private void addChild(T child) {
        children.add(child);
        if (started.get()) {
            child.start();
        }
    }

    private void removeChild(T child) {
        children.remove(child);
    }

    /**
     * @param callback
     * @return true if the UsageManager was full. The callback will only be
     *         called if this method returns true.
     */
    public boolean notifyCallbackWhenNotFull(final Runnable callback) {
        if (parent != null) {
            Runnable r = new Runnable() {

                public void run() {
                    synchronized (usageMutex) {
                        if (percentUsage >= 100) {
                            callbacks.add(callback);
                        } else {
                            callback.run();
                        }
                    }
                }
            };
            if (parent.notifyCallbackWhenNotFull(r)) {
                return true;
            }
        }
        synchronized (usageMutex) {
            if (percentUsage >= 100) {
                callbacks.add(callback);
                return true;
            } else {
                return false;
            }
        }
    }

    /**
     * @return the limiter
     */
    public UsageCapacity getLimiter() {
        return this.limiter;
    }

    /**
     * @param limiter the limiter to set
     */
    public void setLimiter(UsageCapacity limiter) {
        this.limiter = limiter;
    }

    /**
     * @return the pollingTime
     */
    public int getPollingTime() {
        return this.pollingTime;
    }

    /**
     * @param pollingTime the pollingTime to set
     */
    public void setPollingTime(int pollingTime) {
        this.pollingTime = pollingTime;
    }

    public void setName(String name) {
        this.name = name;
    }

    public T getParent() {
        return parent;
    }

    public void setParent(T parent) {
        this.parent = parent;
    }
    
    public void setExecutor (ThreadPoolExecutor executor) {
        this.executor = executor;
    }
    public ThreadPoolExecutor getExecutor() {
        return executor;
    }
}