/* ====================================================================
 * Trove - Copyright (c) 1997-2000 Walt Disney Internet Group
 * ====================================================================
 * The Tea Software License, Version 1.1
 *
 * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Walt Disney Internet Group (http://opensource.go.com/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact opensource@dig.com.
 *
 * 5. Products derived from this software may not be called "Tea",
 *    "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
 *    "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
 *    written permission of the Walt Disney Internet Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * For more information about Tea, please see http://opensource.go.com/.
 */

package com.go.trove.util.tq;

/******************************************************************************
 * Automatically tunes a TransactionQueue by dynamically adjusting the maximum
 * allowed number of worker threads. A TransactionQueueThreadTuner instance
 * should only be added to one TransactionQueue.
 * <p>
 * NOTE: The current implementation of TransactionQueueThreadTuner is
 * experimental and should not be used in production systems.
 * 
 * @author Brian S O'Neill
 * @version
 * <!--$$Revision:--> 5 <!-- $-->, <!--$$JustDate:-->  9/25/00 <!-- $-->
 */
public class TransactionQueueThreadTuner extends TransactionQueueAdapter {
    private long mLastQueueTime;
    private long mLastServiceTime;

    private long mTotalQueueDelta;
    private long mTotalServiceDelta;

    private boolean mBaton;

    public synchronized void transactionDequeued(TransactionQueueEvent e) {
        long queueTime = e.getStageDuration();
        mTotalQueueDelta += queueTime - mLastQueueTime;
        mLastQueueTime = queueTime;

        if (!mBaton) {
            mBaton = true;
            tune(e);
        }
    }

    public synchronized void transactionServiced(TransactionQueueEvent e) {
        long serviceTime = e.getStageDuration();
        mTotalServiceDelta += serviceTime - mLastServiceTime;
        mLastServiceTime = serviceTime;

        if (mBaton) {
            mBaton = false;
            tune(e);
        }
    }

    private void tune(TransactionQueueEvent e) {
        if (mTotalQueueDelta > mTotalServiceDelta) {
            TransactionQueue queue = e.getTransactionQueue();
            int maxThreads = queue.getMaximumThreads();
            if (maxThreads <= queue.getThreadCount() * 2) {
                // Increase the maximum amount of threads.
                queue.setMaximumThreads(maxThreads + 1);
            }
        }
        else if (mTotalServiceDelta > mTotalQueueDelta) {
            TransactionQueue queue = e.getTransactionQueue();
            int maxThreads = queue.getMaximumThreads();
            if (maxThreads > 1) {
                // Decrease the maximum amount of threads.
                queue.setMaximumThreads(maxThreads - 1);
            }
        }
    }
}