exponentialbackoffscheduledmessage.java

pastry的java实现的2.0b版

/*************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

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- Redistributions in binary form must reproduce the above copyright
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- Neither  the name  of Rice  University (RICE) nor  the names  of its
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This software is provided by RICE and the contributors on an "as is"
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********************************************************************************/
/*
 *  Created on May 6, 2004
 *
 *  To change the template for this generated file go to
 *  Window>Preferences>Java>Code Generation>Code and Comments
 */
package rice.pastry;

import rice.pastry.messaging.Message;
import rice.selector.Timer;
import rice.selector.TimerTask;

/**
 * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
 * @author jeffh To change the template for this generated type comment go to
 *      Window>Preferences>Java>Code Generation>Code and Comments
 */
public class ExponentialBackoffScheduledMessage extends ScheduledMessage {
  boolean cancelled = false;
  EBTimerTask myTask;
  Timer timer;
  long initialPeriod;
  double expBase;
  int numTimes = 0;
  long lastTime = 0;

  /**
   * @param node
   * @param msg
   * @param initialPeriod
   * @param expBase
   * @param timer DESCRIBE THE PARAMETER
   * @param delay DESCRIBE THE PARAMETER
   */
  public ExponentialBackoffScheduledMessage(PastryNode node, Message msg, Timer timer, long delay, long initialPeriod, double expBase) {
    super(node, msg);
    this.timer = timer;
    this.initialPeriod = initialPeriod;
    this.expBase = expBase;
    schedule(delay);
  }

  /**
   * Constructor for ExponentialBackoffScheduledMessage.
   *
   * @param node DESCRIBE THE PARAMETER
   * @param msg DESCRIBE THE PARAMETER
   * @param timer DESCRIBE THE PARAMETER
   * @param initialDelay DESCRIBE THE PARAMETER
   * @param expBase DESCRIBE THE PARAMETER
   */
  public ExponentialBackoffScheduledMessage(PastryNode node, Message msg, Timer timer, long initialDelay, double expBase) {
    super(node, msg);
    this.timer = timer;
    this.initialPeriod = initialDelay;
    this.expBase = expBase;
    schedule(initialDelay);
    numTimes = 1;
  }


  /**
   * DESCRIBE THE METHOD
   *
   * @param time DESCRIBE THE PARAMETER
   */
  private void schedule(long time) {
    myTask = new EBTimerTask();
    timer.schedule(myTask, time);
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @return DESCRIBE THE RETURN VALUE
   */
  public boolean cancel() {
    super.cancel();
    if (myTask != null) {
      myTask.cancel();
      myTask = null;
    }
    boolean temp = cancelled;
    cancelled = true;
    return temp;
  }

  /**
   * Main processing method for the ExponentialBackoffScheduledMessage object
   */
  public void run() {
    if (!cancelled) {
      if (myTask != null) {
        lastTime = myTask.scheduledExecutionTime();
      }
      super.run();
      long time = (long) (initialPeriod * Math.pow(expBase, numTimes));
      schedule(time);
      numTimes++;
    }
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @return DESCRIBE THE RETURN VALUE
   */
  public long scheduledExecutionTime() {
    return lastTime;
  }

  /**
   * DESCRIBE THE CLASS
   *
   * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
   * @author jeffh
   */
  class EBTimerTask extends TimerTask {
    /**
     * Main processing method for the EBTimerTask object
     */
    public void run() {
      ExponentialBackoffScheduledMessage.this.run();
    }
  }
}