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/*
*
* 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.qpid.test.framework.clocksynch;
import org.apache.log4j.Logger;
import org.apache.qpid.junit.extensions.ShutdownHookable;
import org.apache.qpid.junit.extensions.Throttle;
/**
* ClockSynchThread is a convenient utility for running a thread that periodically synchronizes the clock against
* a reference. Supply it with a {@link ClockSynchronizer} and a {@link Throttle} and it will continually keep the
* clock up-to-date at a rate determined by the throttle.
*
* <p/><table id="crc"><caption>CRC Card</caption>
* <tr><th> Responsibilities <th> Collaborations
* <tr><td> Continually sychronize the clock at a throttled rate.
* </table>
*/
public class ClockSynchThread extends Thread implements ShutdownHookable
{
/** Used for debugging. */
private static final Logger log = Logger.getLogger(ClockSynchThread.class);
/** Holds the clock syncher for the synch thread. */
private ClockSynchronizer clockSyncher;
/** Holds the throttle to limit the synch rate. */
private Throttle throttle;
/** Flag to indicate that the periodic clock syncher should keep running. */
boolean doSynch = true;
/**
* Creates a clock synchronizer thread from a clock synchronizer and a throttle.
*
* @param syncher The clock synchronizer.
* @param throttle The throttle.
*/
public ClockSynchThread(ClockSynchronizer syncher, Throttle throttle)
{
this.clockSyncher = syncher;
this.throttle = throttle;
}
/**
* Terminates the synchronization thread.
*/
public void terminate()
{
doSynch = false;
}
/**
* Continually updates the clock, until {@link #terminate()} is called.
*/
public void run()
{
while (doSynch)
{
// Perform a clock clockSynch.
try
{
// Wait controlled by the throttle before doing the next synch.
throttle.throttle();
clockSyncher.synch();
log.debug("Clock synched, delta = " + clockSyncher.getDelta() + ", epsilon = " + clockSyncher.getEpsilon()
+ ".");
}
// Terminate the synch thread if the synchronization cannot be achieved.
catch (ClockSynchFailureException e)
{
log.debug("Cannot synchronize the clock (reference service may be down). Terminating the synch thread.");
doSynch = false;
}
}
}
/**
* Gets the clock synchronizer that is kept continually up to date.
*
* @return The clock synchronizer that is kept continually up to date.
*/
public ClockSynchronizer getClockSyncher()
{
return clockSyncher;
}
/**
* Supplies a shutdown hook, that terminates the synching thread.
*
* @return The shut down hook.
*/
public Thread getShutdownHook()
{
return new Thread(new Runnable()
{
public void run()
{
doSynch = false;
}
});
}
}
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