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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;
/**
* ClockSynchronizer provides an interface through which two nodes may synchronize their clocks. It is expected that one
* node will act as the reference clock, to which no delta need be applied, and the other node will act as the slave,
* and which must apply a delta to its local clock to get a clock synchronized with the reference.
*
* <p/>The slave side will initiate the computation of a clock delta by calling the {@link #synch} method. This method
* will not return until the delta has been computed, at which point there is a method to return its value, as well as
* an estimate of the likely error (usually one standard deviation), in the synchronization. For convenience there is a
* {@link #nanoTime} method to return the value of System.nanoTime() with the delta added in.
*
* <p/><table id="crc"><caption>CRC Card</caption>
* <tr><th> Responsibilities <th> Collaborations
* <tr><td> Trigger a clock synchronization.
* <tr><td> Compute a clock delta to apply to the local clock.
* <tr><td> Estimate the error in the synchronzation.
* </table>
*/
public interface ClockSynchronizer
{
/**
* The slave side should call this to copute a clock delta with the reference.
*
* @throws ClockSynchFailureException If synchronization cannot be achieved.
*/
public void synch() throws ClockSynchFailureException;
/**
* Gets the clock delta in nano seconds.
*
* @return The clock delta in nano seconds.
*/
public long getDelta();
/**
* Gets an estimate of the clock error in nan seconds.
*
* @return An estimate of the clock error in nan seconds.
*/
public long getEpsilon();
/**
* Gets the local clock time with any computed delta added in.
*
* @return The local clock time with any computed delta added in.
*/
public long nanoTime();
}
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