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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.junit.extensions;
/**
* Throttle is an interface that supplies a {@link #throttle} method, that can only be called at the rate specified
* in a call to the {@link #setRate} method. This can be used to restict processing to run at a certain number
* of operations per second.
*
* <p/>Throttle also supplies a method to check the throttle rate, without waiting. This could be used to update a user
* interface every time an event occurs, but only up to a maximum rate. For example, as elements are added to a list,
* a count of elements is updated for the user to see, but only up to a maximum rate of ten updates a second, as updating
* faster than that slows the processing of element-by-element additions to the list unnecessarily.
*
* <p/><table id="crc"><caption>CRC Card</caption>
* <tr><th> Responsibilities
* <tr><td> Accept throttling rate in operations per second.
* <tr><td> Inject short pauses to fill-out processing cycles to a specified rate.
* <tr><td> Check against a throttle speed without waiting.
* </table>
*
* @author Rupert Smith
*/
public interface Throttle
{
/**
* Specifies the throttling rate in operations per second. This must be called with with a value, the inverse
* of which is a measurement in nano seconds, such that the number of nano seconds do not overflow a long integer.
* The value must also be larger than zero.
*
* @param hertz The throttling rate in cycles per second.
*/
public void setRate(float hertz);
/**
* This method can only be called at the rate set by the {@link #setRate} method, if it is called faster than this
* it will inject short pauses to restrict the call rate to that rate.
*
* <p/>If the thread executing this method is interrupted, it must ensure that the threads interrupt thread
* remains set upon exit from the method. This method does not expose InterruptedException, to indicate interruption
* of the throttle during a timed wait. It may be changed so that it does.
*/
public void throttle();
/**
* Checks but does not enforce the throttle rate. When this method is called, it checks if a length of time greater
* than that equal to the inverse of the throttling rate has passed since it was last called and returned <tt>true</tt>
*
* @return <tt>true</tt> if a length of time greater than that equal to the inverse of the throttling rate has
* passed since this method was last called and returned <tt>true</tt>, <tt>false</tt> otherwise. The very
* first time this method is called on a throttle, it returns <tt>true</tt> as the base case to the above
* self-referential definition.
*/
public boolean checkThrottle();
}
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