org.apache.activemq.artemis.utils.ReusableLatch Maven / Gradle / Ivy
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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.activemq.artemis.utils;
/**
* This class will use the framework provided to by AbstractQueuedSynchronizer.
* AbstractQueuedSynchronizer is the framework for any sort of concurrent synchronization, such as Semaphores, events, etc, based on AtomicIntegers.
*
* This class works just like CountDownLatch, with the difference you can also increase the counter
*
* It could be used for sync points when one process is feeding the latch while another will wait when everything is done. (e.g. waiting IO completions to finish)
*
* On ActiveMQ Artemis we have the requirement of increment and decrement a counter until the user fires a ready event (commit). At that point we just act as a regular countDown.
*
* Note: This latch is reusable. Once it reaches zero, you can call up again, and reuse it on further waits.
*
* For example: prepareTransaction will wait for the current completions, and further adds will be called on the latch. Later on when commit is called you can reuse the same latch.
*/
public class ReusableLatch extends AbstractLatch {
public ReusableLatch() {
super();
}
public ReusableLatch(int count) {
super(count);
}
@Override
public void countDown() {
control.releaseShared(1);
}
@Override
public void countDown(final int count) {
control.releaseShared(count);
}
}