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/*
*
* Copyright (c) 2006 The Apache Software Foundation
*
* Licensed 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.pool;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* We share the executor service among several PoolingFilters. This class reference counts
* how many filter chains are using the executor service and destroys the service, thus
* freeing up its threads, when the count reaches zero. It recreates the service when
* the count is incremented.
*
* This is particularly important on the client where failing to destroy the executor
* service prevents the JVM from shutting down due to the existence of non-daemon threads.
*
*/
public class ReferenceCountingExecutorService
{
private static final int MINIMUM_POOL_SIZE = 4;
private static final int NUM_CPUS = Runtime.getRuntime().availableProcessors();
private static final int DEFAULT_POOL_SIZE = Math.max(NUM_CPUS, MINIMUM_POOL_SIZE);
/**
* We need to be able to check the current reference count and if necessary
* create the executor service atomically.
*/
private static final ReferenceCountingExecutorService _instance = new ReferenceCountingExecutorService();
private final Object _lock = new Object();
private ExecutorService _pool;
private int _refCount = 0;
private int _poolSize = Integer.getInteger("amqj.read_write_pool_size", DEFAULT_POOL_SIZE);
public static ReferenceCountingExecutorService getInstance()
{
return _instance;
}
private ReferenceCountingExecutorService()
{
}
ExecutorService acquireExecutorService()
{
synchronized (_lock)
{
if (_refCount++ == 0)
{
_pool = Executors.newFixedThreadPool(_poolSize);
}
return _pool;
}
}
void releaseExecutorService()
{
synchronized (_lock)
{
if (--_refCount == 0)
{
_pool.shutdownNow();
}
}
}
/**
* The filters that use the executor service should call this method to get access
* to the service. Note that this method does not alter the reference count.
*
* @return the underlying executor service
*/
public ExecutorService getPool()
{
return _pool;
}
}
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