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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.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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