/**
* 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.ambari.server.controller.utilities;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
/**
* An {@link ExecutorService} that executes each submitted task using one of
* possibly several pooled threads. It also scales up the number of threads in
* the pool if the number of submissions exceeds the core size of the pool. The
* pool can scale up to the specified maximum pool size.
*
* If the number of submissions exceeds the sum of the core and maximum size of
* the thread pool, the submissions are then handled by the provided
* {@link RejectedExecutionHandler}.
*
* If the overflowing submissions need to be handled,
* {@link BufferedThreadPoolExecutorCompletionService} can be used to buffer up
* overflowing submissions for later submission as threads become available.
*
* @see BufferedThreadPoolExecutorCompletionService
*/
public class ScalingThreadPoolExecutor extends ThreadPoolExecutor {
/**
* Constructor.
*
* @param corePoolSize
* the number of threads which will be considered as "core". If core
* thread timeout is not enabled, then this will be the minimum
* number of threads, always. With core timeout enabled, then this
* will be the number of threads spun up to handle incoming work
* regardless of worker queue size.
* @param maximumPoolSize
* the maximum number of threads which can be spawned when an
* {@link ExecutorService} encounters a failure inserting into the
* work queue. These threads are not spawned to handle entries into
* the work queue; they are only spawned if the queue fills and a
* {@link RejectedExecutionHandler} is invoked.
* @param keepAliveTime
* the TTL for core threads
* @param unit
* the time unit for core threads
* @param workerQueueSize
* the size of the worker queue. The threads specified by
* {@link #getMaximumPoolSize()} will only be created if the worker
* queue is exhausted.
*/
public ScalingThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime,
TimeUnit unit, int workerQueueSize) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, new LinkedBlockingQueue<Runnable>(workerQueueSize));
}
}