| 1 | /** |
| 2 | * Licensed to jclouds, Inc. (jclouds) under one or more |
| 3 | * contributor license agreements. See the NOTICE file |
| 4 | * distributed with this work for additional information |
| 5 | * regarding copyright ownership. jclouds licenses this file |
| 6 | * to you under the Apache License, Version 2.0 (the |
| 7 | * "License"); you may not use this file except in compliance |
| 8 | * with the License. You may obtain a copy of the License at |
| 9 | * |
| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | * |
| 12 | * Unless required by applicable law or agreed to in writing, |
| 13 | * software distributed under the License is distributed on an |
| 14 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| 15 | * KIND, either express or implied. See the License for the |
| 16 | * specific language governing permissions and limitations |
| 17 | * under the License. |
| 18 | */ |
| 19 | package org.jclouds.concurrent; |
| 20 | |
| 21 | import java.util.concurrent.ExecutorService; |
| 22 | import java.util.concurrent.Executors; |
| 23 | import java.util.concurrent.RejectedExecutionException; |
| 24 | import java.util.concurrent.ThreadFactory; |
| 25 | import java.util.concurrent.ThreadPoolExecutor; |
| 26 | import java.util.concurrent.TimeUnit; |
| 27 | |
| 28 | /** |
| 29 | * Factory and utility methods for handling {@link DynamicThreadPoolExecutor}. |
| 30 | * |
| 31 | * @author kimchy (shay.banon) |
| 32 | */ |
| 33 | public class DynamicExecutors { |
| 34 | /** |
| 35 | * Creates a thread pool that creates new threads as needed, but will reuse previously |
| 36 | * constructed threads when they are available. Calls to <tt>execute</tt> will reuse previously |
| 37 | * constructed threads if available. If no existing thread is available, a new thread will be |
| 38 | * created and added to the pool. No more than <tt>max</tt> threads will be created. Threads that |
| 39 | * have not been used for a <tt>keepAlive</tt> timeout are terminated and removed from the cache. |
| 40 | * Thus, a pool that remains idle for long enough will not consume any resources other than the |
| 41 | * <tt>min</tt> specified. |
| 42 | * |
| 43 | * @param min |
| 44 | * the number of threads to keep in the pool, even if they are idle. |
| 45 | * @param max |
| 46 | * the maximum number of threads to allow in the pool. |
| 47 | * @param keepAliveTime |
| 48 | * when the number of threads is greater than the min, this is the maximum time that |
| 49 | * excess idle threads will wait for new tasks before terminating (in milliseconds). |
| 50 | * @return the newly created thread pool |
| 51 | */ |
| 52 | public static ExecutorService newScalingThreadPool(int min, int max, long keepAliveTime) { |
| 53 | return newScalingThreadPool(min, max, keepAliveTime, Executors.defaultThreadFactory()); |
| 54 | } |
| 55 | |
| 56 | /** |
| 57 | * Creates a thread pool, same as in {@link #newScalingThreadPool(int, int, long)}, using the |
| 58 | * provided ThreadFactory to create new threads when needed. |
| 59 | * |
| 60 | * @param min |
| 61 | * the number of threads to keep in the pool, even if they are idle. |
| 62 | * @param max |
| 63 | * the maximum number of threads to allow in the pool. |
| 64 | * @param keepAliveTime |
| 65 | * when the number of threads is greater than the min, this is the maximum time that |
| 66 | * excess idle threads will wait for new tasks before terminating (in milliseconds). |
| 67 | * @param threadFactory |
| 68 | * the factory to use when creating new threads. |
| 69 | * @return the newly created thread pool |
| 70 | */ |
| 71 | public static ExecutorService newScalingThreadPool(int min, int max, long keepAliveTime, |
| 72 | ThreadFactory threadFactory) { |
| 73 | DynamicThreadPoolExecutor.DynamicQueue<Runnable> queue = new DynamicThreadPoolExecutor.DynamicQueue<Runnable>(); |
| 74 | ThreadPoolExecutor executor = new DynamicThreadPoolExecutor(min, max, keepAliveTime, |
| 75 | TimeUnit.MILLISECONDS, queue, threadFactory); |
| 76 | executor.setRejectedExecutionHandler(new DynamicThreadPoolExecutor.ForceQueuePolicy()); |
| 77 | queue.setThreadPoolExecutor(executor); |
| 78 | return executor; |
| 79 | } |
| 80 | |
| 81 | /** |
| 82 | * Creates a thread pool similar to that constructed by |
| 83 | * {@link #newScalingThreadPool(int, int, long)}, but blocks the call to <tt>execute</tt> if the |
| 84 | * queue has reached it's capacity, and all <tt>max</tt> threads are busy handling requests. |
| 85 | * <p/> |
| 86 | * If the wait time of this queue has elapsed, a {@link RejectedExecutionException} will be |
| 87 | * thrown. |
| 88 | * |
| 89 | * @param min |
| 90 | * the number of threads to keep in the pool, even if they are idle. |
| 91 | * @param max |
| 92 | * the maximum number of threads to allow in the pool. |
| 93 | * @param keepAliveTime |
| 94 | * when the number of threads is greater than the min, this is the maximum time that |
| 95 | * excess idle threads will wait for new tasks before terminating (in milliseconds). |
| 96 | * @param capacity |
| 97 | * the fixed capacity of the underlying queue (resembles backlog). |
| 98 | * @param waitTime |
| 99 | * the wait time (in milliseconds) for space to become available in the queue. |
| 100 | * @return the newly created thread pool |
| 101 | */ |
| 102 | public static ExecutorService newBlockingThreadPool(int min, int max, long keepAliveTime, |
| 103 | int capacity, long waitTime) { |
| 104 | return newBlockingThreadPool(min, max, keepAliveTime, capacity, waitTime, Executors |
| 105 | .defaultThreadFactory()); |
| 106 | } |
| 107 | |
| 108 | /** |
| 109 | * Creates a thread pool, same as in {@link #newBlockingThreadPool(int, int, long, int, long)}, |
| 110 | * using the provided ThreadFactory to create new threads when needed. |
| 111 | * |
| 112 | * @param min |
| 113 | * the number of threads to keep in the pool, even if they are idle. |
| 114 | * @param max |
| 115 | * the maximum number of threads to allow in the pool. |
| 116 | * @param keepAliveTime |
| 117 | * when the number of threads is greater than the min, this is the maximum time that |
| 118 | * excess idle threads will wait for new tasks before terminating (in milliseconds). |
| 119 | * @param capacity |
| 120 | * the fixed capacity of the underlying queue (resembles backlog). |
| 121 | * @param waitTime |
| 122 | * the wait time (in milliseconds) for space to become available in the queue. |
| 123 | * @param threadFactory |
| 124 | * the factory to use when creating new threads. |
| 125 | * @return the newly created thread pool |
| 126 | */ |
| 127 | public static ExecutorService newBlockingThreadPool(int min, int max, long keepAliveTime, |
| 128 | int capacity, long waitTime, ThreadFactory threadFactory) { |
| 129 | DynamicThreadPoolExecutor.DynamicQueue<Runnable> queue = new DynamicThreadPoolExecutor.DynamicQueue<Runnable>( |
| 130 | capacity); |
| 131 | ThreadPoolExecutor executor = new DynamicThreadPoolExecutor(min, max, keepAliveTime, |
| 132 | TimeUnit.MILLISECONDS, queue, threadFactory); |
| 133 | executor.setRejectedExecutionHandler(new DynamicThreadPoolExecutor.TimedBlockingPolicy( |
| 134 | waitTime)); |
| 135 | queue.setThreadPoolExecutor(executor); |
| 136 | return executor; |
| 137 | } |
| 138 | |
| 139 | /** |
| 140 | * A priority based thread factory, for all Thread priority constants: |
| 141 | * <tt>Thread.MIN_PRIORITY, Thread.NORM_PRIORITY, Thread.MAX_PRIORITY</tt>; |
| 142 | * <p/> |
| 143 | * This factory is used instead of Executers.DefaultThreadFactory to allow manipulation of |
| 144 | * priority and thread owner name. |
| 145 | * |
| 146 | * @param namePrefix |
| 147 | * a name prefix for this thread |
| 148 | * @return a thread factory based on given priority. |
| 149 | */ |
| 150 | public static ThreadFactory daemonThreadFactory(String namePrefix) { |
| 151 | final ThreadFactory f = Executors.defaultThreadFactory(); |
| 152 | final String o = namePrefix + "-"; |
| 153 | |
| 154 | return new ThreadFactory() { |
| 155 | public Thread newThread(Runnable r) { |
| 156 | Thread t = f.newThread(r); |
| 157 | |
| 158 | /* |
| 159 | * Thread name: owner-pool-N-thread-M, where N is the sequence number of this factory, |
| 160 | * and M is the sequence number of the thread created by this factory. |
| 161 | */ |
| 162 | t.setName(o + t.getName()); |
| 163 | |
| 164 | /* override default definition t.setDaemon(false); */ |
| 165 | t.setDaemon(true); |
| 166 | |
| 167 | return t; |
| 168 | } |
| 169 | }; |
| 170 | } |
| 171 | |
| 172 | /** |
| 173 | * A priority based thread factory, for all Thread priority constants: |
| 174 | * <tt>Thread.MIN_PRIORITY, Thread.NORM_PRIORITY, Thread.MAX_PRIORITY</tt>; |
| 175 | * <p/> |
| 176 | * This factory is used instead of Executers.DefaultThreadFactory to allow manipulation of |
| 177 | * priority and thread owner name. |
| 178 | * |
| 179 | * @param priority |
| 180 | * The priority to be assigned to each thread; can be either |
| 181 | * <tt>Thread.MIN_PRIORITY, Thread.NORM_PRIORITY</tt> or Thread.MAX_PRIORITY. |
| 182 | * @param namePrefix |
| 183 | * a name prefix for this thread |
| 184 | * @return a thread factory based on given priority. |
| 185 | */ |
| 186 | public static ThreadFactory priorityThreadFactory(int priority, String namePrefix) { |
| 187 | final ThreadFactory f = DynamicExecutors.daemonThreadFactory(namePrefix); |
| 188 | final int p = priority; |
| 189 | |
| 190 | return new ThreadFactory() { |
| 191 | public Thread newThread(Runnable r) { |
| 192 | Thread t = f.newThread(r); |
| 193 | |
| 194 | /* override default thread priority of Thread.NORM_PRIORITY */ |
| 195 | if (p != Thread.NORM_PRIORITY) |
| 196 | t.setPriority(p); |
| 197 | |
| 198 | return t; |
| 199 | } |
| 200 | }; |
| 201 | } |
| 202 | |
| 203 | /** |
| 204 | * Cannot instantiate. |
| 205 | */ |
| 206 | private DynamicExecutors() { |
| 207 | } |
| 208 | } |