common/util/src/main/java/org/opendaylight/yangtools/util/concurrent/CachedThreadPoolExecutor.java

   1 /*
   2  * Copyright (c) 2014 Brocade Communications Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.yangtools.util.concurrent;
   9
  10 import static java.util.Objects.requireNonNull;
  11
  12 import com.google.common.base.MoreObjects;
  13 import com.google.common.base.MoreObjects.ToStringHelper;
  14 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  15 import java.util.concurrent.BlockingQueue;
  16 import java.util.concurrent.LinkedBlockingQueue;
  17 import java.util.concurrent.RejectedExecutionException;
  18 import java.util.concurrent.RejectedExecutionHandler;
  19 import java.util.concurrent.SynchronousQueue;
  20 import java.util.concurrent.ThreadPoolExecutor;
  21 import java.util.concurrent.TimeUnit;
  22 import org.slf4j.LoggerFactory;
  23
  24 /**
  25  * A ThreadPoolExecutor with a specified bounded queue capacity that favors reusing previously
  26  * constructed threads, when they are available, over creating new threads.
  27  *
  28  * <p>See {@link SpecialExecutors#newBoundedCachedThreadPool} for more details.
  29  *
  30  * @author Thomas Pantelis
  31  */
  32 public class CachedThreadPoolExecutor extends ThreadPoolExecutor {
  33
  34     private static final long IDLE_TIMEOUT_IN_SEC = 60L;
  35
  36     private final ExecutorQueue executorQueue;
  37
  38     private final String threadPrefix;
  39
  40     private final int maximumQueueSize;
  41
  42     private final RejectedTaskHandler rejectedTaskHandler;
  43
  44     /**
  45      * Constructs an instance.
  46      *
  47      * @param maximumPoolSize
  48      *            the maximum number of threads to allow in the pool. Threads will terminate after
  49      *            being idle for 60 seconds.
  50      * @param maximumQueueSize
  51      *            the capacity of the queue.
  52      * @param threadPrefix
  53      *            the name prefix for threads created by this executor.
  54      * @param loggerIdentity
  55      *               the class to use as logger name for logging uncaught exceptions from the threads.
  56      */
  57     // due to loggerIdentity argument usage
  58     @SuppressWarnings("checkstyle:LoggerFactoryClassParameter")
  59     public CachedThreadPoolExecutor(final int maximumPoolSize, final int maximumQueueSize, final String threadPrefix,
  60             final Class<?> loggerIdentity) {
  61         // We're using a custom SynchronousQueue that has a backing bounded LinkedBlockingQueue.
  62         // We don't specify any core threads (first parameter) so, when a task is submitted,
  63         // the base class will always try to offer to the queue. If there is an existing waiting
  64         // thread, the offer will succeed and the task will be handed to the thread to execute. If
  65         // there's no waiting thread, either because there are no threads in the pool or all threads
  66         // are busy, the base class will try to create a new thread. If the maximum thread limit has
  67         // been reached, the task will be rejected. We specify a RejectedTaskHandler that tries
  68         // to offer to the backing queue. If that succeeds, the task will execute as soon as a
  69         // thread becomes available. If the offer fails to the backing queue, the task is rejected.
  70         super(0, maximumPoolSize, IDLE_TIMEOUT_IN_SEC, TimeUnit.SECONDS,
  71                new ExecutorQueue(maximumQueueSize));
  72
  73         this.threadPrefix = requireNonNull(threadPrefix);
  74         this.maximumQueueSize = maximumQueueSize;
  75
  76         setThreadFactory(ThreadFactoryProvider.builder().namePrefix(threadPrefix)
  77                 .logger(LoggerFactory.getLogger(loggerIdentity)).build().get());
  78
  79         executorQueue = (ExecutorQueue)super.getQueue();
  80
  81         rejectedTaskHandler = new RejectedTaskHandler(
  82                 executorQueue.getBackingQueue(), CountingRejectedExecutionHandler.newAbortPolicy());
  83         super.setRejectedExecutionHandler(rejectedTaskHandler);
  84     }
  85
  86     @Override
  87     public void setRejectedExecutionHandler(final RejectedExecutionHandler handler) {
  88         rejectedTaskHandler.setDelegateRejectedExecutionHandler(requireNonNull(handler));
  89     }
  90
  91     @Override
  92     public RejectedExecutionHandler getRejectedExecutionHandler() {
  93         return rejectedTaskHandler.getDelegateRejectedExecutionHandler();
  94     }
  95
  96     @Override
  97     public BlockingQueue<Runnable> getQueue() {
  98         return executorQueue.getBackingQueue();
  99     }
 100
 101     public long getLargestQueueSize() {
 102         return executorQueue.getBackingQueue().getLargestQueueSize();
 103     }
 104
 105     protected ToStringHelper addToStringAttributes(final ToStringHelper toStringHelper) {
 106         return toStringHelper;
 107     }
 108
 109     @Override
 110     public final String toString() {
 111         return addToStringAttributes(MoreObjects.toStringHelper(this)
 112                 .add("Thread Prefix", threadPrefix)
 113                 .add("Current Thread Pool Size", getPoolSize())
 114                 .add("Largest Thread Pool Size", getLargestPoolSize())
 115                 .add("Max Thread Pool Size", getMaximumPoolSize())
 116                 .add("Current Queue Size", executorQueue.getBackingQueue().size())
 117                 .add("Largest Queue Size", getLargestQueueSize())
 118                 .add("Max Queue Size", maximumQueueSize)
 119                 .add("Active Thread Count", getActiveCount())
 120                 .add("Completed Task Count", getCompletedTaskCount())
 121                 .add("Total Task Count", getTaskCount())).toString();
 122     }
 123
 124     /**
 125      * A customized SynchronousQueue that has a backing bounded LinkedBlockingQueue. This class
 126      * overrides the #poll methods to first try to poll the backing queue for a task. If the backing
 127      * queue is empty, it calls the base SynchronousQueue#poll method. In this manner, we get the
 128      * thread reuse behavior of the SynchronousQueue with the added ability to queue tasks when all
 129      * threads are busy.
 130      */
 131     private static class ExecutorQueue extends SynchronousQueue<Runnable> {
 132
 133         private static final long serialVersionUID = 1L;
 134
 135         private static final long POLL_WAIT_TIME_IN_MS = 300;
 136
 137         @SuppressFBWarnings("SE_BAD_FIELD")
 138         // Runnable is not Serializable
 139         private final TrackingLinkedBlockingQueue<Runnable> backingQueue;
 140
 141         ExecutorQueue(final int maxBackingQueueSize) {
 142             backingQueue = new TrackingLinkedBlockingQueue<>(maxBackingQueueSize);
 143         }
 144
 145         TrackingLinkedBlockingQueue<Runnable> getBackingQueue() {
 146             return backingQueue;
 147         }
 148
 149         @Override
 150         public Runnable poll(final long timeout, final TimeUnit unit) throws InterruptedException {
 151             long totalWaitTime = unit.toMillis(timeout);
 152             long waitTime = Math.min(totalWaitTime, POLL_WAIT_TIME_IN_MS);
 153             Runnable task = null;
 154
 155             // We loop here, each time polling the backingQueue first then our queue, instead of
 156             // polling each just once. This is to handle the following timing edge case:
 157             //
 158             //   We poll the backingQueue and it's empty but, before the call to super.poll,
 159             //   a task is offered but no thread is immediately available and the task is put on the
 160             //   backingQueue. There is a slight chance that all the other threads could be at the
 161             //   same point, in which case they would all call super.poll and wait. If we only
 162             //   called poll once, no thread would execute the task (unless/until another task was
 163             //   later submitted). But by looping and breaking the specified timeout into small
 164             //   periods, one thread will eventually wake up and get the task from the backingQueue
 165             //   and execute it, although slightly delayed.
 166
 167             while (task == null) {
 168                 // First try to get a task from the backing queue.
 169                 task = backingQueue.poll();
 170                 if (task == null) {
 171                     // No task in backing - call the base class to wait for one to be offered.
 172                     task = super.poll(waitTime, TimeUnit.MILLISECONDS);
 173
 174                     totalWaitTime -= POLL_WAIT_TIME_IN_MS;
 175                     if (totalWaitTime <= 0) {
 176                         break;
 177                     }
 178
 179                     waitTime = Math.min(totalWaitTime, POLL_WAIT_TIME_IN_MS);
 180                 }
 181             }
 182
 183             return task;
 184         }
 185
 186         @Override
 187         public Runnable poll() {
 188             Runnable task = backingQueue.poll();
 189             return task != null ? task : super.poll();
 190         }
 191     }
 192
 193     /**
 194      * Internal RejectedExecutionHandler that tries to offer rejected tasks to the backing queue.
 195      * If the queue is full, we throw a RejectedExecutionException by default. The client can
 196      * override this behavior be specifying their own RejectedExecutionHandler, in which case we
 197      * delegate to that handler.
 198      */
 199     private static class RejectedTaskHandler implements RejectedExecutionHandler {
 200
 201         private final LinkedBlockingQueue<Runnable> backingQueue;
 202         private volatile RejectedExecutionHandler delegateRejectedExecutionHandler;
 203
 204         RejectedTaskHandler(final LinkedBlockingQueue<Runnable> backingQueue,
 205                              final RejectedExecutionHandler delegateRejectedExecutionHandler) {
 206             this.backingQueue = backingQueue;
 207             this.delegateRejectedExecutionHandler = delegateRejectedExecutionHandler;
 208         }
 209
 210         void setDelegateRejectedExecutionHandler(
 211                 final RejectedExecutionHandler delegateRejectedExecutionHandler) {
 212             this.delegateRejectedExecutionHandler = delegateRejectedExecutionHandler;
 213         }
 214
 215         RejectedExecutionHandler getDelegateRejectedExecutionHandler() {
 216             return delegateRejectedExecutionHandler;
 217         }
 218
 219         @Override
 220         public void rejectedExecution(final Runnable task, final ThreadPoolExecutor executor) {
 221             if (executor.isShutdown()) {
 222                 throw new RejectedExecutionException("Executor has been shutdown.");
 223             }
 224
 225             if (!backingQueue.offer(task)) {
 226                 delegateRejectedExecutionHandler.rejectedExecution(task, executor);
 227             }
 228         }
 229     }
 230 }