org.elasticsearch.common.util.concurrent

クラス ThreadBarrier

java.lang.Object

java.util.concurrent.CyclicBarrier

org.elasticsearch.common.util.concurrent.ThreadBarrier

public class ThreadBarrier
extends CyclicBarrier

A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point. Barriers are useful in programs involving a fixed sized party of threads that must occasionally wait for each other. ThreadBarrier adds a cause to BrokenBarrierException thrown by a CyclicBarrier.reset() operation defined by CyclicBarrier.

Sample usage:

• Barrier as a synchronization and Exception handling aid
• Barrier as a trigger for elapsed notification events

    class MyTestClass implements RemoteEventListener
    {
      final ThreadBarrier barrier;

      class Worker implements Runnable
        {
          public void run()
            {
              barrier.await();    //wait for all threads to reach run
              try
                {
                  prepare();
                  barrier.await();    //wait for all threads to prepare
                  process();
                  barrier.await();    //wait for all threads to process
                }
              catch(Throwable t){
                  log("Worker thread caught exception", t);
                  barrier.reset(t);
                }
            }
        }

      public void testThreads() {
          barrier = new ThreadBarrier(N_THREADS + 1);
          for (int i = 0; i < N; ++i)
           new Thread(new Worker()).start();

          try{
              barrier.await();    //wait for all threads to reach run
              barrier.await();    //wait for all threads to prepare
              barrier.await();    //wait for all threads to process
            }
          catch(BrokenBarrierException bbe) {
              Assert.fail(bbe);
            }
       }

      int actualNotificationCount = 0;
      public synchronized void notify (RemoteEvent event) {
          try{
              actualNotificationCount++;
              if (actualNotificationCount == EXPECTED_COUNT)
                  barrier.await();    //signal when all notifications arrive

               // too many notifications?
               Assert.assertFalse("Exceeded notification count",
                                          actualNotificationCount > EXPECTED_COUNT);
            }
          catch(Throwable t) {
              log("Worker thread caught exception", t);
              barrier.reset(t);
            }
        }

      public void testNotify() {
          barrier = new ThreadBarrier(N_LISTENERS + 1);
          registerNotification();
          triggerNotifications();

          //wait until either all notifications arrive, or
          //until a MAX_TIMEOUT is reached.
          barrier.await(MAX_TIMEOUT);

          //check if all notifications were accounted for or timed-out
          Assert.assertEquals("Notification count",
                                      EXPECTED_COUNT, actualNotificationCount);

          //inspect that the barrier isn't broken
          barrier.inspect(); //throws BrokenBarrierException if broken
        }
    }
 

ネストされたクラスのサマリー

ネストされたクラス

修飾子とタイプ	クラスと説明
static class	ThreadBarrier.BarrierTimer A Barrier action to be used in conjunction with ThreadBarrier to measure performance between barrier awaits.

コンストラクタのサマリー

コンストラクタ

コンストラクタと説明
ThreadBarrier(int parties)
ThreadBarrier(int parties, Runnable barrierAction)

メソッドのサマリー

修飾子とタイプ	メソッドと説明
int	await()
int	await(long timeout, TimeUnit unit)
void	inspect() Inspects if the barrier is broken.
boolean	isBroken() Queries if this barrier is in a broken state.
void	reset(Throwable cause) Resets the barrier to its initial state.

クラスから継承されたメソッド java.util.concurrent.CyclicBarrier

getNumberWaiting, getParties, reset

クラスから継承されたメソッド java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

コンストラクタの詳細

ThreadBarrier

public ThreadBarrier(int parties)

ThreadBarrier

public ThreadBarrier(int parties,
                     Runnable barrierAction)

メソッドの詳細

await

public int await()
          throws InterruptedException,
                 BrokenBarrierException

オーバーライド:

await クラス内 CyclicBarrier

例外:

InterruptedException

BrokenBarrierException

await

public int await(long timeout,
                 TimeUnit unit)
          throws InterruptedException,
                 BrokenBarrierException,
                 TimeoutException

オーバーライド:

await クラス内 CyclicBarrier

例外:

InterruptedException

BrokenBarrierException

TimeoutException

reset

public void reset(Throwable cause)

Resets the barrier to its initial state. If any parties are currently waiting at the barrier, they will return with a BrokenBarrierException. Note that resets after a breakage has occurred for other reasons can be complicated to carry out; threads need to re-synchronize in some other way, and choose one to perform the reset. It may be preferable to instead create a new barrier for subsequent use.

パラメータ:

cause - The cause of the BrokenBarrierException

isBroken

public boolean isBroken()

Queries if this barrier is in a broken state. Note that if reset(Throwable) is invoked the barrier will remain broken, while CyclicBarrier.reset() will reset the barrier to its initial state and isBroken() will return false.

オーバーライド:

isBroken クラス内 CyclicBarrier

戻り値:

true if one or more parties broke out of this barrier due to interruption or timeout since construction or the last reset, or a barrier action failed due to an exception; false otherwise.

関連項目:

inspect()

inspect

public void inspect()
             throws BrokenBarrierException

Inspects if the barrier is broken. If for any reason, the barrier was broken, a BrokenBarrierException will be thrown. Otherwise, would return gracefully.

例外:

BrokenBarrierException - With a nested broken cause.