com.hazelcast.core.ICountDownLatch Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2013, Hazelcast, Inc. All Rights Reserved.
*
* Licensed 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 com.hazelcast.core;
import java.util.concurrent.TimeUnit;
/**
* ICountDownLatch is a backed-up distributed alternative to the
* {@link java.util.concurrent.CountDownLatch java.util.concurrent.CountDownLatch}.
*
* ICountDownLatch is a cluster-wide synchronization aid
* that allows one or more threads to wait until a set of operations being
* performed in other threads completes.
*
* There are a few differences compared to the {@link ICountDownLatch}:
*
* -
* the ICountDownLatch count can be re-set using {@link #trySetCount(int)} after a countdown
* has finished but not during an active count. This allows the same latch instance to be reused.
*
* -
* there is no await() method to do an unbound wait since this is undesirable in a distributed
* application: it can happen that for example a cluster is split or that the master and
* replica's all die. So in most cases it is best to configure an explicit timeout so have the ability
* to deal with these situations.
*
*
*
*/
public interface ICountDownLatch extends DistributedObject {
/**
* Causes the current thread to wait until the latch has counted down to
* zero, an exception is thrown, or the specified waiting time elapses.
*
* If the current count is zero then this method returns immediately
* with the value {@code true}.
*
* If the current count is greater than zero then the current
* thread becomes disabled for thread scheduling purposes and lies
* dormant until one of five things happen:
*
* - The count reaches zero due to invocations of the
* {@link #countDown} method;
*
- This ICountDownLatch instance is destroyed;
*
- The countdown owner becomes disconnected;
*
- Some other thread {@linkplain Thread#interrupt interrupts}
* the current thread; or
*
- The specified waiting time elapses.
*
*
* If the count reaches zero then the method returns with the
* value {@code true}.
*
* If the current thread:
*
* - has its interrupted status set on entry to this method; or
*
- is {@linkplain Thread#interrupt interrupted} while waiting,
*
* then {@link InterruptedException} is thrown and the current thread's
* interrupted status is cleared.
* If the specified waiting time elapses then the value {@code false}
* is returned. If the time is less than or equal to zero, the method
* will not wait at all.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the {@code timeout} argument
* @return {@code true} if the count reached zero and {@code false}
* if the waiting time elapsed before the count reached zero
* @throws InterruptedException if the current thread is interrupted
* @throws IllegalStateException if hazelcast instance is shutdown while waiting
*/
boolean await(long timeout, TimeUnit unit) throws InterruptedException;
/**
* Decrements the count of the latch, releasing all waiting threads if
* the count reaches zero.
*
* If the current count is greater than zero then it is decremented.
* If the new count is zero:
*
* - All waiting threads are re-enabled for thread scheduling purposes; and
*
- Countdown owner is set to {@code null}.
*
*
* If the current count equals zero then nothing happens.
*/
void countDown();
/**
* Returns the current count.
*
* @return current count
*/
int getCount();
/**
* Sets the count to the given value if the current count is zero.
* If count is not zero then this method does nothing and returns {@code false}.
*
* @param count the number of times {@link #countDown} must be invoked
* before threads can pass through {@link #await}
* @return {@code true} if the new count was set or {@code false} if the current
* count is not zero
* @throws IllegalArgumentException if {@code count} is negative
*/
boolean trySetCount(int count);
}