com.alipay.disruptor.LiteTimeoutBlockingWaitStrategy Maven / Gradle / Ivy

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/*
 * Copyright 2011 LMAX Ltd.
 *
 * 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.alipay.disruptor;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Variation of the {@link TimeoutBlockingWaitStrategy} that attempts to elide conditional wake-ups
 * when the lock is uncontended.
 */
public class LiteTimeoutBlockingWaitStrategy implements WaitStrategy {
    private final Lock          lock                     = new ReentrantLock();
    private final Condition     processorNotifyCondition = lock.newCondition();
    private final AtomicBoolean signalNeeded             = new AtomicBoolean(false);
    private final long          timeoutInNanos;

    public LiteTimeoutBlockingWaitStrategy(final long timeout, final TimeUnit units) {
        timeoutInNanos = units.toNanos(timeout);
    }

    @Override
    public long waitFor(final long sequence, final Sequence cursorSequence,
                        final Sequence dependentSequence, final SequenceBarrier barrier)
                                                                                        throws AlertException,
                                                                                        InterruptedException,
                                                                                        TimeoutException {
        long nanos = timeoutInNanos;

        long availableSequence;
        if (cursorSequence.get() < sequence) {
            lock.lock();
            try {
                while (cursorSequence.get() < sequence) {
                    signalNeeded.getAndSet(true);

                    barrier.checkAlert();
                    nanos = processorNotifyCondition.awaitNanos(nanos);
                    if (nanos <= 0) {
                        throw TimeoutException.INSTANCE;
                    }
                }
            } finally {
                lock.unlock();
            }
        }

        while ((availableSequence = dependentSequence.get()) < sequence) {
            barrier.checkAlert();
        }

        return availableSequence;
    }

    @Override
    public void signalAllWhenBlocking() {
        if (signalNeeded.getAndSet(false)) {
            lock.lock();
            try {
                processorNotifyCondition.signalAll();
            } finally {
                lock.unlock();
            }
        }
    }

    @Override
    public String toString() {
        return "LiteTimeoutBlockingWaitStrategy{" + "processorNotifyCondition="
               + processorNotifyCondition + '}';
    }
}