ConsumerBarrier.java

/*
 * 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.lmax.disruptor;

import java.util.concurrent.TimeUnit;

/**
 * Coordination barrier for tracking the cursor for producers and sequence of
 * dependent {@link Consumer}s for a {@link RingBuffer}
 *
 * @param <T> {@link AbstractEntry} implementation stored in the {@link RingBuffer}
 */
public interface ConsumerBarrier<T extends AbstractEntry>
{
    /**
     * Get the {@link AbstractEntry} for a given sequence from the underlying {@link RingBuffer}.
     *
     * @param sequence of the {@link AbstractEntry} to get.
     * @return the {@link AbstractEntry} for the sequence.
     */
    T getEntry(long sequence);

    /**
     * Wait for the given sequence to be available for consumption.
     *
     * @param sequence to wait for
     * @return the sequence up to which is available
     * @throws AlertException if a status change has occurred for the Disruptor
     * @throws InterruptedException if the thread needs awaking on a condition variable.
     */
    long waitFor(long sequence) throws AlertException, InterruptedException;

    /**
     * Wait for the given sequence to be available for consumption with a time out.
     *
     * @param sequence to wait for
     * @param timeout value
     * @param units for the timeout value
     * @return the sequence up to which is available
     * @throws AlertException if a status change has occurred for the Disruptor
     * @throws InterruptedException if the thread needs awaking on a condition variable.
     */
    long waitFor(long sequence, long timeout, TimeUnit units) throws AlertException, InterruptedException;

    /**
     * Delegate a call to the {@link RingBuffer#getCursor()}
     * @return value of the cursor for entries that have been published.
     */
    long getCursor();

    /**
     * The current alert status for the barrier.
     *
     * @return true if in alert otherwise false.
     */
    boolean isAlerted();

    /**
     * Alert the consumers of a status change and stay in this status until cleared.
     */
    void alert();

    /**
     * Clear the current alert status.
     */
    void clearAlert();

}