co.cask.tigon.internal.app.queue.TimeTrackingQueueReader.java Source code

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Here is the source code for co.cask.tigon.internal.app.queue.TimeTrackingQueueReader.java

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/*
 * Copyright  2014 Cask Data, Inc.
 *
 * 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 co.cask.tigon.internal.app.queue;

import co.cask.tigon.app.queue.InputDatum;
import co.cask.tigon.app.queue.QueueReader;
import com.google.common.base.Stopwatch;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

/**
 * A {@link QueueReader} that track time spent when trying to dequeue.
 *
 * @param <T> Type of input dequeued from this reader.
 */
public abstract class TimeTrackingQueueReader<T> implements QueueReader<T> {

    // Maximum number of times to try to deuque an non-empty result.
    private static final int DEQUEUE_TRAILS = 10;

    @Override
    public final InputDatum<T> dequeue(long timeout, TimeUnit timeoutUnit)
            throws IOException, InterruptedException {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.start();
        long sleepNano = computeSleepNano(timeout, timeoutUnit);
        long timeoutNano = timeoutUnit.toNanos(timeout);

        InputDatum<T> result = tryDequeue(timeout, timeoutUnit);
        while (!result.needProcess()) {
            if (timeoutNano <= 0) {
                break;
            }

            long elapsedNano = stopwatch.elapsedTime(TimeUnit.NANOSECONDS);
            if (elapsedNano + sleepNano >= timeoutNano) {
                break;
            }
            TimeUnit.NANOSECONDS.sleep(sleepNano);
            result = tryDequeue(timeoutNano - elapsedNano, TimeUnit.NANOSECONDS);
        }
        return result;
    }

    /**
     * Children class override it to try to dequeue.
     */
    protected abstract InputDatum<T> tryDequeue(long timeout, TimeUnit timeoutUnit)
            throws IOException, InterruptedException;

    private long computeSleepNano(long timeout, TimeUnit unit) {
        long sleepNano = TimeUnit.NANOSECONDS.convert(timeout, unit) / DEQUEUE_TRAILS;
        return sleepNano <= 0 ? 1 : sleepNano;
    }
}