org.apache.hadoop.dynamodb.preader.ReadWorker.java Source code

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Here is the source code for org.apache.hadoop.dynamodb.preader.ReadWorker.java

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/**
 * Copyright 2012-2016 Amazon.com, Inc. or its affiliates. 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. A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0/
 *
 * or in the "LICENSE.TXT" file accompanying this file. This file 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 org.apache.hadoop.dynamodb.preader;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.dynamodb.preader.RateController.RequestLimit;
import org.apache.hadoop.mapred.Reporter;

import java.util.Random;
import java.util.concurrent.atomic.AtomicInteger;

public class ReadWorker extends Thread {

    private static final int SLEEP_TIME_MS = 80;
    private static final int SLEEP_JITTER_MS = 40;

    private static final Log log = LogFactory.getLog(ReadWorker.class);
    private static final AtomicInteger workerId = new AtomicInteger();
    protected final AbstractReadManager readMgr;
    private final Reporter reporter;
    private final Random rnd = new Random();
    protected volatile boolean alive = true;

    public ReadWorker(AbstractReadManager mgr, Reporter reporter) {
        super("ReadWorker-" + workerId.incrementAndGet());
        this.readMgr = mgr;
        this.reporter = reporter;
    }

    @Override
    public void run() {
        while (alive) {
            try {
                runInternal();
            } catch (InterruptedException e) {
                Thread.interrupted();
            } catch (Throwable e) {
                log.error("Unknown exception thrown!", e);
            }
        }

        log.info("Worker shutting down, no longer alive");
    }

    public void setAlive(boolean alive) {
        this.alive = alive;
    }

    private void runInternal() throws Throwable {
        // We're alive, even though we might not get tokens or find work below
        if (reporter != null) {
            reporter.progress();
        }

        AbstractRecordReadRequest req = readMgr.dequeueReadRequest();
        if (req == null) {
            log.info("Worker found read request queue empty, sleeping.");
            Thread.sleep(getSleepTime());
            return;
        }

        // Find the limit for the next request
        RequestLimit lim = readMgr.rateController.getNextRequestLimit();
        if (lim == RateController.RequestLimit.ZERO) {
            log.info("No read token from rate controller. Putting the request back");
            readMgr.enqueueReadRequestToHead(req);
            Thread.sleep(getSleepTime());
            return;
        }

        // Trigger the read request
        req.read(lim);
    }

    private long getSleepTime() {
        int base = SLEEP_TIME_MS - SLEEP_JITTER_MS;
        int jitter = rnd.nextInt(SLEEP_JITTER_MS * 2);
        return base + jitter;
    }

}