org.apache.hadoop.hive.ql.exec.mr.Throttle.java Source code

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Here is the source code for org.apache.hadoop.hive.ql.exec.mr.Throttle.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.hadoop.hive.ql.exec.mr;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.mapred.JobConf;

/**
 * Intelligence to make clients wait if the cluster is in a bad state.
 */
public final class Throttle {

    // The percentage of maximum allocated memory that triggers GC
    // on job tracker. This could be overridden thru the jobconf.
    // The default is such that there is no throttling.
    private static final int DEFAULT_MEMORY_GC_PERCENT = 100;

    // sleep this many seconds between each retry.
    // This could be overridden thru the jobconf.
    private static final int DEFAULT_RETRY_PERIOD = 60;

    /**
     * Fetch http://tracker.om:/gc.jsp?threshold=period.
     */
    public static void checkJobTracker(JobConf conf, Log LOG) {

        try {
            byte[] buffer = new byte[1024];
            int threshold = conf.getInt("mapred.throttle.threshold.percent", DEFAULT_MEMORY_GC_PERCENT);
            int retry = conf.getInt("mapred.throttle.retry.period", DEFAULT_RETRY_PERIOD);

            // If the threshold is 100 percent, then there is no throttling
            if (threshold == 100) {
                return;
            }

            // This is the Job Tracker URL
            String tracker = JobTrackerURLResolver.getURL(conf) + "/gc.jsp?threshold=" + threshold;

            while (true) {
                // read in the first 1K characters from the URL
                URL url = new URL(tracker);
                LOG.debug("Throttle: URL " + tracker);
                InputStream in = null;
                try {
                    in = url.openStream();
                    in.read(buffer);
                    in.close();
                    in = null;
                } finally {
                    IOUtils.closeStream(in);
                }
                String fetchString = new String(buffer);

                // fetch the xml tag <dogc>xxx</dogc>
                Pattern dowait = Pattern.compile("<dogc>",
                        Pattern.CASE_INSENSITIVE | Pattern.DOTALL | Pattern.MULTILINE);
                String[] results = dowait.split(fetchString);
                if (results.length != 2) {
                    throw new IOException(
                            "Throttle: Unable to parse response of URL " + url + ". Get retuned " + fetchString);
                }
                dowait = Pattern.compile("</dogc>", Pattern.CASE_INSENSITIVE | Pattern.DOTALL | Pattern.MULTILINE);
                results = dowait.split(results[1]);
                if (results.length < 1) {
                    throw new IOException(
                            "Throttle: Unable to parse response of URL " + url + ". Get retuned " + fetchString);
                }

                // if the jobtracker signalled that the threshold is not exceeded,
                // then we return immediately.
                if (results[0].trim().compareToIgnoreCase("false") == 0) {
                    return;
                }

                // The JobTracker has exceeded its threshold and is doing a GC.
                // The client has to wait and retry.
                LOG.warn("Job is being throttled because of resource crunch on the " + "JobTracker. Will retry in "
                        + retry + " seconds..");
                Thread.sleep(retry * 1000L);
            }
        } catch (Exception e) {
            LOG.warn("Job is not being throttled. " + e);
        }
    }

    private Throttle() {
        // prevent instantiation
    }
}