org.apache.hadoop.metrics2.lib.MetricMutableQuantiles.java Source code

Introduction

Here is the source code for org.apache.hadoop.metrics2.lib.MetricMutableQuantiles.java

Source

/**
 * 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.metrics2.lib;

import static org.apache.hadoop.metrics2.lib.Interns.info;

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

import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.metrics2.MetricHistogram;
import org.apache.hadoop.metrics2.MetricsExecutor;
import org.apache.hadoop.metrics2.MetricsInfo;
import org.apache.hadoop.metrics2.MetricsRecordBuilder;
import org.apache.hadoop.metrics2.util.MetricQuantile;
import org.apache.hadoop.metrics2.util.MetricSampleQuantiles;

import com.google.common.annotations.VisibleForTesting;

/**
 * Watches a stream of long values, maintaining online estimates of specific quantiles with provably
 * low error bounds. This is particularly useful for accurate high-percentile (e.g. 95th, 99th)
 * latency metrics.
 */
@InterfaceAudience.Private
public class MetricMutableQuantiles extends MutableMetric implements MetricHistogram {

    static final MetricQuantile[] quantiles = { new MetricQuantile(0.50, 0.050), new MetricQuantile(0.75, 0.025),
            new MetricQuantile(0.90, 0.010), new MetricQuantile(0.95, 0.005), new MetricQuantile(0.99, 0.001) };

    private final MetricsInfo numInfo;
    private final MetricsInfo[] quantileInfos;
    private final int interval;

    private MetricSampleQuantiles estimator;
    private long previousCount = 0;
    private MetricsExecutor executor;

    @VisibleForTesting
    protected Map<MetricQuantile, Long> previousSnapshot = null;

    /**
     * Instantiates a new {@link MetricMutableQuantiles} for a metric that rolls itself over on the
     * specified time interval.
     *
     * @param name        of the metric
     * @param description long-form textual description of the metric
     * @param sampleName  type of items in the stream (e.g., "Ops")
     * @param valueName   type of the values
     * @param interval    rollover interval (in seconds) of the estimator
     */
    public MetricMutableQuantiles(String name, String description, String sampleName, String valueName,
            int interval) {
        String ucName = StringUtils.capitalize(name);
        String usName = StringUtils.capitalize(sampleName);
        String uvName = StringUtils.capitalize(valueName);
        String desc = StringUtils.uncapitalize(description);
        String lsName = StringUtils.uncapitalize(sampleName);
        String lvName = StringUtils.uncapitalize(valueName);

        numInfo = info(ucName + "Num" + usName,
                String.format("Number of %s for %s with %ds interval", lsName, desc, interval));
        // Construct the MetricsInfos for the quantiles, converting to percentiles
        quantileInfos = new MetricsInfo[quantiles.length];
        String nameTemplate = "%s%dthPercentile%dsInterval%s";
        String descTemplate = "%d percentile %s with %d second interval for %s";
        for (int i = 0; i < quantiles.length; i++) {
            int percentile = (int) (100 * quantiles[i].quantile);
            quantileInfos[i] = info(String.format(nameTemplate, ucName, percentile, interval, uvName),
                    String.format(descTemplate, percentile, lvName, interval, desc));
        }

        estimator = new MetricSampleQuantiles(quantiles);
        executor = new MetricsExecutorImpl();
        this.interval = interval;
        executor.getExecutor().scheduleAtFixedRate(new RolloverSample(this), interval, interval, TimeUnit.SECONDS);
    }

    @Override
    public synchronized void snapshot(MetricsRecordBuilder builder, boolean all) {
        if (all || changed()) {
            builder.addGauge(numInfo, previousCount);
            for (int i = 0; i < quantiles.length; i++) {
                long newValue = 0;
                // If snapshot is null, we failed to update since the window was empty
                if (previousSnapshot != null) {
                    newValue = previousSnapshot.get(quantiles[i]);
                }
                builder.addGauge(quantileInfos[i], newValue);
            }
            if (changed()) {
                clearChanged();
            }
        }
    }

    public synchronized void add(long value) {
        estimator.insert(value);
    }

    public int getInterval() {
        return interval;
    }

    /** Runnable used to periodically roll over the internal {@link org.apache.hadoop.metrics2.util.MetricSampleQuantiles} every interval. */
    private static class RolloverSample implements Runnable {

        MetricMutableQuantiles parent;

        public RolloverSample(MetricMutableQuantiles parent) {
            this.parent = parent;
        }

        @Override
        public void run() {
            synchronized (parent) {
                try {
                    parent.previousCount = parent.estimator.getCount();
                    parent.previousSnapshot = parent.estimator.snapshot();
                } catch (IOException e) {
                    // Couldn't get a new snapshot because the window was empty
                    parent.previousCount = 0;
                    parent.previousSnapshot = null;
                }
                parent.estimator.clear();
            }
            parent.setChanged();
        }

    }
}