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

Introduction

Here is the source code for org.apache.hadoop.metrics2.lib.MutableHistogram.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 java.util.concurrent.atomic.AtomicLong;

import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.metrics2.MetricHistogram;
import org.apache.hadoop.metrics2.MetricsInfo;
import org.apache.hadoop.metrics2.MetricsRecordBuilder;

import com.yammer.metrics.stats.ExponentiallyDecayingSample;
import com.yammer.metrics.stats.Sample;
import com.yammer.metrics.stats.Snapshot;

/**
 * A histogram implementation that runs in constant space, and exports to hadoop2's metrics2 system.
 */
@InterfaceAudience.Private
public class MutableHistogram extends MutableMetric implements MetricHistogram {

    private static final int DEFAULT_SAMPLE_SIZE = 2046;
    // the bias towards sampling from more recent data.
    // Per Cormode et al. an alpha of 0.015 strongly biases to the last 5 minutes
    private static final double DEFAULT_ALPHA = 0.015;

    private final String name;
    private final String desc;
    private final Sample sample;
    private final AtomicLong min;
    private final AtomicLong max;
    private final AtomicLong sum;
    private final AtomicLong count;

    public MutableHistogram(MetricsInfo info) {
        this(info.name(), info.description());
    }

    public MutableHistogram(String name, String description) {
        this.name = StringUtils.capitalize(name);
        this.desc = StringUtils.uncapitalize(description);
        sample = new ExponentiallyDecayingSample(DEFAULT_SAMPLE_SIZE, DEFAULT_ALPHA);
        count = new AtomicLong();
        min = new AtomicLong(Long.MAX_VALUE);
        max = new AtomicLong(Long.MIN_VALUE);
        sum = new AtomicLong();
    }

    public void add(final long val) {
        setChanged();
        count.incrementAndGet();
        sample.update(val);
        setMax(val);
        setMin(val);
        sum.getAndAdd(val);
    }

    private void setMax(final long potentialMax) {
        boolean done = false;
        while (!done) {
            final long currentMax = max.get();
            done = currentMax >= potentialMax || max.compareAndSet(currentMax, potentialMax);
        }
    }

    private void setMin(long potentialMin) {
        boolean done = false;
        while (!done) {
            final long currentMin = min.get();
            done = currentMin <= potentialMin || min.compareAndSet(currentMin, potentialMin);
        }
    }

    public long getMax() {
        if (count.get() > 0) {
            return max.get();
        }
        return 0L;
    }

    public long getMin() {
        if (count.get() > 0) {
            return min.get();
        }
        return 0L;
    }

    public double getMean() {
        long cCount = count.get();
        if (cCount > 0) {
            return sum.get() / (double) cCount;
        }
        return 0.0;
    }

    @Override
    public void snapshot(MetricsRecordBuilder metricsRecordBuilder, boolean all) {
        if (all || changed()) {
            clearChanged();
            final Snapshot s = sample.getSnapshot();
            metricsRecordBuilder.addCounter(Interns.info(name + NUM_OPS_METRIC_NAME, desc), count.get());

            metricsRecordBuilder.addGauge(Interns.info(name + MIN_METRIC_NAME, desc), getMin());
            metricsRecordBuilder.addGauge(Interns.info(name + MAX_METRIC_NAME, desc), getMax());
            metricsRecordBuilder.addGauge(Interns.info(name + MEAN_METRIC_NAME, desc), getMean());

            metricsRecordBuilder.addGauge(Interns.info(name + MEDIAN_METRIC_NAME, desc), s.getMedian());
            metricsRecordBuilder.addGauge(Interns.info(name + SEVENTY_FIFTH_PERCENTILE_METRIC_NAME, desc),
                    s.get75thPercentile());
            metricsRecordBuilder.addGauge(Interns.info(name + NINETY_FIFTH_PERCENTILE_METRIC_NAME, desc),
                    s.get95thPercentile());
            metricsRecordBuilder.addGauge(Interns.info(name + NINETY_NINETH_PERCENTILE_METRIC_NAME, desc),
                    s.get99thPercentile());
        }
    }
}