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

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Here is the source code for org.apache.hadoop.metrics2.lib.MutableRatesWithAggregation.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.metrics2.lib;

import com.google.common.collect.Sets;
import java.lang.ref.WeakReference;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedDeque;
import java.util.concurrent.ConcurrentMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.metrics2.MetricsRecordBuilder;
import org.apache.hadoop.metrics2.util.SampleStat;

/**
 * Helper class to manage a group of mutable rate metrics.
 *
 * Each thread will maintain a local rate count, and upon snapshot,
 * these values will be aggregated into a global rate. This class
 * should only be used for long running threads, as any metrics
 * produced between the last snapshot and the death of a thread
 * will be lost. This allows for significantly higher concurrency
 * than {@link MutableRates}. See HADOOP-24420.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class MutableRatesWithAggregation extends MutableMetric {
    static final Log LOG = LogFactory.getLog(MutableRatesWithAggregation.class);
    private final Map<String, MutableRate> globalMetrics = new HashMap<>();
    private final Set<Class<?>> protocolCache = Sets.newHashSet();

    private final ConcurrentLinkedDeque<WeakReference<ConcurrentMap<String, ThreadSafeSampleStat>>> weakReferenceQueue = new ConcurrentLinkedDeque<>();
    private final ThreadLocal<ConcurrentMap<String, ThreadSafeSampleStat>> threadLocalMetricsMap = new ThreadLocal<>();

    /**
     * Initialize the registry with all the methods in a protocol
     * so they all show up in the first snapshot.
     * Convenient for JMX implementations.
     * @param protocol the protocol class
     */
    public void init(Class<?> protocol) {
        if (protocolCache.contains(protocol)) {
            return;
        }
        protocolCache.add(protocol);
        for (Method method : protocol.getDeclaredMethods()) {
            String name = method.getName();
            LOG.debug(name);
            addMetricIfNotExists(name);
        }
    }

    /**
     * Add a rate sample for a rate metric.
     * @param name of the rate metric
     * @param elapsed time
     */
    public void add(String name, long elapsed) {
        ConcurrentMap<String, ThreadSafeSampleStat> localStats = threadLocalMetricsMap.get();
        if (localStats == null) {
            localStats = new ConcurrentHashMap<>();
            threadLocalMetricsMap.set(localStats);
            weakReferenceQueue.add(new WeakReference<>(localStats));
        }
        ThreadSafeSampleStat stat = localStats.get(name);
        if (stat == null) {
            stat = new ThreadSafeSampleStat();
            localStats.put(name, stat);
        }
        stat.add(elapsed);
    }

    @Override
    public synchronized void snapshot(MetricsRecordBuilder rb, boolean all) {
        Iterator<WeakReference<ConcurrentMap<String, ThreadSafeSampleStat>>> iter = weakReferenceQueue.iterator();
        while (iter.hasNext()) {
            ConcurrentMap<String, ThreadSafeSampleStat> map = iter.next().get();
            if (map == null) {
                // Thread has died; clean up its state
                iter.remove();
            } else {
                // Aggregate the thread's local samples into the global metrics
                for (Map.Entry<String, ThreadSafeSampleStat> entry : map.entrySet()) {
                    String name = entry.getKey();
                    MutableRate globalMetric = addMetricIfNotExists(name);
                    entry.getValue().snapshotInto(globalMetric);
                }
            }
        }
        for (MutableRate globalMetric : globalMetrics.values()) {
            globalMetric.snapshot(rb, all);
        }
    }

    private synchronized MutableRate addMetricIfNotExists(String name) {
        MutableRate metric = globalMetrics.get(name);
        if (metric == null) {
            metric = new MutableRate(name, name, false);
            globalMetrics.put(name, metric);
        }
        return metric;
    }

    private static class ThreadSafeSampleStat {

        private SampleStat stat = new SampleStat();

        synchronized void add(double x) {
            stat.add(x);
        }

        synchronized void snapshotInto(MutableRate metric) {
            if (stat.numSamples() > 0) {
                metric.add(stat.numSamples(), Math.round(stat.total()));
                stat.reset();
            }
        }
    }

}