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1   /**
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.metrics2.lib;
20  
21  import static org.apache.hadoop.metrics2.lib.Interns.info;
22  
23  import java.io.IOException;
24  import java.util.Map;
25  import java.util.concurrent.TimeUnit;
26  
27  import org.apache.commons.lang.StringUtils;
28  import org.apache.hadoop.classification.InterfaceAudience;
29  import org.apache.hadoop.metrics2.MetricHistogram;
30  import org.apache.hadoop.metrics2.MetricsExecutor;
31  import org.apache.hadoop.metrics2.MetricsInfo;
32  import org.apache.hadoop.metrics2.MetricsRecordBuilder;
33  import org.apache.hadoop.metrics2.util.MetricQuantile;
34  import org.apache.hadoop.metrics2.util.MetricSampleQuantiles;
35  
36  import com.google.common.annotations.VisibleForTesting;
37  
38  /**
39   * Watches a stream of long values, maintaining online estimates of specific quantiles with provably
40   * low error bounds. This is particularly useful for accurate high-percentile (e.g. 95th, 99th)
41   * latency metrics.
42   */
43  @InterfaceAudience.Private
44  public class MetricMutableQuantiles extends MutableMetric implements MetricHistogram {
45  
46    static final MetricQuantile[] quantiles = {new MetricQuantile(0.50, 0.050),
47        new MetricQuantile(0.75, 0.025), new MetricQuantile(0.90, 0.010),
48        new MetricQuantile(0.95, 0.005), new MetricQuantile(0.99, 0.001)};
49  
50    private final MetricsInfo numInfo;
51    private final MetricsInfo[] quantileInfos;
52    private final int interval;
53  
54    private MetricSampleQuantiles estimator;
55    private long previousCount = 0;
56    private MetricsExecutor executor;
57  
58  
59    @VisibleForTesting
60    protected Map<MetricQuantile, Long> previousSnapshot = null;
61  
62    /**
63     * Instantiates a new {@link MetricMutableQuantiles} for a metric that rolls itself over on the
64     * specified time interval.
65     *
66     * @param name        of the metric
67     * @param description long-form textual description of the metric
68     * @param sampleName  type of items in the stream (e.g., "Ops")
69     * @param valueName   type of the values
70     * @param interval    rollover interval (in seconds) of the estimator
71     */
72    public MetricMutableQuantiles(String name, String description, String sampleName,
73                                  String valueName, int interval) {
74      String ucName = StringUtils.capitalize(name);
75      String usName = StringUtils.capitalize(sampleName);
76      String uvName = StringUtils.capitalize(valueName);
77      String desc = StringUtils.uncapitalize(description);
78      String lsName = StringUtils.uncapitalize(sampleName);
79      String lvName = StringUtils.uncapitalize(valueName);
80  
81      numInfo = info(ucName + "Num" + usName, String.format(
82          "Number of %s for %s with %ds interval", lsName, desc, interval));
83      // Construct the MetricsInfos for the quantiles, converting to percentiles
84      quantileInfos = new MetricsInfo[quantiles.length];
85      String nameTemplate = "%s%dthPercentile%dsInterval%s";
86      String descTemplate = "%d percentile %s with %d second interval for %s";
87      for (int i = 0; i < quantiles.length; i++) {
88        int percentile = (int) (100 * quantiles[i].quantile);
89        quantileInfos[i] = info(String.format(nameTemplate, ucName, percentile, interval, uvName),
90            String.format(descTemplate, percentile, lvName, interval, desc));
91      }
92  
93      estimator = new MetricSampleQuantiles(quantiles);
94      executor = new MetricsExecutorImpl();
95      this.interval = interval;
96      executor.getExecutor().scheduleAtFixedRate(new RolloverSample(this),
97          interval,
98          interval,
99          TimeUnit.SECONDS);
100   }
101 
102   @Override
103   public synchronized void snapshot(MetricsRecordBuilder builder, boolean all) {
104     if (all || changed()) {
105       builder.addGauge(numInfo, previousCount);
106       for (int i = 0; i < quantiles.length; i++) {
107         long newValue = 0;
108         // If snapshot is null, we failed to update since the window was empty
109         if (previousSnapshot != null) {
110           newValue = previousSnapshot.get(quantiles[i]);
111         }
112         builder.addGauge(quantileInfos[i], newValue);
113       }
114       if (changed()) {
115         clearChanged();
116       }
117     }
118   }
119 
120   public synchronized void add(long value) {
121     estimator.insert(value);
122   }
123 
124   public int getInterval() {
125     return interval;
126   }
127 
128   /** Runnable used to periodically roll over the internal {@link org.apache.hadoop.metrics2.util.MetricSampleQuantiles} every interval. */
129   private static class RolloverSample implements Runnable {
130 
131     MetricMutableQuantiles parent;
132 
133     public RolloverSample(MetricMutableQuantiles parent) {
134       this.parent = parent;
135     }
136 
137     @Override
138     public void run() {
139       synchronized (parent) {
140         try {
141           parent.previousCount = parent.estimator.getCount();
142           parent.previousSnapshot = parent.estimator.snapshot();
143         } catch (IOException e) {
144           // Couldn't get a new snapshot because the window was empty
145           parent.previousCount = 0;
146           parent.previousSnapshot = null;
147         }
148         parent.estimator.clear();
149       }
150       parent.setChanged();
151     }
152 
153   }
154 }