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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;
20  
21  /**
22   * Metrics Histogram interface.  Implementing classes will expose computed
23   * quartile values through the metrics system.
24   */
25  public interface MetricHistogram {
26  
27    //Strings used to create metrics names.
28    String NUM_OPS_METRIC_NAME = "_num_ops";
29    String MIN_METRIC_NAME = "_min";
30    String MAX_METRIC_NAME = "_max";
31    String MEAN_METRIC_NAME = "_mean";
32    String MEDIAN_METRIC_NAME = "_median";
33    String TWENTY_FIFTH_PERCENTILE_METRIC_NAME = "_25th_percentile";
34    String SEVENTY_FIFTH_PERCENTILE_METRIC_NAME = "_75th_percentile";
35    String NINETIETH_PERCENTILE_METRIC_NAME = "_90th_percentile";
36    String NINETY_FIFTH_PERCENTILE_METRIC_NAME = "_95th_percentile";
37    String NINETY_EIGHTH_PERCENTILE_METRIC_NAME = "_98th_percentile";
38    String NINETY_NINETH_PERCENTILE_METRIC_NAME = "_99th_percentile";
39    String NINETY_NINE_POINT_NINETH_PERCENTILE_METRIC_NAME = "_99.9th_percentile";
40  
41    /**
42     * Add a single value to a histogram's stream of values.
43     * @param value
44     */
45    void add(long value);
46  
47  }