/*
 * 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;

import org.apache.yetus.audience.InterfaceAudience;

/**
 * Metrics Histogram interface. Implementing classes will expose computed quartile values through
 * the metrics system.
 */
@InterfaceAudience.Private
public interface MetricHistogram {

  // Strings used to create metrics names.
  String NUM_OPS_METRIC_NAME = "_num_ops";
  String MIN_METRIC_NAME = "_min";
  String MAX_METRIC_NAME = "_max";
  String MEAN_METRIC_NAME = "_mean";
  String MEDIAN_METRIC_NAME = "_median";
  String TWENTY_FIFTH_PERCENTILE_METRIC_NAME = "_25th_percentile";
  String SEVENTY_FIFTH_PERCENTILE_METRIC_NAME = "_75th_percentile";
  String NINETIETH_PERCENTILE_METRIC_NAME = "_90th_percentile";
  String NINETY_FIFTH_PERCENTILE_METRIC_NAME = "_95th_percentile";
  String NINETY_EIGHTH_PERCENTILE_METRIC_NAME = "_98th_percentile";
  String NINETY_NINETH_PERCENTILE_METRIC_NAME = "_99th_percentile";
  String NINETY_NINE_POINT_NINETH_PERCENTILE_METRIC_NAME = "_99.9th_percentile";

  /**
   * Add a single value to a histogram's stream of values.
   */
  void add(long value);

  /**
   * Return the total number of values added to the histogram.
   * @return the total number of values.
   */
  long getCount();

}
