/**
    * 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 org.apache.commons.lang.StringUtils;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.metrics.Histogram;
  import org.apache.hadoop.hbase.metrics.Interns;
  import org.apache.hadoop.hbase.metrics.Snapshot;
  import org.apache.hadoop.hbase.metrics.impl.HistogramImpl;
  import org.apache.hadoop.metrics2.MetricHistogram;
  import org.apache.hadoop.metrics2.MetricsInfo;
  import org.apache.hadoop.metrics2.MetricsRecordBuilder;
  
  /**
   * A histogram implementation that runs in constant space, and exports to hadoop2's metrics2 system.
   */
  @InterfaceAudience.Private
  public class MutableHistogram extends MutableMetric implements MetricHistogram {
    protected HistogramImpl histogram;
    protected final String name;
    protected final String desc;
  
    public MutableHistogram(MetricsInfo info) {
      this(info.name(), info.description());
    }
  
    public MutableHistogram(String name, String description) {
      this(name, description, Integer.MAX_VALUE << 2);
    }
  
    protected MutableHistogram(String name, String description, long maxExpected) {
      this.name = StringUtils.capitalize(name);
      this.desc = StringUtils.uncapitalize(description);
      this.histogram = new HistogramImpl();
    }
  
    public void add(final long val) {
      histogram.update(val);
    }
  
    public long getMax() {
      return histogram.getMax();
    }
  
    @Override
    public synchronized void snapshot(MetricsRecordBuilder metricsRecordBuilder, boolean all) {
      snapshot(name, desc, histogram, metricsRecordBuilder, all);
    }
  
    public static void snapshot(String name, String desc, Histogram histogram,
                                MetricsRecordBuilder metricsRecordBuilder, boolean all) {
      // Get a reference to the old histogram.
      Snapshot snapshot = histogram.snapshot();
      if (snapshot != null) {
        updateSnapshotMetrics(name, desc, histogram, snapshot, metricsRecordBuilder);
      }
    }
  
    protected static void updateSnapshotMetrics(String name, String desc, Histogram histogram,
        Snapshot snapshot, MetricsRecordBuilder metricsRecordBuilder) {
      metricsRecordBuilder.addCounter(Interns.info(name + NUM_OPS_METRIC_NAME, desc),
          histogram.getCount());
      metricsRecordBuilder.addGauge(Interns.info(name + MIN_METRIC_NAME, desc), snapshot.getMin());
      metricsRecordBuilder.addGauge(Interns.info(name + MAX_METRIC_NAME, desc), snapshot.getMax());
      metricsRecordBuilder.addGauge(Interns.info(name + MEAN_METRIC_NAME, desc), snapshot.getMean());
  
      metricsRecordBuilder.addGauge(Interns.info(name + TWENTY_FIFTH_PERCENTILE_METRIC_NAME, desc),
          snapshot.get25thPercentile());
      metricsRecordBuilder.addGauge(Interns.info(name + MEDIAN_METRIC_NAME, desc),
          snapshot.getMedian());
      metricsRecordBuilder.addGauge(Interns.info(name + SEVENTY_FIFTH_PERCENTILE_METRIC_NAME, desc),
          snapshot.get75thPercentile());
      metricsRecordBuilder.addGauge(Interns.info(name + NINETIETH_PERCENTILE_METRIC_NAME, desc),
          snapshot.get90thPercentile());
      metricsRecordBuilder.addGauge(Interns.info(name + NINETY_FIFTH_PERCENTILE_METRIC_NAME, desc),
          snapshot.get95thPercentile());
      metricsRecordBuilder.addGauge(Interns.info(name + NINETY_EIGHTH_PERCENTILE_METRIC_NAME, desc),
          snapshot.get98thPercentile());
      metricsRecordBuilder.addGauge(Interns.info(name + NINETY_NINETH_PERCENTILE_METRIC_NAME, desc),
          snapshot.get99thPercentile());
      metricsRecordBuilder.addGauge(
          Interns.info(name + NINETY_NINE_POINT_NINETH_PERCENTILE_METRIC_NAME, desc),
         snapshot.get999thPercentile());
   }
 }