content: /*
   * 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.cassandra.metrics;
  
  import com.codahale.metrics.Snapshot;
  
  /**
   * An alternative to Dropwizard Histogram which implements the same kind of API.
   * it has more efficent counting operations and consumes less memory.
   * The counter logic is implemented using {@link ThreadLocalMetrics} functionality.
   *
   * NOTE: Dropwizard Histogram is a concrete class and there is no an interface for Dropwizard Histogram logic,
   *   so we have to create an alternative API hierarchy.
   */
  public class ThreadLocalHistogram extends OverrideHistogram
  {
      private final int countMetricId;
  
      /**
       * Creates a new {@link ThreadLocalHistogram} with the given reservoir.
       *
       * @param reservoir the reservoir to create a histogram from
       */
      public ThreadLocalHistogram(CassandraReservoir reservoir)
      {
          super(reservoir);
          this.countMetricId = ThreadLocalMetrics.allocateMetricId();
          ThreadLocalMetrics.destroyWhenUnreachable(this, countMetricId);
      }
  
      /**
       * Adds a recorded value.
       *
       * @param value the length of the value
       */
      public void update(int value)
      {
          update((long) value);
      }
  
      /**
       * Adds a recorded value.
       *
       * @param value the length of the value
       */
      public void update(long value)
      {
          ThreadLocalMetrics.add(countMetricId, 1);
          reservoir.update(value);
      }
  
      /**
       * Returns the number of values recorded.
       *
       * @return the number of values recorded
       */
      @Override
      public long getCount()
      {
          return ThreadLocalMetrics.getCount(countMetricId);
      }
  
      public void reset()
      {
          ThreadLocalMetrics.getCountAndReset(countMetricId);
      }
  
      @Override
      public Snapshot getSnapshot()
      {
          return reservoir.getSnapshot();
      }
  }
  