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.bookkeeper.stats;
  
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import org.apache.commons.configuration2.Configuration;
  
  /**
   * A {@code CachingStatsProvider} adds the caching functionality to an existing {@code StatsProvider}.
   *
   * <p>The stats provider will cache the stats objects created by the other {@code StatsProvider} to allow
   * the reusability of stats objects and avoid creating a lot of stats objects.
   */
  public class CachingStatsProvider implements StatsProvider {
  
      protected final StatsProvider underlying;
      protected final ConcurrentMap<String, StatsLogger> statsLoggers;
  
      public CachingStatsProvider(StatsProvider provider) {
          this.underlying = provider;
          this.statsLoggers = new ConcurrentHashMap<String, StatsLogger>();
      }
  
      @Override
      public void start(Configuration conf) {
          this.underlying.start(conf);
      }
  
      @Override
      public void stop() {
          this.underlying.stop();
      }
  
      @Override
      public StatsLogger getStatsLogger(String scope) {
          StatsLogger statsLogger = statsLoggers.get(scope);
          if (null == statsLogger) {
              StatsLogger newStatsLogger =
                      new CachingStatsLogger(underlying.getStatsLogger(scope));
              StatsLogger oldStatsLogger = statsLoggers.putIfAbsent(scope, newStatsLogger);
              statsLogger = (null == oldStatsLogger) ? newStatsLogger : oldStatsLogger;
          }
          return statsLogger;
      }
  
      @Override
      public String getStatsName(String... statsComponents) {
          return underlying.getStatsName(statsComponents);
      }
  }
  