/**
    * 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.hbase.client;
  
  import com.google.common.annotations.VisibleForTesting;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.client.backoff.ServerStatistics;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos;
  
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  /**
   * Tracks the statistics for multiple regions
   */
  @InterfaceAudience.Private
  public class ServerStatisticTracker implements StatisticTrackable {
  
    private final ConcurrentHashMap<ServerName, ServerStatistics> stats =
        new ConcurrentHashMap<ServerName, ServerStatistics>();
  
    @Override
    public void updateRegionStats(ServerName server, byte[] region, ClientProtos.RegionLoadStats
        currentStats) {
      ServerStatistics stat = stats.get(server);
  
      if (stat == null) {
        stat = stats.get(server);
        // We don't have stats for that server yet, so we need to make an entry.
        // If we race with another thread it's a harmless unnecessary allocation.
        if (stat == null) {
          stat = new ServerStatistics();
          ServerStatistics old = stats.putIfAbsent(server, stat);
          if (old != null) {
            stat = old;
  	}
        }
      }
      stat.update(region, currentStats);
    }
  
    public ServerStatistics getStats(ServerName server) {
      return this.stats.get(server);
    }
  
    public static ServerStatisticTracker create(Configuration conf) {
      if (!conf.getBoolean(HConstants.ENABLE_CLIENT_BACKPRESSURE,
          HConstants.DEFAULT_ENABLE_CLIENT_BACKPRESSURE)) {
        return null;
      }
      return new ServerStatisticTracker();
    }
  
    @VisibleForTesting
    ServerStatistics getServerStatsForTesting(ServerName server) {
      return stats.get(server);
    }
  }