hbase-server/src/main/java/org/apache/hadoop/hbase/master/RackManager.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18 package org.apache.hadoop.hbase.master;
  19
  20 import java.util.ArrayList;
  21 import java.util.Arrays;
  22 import java.util.Collections;
  23 import java.util.List;
  24
  25 import org.apache.yetus.audience.InterfaceAudience;
  26 import org.slf4j.Logger;
  27 import org.slf4j.LoggerFactory;
  28 import org.apache.hadoop.conf.Configuration;
  29 import org.apache.hadoop.hbase.ServerName;
  30 import org.apache.hadoop.hbase.util.ReflectionUtils;
  31 import org.apache.hadoop.net.DNSToSwitchMapping;
  32 import org.apache.hadoop.net.ScriptBasedMapping;
  33 /**
  34  * Wrapper over the rack resolution utility in Hadoop. The rack resolution
  35  * utility in Hadoop does resolution from hosts to the racks they belong to.
  36  *
  37  */
  38 @InterfaceAudience.Private
  39 public class RackManager {
  40   private static final Logger LOG = LoggerFactory.getLogger(RackManager.class);
  41   public static final String UNKNOWN_RACK = "Unknown Rack";
  42
  43   private DNSToSwitchMapping switchMapping;
  44
  45   public RackManager() {
  46   }
  47
  48   public RackManager(Configuration conf) {
  49     switchMapping = ReflectionUtils.instantiateWithCustomCtor(
  50         conf.getClass("hbase.util.ip.to.rack.determiner", ScriptBasedMapping.class,
  51              DNSToSwitchMapping.class).getName(), new Class<?>[]{Configuration.class},
  52                new Object[]{conf});
  53   }
  54
  55   /**
  56    * Get the name of the rack containing a server, according to the DNS to
  57    * switch mapping.
  58    * @param server the server for which to get the rack name
  59    * @return the rack name of the server
  60    */
  61   public String getRack(ServerName server) {
  62     if (server == null) {
  63       return UNKNOWN_RACK;
  64     }
  65     // just a note - switchMapping caches results (at least the implementation should unless the
  66     // resolution is really a lightweight process)
  67     List<String> racks = switchMapping.resolve(Collections.singletonList(server.getHostname()));
  68     if (racks != null && !racks.isEmpty()) {
  69       return racks.get(0);
  70     }
  71
  72     return UNKNOWN_RACK;
  73   }
  74
  75   /**
  76    * Same as {@link #getRack(ServerName)} except that a list is passed
  77    * @param servers list of servers we're requesting racks information for
  78    * @return list of racks for the given list of servers
  79    */
  80   public List<String> getRack(List<ServerName> servers) {
  81     // just a note - switchMapping caches results (at least the implementation should unless the
  82     // resolution is really a lightweight process)
  83     List<String> serversAsString = new ArrayList<>(servers.size());
  84     for (ServerName server : servers) {
  85       serversAsString.add(server.getHostname());
  86     }
  87     List<String> racks = switchMapping.resolve(serversAsString);
  88     return racks;
  89   }
  90 }