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.Arrays;
21 import java.util.List;
22
23 import org.apache.commons.logging.Log;
24 import org.apache.commons.logging.LogFactory;
25 import org.apache.hadoop.classification.InterfaceAudience;
26 import org.apache.hadoop.conf.Configuration;
27 import org.apache.hadoop.hbase.ServerName;
28 import org.apache.hadoop.hbase.util.ReflectionUtils;
29 import org.apache.hadoop.net.DNSToSwitchMapping;
30 import org.apache.hadoop.net.ScriptBasedMapping;
31 /**
32 * Wrapper over the rack resolution utility in Hadoop. The rack resolution
33 * utility in Hadoop does resolution from hosts to the racks they belong to.
34 *
35 */
36 @InterfaceAudience.Private
37 public class RackManager {
38 static final Log LOG = LogFactory.getLog(RackManager.class);
39 public static final String UNKNOWN_RACK = "Unknown Rack";
40
41 private DNSToSwitchMapping switchMapping;
42
43 public RackManager(Configuration conf) {
44 switchMapping = ReflectionUtils.instantiateWithCustomCtor(
45 conf.getClass("hbase.util.ip.to.rack.determiner", ScriptBasedMapping.class,
46 DNSToSwitchMapping.class).getName(), new Class<?>[]{Configuration.class},
47 new Object[]{conf});
48 }
49
50 /**
51 * Get the name of the rack containing a server, according to the DNS to
52 * switch mapping.
53 * @param server the server for which to get the rack name
54 * @return the rack name of the server
55 */
56 public String getRack(ServerName server) {
57 if (server == null) {
58 return UNKNOWN_RACK;
59 }
60 // just a note - switchMapping caches results (at least the implementation should unless the
61 // resolution is really a lightweight process)
62 List<String> racks = switchMapping.resolve(Arrays.asList(server.getHostname()));
63 if (racks != null && !racks.isEmpty()) {
64 return racks.get(0);
65 }
66
67 return UNKNOWN_RACK;
68 }
69 }