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.List;
23
24 import org.apache.commons.logging.Log;
25 import org.apache.commons.logging.LogFactory;
26 import org.apache.hadoop.hbase.classification.InterfaceAudience;
27 import org.apache.hadoop.conf.Configuration;
28 import org.apache.hadoop.hbase.ServerName;
29 import org.apache.hadoop.hbase.util.ReflectionUtils;
30 import org.apache.hadoop.net.DNSToSwitchMapping;
31 import org.apache.hadoop.net.ScriptBasedMapping;
32 /**
33 * Wrapper over the rack resolution utility in Hadoop. The rack resolution
34 * utility in Hadoop does resolution from hosts to the racks they belong to.
35 *
36 */
37 @InterfaceAudience.Private
38 public class RackManager {
39 private static final Log LOG = LogFactory.getLog(RackManager.class);
40 public static final String UNKNOWN_RACK = "Unknown Rack";
41
42 private DNSToSwitchMapping switchMapping;
43
44 public RackManager() {
45 }
46
47 public RackManager(Configuration conf) {
48 switchMapping = ReflectionUtils.instantiateWithCustomCtor(
49 conf.getClass("hbase.util.ip.to.rack.determiner", ScriptBasedMapping.class,
50 DNSToSwitchMapping.class).getName(), new Class<?>[]{Configuration.class},
51 new Object[]{conf});
52 }
53
54 /**
55 * Get the name of the rack containing a server, according to the DNS to
56 * switch mapping.
57 * @param server the server for which to get the rack name
58 * @return the rack name of the server
59 */
60 public String getRack(ServerName server) {
61 if (server == null) {
62 return UNKNOWN_RACK;
63 }
64 // just a note - switchMapping caches results (at least the implementation should unless the
65 // resolution is really a lightweight process)
66 List<String> racks = switchMapping.resolve(Arrays.asList(server.getHostname()));
67 if (racks != null && !racks.isEmpty()) {
68 return racks.get(0);
69 }
70
71 return UNKNOWN_RACK;
72 }
73
74 /**
75 * Same as {@link #getRack(ServerName)} except that a list is passed
76 * @param servers list of servers we're requesting racks information for
77 * @return list of racks for the given list of servers
78 */
79 public List<String> getRack(List<ServerName> servers) {
80 // just a note - switchMapping caches results (at least the implementation should unless the
81 // resolution is really a lightweight process)
82 List<String> serversAsString = new ArrayList<String>(servers.size());
83 for (ServerName server : servers) {
84 serversAsString.add(server.getHostname());
85 }
86 List<String> racks = switchMapping.resolve(serversAsString);
87 return racks;
88 }
89 }