1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to you under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.hadoop.hbase.util;
18
19 import java.lang.reflect.Method;
20 import java.net.UnknownHostException;
21
22 import org.apache.hadoop.hbase.classification.InterfaceAudience;
23
24 /**
25 * Wrapper around Hadoop's DNS class to hide reflection.
26 */
27 @InterfaceAudience.Private
28 public final class DNS {
29 private static boolean HAS_NEW_DNS_GET_DEFAULT_HOST_API;
30 private static Method GET_DEFAULT_HOST_METHOD;
31
32 static {
33 try {
34 GET_DEFAULT_HOST_METHOD = org.apache.hadoop.net.DNS.class
35 .getMethod("getDefaultHost", String.class, String.class, boolean.class);
36 HAS_NEW_DNS_GET_DEFAULT_HOST_API = true;
37 } catch (Exception e) {
38 HAS_NEW_DNS_GET_DEFAULT_HOST_API = false;
39 }
40 }
41
42 private DNS() {}
43
44 /**
45 * Wrapper around DNS.getDefaultHost(String, String), calling
46 * DNS.getDefaultHost(String, String, boolean) when available.
47 *
48 * @param strInterface The network interface to query.
49 * @param nameserver The DNS host name.
50 * @return The default host names associated with IPs bound to the network interface.
51 */
52 public static String getDefaultHost(String strInterface, String nameserver)
53 throws UnknownHostException {
54 if (HAS_NEW_DNS_GET_DEFAULT_HOST_API) {
55 try {
56 // Hadoop-2.8 includes a String, String, boolean variant of getDefaultHost
57 // which properly handles multi-homed systems with Kerberos.
58 return (String) GET_DEFAULT_HOST_METHOD.invoke(null, strInterface, nameserver, true);
59 } catch (Exception e) {
60 // If we can't invoke the method as it should exist, throw an exception
61 throw new RuntimeException("Failed to invoke DNS.getDefaultHost via reflection", e);
62 }
63 } else {
64 return org.apache.hadoop.net.DNS.getDefaultHost(strInterface, nameserver);
65 }
66 }
67 }