001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to you under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.hadoop.hbase.util;
018
019import edu.umd.cs.findbugs.annotations.NonNull;
020import java.lang.reflect.Method;
021import java.net.UnknownHostException;
022
023import org.apache.hadoop.conf.Configuration;
024import org.apache.hadoop.hbase.HBaseInterfaceAudience;
025import org.apache.yetus.audience.InterfaceAudience;
026
027/**
028 * Wrapper around Hadoop's DNS class to hide reflection.
029 */
030@InterfaceAudience.Private
031@edu.umd.cs.findbugs.annotations.SuppressWarnings(value="REC_CATCH_EXCEPTION",
032  justification="If exception, presume HAS_NEW_DNS_GET_DEFAULT_HOST_API false")
033public final class DNS {
034  // key to the config parameter of server hostname
035  // the specification of server hostname is optional. The hostname should be resolvable from
036  // both master and region server
037  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
038  public static final String RS_HOSTNAME_KEY = "hbase.regionserver.hostname";
039  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
040  public static final String MASTER_HOSTNAME_KEY = "hbase.master.hostname";
041
042  private static boolean HAS_NEW_DNS_GET_DEFAULT_HOST_API;
043  private static Method GET_DEFAULT_HOST_METHOD;
044
045  static {
046    try {
047      GET_DEFAULT_HOST_METHOD = org.apache.hadoop.net.DNS.class
048          .getMethod("getDefaultHost", String.class, String.class, boolean.class);
049      HAS_NEW_DNS_GET_DEFAULT_HOST_API = true;
050    } catch (Exception e) {
051      HAS_NEW_DNS_GET_DEFAULT_HOST_API = false; // FindBugs: Causes REC_CATCH_EXCEPTION. Suppressed
052    }
053  }
054
055  public enum ServerType {
056    MASTER("master"),
057    REGIONSERVER("regionserver");
058
059    private String name;
060    ServerType(String name) {
061      this.name = name;
062    }
063
064    public String getName() {
065      return name;
066    }
067  }
068
069  private DNS() {}
070
071  /**
072   * Wrapper around DNS.getDefaultHost(String, String), calling
073   * DNS.getDefaultHost(String, String, boolean) when available.
074   *
075   * @param strInterface The network interface to query.
076   * @param nameserver The DNS host name.
077   * @return The default host names associated with IPs bound to the network interface.
078   */
079  public static String getDefaultHost(String strInterface, String nameserver)
080      throws UnknownHostException {
081    if (HAS_NEW_DNS_GET_DEFAULT_HOST_API) {
082      try {
083        // Hadoop-2.8 includes a String, String, boolean variant of getDefaultHost
084        // which properly handles multi-homed systems with Kerberos.
085        return (String) GET_DEFAULT_HOST_METHOD.invoke(null, strInterface, nameserver, true);
086      } catch (Exception e) {
087        // If we can't invoke the method as it should exist, throw an exception
088        throw new RuntimeException("Failed to invoke DNS.getDefaultHost via reflection", e);
089      }
090    } else {
091      return org.apache.hadoop.net.DNS.getDefaultHost(strInterface, nameserver);
092    }
093  }
094
095  /**
096   * Get the configured hostname for a given ServerType. Gets the default hostname if not specified
097   * in the configuration.
098   * @param conf Configuration to look up.
099   * @param serverType ServerType to look up in the configuration for overrides.
100   */
101  public static String getHostname(@NonNull Configuration conf, @NonNull ServerType serverType)
102      throws UnknownHostException {
103    String hostname;
104    switch (serverType) {
105      case MASTER:
106        hostname = conf.get(MASTER_HOSTNAME_KEY);
107        break;
108      case REGIONSERVER:
109        hostname = conf.get(RS_HOSTNAME_KEY);
110        break;
111      default:
112        hostname = null;
113    }
114    if (hostname == null || hostname.isEmpty()) {
115      return Strings.domainNamePointerToHostName(getDefaultHost(
116          conf.get("hbase." + serverType.getName() + ".dns.interface", "default"),
117          conf.get("hbase." + serverType.getName() + ".dns.nameserver", "default")));
118    } else {
119      return hostname;
120    }
121  }
122}