001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.util;
019
020import edu.umd.cs.findbugs.annotations.NonNull;
021import java.lang.reflect.Method;
022import java.net.UnknownHostException;
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 UNSAFE_RS_HOSTNAME_KEY = "hbase.unsafe.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  /**
046   * Hostname configuration key
047   * @deprecated since 2.4.0 and will be removed in 4.0.0. Use {@link DNS#UNSAFE_RS_HOSTNAME_KEY}
048   *             instead.
049   * @see <a href="https://issues.apache.org/jira/browse/HBASE-24667">HBASE-24667</a>
050   */
051  @Deprecated
052  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
053  public static final String RS_HOSTNAME_KEY = "hbase.regionserver.hostname";
054
055  static {
056    try {
057      GET_DEFAULT_HOST_METHOD = org.apache.hadoop.net.DNS.class.getMethod("getDefaultHost",
058        String.class, String.class, boolean.class);
059      HAS_NEW_DNS_GET_DEFAULT_HOST_API = true;
060    } catch (Exception e) {
061      HAS_NEW_DNS_GET_DEFAULT_HOST_API = false; // FindBugs: Causes REC_CATCH_EXCEPTION. Suppressed
062    }
063  }
064
065  public enum ServerType {
066    MASTER("master"),
067    REGIONSERVER("regionserver");
068
069    private final String name;
070
071    private ServerType(String name) {
072      this.name = name;
073    }
074
075    public String getName() {
076      return name;
077    }
078  }
079
080  private DNS() {
081  }
082
083  /**
084   * Wrapper around DNS.getDefaultHost(String, String), calling DNS.getDefaultHost(String, String,
085   * boolean) when available.
086   * @param strInterface The network interface to query.
087   * @param nameserver   The DNS host name.
088   * @return The default host names associated with IPs bound to the network interface.
089   */
090  public static String getDefaultHost(String strInterface, String nameserver)
091    throws UnknownHostException {
092    if (HAS_NEW_DNS_GET_DEFAULT_HOST_API) {
093      try {
094        // Hadoop-2.8 includes a String, String, boolean variant of getDefaultHost
095        // which properly handles multi-homed systems with Kerberos.
096        return (String) GET_DEFAULT_HOST_METHOD.invoke(null, strInterface, nameserver, true);
097      } catch (Exception e) {
098        // If we can't invoke the method as it should exist, throw an exception
099        throw new RuntimeException("Failed to invoke DNS.getDefaultHost via reflection", e);
100      }
101    } else {
102      return org.apache.hadoop.net.DNS.getDefaultHost(strInterface, nameserver);
103    }
104  }
105
106  /**
107   * Get the configured hostname for a given ServerType. Gets the default hostname if not specified
108   * in the configuration.
109   * @param conf       Configuration to look up.
110   * @param serverType ServerType to look up in the configuration for overrides.
111   */
112  public static String getHostname(@NonNull Configuration conf, @NonNull ServerType serverType)
113    throws UnknownHostException {
114    String hostname;
115    switch (serverType) {
116      case MASTER:
117        hostname = conf.get(MASTER_HOSTNAME_KEY);
118        break;
119      case REGIONSERVER:
120        hostname = conf.get(UNSAFE_RS_HOSTNAME_KEY);
121        break;
122      default:
123        hostname = null;
124    }
125    if (hostname == null || hostname.isEmpty()) {
126      return Strings.domainNamePointerToHostName(
127        getDefaultHost(conf.get("hbase." + serverType.getName() + ".dns.interface", "default"),
128          conf.get("hbase." + serverType.getName() + ".dns.nameserver", "default")));
129    } else {
130      return hostname;
131    }
132  }
133}