Source code

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,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.wake.remote.address;
020
021import org.apache.reef.tang.Configuration;
022import org.apache.reef.tang.Tang;
023
024import javax.inject.Inject;
025import java.net.Inet4Address;
026import java.net.UnknownHostException;
027import java.util.logging.Level;
028import java.util.logging.Logger;
029
030/**
031 * A LocalAddressProvider that uses <code>Inet4Address.getLocalHost().getHostAddress()</code>.
032 */
033public final class HostnameBasedLocalAddressProvider implements LocalAddressProvider {
034  private static final Logger LOG = Logger.getLogger(HostnameBasedLocalAddressProvider.class.getName());
035  private String cached = null;
036
037  /**
038   * The constructor is for Tang only.
039   */
040  @Inject
041  private HostnameBasedLocalAddressProvider() {
042    LOG.log(Level.FINE, "Instantiating HostnameBasedLocalAddressProvider");
043  }
044
045  @Override
046  public synchronized String getLocalAddress() {
047    if (null == cached) {
048      try {
049        cached = Inet4Address.getLocalHost().getHostAddress();
050      } catch (final UnknownHostException ex) {
051        final String message = "Unable to resolve LocalHost. This is fatal.";
052        LOG.log(Level.SEVERE, message, ex);
053        throw new RuntimeException(message, ex);
054      }
055    }
056    assert null != cached;
057    return cached;
058  }
059
060  @Override
061  public Configuration getConfiguration() {
062    return Tang.Factory.getTang().newConfigurationBuilder()
063        .bind(LocalAddressProvider.class, HostnameBasedLocalAddressProvider.class)
064        .build();
065  }
066}