content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.bookkeeper.net;
  
  import com.google.common.annotations.Beta;
  import java.util.List;
  import org.apache.bookkeeper.proto.BookieAddressResolver;
  
  /**
   * An interface that must be implemented to allow pluggable
   * DNS-name/IP-address to RackID resolvers.
   *
   */
  @Beta
  public interface DNSToSwitchMapping {
      /**
       * Resolves a list of DNS-names/IP-addresses and returns back a list of
       * switch information (network paths). One-to-one correspondence must be
       * maintained between the elements in the lists.
       * Consider an element in the argument list - x.y.com. The switch information
       * that is returned must be a network path of the form /foo/rack,
       * where / is the root, and 'foo' is the switch where 'rack' is connected.
       * Note the hostname/ip-address is not part of the returned path.
       * The network topology of the cluster would determine the number of
       * components in the network path.
       *
       * <p>If a name cannot be resolved to a rack, the implementation
       * should return {@link NetworkTopology#DEFAULT_REGION_AND_RACK}. This
       * is what the bundled implementations do, though it is not a formal requirement
       *
       * @param names the list of hosts to resolve (can be empty)
       * @return list of resolved network paths.
       * If <i>names</i> is empty, the returned list is also empty
       */
      List<String> resolve(List<String> names);
  
      /**
       * Reload all of the cached mappings.
       *
       * <p>If there is a cache, this method will clear it, so that future accesses
       * will get a chance to see the new data.
       */
      void reloadCachedMappings();
  
      /**
       * Hints what to use with implementation when InetSocketAddress is converted
       * to String:
       * hostname (addr.getHostName(), default)
       * or IP address (addr.getAddress().getHostAddress()).
       * @return true if hostname, false if IP address. Default is true.
        */
      default boolean useHostName() {
          return true;
      }
  
      /**
       * Receives the current BookieAddressResolver.
       * @param bookieAddressResolver
       */
      default void setBookieAddressResolver(BookieAddressResolver bookieAddressResolver) {
      }
  }
  