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.apex.malhar.flume.discovery;
  
  import java.util.Collection;
  
  /**
   * When FlumeSink server instance binds to the network interface, it can publish
   * its whereabouts by invoking advertise method on the Discovery object. Similarly
   * when it ceases accepting any more connections, it can publish its intent to do
   * so by invoking unadvertise.<p />
   * Interesting parties can call discover method to get the list of addresses where
   * they can find an available FlumeSink server instance.
   *
   * @param <T> - Type of the objects which can be discovered
   * @since 0.9.3
   */
  public interface Discovery<T>
  {
    /**
     * Recall the previously published address as it's no longer valid.
     *
     * @param service
     */
    void unadvertise(Service<T> service);
  
    /**
     * Advertise the host/port address where FlumeSink is accepting a client connection.
     *
     * @param service
     */
    void advertise(Service<T> service);
  
    /**
     * Discover all the addresses which are actively accepting the client connections.
     *
     * @return - Active server addresses which can accept the connections.
     */
    Collection<Service<T>> discover();
  
    interface Service<T>
    {
      String getHost();
  
      int getPort();
  
      T getPayload();
  
      String getId();
  
    }
  
  }
  