/*

  * 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.giraph.comm;

 import java.io.IOException;

 import org.apache.giraph.comm.flow_control.FlowControl;

 import org.apache.giraph.comm.requests.WritableRequest;

 import org.apache.hadoop.io.Writable;

 /**

  * Interface for master to send messages to workers

  */

 public interface MasterClient {

   /**

    * Make sure that all the connections to workers have been established.

    */

   void openConnections();

   /**

    * Sends aggregator to its owner

    *

    * @param name Name of the object

    * @param type Global communication type

    * @param value Object value

    * @throws IOException

    */

   void sendToOwner(String name, GlobalCommType type, Writable value)

     throws IOException;

   /**

    * Flush aggregated values cache.

    */

   void finishSendingValues() throws IOException;

   /**

    * Flush all outgoing messages.  This will synchronously ensure that all

    * messages have been send and delivered prior to returning.

    */

   void flush();

   /**

    * Send a request to a remote server (should be already connected)

    *

    * @param destTaskId Destination worker id

    * @param request Request to send

    */

   void sendWritableRequest(int destTaskId, WritableRequest request);

   /**

    * Closes all connections.

    */

   void closeConnections();

   /**

    * Get the reference to the flow control policy used for sending requests

    *

    * @return reference to the flow control policy

    */

   FlowControl getFlowControl();

 }