/*

  * 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.requests;

 import org.apache.giraph.comm.ServerData;

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

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

 import java.io.DataInput;

 import java.io.DataOutput;

 import java.io.IOException;

 import static com.google.common.base.Preconditions.checkState;

 /**

  * Send to a worker a signal to resume sending messages to sender worker. This

  * type of request is used in adaptive credit-based flow control, where a

  * worker (W) may assign credit value of 0 to some worker (U), so that U would

  * stop sending messages to W. Later on, W may want to notify U to continue

  * sending messages to W. Along with the resume signal, W also announces a new

  * credit value to U.

  */

 public class SendResumeRequest extends WritableRequest

     implements WorkerRequest {

   /** credit value */

   private short credit;

   /** Constructor used for reflection only */

   public SendResumeRequest() { }

   /**

    * Constructor

    *

    * @param credit credit value

    */

   public SendResumeRequest(short credit) {

     checkState(credit > 0);

     this.credit = credit;

   }

   @Override

   public void doRequest(ServerData serverData) {

     FlowControl flowControl =

         serverData.getServiceWorker().getWorkerClient().getFlowControl();

     checkState(flowControl != null);

     ((CreditBasedFlowControl) flowControl).processResumeSignal(getClientId(),

         credit, getRequestId());

   }

   @Override

   public RequestType getType() {

     return RequestType.SEND_RESUME_REQUEST;

   }

   @Override

   void readFieldsRequest(DataInput input) throws IOException {

     credit = input.readShort();

   }

   @Override

   void writeRequest(DataOutput output) throws IOException {

     output.writeShort(credit);

   }

 }