hadoop/hadoop-common-project/hadoop-common/src/main/proto/RpcHeader.proto

/**
 * 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.
 */
option java_package = "org.apache.hadoop.ipc.protobuf";
option java_outer_classname = "RpcHeaderProtos";
option java_generate_equals_and_hash = true;
package hadoop.common;

/**
 * This is the rpc request header. It is sent with every rpc call.
 * 
 * The format of RPC call is as follows:
 * +--------------------------------------------------------------+
 * | Rpc length in bytes (4 bytes int) sum of next two parts      |
 * +--------------------------------------------------------------+
 * | RpcRequestHeaderProto - serialized delimited ie has len      |
 * +--------------------------------------------------------------+
 * | RpcRequest The actual rpc request                            |
 * | This request is serialized based on RpcKindProto             |
 * +--------------------------------------------------------------+
 *
 */

/**
 * RpcKind determine the rpcEngine and the serialization of the rpc request
 */
enum RpcKindProto {
  RPC_BUILTIN          = 0;  // Used for built in calls by tests
  RPC_WRITABLE         = 1;  // Use WritableRpcEngine 
  RPC_PROTOCOL_BUFFER  = 2;  // Use ProtobufRpcEngine
}


   
message RpcRequestHeaderProto { // the header for the RpcRequest
  enum OperationProto {
    RPC_FINAL_PACKET        = 0; // The final RPC Packet
    RPC_CONTINUATION_PACKET = 1; // not implemented yet
    RPC_CLOSE_CONNECTION     = 2; // close the rpc connection
  }

  optional RpcKindProto rpcKind = 1;
  optional OperationProto rpcOp = 2;
  required uint32 callId = 3; // each rpc has a callId that is also used in response
}



/**
 * Rpc Response Header
 * ** If request is successfull response is returned as below ********
 * +------------------------------------------------------------------+
 * | Rpc reponse length in bytes (4 bytes int)                        |
 * |  (sum of next two parts)                                         |
 * +------------------------------------------------------------------+
 * | RpcResponseHeaderProto - serialized delimited ie has len         |
 * +------------------------------------------------------------------+
 * | if request is successful:                                        |
 * |   - RpcResponse -  The actual rpc response  bytes follow         |
 *       the response header                                          |
 * |     This response is serialized based on RpcKindProto            |
 * | if request fails :                                               |
 * |   The rpc response header contains the necessary info            |
 * +------------------------------------------------------------------+
 *
 */
message RpcResponseHeaderProto {
  enum RpcStatusProto {
   SUCCESS = 0;  // RPC succeeded
   ERROR = 1;    // RPC Failed
   FATAL = 2;    // Fatal error - connection is closed
  }

  required uint32 callId = 1; // callId used in Request
  required RpcStatusProto status = 2;
  optional uint32 serverIpcVersionNum = 3; // Sent if success or fail
  optional string exceptionClassName = 4;  // if request fails
  optional string errorMsg = 5;  // if request fails, often contains strack trace
}