/**
 * 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.ha.proto";
option java_outer_classname = "HAServiceProtocolProtos";
option java_generic_services = true;
option java_generate_equals_and_hash = true;

enum HAServiceStateProto {
  INITIALIZING = 0;
  ACTIVE = 1;
  STANDBY = 2;
}

/**
 * void request
 */
message MonitorHealthRequestProto { 
}

/**
 * void response
 */
message MonitorHealthResponseProto { 
}

/**
 * void request
 */
message TransitionToActiveRequestProto { 
}

/**
 * void response
 */
message TransitionToActiveResponseProto { 
}

/**
 * void request
 */
message TransitionToStandbyRequestProto { 
}

/**
 * void response
 */
message TransitionToStandbyResponseProto { 
}

/**
 * void request
 */
message GetServiceStatusRequestProto { 
}

/**
 * Returns the state of the service
 */
message GetServiceStatusResponseProto { 
  required HAServiceStateProto state = 1;

  // If state is STANDBY, indicate whether it is
  // ready to become active.
  optional bool readyToBecomeActive = 2;
  // If not ready to become active, a textual explanation of why not
  optional string notReadyReason = 3;
}

/**
 * Protocol interface provides High availability related 
 * primitives to monitor and failover a service.
 *
 * For details see o.a.h.ha.HAServiceProtocol.
 */
service HAServiceProtocolService {
  /**
   * Monitor the health of a service.
   */
  rpc monitorHealth(MonitorHealthRequestProto)
      returns(MonitorHealthResponseProto);

  /**
   * Request service to tranisition to active state.
   */
  rpc transitionToActive(TransitionToActiveRequestProto)
      returns(TransitionToActiveResponseProto);

  /**
   * Request service to transition to standby state.
   */
  rpc transitionToStandby(TransitionToStandbyRequestProto)
      returns(TransitionToStandbyResponseProto);

  /**
   * Get the current status of the service.
   */
  rpc getServiceStatus(GetServiceStatusRequestProto)
      returns(GetServiceStatusResponseProto);
}
