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.bifromq.baserpc.client;
  
  import static java.util.Collections.emptyMap;
  
  import java.util.Map;
  import java.util.concurrent.CompletableFuture;
  
  /**
   * The caller for unary RPC.
   *
   * @param <ReqT>  the request type
   * @param <RespT> the response type
   */
  interface IUnaryCaller<ReqT, RespT> {
      /**
       * Invoke a request to the desired server.
       *
       * @param tenantId         the tenant id
       * @param targetServerId   the target server id, can be null
       * @param req              the request to send
       * @return a CompletableFuture of the response
       */
      default CompletableFuture<RespT> invoke(String tenantId, String targetServerId, ReqT req) {
          return invoke(tenantId, targetServerId, req, emptyMap());
      }
  
      /**
       * Invoke a request to the desired server with metadata.
       *
       * @param tenantId the tenant id
       * @param targetServerId the target server id, can be null
       * @param req the request to send
       * @param metadata additional metadata to attach to the request
       * @return a CompletableFuture of the response
       */
      CompletableFuture<RespT> invoke(String tenantId,
                                      String targetServerId,
                                      ReqT req,
                                      Map<String, String> metadata);
  }
  