grpc C++，服务器关闭

Question

wait() 函数的 grpc 文档指出： ...或其他一些线程必须调用 Shutdown 才能使此函数返回。 我不得不承认，我不知道该怎么做。有什么帮助吗？谢谢。

Answer 1

Shutdown() 是服务器接口上的一个方法： https://grpc.github.io/grpc/cpp/classgrpc_1_1_server_interface.html#a6a1d337270116c95f387e0abf01f6c6c

另一个线程需要在您定义的某个触发器上调用它以彻底关闭 gRPC 服务器。

Answer 2

我想出了以下解决方案（基于 Hello World 示例）。任何 cmet 表示赞赏。

/*
 *
 * Copyright 2015 gRPC authors.
 *
 * Licensed 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.
 *
 */


///The trace macro
#if defined NDEBUG
#define TRACE( format, ... )
#else
#define TRACE( format, ... )   printf( "+++  %s::%s(%d) +++ " format, __FILE__, __FUNCTION__,  __LINE__, __VA_ARGS__ )
#endif


#include <iostream>
#include <memory>
#include <string>
//Add
#include <pthread.h>

#include <grpcpp/ext/proto_server_reflection_plugin.h>
#include <grpcpp/grpcpp.h>
#include <grpcpp/health_check_service_interface.h>

#ifdef BAZEL_BUILD
#include "examples/protos/helloworld.grpc.pb.h"
#else
#include "helloworld.grpc.pb.h"
#endif

using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerContext;
using grpc::Status;
using helloworld::Greeter;
using helloworld::HelloReply;
using helloworld::HelloRequest;

// Logic and data behind the server's behavior.
class GreeterServiceImpl final : public Greeter::Service {
    //Add constructor and destructor (optional)
        GreeterServiceImpl() :
            Greeter::Service ()     {
         TRACE("Executing GreeterServiceImpl constructor%s", "\n");
    }
    ~GreeterServiceImpl()   {
         TRACE("Executing GreeterServiceImpl destructor%s", "\n");
    }

  Status SayHello(ServerContext* context, const HelloRequest* request,
                  HelloReply* reply) override {
    std::string prefix("Hello ");
    reply->set_message(prefix + request->name());
    return Status::OK;
  }
};

pthread_t tid; // Shutdown thread handle

//thread function
void* doShutdown(void  *server)
{
    TRACE("Entering doShutdown  %s", "\n");
                    
    getchar();  // press a key to shutdown the thread

    ((Server*)(server))->Shutdown();        
    std::cout << "Server is shutting down. "<< std::endl;
    return NULL;
}

void RunServer() {
  std::string server_address("0.0.0.0:50051");
  GreeterServiceImpl service;

  grpc::EnableDefaultHealthCheckService(true);
  grpc::reflection::InitProtoReflectionServerBuilderPlugin();
  ServerBuilder builder;
  // Listen on the given address without any authentication mechanism.
  builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
  // Register "service" as the instance through which we'll communicate with
  // clients. In this case it corresponds to an *synchronous* service.
  builder.RegisterService(&service);
  // Finally assemble the server.
  std::unique_ptr<Server> server(builder.BuildAndStart());
  std::cout << "Server listening on " << server_address << std::endl;

  // Wait for the server to shutdown. Note that some other thread must be
  // responsible for shutting down the server for this call to ever return.
      int err = pthread_create(&(tid), NULL, &doShutdown, &(*server));
     if (err != 0)
             TRACE("Can't create Shutdown thread :[%s]", strerror(err));
     else
             std::cout << "Press the <ENTER> key to shutdown the server." << std::endl;
  
  
  server->Wait();
}

int main(int argc, char** argv) {
  RunServer();

  return 0;
}