grpc+protobuf 的C++ service 实例解析

这篇文章将会简单的描述一下grpc+protobuf 的C++ service的搭建过程，告诉读者在linux系统下怎样实现一个service接口的流程。

一、.proto文件的

实现一个简单的helloworld回显功能，首先需要一个.proto文件，我将它命名为example.proto，文件内容如下：

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syntax = "proto3";  
  
message SearchRequest  
{  
    string Request = 1;  
}  
  
message SearchResponse  
{  
    string Response = 2;  
}  
  
service SearchService {  
        rpc Search (SearchRequest) returns (SearchResponse);  
}  

二、自动生成代码

使用example.proto文件自动生成grpc和protobuf的代码

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protoc --cpp_out=./ examples.proto  
protoc --grpc_out=./ --plugin=protoc-gen-grpc=/usr/local/bin/grpc_cpp_plugin examples.proto  

这两个命令将会生成四个文件，examples.grpc.pb.cc、examples.grpc.pb.h、examples.pb.cc、examples.pb.h。

三、服务器代码

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#include <iostream>  
#include <memory>  
#include <string>  
  
#include <grpc++/grpc++.h>  
#include <grpc/grpc.h>  
#include <grpc++/server.h>  
#include <grpc++/server_builder.h>  
#include <grpc++/server_context.h>  
  
#include "examples.grpc.pb.h"  
  
using grpc::Server;  
using grpc::ServerBuilder;  
using grpc::ServerContext;  
using grpc::Status;  
  
class SearchRequestImpl final : public SearchService::Service {  
  Status Search(ServerContext* context, const SearchRequest* request,  
                  SearchResponse* reply) override {  
    std::string prefix("Hello ");  
    reply->set_response(prefix + request->request());  
    return Status::OK;  
  }  
};  
  
void RunServer() {  
  std::string server_address("0.0.0.0:50051");  
  SearchRequestImpl service;  
  
  ServerBuilder builder;  
  builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());  
  builder.RegisterService(&service);  
  std::unique_ptr<Server> server(builder.BuildAndStart());  
  std::cout << "Server listening on " << server_address << std::endl;  
  
  server->Wait();  
}  
  
int main(int argc, char** argv) {  
  RunServer();  
  
  return 0;  
}  

四、客户端代码

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#include <iostream>  
#include <memory>  
#include <string>  
  
#include <grpc++/grpc++.h>  
#include <grpc/support/log.h>  
  
#include "examples.grpc.pb.h"  
  
using grpc::Channel;  
using grpc::ClientAsyncResponseReader;  
using grpc::ClientContext;  
using grpc::CompletionQueue;  
using grpc::Status;  
  
  
class ExampleClient {  
 public:  
  explicit ExampleClient(std::shared_ptr<Channel> channel)  
      : stub_(SearchService::NewStub(channel)) {}  
   
  std::string Search(const std::string& user) {  
   
    SearchRequest request;  
    request.set_request(user);  
   
    SearchResponse reply;  
     
    ClientContext context;  
  
    CompletionQueue cq;  
  
    Status status;  
  
    std::unique_ptr<ClientAsyncResponseReader<SearchResponse> > rpc(  
        stub_->AsyncSearch(&context, request, &cq));  
  
    rpc->Finish(&reply, &status, (void*)1);  
    void* got_tag;  
    bool ok = false;  
    
    GPR_ASSERT(cq.Next(&got_tag, &ok));  
  
     
    GPR_ASSERT(got_tag == (void*)1);  
    
    GPR_ASSERT(ok);  
  
    if (status.ok()) {  
      return reply.response();  
    } else {  
      return "RPC failed";  
    }  
  }  
  
 private:  
   
  std::unique_ptr<SearchService::Stub> stub_;  
};  
  
int main(int argc, char** argv) {  
  ExampleClient client(grpc::CreateChannel(  
      "localhost:50051", grpc::InsecureChannelCredentials()));  
  std::string user("world");  
  std::string reply = client.Search(user);  // The actual RPC call!  
  std::cout << "client received: " << reply << std::endl;  
  
  return 0;  
}  

五、Makefile文件

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subdir = ./  
  
export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig  
  
SOURCES = $(wildcard $(subdir)*.cc)  
SRCOBJS = $(patsubst %.cc,%.o,$(SOURCES))  
CC = g++  
  
%.o:%.cc  
    $(CC) -std=c++11 -I/usr/local/include -pthread -c $< -o $@  
  
all: client server  
  
client: examples.grpc.pb.o examples.pb.o examples_client.o  
    $(CC) $^ -L/usr/local/lib `pkg-config --libs grpc++ grpc` -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed -lprotobuf -lpthread -ldl -lssl -o $@  
  
server: examples.grpc.pb.o examples.pb.o examples_server.o  
    $(CC) $^ -L/usr/local/lib `pkg-config --libs grpc++ grpc` -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed -lprotobuf -lpthread -ldl -lssl -o $@  
#chmod 777 $@  
  
clean:  
    sudo rm *.o  

六、运行

运行./server启动service，在另一个端口运行./client 打印出：client received: Hello world表示两边已通，grpc+protobuf 搭建完成。