什么是gRPC

RPC 即远程过程调用协议（Remote Procedure Call Protocol），可以让我们像调用本地对象一样发起
远程调用。RPC 凭借其强大的治理功能，成为解决分布式系统通信问题的一大利器。
gRPC是一个现代的、高性能、开源的和语言无关的通用 RPC 框架，基于 HTTP2 协议设计，序列化使用
PB(Protocol Buffer)，PB 是一种语言无关的高性能序列化框架，基于 HTTP2+PB 保证了的高性能。

本文介绍如何使用C++利用gRPC来编写client和server的代码。

rpc范例的一般编写流程

1. 编写proto文件
2. 根据proto文件生成对应的.cc和.h文件
3. server程序继承service
4. client程序使用stub
5. 编译server和client程序

proto文件编写

syntax = "proto3";
package IM.Login; //生成.h文件后变为IM::Login namespace//定义服务
service ImLogin {//定义服务函数rpc Regist (IMRegisterReq) returns (IMRegisterRes) {}rpc Login (IMLoginReq) returns (IMLoginRes) {}
}//注册账号,根据这个生成一个C++类，并自动提供一些修改和获取成员的方法
message IMRegisterReq {string user_name = 1;string password = 2;
}message IMRegisterRes {string user_name = 1;uint32 user_id = 2;uint32 result_code = 3;
}message IMLoginReq {string user_name = 1;string password = 2;
}message IMLoginRes {uint32 user_id = 1;uint32 result_code = 2;
}

输入如下指令生成protobuf序列化后的代码 IM.Login.pb.cc和IM.Login.pb.h：

jyhlinux@ubuntu:~/grpc-v1.45.2/examples/cpp/im_login$ protoc --cpp_out=. IM.Login.proto

// $SRC_DIR: .proto 所在的源目录
// --cpp_out: 生成 c++ 代码
// $DST_DIR: 生成代码的目标目录
// xxx.proto: 要针对哪个 proto 文件生成接口代码
protoc -I=$SRC_DIR --cpp_out=$DST_DIR $SRC_DIR/xxx.proto

生成的.cc文件和.h文件的类型是什么样呢？举个例子，比如下方proto代码

message IMLoginReq {string user_name = 1;string password = 2;
}

生成类似于如下的C++代码：IM.Login.pb.h(不完全)

class IMLoginReq final {// string user_name = 1;void clear_user_name();void set_user_name(ArgT0&& arg0, ArgT... args);// string password = 2;void clear_password();void set_user_name(ArgT0&& arg0, ArgT... args);};

输入下方指令生成服务框架代码

jyhlinux@ubuntu:~/grpc-v1.45.2/examples/cpp/im_login$ protoc --cpp_out=. --grpc_out=. --plugin=protoc-gen-grpc=/usr/local/bin/grpc_cpp_plugin IM.Login.proto

生成服务框架的代码，在当前目录下生成 simple.grpc.pb.h 和 simple.grpc.pb.cc 文件

grpc server端代码编写

注意要引入正确的命名空间和头文件

#include 
#include 
#include //grpc头文件
#include 
#include 
#include #include "IM.Login.grpc.pb.h"
#include "IM.Login.pb.h"using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerContext;
using grpc::Status;using IM::Login::ImLogin;
using IM::Login::IMRegisterReq;
using IM::Login::IMRegisterRes;
using IM::Login::IMLoginReq;
using IM::Login::IMLoginRes;class IMLoginServiceImpl : public ImLogin::Service{virtual Status Regist(ServerContext* context, const IMRegisterReq* request, IMRegisterRes* response) override {std::cout<<"Regist user_name:" << request->user_name() << std::endl;response->set_user_name(request->user_name()); // 这也是插件自动生成的函数 set_属性名()response->set_user_id(10);response->set_result_code(0);return Status::OK;}virtual Status Login(ServerContext* context, const IMLoginReq* request, IMLoginRes* response) override {std::cout << "Login user_name: " << request->user_name() << std::endl;response->set_user_id(10);response->set_result_code(0);return Status::OK;}
};void RunServer() {std::string server_addr("0.0.0.0:50001");//服务类实例IMLoginServiceImpl service;ServerBuilder builder;//第二参数: The credentials associated with the server.builder.AddListeningPort(server_addr, grpc::InsecureServerCredentials());builder.AddChannelArgument(GRPC_ARG_KEEPALIVE_TIME_MS, 5000);builder.AddChannelArgument(GRPC_ARG_KEEPALIVE_TIMEOUT_MS, 10000);//是否允许在没有任何未完成流的情况下发送保持连接的ping包builder.AddChannelArgument(GRPC_ARG_KEEPALIVE_PERMIT_WITHOUT_CALLS, 1);builder.RegisterService(&service);//创建启动std::unique_ptr server(builder.BuildAndStart());std::cout << "Server listening on " << server_addr << std::endl;server->Wait();
}int main(int argc, const char** argv) {RunServer();return 0;
}

grpc client端

#include 
#include 
#include //grpc头文件
#include 
#include 
#include #include "IM.Login.grpc.pb.h"
#include "IM.Login.pb.h"using grpc::Channel;
using grpc::ClientContext;
using grpc::Status;using IM::Login::ImLogin;
using IM::Login::IMRegisterReq;
using IM::Login::IMRegisterRes;
using IM::Login::IMLoginReq;
using IM::Login::IMLoginRes;class ImLoginClient{
public:ImLoginClient(std::shared_ptr channel):stub_(ImLogin::NewStub(channel)){}void Regist(const std::string &user_name, const std::string &password) {IMRegisterReq request;request.set_user_name(user_name);request.set_password(password);IMRegisterRes response;ClientContext context;std::cout << "-> Regist req" << std::endl; Status status = stub_->Regist(&context, request, &response);if(status.ok()) {std::cout << "user_name: " << response.user_name() << ", user_id: " << response.user_id() << std::endl;} else {std::cout << "user_name: " << response.user_name() << ",Regist failed: " << response.result_code() << std::endl;}}void Login(const std::string &user_name, const std::string &password) {IMLoginReq request;request.set_user_name(user_name);request.set_password(password);IMLoginRes response;ClientContext context;std::cout << "-> Login req" << std::endl; Status status = stub_->Login(&context, request, &response);if(status.ok()) {std::cout << "user_id: " << response.user_id() << ", login ok" << std::endl;} else {std::cout << "user_name: " << request.user_name() << ",Login failed: " << response.result_code() << std::endl;}}private:std::unique_ptr stub_;
};int main() {std::string server_addr = "localhost:50001";ImLoginClient im_login_client(grpc::CreateChannel(server_addr, grpc::InsecureChannelCredentials()));std::string user_name = "jyh";std::string password = "123456";im_login_client.Regist(user_name, password);im_login_client.Login(user_name, password);return 0;
}

异步gRPC server端代码编写

#include 
#include 
#include 
#include #include "IM.Login.grpc.pb.h"
#include "IM.Login.pb.h"
#include 
#include using grpc::Server;
using grpc::ServerAsyncResponseWriter;
using grpc::ServerBuilder;
using grpc::ServerCompletionQueue; // 
using grpc::ServerContext;
using grpc::Status;using IM::Login::ImLogin;
using IM::Login::IMRegisterReq;
using IM::Login::IMRegisterRes;
using IM::Login::IMLoginReq;
using IM::Login::IMLoginRes;class ServerImpl final {
public:~ServerImpl() {server_->Shutdown();cq_->Shutdown();}void Run() {std::string server_address("0.0.0.0:50001");//成员初始化ServerBuilder builder;builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());builder.RegisterService(&service_); // 初始化service_cq_ = builder.AddCompletionQueue();server_ = builder.BuildAndStart(); // std::cout << "Server listening on " << server_address << std::endl;//Proceed to the server's main loopHandleRpcs();}private:class CallData{public:CallData(ImLogin::AsyncService* service, ServerCompletionQueue* cq):service_(service), cq_(cq), status_(CREATE){std::cout << "CallData constructing, this:" << this << std::endl;Proceed();}virtual ~CallData(){}virtual void Proceed() {return;}//与异步服务器的 gRPC 运行时进行通信的方式。ImLogin::AsyncService* service_;ServerCompletionQueue *cq_;ServerContext ctx_;enum CallStatus{CREATE, PROCESS, FINISH};CallStatus status_; //current serving state};class RegistCallData : public CallData {public:RegistCallData(ImLogin::AsyncService* service, ServerCompletionQueue* cq):CallData(service, cq), responder_(&ctx_){Proceed();}~RegistCallData(){}void Proceed() override {std::cout << "this: " << this <<" RegistCallData Proceed(), status : " << status_<< std::endl;//状态机if(status_ == CREATE) {std::cout << "this: " << this <<" RegistCallData Proceed(), status : " << "CREATE"<< std::endl;status_ = PROCESS; // //this唯一标识这个request(故不同实例可并发的服务不同的requests)service_->RequestRegist(&ctx_, &request_, &responder_, cq_, cq_,this);} else if(status_ == PROCESS) {std::cout << "this: " << this <<" RegistCallData Proceed(), status : " << "PROCESS"<< std::endl;new RegistCallData(service_, cq_); //1. 创建处理逻辑reply_.set_user_name(request_.user_name());reply_.set_user_id(10);reply_.set_result_code(0);status_ = FINISH;responder_.Finish(reply_, Status::OK, this);} else  {std::cout << "this: " << this <<" RegistCallData Proceed(), status : " << "FINISH"<< std::endl;GPR_ASSERT(status_ == FINISH);delete this;}}private:IMRegisterReq request_;IMRegisterRes reply_;ServerAsyncResponseWriter responder_;};class LoginCallData : public CallData {public:LoginCallData(ImLogin::AsyncService* service, ServerCompletionQueue* cq):CallData(service, cq), responder_(&ctx_){Proceed();}~LoginCallData(){}void Proceed() override {std::cout << "this: " << this <<" LoginCallData Proceed(), status : " << status_<< std::endl;//状态机if(status_ == CREATE) {std::cout << "this: " << this <<" LoginCallData Proceed(), status : " << "CREATE"<< std::endl;status_ = PROCESS; // //this唯一标识这个request(故不同实例可并发的服务不同的requests)service_->RequestLogin(&ctx_, &request_, &responder_, cq_, cq_,this);} else if(status_ == PROCESS) {std::cout << "this: " << this <<" LoginCallData Proceed(), status : " << "PROCESS"<< std::endl;new LoginCallData(service_, cq_); //1. 创建处理逻辑reply_.set_user_id(10);reply_.set_result_code(0);status_ = FINISH;responder_.Finish(reply_, Status::OK, this);} else  {std::cout << "this: " << this <<" LoginCallData Proceed(), status : " << "FINISH"<< std::endl;GPR_ASSERT(status_ == FINISH);delete this;}}private:IMLoginReq request_;IMLoginRes reply_;ServerAsyncResponseWriter responder_;};void HandleRpcs() { // 可运行在多线程new RegistCallData(&service_, cq_.get()); //new LoginCallData(&service_, cq_.get());void* tag;bool ok;while(true) {std::cout << "before cq_->Next "<< std::endl;// Read from the queue, blocking until an event is available or the queue is// shutting down.GPR_ASSERT(cq_->Next(&tag, &ok));std::cout << "after cq_->Next " << std::endl;          GPR_ASSERT(ok);std::cout << "before static_cast" << std::endl;static_cast(tag)->Proceed();std::cout << "after static_cast" << std::endl;}}std::unique_ptr cq_;ImLogin::AsyncService service_; //与异步服务器的 gRPC 运行时进行通信的方式std::unique_ptr server_;
};int main() {ServerImpl server;server.Run();    return 0;
}

CMakeLists文件编写

这个CMakeLists.txt是从/grpc-v1.45.2/examples/cpp/helloworld中拷贝出来进行修改的,

这个CMakeLists.txt文件放在稍后会创建的build目录下（examples/cpp/im_login/build/）

#修改的地方用changed标记cmake_minimum_required(VERSION 3.5.1)project(IMLogin C CXX)  #changedinclude(../cmake/common.cmake)# Proto file
get_filename_component(im_proto "./IM.Login.proto" ABSOLUTE) #changed
get_filename_component(im_proto_path "${im_proto}" PATH) #changed# Generated sources
set(im_proto_srcs "${CMAKE_CURRENT_BINARY_DIR}/IM.Login.pb.cc") #changed
set(im_proto_hdrs "${CMAKE_CURRENT_BINARY_DIR}/IM.Login.pb.h") #changed
set(im_grpc_srcs "${CMAKE_CURRENT_BINARY_DIR}/IM.Login.grpc.pb.cc") #changed
set(im_grpc_hdrs "${CMAKE_CURRENT_BINARY_DIR}/IM.Login.grpc.pb.h") #changed
add_custom_command( #changedOUTPUT "${im_proto_srcs}" "${im_proto_hdrs}" "${im_grpc_srcs}" "${im_grpc_hdrs}"COMMAND ${_PROTOBUF_PROTOC}ARGS --grpc_out "${CMAKE_CURRENT_BINARY_DIR}"--cpp_out "${CMAKE_CURRENT_BINARY_DIR}"-I "${im_proto_path}"--plugin=protoc-gen-grpc="${_GRPC_CPP_PLUGIN_EXECUTABLE}""${im_proto}"DEPENDS "${im_proto}")# Include generated *.pb.h files
include_directories("${CMAKE_CURRENT_BINARY_DIR}")# im_grpc_proto
#changed
add_library(im_grpc_proto${im_grpc_srcs}${im_grpc_hdrs}${im_proto_srcs}${im_proto_hdrs})
target_link_libraries(im_grpc_proto${_REFLECTION}${_GRPC_GRPCPP}${_PROTOBUF_LIBPROTOBUF})# Targets greeter_[async_](client|server)
foreach(_targetclient server async_server #生成的可执行程序名)add_executable(${_target} "${_target}.cc")target_link_libraries(${_target}im_grpc_proto${_REFLECTION}${_GRPC_GRPCPP}${_PROTOBUF_LIBPROTOBUF})
endforeach()

编译测试

cd ~/grpc-v1.45.2/examples/cpp/im_login/
mkdir build 
cmake ..
make

进行测试1

#终端1执行
./server
#终端2执行
./client

进行测试2

#终端1执行
./async_server
#终端2执行
./client

测试结果：

服务端

jyhlinux@ubuntu:~/grpc-v1.45.2/examples/cpp/im_login/build$ ./async_server 
Server listening on 0.0.0.0:50001
CallData constructing, this:0x55a0d9d11c50
this: 0x55a0d9d11c50 RegistCallData Proceed(), status : 0
this: 0x55a0d9d11c50 RegistCallData Proceed(), status : CREATE
CallData constructing, this:0x55a0d9d12420
this: 0x55a0d9d12420 LoginCallData Proceed(), status : 0
this: 0x55a0d9d12420 LoginCallData Proceed(), status : CREATE
before cq_->Next 
after cq_->Next 
before static_cast
this: 0x55a0d9d11c50 RegistCallData Proceed(), status : 1
this: 0x55a0d9d11c50 RegistCallData Proceed(), status : PROCESS
CallData constructing, this:0x55a0d9d28620
this: 0x55a0d9d28620 RegistCallData Proceed(), status : 0
this: 0x55a0d9d28620 RegistCallData Proceed(), status : CREATE
after static_cast
before cq_->Next 
after cq_->Next 
before static_cast
this: 0x55a0d9d11c50 RegistCallData Proceed(), status : 2
this: 0x55a0d9d11c50 RegistCallData Proceed(), status : FINISH
after static_cast
before cq_->Next 
after cq_->Next 
before static_cast
this: 0x55a0d9d12420 LoginCallData Proceed(), status : 1
this: 0x55a0d9d12420 LoginCallData Proceed(), status : PROCESS
CallData constructing, this:0x55a0d9d11c50
this: 0x55a0d9d11c50 LoginCallData Proceed(), status : 0
this: 0x55a0d9d11c50 LoginCallData Proceed(), status : CREATE
after static_cast
before cq_->Next 
after cq_->Next 
before static_cast
this: 0x55a0d9d12420 LoginCallData Proceed(), status : 2
this: 0x55a0d9d12420 LoginCallData Proceed(), status : FINISH
after static_cast
before cq_->Next 

客户端

jyhlinux@ubuntu:~/grpc-v1.45.2/examples/cpp/im_login/build$ ./client 
-> Regist req
user_name: jyh, user_id: 10
-> Login req
user_id: 10, login ok