有没有实例-Go服务器开发

以下是一个简单的示例，展示如何使用gRPC构建C++观察者模式的分布式系统。

在这个示例中，我们假设存在一个名为”Sensor”的主题，它负责传递温度数据给注册的观察者。当温度发生变化时，所有观察者都会收到更新通知。

首先，定义 protobuf 文件（sensor.proto）：

syntax = "proto3";
package sensor;
message Temperature {
  float value = 1;
}
service SensorService {
  rpc RegisterObserver(stream Temperature) returns (stream Temperature);
}

然后生成 C++ 代码库：

protoc -I=. --grpc_out=. --cpp_out=. sensor.proto

接下来，实现服务器端代码（sensor_server.cc）：

#include <iostream>
#include <memory>
#include <string>
#include <unordered_set>
#include <grpcpp/grpcpp.h>
#include "sensor.grpc.pb.h"
using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerContext;
using grpc::Status;
using sensor::Temperature;
using sensor::SensorService;
class SensorServiceImpl final : public SensorService::Service {
public:
    Status RegisterObserver(ServerContext* context, grpc::ServerReader<Temperature>* reader,
                            grpc::ServerWriter<Temperature>* writer) override {
        std::cout << "New observer registered." << std::endl;
        while(reader->Read(&temperature_)) {
            // 假设温度变化后通知所有观察者
            for(auto& observer : observers_) {
                observer->Write(temperature_);
            }
        }
        return Status::OK;
    }
    void RegisterObserver(std::unique_ptr<grpc::ServerReaderWriter<Temperature, Temperature>> observer) {
        observers_.insert(std::move(observer));
    }
private:
    Temperature temperature_;
    std::unordered_set<std::unique_ptr<grpc::ServerReaderWriter<Temperature, Temperature>>> observers_;
};
void RunServer() {
    std::string server_address("0.0.0.0:50051");
    SensorServiceImpl 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;
}

最后，实现客户端代码（sensor_client.cc）：

#include <iostream>
#include <memory>
#include <string>
#include <grpcpp/grpcpp.h>
#include "sensor.grpc.pb.h"
using grpc::Channel;
using grpc::ClientContext;
using grpc::ClientReaderWriter;
using grpc::Status;
using sensor::Temperature;
using sensor::SensorService;
class SensorClient {
public:
    explicit SensorClient(std::shared_ptr<Channel> channel)
        : stub_(SensorService::NewStub(channel)) {}
    void RegisterAsObserver() {
        ClientContext context;
        std::shared_ptr<ClientReaderWriter<Temperature, Temperature>> stream(
            stub_->RegisterObserver(&context));
        Temperature temperature;
        while(true) {
            // 假设从传感器获取温度数据并发送到服务器
            temperature.set_value(getTemperatureFromSensor());
            stream->Write(temperature);
            
            if(!stream->Read(&temperature)) {
                break; // 读取失败，退出循环
            }
            std::cout << "Temperature update received: " << temperature.value() << std::endl;
        }
        stream->WritesDone();
        Status status = stream->Finish();
        if(!status.ok()) {
            std::cout << "Observer disconnected with error: " << status.error_message() << std::endl;
        }
    }
private:
    float getTemperatureFromSensor() {
        // 假设从传感器获取温度数据的实现
        // 这里只是返回一个随机数
        return rand() % 100;
    }
    std::unique_ptr<SensorService::Stub> stub_;
};
int main(int argc, char** argv) {
    SensorClient client(grpc::CreateChannel("localhost:50051", grpc::InsecureChannelCredentials()));
    
    client.RegisterAsObserver();
    return 0;
}