【仿RabbitMQ消息队列项目day2】使用muduo库中基于protobuf的应用层协议进行通信_比特仿rabbitmq

作者：小蓝xlanll | 2024-05-29 22:06:56

踩

比特仿rabbitmq

一.什么是muduo?

muduo库是⼀个基于非阻塞IO和事件驱动的C++高并发TCP网络编程库。

简单来理解，它就是对原生的TCP套接字的封装，是一个比socket编程接口更好用的编程库。

二.使用muduo库完成一个英译汉翻译服务

TranslateServer.hpp:


#pragma once
#include <iostream>
#include <functional>
#include <unordered_map>
#include <string>
#include "muduo/net/TcpConnection.h"
#include "muduo/net/TcpServer.h"
#include "muduo/net/EventLoop.h"
 
using std::cout;
using std::endl;
class TranslateServer
{
private:
    muduo::net::EventLoop _baseloop;
    muduo::net::TcpServer _server;
public:
    TranslateServer(int port)
        :_server(&_baseloop, muduo::net::InetAddress("0.0.0.0", port), \
            "TranslateServer", muduo::net::TcpServer::kReusePort)
    {
        //bind是一个函数适配器
        _server.setConnectionCallback(std::bind(&TranslateServer::_onConnection, this, std::placeholders::_1));
        _server.setMessageCallback(std::bind(&TranslateServer::_onMessage, this, std::placeholders::_1, \
            std::placeholders::_2, std::placeholders::_3));
        
    }
    void start()
    {
        _server.start(); //开始事件监听
        _baseloop.loop(); //开始事件监控，这是一个死循环阻塞接口
    }
 
// typedef std::function<void (const TcpConnectionPtr&)> ConnectionCallback;
// typedef std::function<void (const TcpConnectionPtr&,
//                             Buffer*,
//                             Timestamp)> MessageCallback;
 
    //连接建立成功或者关闭时侯的回调函数
    void _onConnection(const muduo::net::TcpConnectionPtr& conn)
    {
        if (conn->connected())
        {
            cout << "新连接建立成功\n";
        }
        else
        {
            cout << "连接关闭\n";
        }
    }
    //通信连接收到请求时的回调函数
    void _onMessage(const muduo::net::TcpConnectionPtr& conn, muduo::net::Buffer* buffer, muduo::Timestamp time)
    {
        std::string str = buffer->retrieveAllAsString();
        std::string resp = translate(str);
        conn->send(resp);
    }
 
    std::string translate(const std::string& str)
    {
        static std::unordered_map<std::string, std::string> _dict = {
            {"hello", "你好"},
            {"white", "白色"}
        };
 
        if (_dict.count(str))
        {
            return _dict[str];
        }
        return "没找到";
    }
    
};

TranslateClient.hpp:


#pragma once
#include <functional>
#include <iostream>
#include "muduo/net/TcpClient.h"
#include "muduo/net/TcpConnection.h"
#include "muduo/net/EventLoopThread.h"
 
class TranslateClient
{
private:
    muduo::net::EventLoopThread _loopThread; //EventLoop是阻塞式死循环，必须另起一个线程，否则用户无法在主线程输入。
    //_loopThread一建立就立马启动
 
    muduo::net::TcpClient _client;
    muduo::net::TcpConnectionPtr _conn;
    //TcpClient的connect是非阻塞接口，调用立马返回，这有可能导致用户send时尚未建立连接，而解引用空指针
    muduo::CountDownLatch _latch; //保证建立连接和send之间的同步关系
public:
    TranslateClient(const std::string& serverIp, int serverPort)
        :_client(_loopThread.startLoop(), muduo::net::InetAddress(serverIp, serverPort), "TranslateClient")
        ,_latch(1)
    {
        _client.setConnectionCallback(std::bind(&TranslateClient::_onConnection, this, std::placeholders::_1));
        _client.setMessageCallback(std::bind(&TranslateClient::_onMessage, this, std::placeholders::_1, \
            std::placeholders::_2,std::placeholders::_3));
    }
 
    void connect()
    {
        _client.connect();
        _latch.wait();
    }
 
    bool send(std::string& msg)
    {
        if (_conn->connected())
        {
            _conn->send(msg);
            return true;
        }
        else
        {
            return false;
        }
    }
 
private:
    /**************
     * 连接建立或者断开时的回调函数
     * **************/
    void _onConnection(const muduo::net::TcpConnectionPtr &conn)
    {
        if (conn->connected())
        {
            _latch.countDown();
            _conn = conn;
        }
        else
        {
            _conn.reset();
        }
    }
 
    void _onMessage(const muduo::net::TcpConnectionPtr& conn, muduo::net::Buffer* buffer, muduo::Timestamp time)
    {
        std::cout << "翻译结果：" << buffer->retrieveAllAsString() << std::endl;
    }
};

muduo的精髓在于大量的回调函数，建立或断开连接，收到消息时，都会调用我们传入的回调函数，回调函数就是我们处理业务的地方。

三.muduo中基于protobuf的自定义协议

像上述的英译汉服务，双方肯定是能正常通信，但这绝不是一个成熟的方案。TCP通信时面向字节流的，存在数据粘包问题，要想解决必须使用用户层协议。

用户层协议主要就是解决数据粘包问题，另外序列化和反序列化也是其中的重要环节。muduo库是由陈硕大佬编写的，在安装好的muduo库中，他提供了一些编程样例，其中有一个就是基于protobuf，定制了一个用户层协议，用于网络通信。所以严格来说，该自定义协议并不是muduo库中的一部分。


class ProtobufCodec : muduo::noncopyable
{
 public:
 
  enum ErrorCode
  {
    kNoError = 0,
    kInvalidLength,
    kCheckSumError,
    kInvalidNameLen,
    kUnknownMessageType,
    kParseError,
  };
 
  typedef std::function<void (const muduo::net::TcpConnectionPtr&,
                                const MessagePtr&,
                                muduo::Timestamp)> ProtobufMessageCallback;
 
  typedef std::function<void (const muduo::net::TcpConnectionPtr&,
                                muduo::net::Buffer*,
                                muduo::Timestamp,
                                ErrorCode)> ErrorCallback;
 
  explicit ProtobufCodec(const ProtobufMessageCallback& messageCb)
    : messageCallback_(messageCb),
      errorCallback_(defaultErrorCallback)
  {
  }
 
  ProtobufCodec(const ProtobufMessageCallback& messageCb, const ErrorCallback& errorCb)
    : messageCallback_(messageCb),
      errorCallback_(errorCb)
  {
  }
 
  void onMessage(const muduo::net::TcpConnectionPtr& conn,
                 muduo::net::Buffer* buf,
                 muduo::Timestamp receiveTime);
 
  void send(const muduo::net::TcpConnectionPtr& conn,
            const google::protobuf::Message& message)
  {
    // FIXME: serialize to TcpConnection::outputBuffer()
    muduo::net::Buffer buf;
    fillEmptyBuffer(&buf, message);
    conn->send(&buf);
  }
 
  static const muduo::string& errorCodeToString(ErrorCode errorCode);
  static void fillEmptyBuffer(muduo::net::Buffer* buf, const google::protobuf::Message& message);
  static google::protobuf::Message* createMessage(const std::string& type_name);
  static MessagePtr parse(const char* buf, int len, ErrorCode* errorCode);
 
 private:
  static void defaultErrorCallback(const muduo::net::TcpConnectionPtr&,
                                   muduo::net::Buffer*,
                                   muduo::Timestamp,
                                   ErrorCode);
 
  ProtobufMessageCallback messageCallback_;
  ErrorCallback errorCallback_;
 
  const static int kHeaderLen = sizeof(int32_t);
  const static int kMinMessageLen = 2*kHeaderLen + 2; // nameLen + typeName + checkSum
  const static int kMaxMessageLen = 64*1024*1024; // same as codec_stream.h kDefaultTotalBytesLimit
};

ProtobufCodec类就是基于protobuf定义的结构化数据的应用层协议，协议格式如下：

onMessage的实现如下：


void ProtobufCodec::onMessage(const TcpConnectionPtr& conn,
                              Buffer* buf,
                              Timestamp receiveTime)
{
  while (buf->readableBytes() >= kMinMessageLen + kHeaderLen)
  {
    const int32_t len = buf->peekInt32();
    if (len > kMaxMessageLen || len < kMinMessageLen)
    {
      errorCallback_(conn, buf, receiveTime, kInvalidLength);
      break;
    }
    else if (buf->readableBytes() >= implicit_cast<size_t>(len + kHeaderLen))
    {
      ErrorCode errorCode = kNoError;
      MessagePtr message = parse(buf->peek()+kHeaderLen, len, &errorCode);
      if (errorCode == kNoError && message)
      {
        messageCallback_(conn, message, receiveTime);
        buf->retrieve(kHeaderLen+len);
      }
      else
      {
        errorCallback_(conn, buf, receiveTime, errorCode);
        break;
      }
    }
    else
    {
      break;
    }
  }
}

onMessage函数解决了TCP粘包的问题，从缓冲区中解析出一个完整的protobuf结构化数据(一个message)后，再调用messageCallback_处理。messageCallback_是构造ProtobufCodec时传入的回调函数。

如果我们的业务场景很单一，例如上面的英译汉服务器，直接把我们写的业务逻辑作为回调传给messageCallback_就OK了。但如果我们有多种业务，例如翻译和计算业务，则还可以在此基础上引入任务分发器ProtobufDispatcher，回调它的ProtobufDispatcher函数。


class ProtobufDispatcher
{
 public:
  typedef std::function<void (const muduo::net::TcpConnectionPtr&,
                                const MessagePtr& message,
                                muduo::Timestamp)> ProtobufMessageCallback;
 
  explicit ProtobufDispatcher(const ProtobufMessageCallback& defaultCb)
    : defaultCallback_(defaultCb)
  {
  }
 
  void onProtobufMessage(const muduo::net::TcpConnectionPtr& conn,
                         const MessagePtr& message,
                         muduo::Timestamp receiveTime) const
  {
    CallbackMap::const_iterator it = callbacks_.find(message->GetDescriptor());
    if (it != callbacks_.end())
    {
      it->second->onMessage(conn, message, receiveTime);
    }
    else
    {
      defaultCallback_(conn, message, receiveTime);
    }
  }
 
  template<typename T>
  void registerMessageCallback(const typename CallbackT<T>::ProtobufMessageTCallback& callback)
  {
    std::shared_ptr<CallbackT<T> > pd(new CallbackT<T>(callback));
    callbacks_[T::descriptor()] = pd;
  }
 
 private:
  typedef std::map<const google::protobuf::Descriptor*, std::shared_ptr<Callback> > CallbackMap;
 
  CallbackMap callbacks_;
  ProtobufMessageCallback defaultCallback_;
};

onProtobufMessage会根据你传入的结构化数据类型(message)，调用不同的回调函数，这些回调函数就是我们注册的业务处理方法。

四.编写一个翻译+加法服务

编写.并翻译proto文件，构建翻译的请求和响应，加法的请求和响应的类
编写服务端
编写客户端

Server.cc:


#include <memory>
#include "muduo/protobuf/codec.h"
#include "muduo/protobuf/dispatcher.h"
#include "muduo/base/Logging.h"
 
#include "muduo/net/TcpServer.h"
#include "muduo/net/TcpConnection.h"
#include "muduo/net/EventLoop.h"
 
#include "business.pb.h"
 
using std::placeholders::_1;
using std::placeholders::_2;
using std::placeholders::_3;
class Server
{
public:
    typedef std::shared_ptr<google::protobuf::Message> MessagePtr;
    typedef std::shared_ptr<business::TranslateRequest> TranslateRequestPtr;
    typedef std::shared_ptr<business::AddRequest> AddRequestPtr;
 
private:
    muduo::net::EventLoop _baseLoop;
    muduo::net::TcpServer _server;
    ProtobufDispatcher _dispatcher; // 请求分发器
    ProtobufCodec _codec;           // protobuf处理器--解析出结构化数据，发送结构化数据(序列化和发序列化内部会做)
public:
    Server(int port)
        : _server(&_baseLoop, muduo::net::InetAddress("0.0.0.0", port), "Server",
                  muduo::net::TcpServer::kReusePort)
        ,_dispatcher(std::bind(&Server::_onUnknownMessage, this,\
            std::placeholders::_1, std::placeholders::_2, std::placeholders::_3))
        ,_codec(std::bind(&ProtobufDispatcher::onProtobufMessage, &_dispatcher,
            std::placeholders::_1, std::placeholders::_2, std::placeholders::_3))
    {
        // 注册业务处理函数
       _dispatcher.registerMessageCallback<business::AddRequest>(bind(&Server::_onAdd, this, _1, _2, _3));
       _dispatcher.registerMessageCallback<business::TranslateRequest>(bind(&Server::_onTranslate, this, _1, _2, _3));
 
        //注册_server的回调函数
        _server.setMessageCallback(std::bind(&ProtobufCodec::onMessage, &_codec,
            std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
        _server.setConnectionCallback(std::bind(&Server::_onConnection, this, std::placeholders::_1));
    }
 
    void start()
    {
        _server.start();
        _baseLoop.loop();
    }
 
private:
    void _onUnknownMessage(const muduo::net::TcpConnectionPtr &conn, const MessagePtr &message, muduo::Timestamp)
    {
        LOG_INFO << "onUnknownMessage: " << message->GetTypeName();
        conn->shutdown();
    }
 
    void _onAdd(const muduo::net::TcpConnectionPtr& conn, const AddRequestPtr &messagePtr, muduo::Timestamp time)
    {
        int x = messagePtr->num1();
        int y = messagePtr->num2();
        
        business::AddResponse resp;
        resp.set_result(x + y);
        _codec.send(conn, resp); //让protobuf处理器帮我们序列化并用conn发送
    }
 
    void _onTranslate(const muduo::net::TcpConnectionPtr& conn, const TranslateRequestPtr &messagePtr, muduo::Timestamp time)
    {
        const std::string& ret = translate(messagePtr->msg());
        business::TranslateResponse resp;
        resp.set_msg(ret);
        _codec.send(conn, resp);
    }
 
    void _onConnection(const muduo::net::TcpConnectionPtr &conn)
    {
        if (conn->connected())
        {
            LOG_INFO << "新连接建立成功！";
        }
        else
        {
            LOG_INFO << "连接即将关闭！";
        }
    }
 
    std::string translate(const std::string& str)
    {
        static std::unordered_map<std::string, std::string> dict_map = {
                {"hello", "你好"},
                {"Hello", "你好"},
                {"你好", "Hello"},
                {"吃了吗", "油泼面"}
        };
        auto it = dict_map.find(str);
        if (it == dict_map.end()) {
            return "没听懂！！";
        }
        return it->second;
    }
};
 
int main()
{
    Server server(8085);
    server.start();
    return 0;
}

Client.cc:


 
#include "muduo/protobuf/codec.h"
#include "muduo/protobuf/dispatcher.h"
#include "muduo/base/Logging.h"
#include "muduo/base/Mutex.h"
#include "muduo/net/EventLoop.h"
#include "muduo/net/TcpClient.h"
#include "muduo/net/EventLoopThread.h"
#include "muduo/base/CountDownLatch.h"
 
#include "business.pb.h"
#include <iostream>
#include <functional>
 
class Client {
    public:
        typedef std::shared_ptr<google::protobuf::Message> MessagePtr; //这是Protobuf库的头文件
        typedef std::shared_ptr<business::AddResponse> AddResponsePtr;
        typedef std::shared_ptr<business::TranslateResponse> TranslateResponsePtr;
        Client(const std::string &sip, int sport):
            _latch(1), _client(_loopthread.startLoop(), muduo::net::InetAddress(sip, sport), "Client"),
            _dispatcher(std::bind(&Client::onUnknownMessage, this, std::placeholders::_1, 
                std::placeholders::_2, std::placeholders::_3)),
            _codec(std::bind(&ProtobufDispatcher::onProtobufMessage, &_dispatcher, 
                std::placeholders::_1, std::placeholders::_2, std::placeholders::_3)){
 
            _dispatcher.registerMessageCallback<business::TranslateResponse>(std::bind(&Client::onTranslate, this, 
                std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
                
            _dispatcher.registerMessageCallback<business::AddResponse>(std::bind(&Client::onAdd, this, 
                std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
 
            _client.setMessageCallback(std::bind(&ProtobufCodec::onMessage, &_codec,
                std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
            _client.setConnectionCallback(std::bind(&Client::onConnection, this, std::placeholders::_1));      
        }
        void connect() {
            _client.connect();
            _latch.wait();//阻塞等待，直到连接建立成功
        }
        void Translate(const std::string &msg){
            business::TranslateRequest req;
            req.set_msg(msg);
            send(&req);
        }
        void Add(int num1, int num2) {
            business::AddRequest req;
            req.set_num1(num1);
            req.set_num2(num2);
            send(&req);
        }
    private:
        bool send(const google::protobuf::Message *message) {
            if (_conn->connected()) {//连接状态正常，再发送，否则就返回false
                _codec.send(_conn, *message);
                return true;
            }
            return false;
        }  
        void onTranslate(const muduo::net::TcpConnectionPtr& conn, const TranslateResponsePtr& message, muduo::Timestamp) {
            std::cout << "翻译结果：" << message->msg() << std::endl;
        }
        void onAdd(const muduo::net::TcpConnectionPtr& conn, const AddResponsePtr& message, muduo::Timestamp) {
            std::cout << "加法结果：" << message->result() << std::endl;
        }
        void onUnknownMessage(const muduo::net::TcpConnectionPtr& conn, const MessagePtr& message, muduo::Timestamp) {
            LOG_INFO << "onUnknownMessage: " << message->GetTypeName();
            conn->shutdown();
        }
        void onConnection(const muduo::net::TcpConnectionPtr&conn){
            if (conn->connected()) {
                _latch.countDown();//唤醒主线程中的阻塞
                _conn = conn;
            }else {
                //连接关闭时的操作
                _conn.reset();
            }
        }
    private:
        muduo::CountDownLatch _latch;//实现同步的
        muduo::net::EventLoopThread _loopthread;//异步循环处理线程
        muduo::net::TcpConnectionPtr _conn;//客户端对应的连接
        muduo::net::TcpClient _client;//客户端
        ProtobufDispatcher _dispatcher;//请求分发器
        ProtobufCodec _codec; //Protobuf处理器
};
 
int main() 
{
    Client client("127.0.0.1", 8085);
    client.connect();
 
    client.Translate("hello");
    client.Add(11, 22);
 
    sleep(1);
    return 0;
}

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【仿RabbitMQ消息队列项目day2】使用muduo库中基于protobuf的应用层协议进行通信_比特 仿rabbitmq

一.什么是muduo?

二.使用muduo库完成一个英译汉翻译服务

三.muduo中基于protobuf的自定义协议

四.编写一个翻译+加法服务

【仿RabbitMQ消息队列项目day2】使用muduo库中基于protobuf的应用层协议进行通信_比特仿rabbitmq