muduo源码剖析之TcpServer服务端

简介

TcpServer拥有Acceptor类，新连接到达时new TcpConnection后续客户端和TcpConnection类交互。TcpServer管理连接和启动线程池，用Acceptor接受连接。

服务端封装 - muduo的server端维护了多个tcpconnection
注意TcpServer本身不带Channel，而是使用Acceptor的Channel

成员及属性解析

主要接口

回调setters

这些回调函数会在新连接建立时传递给TcpConnction对象

start

启动threadPool线程池
在runInLoop中执行acceptor的listen
这里专门设置了一个started标记，防止多次运行start

核心实现：newConnection

从accept回调中获得的fd动态创建新的TcpConnection对象
为连接对象注册各类回调函数
将连接对象存入connectionMap_映射表里

主要成员

loop

这个loop也是acceptor的loop

acceptor

threadPool

一个EventLoopThreadPool，用来存放io线程的EventLoopThread

socket

服务端用来监听的socket

ConnectionMap

一个连接名和实例（TcpConnectionPtr）的映射容器

TcpServer中回调的传递示意简图：

源码剖析

源码已经编写注释

TcpServer.h

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)
//
// This is a public header file, it must only include public header files.

#ifndef MUDUO_NET_TCPSERVER_H
#define MUDUO_NET_TCPSERVER_H

#include "muduo/base/Atomic.h"
#include "muduo/base/Types.h"
#include "muduo/net/TcpConnection.h"

#include <map>

namespace muduo
{
   
   
namespace net
{
   
   

class Acceptor;
class EventLoop;
class EventLoopThreadPool;

///
/// TCP server, supports single-threaded and thread-pool models.
///
/// This is an interface class, so don't expose too much details.
class TcpServer : noncopyable
{
   
   
 public:
  typedef std::function<void(EventLoop*)> ThreadInitCallback;
  enum Option
  {
   
   
    kNoReusePort,//不设置端口复用
    kReusePort,//设置端口复用
  };

  //TcpServer(EventLoop* loop, const InetAddress& listenAddr);
  TcpServer(EventLoop* loop,//mainloop
            const InetAddress& listenAddr,
            const string& nameArg,
            Option option = kNoReusePort);
  ~TcpServer();  // force out-line dtor, for std::unique_ptr members.

  const string& ipPort() const {
   
    return ipPort_; }
  const string& name() const {
   
    return name_; }
  EventLoop* getLoop() const {
   
    return loop_; }

  /// Set the number of threads for handling input.
  ///
  /// Always accepts new connection in loop's thread.
  /// Must be called before @c start
  /// @param numThreads
  /// - 0 means all I/O in loop's thread, no thread will created.
  ///   this is the default value.
  /// - 1 means all I/O in another thread.
  /// - N means a thread pool with N threads, new connections
  ///   are assigned on a round-robin basis.
  void setThreadNum(int numThreads);//设置subloop数量
  void setThreadInitCallback(const ThreadInitCallback& cb)//设置subloop线程初始化时调用的函数
  {
   
    threadInitCallback_ = cb; }
  /// valid after calling start()
  std::shared_ptr<EventLoopThreadPool> threadPool()//返回EventLoopThread线程池
  {
   
    return threadPool_; }

  /// Starts the server if it's not listening.
  ///
  /// It's harmless to call it multiple times.
  /// Thread safe.
  void start();

  /// Set connection callback.
  /// Not thread safe.
  void setConnectionCallback(const ConnectionCallback& cb)
  {
   
    connectionCallback_ = cb; }

  /// Set message callback.
  /// Not thread safe.
  void setMessageCallback(const MessageCallback& cb)
  {
   
    messageCallback_ = cb; }




  /// Set write complete callback.
  /// Not thread safe.
  void setWriteCompleteCallback(const WriteCompleteCallback& cb)
  {
   
    writeCompleteCallback_ = cb; }

 private:
  /// Not thread safe, but in loop
  void newConnection(int sockfd, const InetAddress& peerAddr);
  /// Thread safe.
  void removeConnection(const TcpConnectionPtr& conn);
  /// Not thread safe, but in loop
  void removeConnectionInLoop(const TcpConnectionPtr& conn);

  typedef std::map<string, TcpConnectionPtr> ConnectionMap;

  EventLoop* loop_;  // the acceptor loop
  const string ipPort_;
  const string name_;
  std::unique_ptr<Acceptor> acceptor_; // avoid revealing Acceptor
  std::shared_ptr<EventLoopThreadPool> threadPool_;
  ConnectionCallback connectionCallback_;
  MessageCallback messageCallback_;
  WriteCompleteCallback writeCompleteCallback_;
  ThreadInitCallback threadInitCallback_;
  AtomicInt32 started_;
  // always in loop thread
  int nextConnId_;
  ConnectionMap connections_;
};

}  // namespace net
}  // namespace muduo

#endif  // MUDUO_NET_TCPSERVER_H

TcpServer.cc

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include "muduo/net/TcpServer.h"

#include "muduo/base/Logging.h"
#include "muduo/net/Acceptor.h"
#include "muduo/net/EventLoop.h"
#include "muduo/net/EventLoopThreadPool.h"
#include "muduo/net/SocketsOps.h"

#include <stdio.h>  // snprintf

using namespace muduo;
using namespace muduo::net;

TcpServer::TcpServer(EventLoop* loop,
                     const InetAddress& listenAddr,
                     const string& nameArg,
                     Option option)
  : loop_(CHECK_NOTNULL(loop)), //TcpServer所在的主线程下运行的事件驱动循环
    ipPort_(listenAddr.toIpPort()),/* 服务器负责监听的本地ip和端口 */
    name_(nameArg),/* 服务器名字，创建时传入 */
    acceptor_(new Acceptor(loop, listenAddr, option == kReusePort)),/* Acceptor对象，负责监听客户端连接请求，运行在主线程的EventLoop中 */
    threadPool_(new EventLoopThreadPool(loop, name_)),/* 事件驱动线程池，池中每个线程运行一个EventLoop */
    connectionCallback_(defaultConnectionCallback),/* 用户传入，有tcp连接到达或tcp连接关闭时调用，传给TcpConnection */
    messageCallback_(defaultMessageCallback),/* 用户传入，对端发来消息时调用，传给TcpConnection */
    nextConnId_(1) /* TcpConnection特有id，每增加一个TcpConnection，nextConnId_加一 */
{
   
    
  /* 
   * 设置回调函数，当有客户端请求时，Acceptor接收客户端请求，然后调用这里设置的回调函数
   * 回调函数用于创建TcpConnection连接
   */
  acceptor_->setNewConnectionCallback(
      std::bind(&TcpServer::newConnection, this, _1, _2));
}

TcpServer::~TcpServer()
{
   
   
  loop_->assertInLoopThread();
  LOG_TRACE << "TcpServer::~TcpServer [" << name_ << "] destructing";

  for (auto& item : connections_)
  {
   
   
    TcpConnectionPtr conn(item.second);
    item.second.reset();
    conn->getLoop()->runInLoop(
      std::bind(&TcpConnection::connectDestroyed, conn));
  }
}

void TcpServer::setThreadNum(int numThreads)
{
   
   
  assert(0 <= numThreads);
  threadPool_->setThreadNum(numThreads);
}

void TcpServer::start()
{
   
   
  if (started_.getAndSet(1) == 0)
  {
   
   
    threadPool_->start(threadInitCallback_);//启动线程池,threadInitCallback_创建好所有线程后调用的回调函数

    assert(!acceptor_->listenning());
    loop_->runInLoop(       //直接调用linsten函数
        std::bind(&Acceptor::listen, get_pointer(acceptor_)));
  }
}

/* 
 * Acceptor接收客户端请求后调用的回调函数
 * @param sockfd: 已经接收完成（三次握手完成）后的客户端套接字
 * @param peerAddr: 客户端地址
 * 
 * Acceptor只负责接收客户端请求
 * TcpServer需要生成一个TcpConnection用于管理tcp连接
 * 
 * 1.TcpServer内有一个EventLoopThreadPool，即事件循环线程池，池子中每个线程都是一个EventLoop
 * 2.每个EventLoop包含一个Poller用于监听注册到这个EventLoop上的所有Channel
 * 3.当建立起一个新的TcpConnection时，这个连接会放到线程池中的某个EventLoop中
 * 4.TcpServer中的baseLoop只用来检测客户端的连接
 * 
 * 从libevent的角度看就是
 * 1.EventLoopThreadPool是一个struct event_base的池子，池子中全是struct event_base
 * 2.TcpServer独占一个event_base，这个event_base不在池子中
 * 3.TcpConnection会扔到这个池子中的某个event_base中
 */
void TcpServer::newConnection(int sockfd, const InetAddress& peerAddr)
{
   
   
  loop_->assertInLoopThread();
  EventLoop* ioLoop = threadPool_->getNextLoop();//从事件驱动线程池中取出一个线程给TcpConnection 
   /* 为TcpConnection生成独一无二的名字 */
  char buf[64];
  snprintf(buf, sizeof buf, "-%s#%d", ipPort_.c_str(), nextConnId_);
  ++nextConnId_;
  string connName = name_ + buf;

  LOG_INFO << "TcpServer::newConnection [" << name_
           << "] - new connection [" << connName
           << "] from " << peerAddr.toIpPort();
  /* 
   * 根据sockfd获取tcp连接在本地的<地址，端口>
   * getsockname(int fd, struct sockaddr*, int *size);
   */
  InetAddress localAddr(sockets::getLocalAddr(sockfd));
  // FIXME poll with zero timeout to double confirm the new connection
  // FIXME use make_shared if necessary
  /* 创建一个新的TcpConnection代表一个Tcp连接 */
  TcpConnectionPtr conn(new TcpConnection(ioLoop,
                                          connName,
                                          sockfd,
                                          localAddr,
                                          peerAddr));
   /* 添加到所有tcp 连接的map中，键是tcp连接独特的名字（服务器名+客户端<地址，端口>） */
  connections_[connName] = conn;
   /* 为tcp连接设置回调函数（由用户提供） */
  conn->setConnectionCallback(connectionCallback_);
  conn->setMessageCallback(messageCallback_);
  conn->setWriteCompleteCallback(writeCompleteCallback_);
  /* 
   * 关闭回调函数，由TcpServer设置，作用是将这个关闭的TcpConnection从map中删除
   * 当poll返回后，发现被激活的原因是EPOLLHUP，此时需要关闭tcp连接
   * 调用Channel的CloseCallback，进而调用TcpConnection的handleClose，进而调用removeConnection
   */
  conn->setCloseCallback(
      std::bind(&TcpServer::removeConnection, this, _1)); // FIXME: unsafe

  /* 
   * 连接建立后，调用TcpConnection连接建立成功的函数
   * 1.新建的TcpConnection所在事件循环是在事件循环线程池中的某个线程
   * 2.所以TcpConnection也就属于它所在的事件驱动循环所在的那个线程
   * 3.调用TcpConnection的函数时也就应该在自己所在线程调用
   * 4.所以需要调用runInLoop在自己的那个事件驱动循环所在线程调用这个函数
   * 5.当前线程是TcpServer的主线程，不是TcpConnection的线程，如果在这个线程直接调用会阻塞监听客户端请求
   * 6.其实这里不是因为线程不安全，即使在这个线程调用也不会出现线程不安全，因为TcpConnection本就是由这个线程创建的
   */
  ioLoop->runInLoop(std::bind(&TcpConnection::connectEstablished, conn));
}

void TcpServer::removeConnection(const TcpConnectionPtr& conn)
{
   
   
  // FIXME: unsafe
  loop_->runInLoop(std::bind(&TcpServer::removeConnectionInLoop, this, conn));
}

void TcpServer::removeConnectionInLoop(const TcpConnectionPtr& conn)
{
   
   
  //关闭连接,把fd从epoll中del掉,要释放connector(包括描述符)和channel
  loop_->assertInLoopThread();
  LOG_INFO << "TcpServer::removeConnectionInLoop [" << name_
           << "] - connection " << conn->name();
  size_t n = connections_.erase(conn->name());
  (void)n;
  assert(n == 1);
  EventLoop* ioLoop = conn->getLoop();
  ioLoop->queueInLoop(
      std::bind(&TcpConnection::connectDestroyed, conn));
}