muduo 源码学习之 Connector 以及 TcpClient

文章目录

• Connector class
• Connector.h
• Connector.cc
• TcpClient
• TcpClient.h
• TcpClient.cc
• 判断连接建立成功

---

Connector class

Connector class负责主动发起连接, 他不单独使用, 而是包含在TcpClient class内, Connector不负责创建 socket, 只负责连接的建立, 包括这其中的错误处理和重连
需要考虑的难点:

• socket 是一次性的, 当 connect 出错, 我们必须关闭该 socket, 重新创建一个 socket, 但是Connector是可以反复使用的,
• 错误码和Acceptor不同, EAGAIN 是真的出错了, 表明本机临时端口暂时用完了( ephemeral port ), 需要延期重试, “正在连接” 的的返回码是 EINPROGRESS,
• 重试的间隔应该逐渐延长,
• 需要处理自连接

Connector.h

#ifndef MUDUO_NET_CONNECTOR_H
#define MUDUO_NET_CONNECTOR_H

#include <muduo/base/noncopyable.h>
#include <muduo/net/InetAddress.h>

#include <functional>
#include <memory>
 
namespace muduo
{
namespace net
{

class Channel;
class EventLoop;

class Connector : noncopyable,
                  public std::enable_shared_from_this<Connector>
{
 public:
  typedef std::function<void (int sockfd)> NewConnectionCallback;

  Connector(EventLoop* loop, const InetAddress& serverAddr);
  ~Connector();

  void setNewConnectionCallback(const NewConnectionCallback& cb)
  { newConnectionCallback_ = cb; }

  void start();  // can be called in any thread
  void restart();  // must be called in loop thread
  void stop();  // can be called in any thread

  const InetAddress& serverAddress() const { return serverAddr_; }

 private:
  enum States { kDisconnected, kConnecting, kConnected };
  static const int kMaxRetryDelayMs = 30*1000;  //最大重连延迟30000ms
  static const int kInitRetryDelayMs = 500;     //初始化重连延迟500ms

  void setState(States s) { state_ = s; }
  void startInLoop();
  void stopInLoop();
  void connect();
  void connecting(int sockfd);
  void handleWrite();
  void handleError();
  void retry(int sockfd);
  int removeAndResetChannel();
  void resetChannel();

  EventLoop* loop_; //所属的EventLoop
  InetAddress serverAddr_;  //要连接的server地址
  bool connect_; // atomic
  States state_;  // FIXME: use atomic variable
  std::unique_ptr<Channel> channel_;    //对应的channel
  NewConnectionCallback newConnectionCallback_; //连接成功时的回调函数
  int retryDelayMs_;  //连接失败时的重连延迟时间
};

}  // namespace net
}  // namespace muduo

#endif  // MUDUO_NET_CONNECTOR_H

Connector.cc

#include <muduo/net/Connector.h>

#include <muduo/base/Logging.h>
#include <muduo/net/Channel.h>
#include <muduo/net/EventLoop.h>
#include <muduo/net/SocketsOps.h>

#include <errno.h>

using namespace muduo;
using namespace muduo::net;
 
const int Connector::kMaxRetryDelayMs;

Connector::Connector(EventLoop* loop, const InetAddress& serverAddr)
  : loop_(loop),
    serverAddr_(serverAddr),
    connect_(false),
    state_(kDisconnected),
    retryDelayMs_(kInitRetryDelayMs)
{
  LOG_DEBUG << "ctor[" << this << "]";
}

Connector::~Connector()
{
  LOG_DEBUG << "dtor[" << this << "]";
  assert(!channel_);
}

void Connector::start()
{
  connect_ = true;
  //在所属IO线程Lloop中调用该函数
  loop_->runInLoop(std::bind(&Connector::startInLoop, this)); // FIXME: unsafe
}


void Connector::startInLoop()
{
  loop_->assertInLoopThread();
  assert(state_ == kDisconnected);
  if (connect_) //在start中会将其设置为true
  {
    connect();  //请求连接
  }
  else
  {
    LOG_DEBUG << "do not connect";
  }
}

void Connector::stop()
{
  connect_ = false;
  loop_->queueInLoop(std::bind(&Connector::stopInLoop, this)); // FIXME: unsafe
  // FIXME: cancel timer
}

void Connector::stopInLoop()
{
  loop_->assertInLoopThread();
  if (state_ == kConnecting)
  {
    setState(kDisconnected);
    int sockfd = removeAndResetChannel();
    retry(sockfd);
  }
}

void Connector::connect()
{
  //使用socket选项SOCK_NONBLOCK创建一个非阻塞socket
  int sockfd = sockets::createNonblockingOrDie(serverAddr_.family());
  //调用connect进行请求连接
  int ret = sockets::connect(sockfd, serverAddr_.getSockAddr());
  int savedErrno = (ret == 0) ? 0 : errno;
  switch (savedErrno)
  {
    case 0:
    case EINPROGRESS: //socket是非阻塞,返回这个错误码表示正在连接
    case EINTR:
    case EISCONN: //连接成功
      connecting(sockfd);
      break;

    case EAGAIN:  //connect返回EAGAIN是真的错误了
    case EADDRINUSE:
    case EADDRNOTAVAIL:
    case ECONNREFUSED:
    case ENETUNREACH:
      retry(sockfd);  //重连
      break;

    case EACCES:
    case EPERM:
    case EAFNOSUPPORT:
    case EALREADY:
    case EBADF:
    case EFAULT:
    case ENOTSOCK:
      LOG_SYSERR << "connect error in Connector::startInLoop " << savedErrno;
      sockets::close(sockfd); //关闭socket
      break;

    default:
      LOG_SYSERR << "Unexpected error in Connector::startInLoop " << savedErrno;
      sockets::close(sockfd);
      // connectErrorCallback_();
      break;
  }
}

void Connector::restart()
{
  loop_->assertInLoopThread();
  setState(kDisconnected);
  retryDelayMs_ = kInitRetryDelayMs;
  connect_ = true;
  startInLoop();
}

void Connector::connecting(int sockfd)
{
  //设置状态为正在进行连接
  setState(kConnecting);
  assert(!channel_);
  //将该channel和EventLoop,socket关联
  //channel对应于一个文件描述符,所以在有了socket后才能创建channel
  channel_.reset(new Channel(loop_, sockfd));
  //设置回调函数
  channel_->setWriteCallback(
      std::bind(&Connector::handleWrite, this)); // FIXME: unsafe
  channel_->setErrorCallback(
      std::bind(&Connector::handleError, this)); // FIXME: unsafe

  // channel_->tie(shared_from_this()); is not working,
  // as channel_ is not managed by shared_ptr
  //注册可写事件
  channel_->enableWriting();
}

int Connector::removeAndResetChannel()
{
  channel_->disableAll();
  channel_->remove();
  int sockfd = channel_->fd();
  // Can't reset channel_ here, because we are inside Channel::handleEvent
  loop_->queueInLoop(std::bind(&Connector::resetChannel, this)); // FIXME: unsafe
  return sockfd;
}

void Connector::resetChannel()
{
  channel_.reset();
}

//可写事件的回调函数
void Connector::handleWrite()
{
  LOG_TRACE << "Connector::handleWrite " << state_;

  if (state_ == kConnecting)
  {
    //移除channel(Connector的channel只管理建立连接的阶段),成功建立连接后
    //交给TcpClient的TcpConnection来管理
    int sockfd = removeAndResetChannel();
    //可写并不一定连接建立成功
    //如果连接发生错误,socket会是可读可写的
    //所以还需要调用getsockopt检查是否出错
    int err = sockets::getSocketError(sockfd);
    if (err)
    {
      LOG_WARN << "Connector::handleWrite - SO_ERROR = "
               << err << " " << strerror_tl(err);
      retry(sockfd);  //出错重连
    }
    else if (sockets::isSelfConnect(sockfd))  //是否是自连接
    {
      LOG_WARN << "Connector::handleWrite - Self connect";
      retry(sockfd);  //自连接的话断开重连
    }
    else
    {
      //连接成功建立,更改状态
      //调用TcpClient设置的回调函数,创建TcpConnection对象
      setState(kConnected);
      if (connect_)
      {
        newConnectionCallback_(sockfd);
      }
      else
      {
        sockets::close(sockfd);
      }
    }
  }
  else
  {
    // what happened?
    assert(state_ == kDisconnected);
  }
}

void Connector::handleError()
{
  LOG_ERROR << "Connector::handleError state=" << state_;
  if (state_ == kConnecting)
  {
    int sockfd = removeAndResetChannel();
    int err = sockets::getSocketError(sockfd);
    LOG_TRACE << "SO_ERROR = " << err << " " << strerror_tl(err);
    retry(sockfd);
  }
}

void Connector::retry(int sockfd)
{
  //socket是一次性的,失败后需要关闭重新创建
  sockets::close(sockfd);
  setState(kDisconnected);
  if (connect_)
  {
    LOG_INFO << "Connector::retry - Retry connecting to " << serverAddr_.toIpPort()
             << " in " << retryDelayMs_ << " milliseconds. ";
    //隔一段时间后重连,重新执行startInLoop
    loop_->runAfter(retryDelayMs_/1000.0,
                    std::bind(&Connector::startInLoop, shared_from_this()));
    //间隔时间翻倍
    retryDelayMs_ = std::min(retryDelayMs_ * 2, kMaxRetryDelayMs);
  }
  else
  {
    LOG_DEBUG << "do not connect";
  }
}

TcpClient

TCPClient使用Conneccor发起连接, 连接建立成功后, 用 socket 创建TcpConnection来管理连接, 每个TcpClient class只管理一个TcpConnecction

TcpClient.h

#ifndef MUDUO_NET_TCPCLIENT_H
#define MUDUO_NET_TCPCLIENT_H

#include <muduo/base/Mutex.h>
#include <muduo/net/TcpConnection.h>

namespace muduo
{
namespace net
{

class Connector;
typedef std::shared_ptr<Connector> ConnectorPtr;

class TcpClient : noncopyable
{
 public:
  // TcpClient(EventLoop* loop);
  // TcpClient(EventLoop* loop, const string& host, uint16_t port);
  TcpClient(EventLoop* loop,
            const InetAddress& serverAddr,
            const string& nameArg);
  ~TcpClient();  // force out-line dtor, for std::unique_ptr members.

  void connect();
  void disconnect();
  void stop();

  TcpConnectionPtr connection() const
  {
    MutexLockGuard lock(mutex_);
    return connection_;
  }

  EventLoop* getLoop() const { return loop_; }
  bool retry() const { return retry_; }
  void enableRetry() { retry_ = true; }

  const string& name() const
  { return name_; }

  /// Set connection callback.
  /// Not thread safe.
  void setConnectionCallback(ConnectionCallback cb)
  { connectionCallback_ = std::move(cb); }

  /// Set message callback.
  /// Not thread safe.
  void setMessageCallback(MessageCallback cb)
  { messageCallback_ = std::move(cb); }

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

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

  //用户创建传入的EventLoop
  EventLoop* loop_;
  //指向Connector的shared_ptr
  ConnectorPtr connector_; // avoid revealing Connector
  //用户指定的名字
  const string name_;
  //这些回调函数都需要显示设置
  ConnectionCallback connectionCallback_;
  MessageCallback messageCallback_;
  WriteCompleteCallback writeCompleteCallback_;
  //连接断开后是否重连
  bool retry_;   // atomic
  bool connect_; // atomic
  // always in loop thread
  int nextConnId_;
  mutable MutexLock mutex_;
  TcpConnectionPtr connection_ GUARDED_BY(mutex_);
};

}  // namespace net
}  // namespace muduo

#endif  // MUDUO_NET_TCPCLIENT_H

TcpClient.cc

#include <muduo/net/TcpClient.h>

#include <muduo/base/Logging.h>
#include <muduo/net/Connector.h>
#include <muduo/net/EventLoop.h>
#include <muduo/net/SocketsOps.h>

#include <stdio.h>  // snprintf 

using namespace muduo;
using namespace muduo::net;

// TcpClient::TcpClient(EventLoop* loop)
//   : loop_(loop)
// {
// }

// TcpClient::TcpClient(EventLoop* loop, const string& host, uint16_t port)
//   : loop_(CHECK_NOTNULL(loop)),
//     serverAddr_(host, port)
// {
// }

namespace muduo
{
namespace net
{
namespace detail
{

void removeConnection(EventLoop* loop, const TcpConnectionPtr& conn)
{
  loop->queueInLoop(std::bind(&TcpConnection::connectDestroyed, conn));
}

void removeConnector(const ConnectorPtr& connector)
{
  //connector->
}

}  // namespace detail
}  // namespace net
}  // namespace muduo

TcpClient::TcpClient(EventLoop* loop,
                     const InetAddress& serverAddr,
                     const string& nameArg)
  : loop_(CHECK_NOTNULL(loop)),
    connector_(new Connector(loop, serverAddr)),//初始化一个Connector
    name_(nameArg),
    connectionCallback_(defaultConnectionCallback),
    messageCallback_(defaultMessageCallback),
    retry_(false),
    connect_(true),
    nextConnId_(1)
{
  //将Connector的的连接回调函数设置为TcpClient::newConnection
  //该函数在Connector::handleWrite中被调用
  connector_->setNewConnectionCallback(
      std::bind(&TcpClient::newConnection, this, _1));
  // FIXME setConnectFailedCallback
  LOG_INFO << "TcpClient::TcpClient[" << name_
           << "] - connector " << get_pointer(connector_);
}

TcpClient::~TcpClient()
{
  LOG_INFO << "TcpClient::~TcpClient[" << name_
           << "] - connector " << get_pointer(connector_);
  TcpConnectionPtr conn;
  bool unique = false;
  {
    MutexLockGuard lock(mutex_);
    unique = connection_.unique();
    conn = connection_;
  }
  if (conn)
  {
    assert(loop_ == conn->getLoop());
    // FIXME: not 100% safe, if we are in different thread
    CloseCallback cb = std::bind(&detail::removeConnection, loop_, _1);
    loop_->runInLoop(
        std::bind(&TcpConnection::setCloseCallback, conn, cb));
    if (unique)
    {
      conn->forceClose();
    }
  }
  else
  {
    connector_->stop();
    // FIXME: HACK
    loop_->runAfter(1, std::bind(&detail::removeConnector, connector_));
  }
}

void TcpClient::connect()
{
  // FIXME: check state
  LOG_INFO << "TcpClient::connect[" << name_ << "] - connecting to "
           << connector_->serverAddress().toIpPort();
  connect_ = true;
  //调用Connector::start,发起连接
  connector_->start();
}

void TcpClient::disconnect()
{
  connect_ = false;

  {
    MutexLockGuard lock(mutex_);
    if (connection_)
    {
      connection_->shutdown();
    }
  }
}

void TcpClient::stop()
{
  connect_ = false;
  connector_->stop();
}

//新连接的回调函数
//将新连接封装为TcpConnection交给TcpClient来管理
void TcpClient::newConnection(int sockfd)
{
  loop_->assertInLoopThread();
  InetAddress peerAddr(sockets::getPeerAddr(sockfd));
  char buf[32];
  snprintf(buf, sizeof buf, ":%s#%d", peerAddr.toIpPort().c_str(), nextConnId_);
  ++nextConnId_;
  string connName = name_ + buf;

  InetAddress localAddr(sockets::getLocalAddr(sockfd));
  // FIXME poll with zero timeout to double confirm the new connection
  // FIXME use make_shared if necessary
  TcpConnectionPtr conn(new TcpConnection(loop_,
                                          connName,
                                          sockfd,
                                          localAddr,
                                          peerAddr));

  conn->setConnectionCallback(connectionCallback_);
  conn->setMessageCallback(messageCallback_);
  conn->setWriteCompleteCallback(writeCompleteCallback_);
  conn->setCloseCallback(
      std::bind(&TcpClient::removeConnection, this, _1)); // FIXME: unsafe
  {
    MutexLockGuard lock(mutex_);
    //将新创建的TcpConnection赋给TcpClient类内成员connection_
    connection_ = conn;
  }
  conn->connectEstablished();
}

void TcpClient::removeConnection(const TcpConnectionPtr& conn)
{
  loop_->assertInLoopThread();
  assert(loop_ == conn->getLoop());

  {
    MutexLockGuard lock(mutex_);
    assert(connection_ == conn);
    connection_.reset();
  }

  loop_->queueInLoop(std::bind(&TcpConnection::connectDestroyed, conn));
  if (retry_ && connect_)
  {
    LOG_INFO << "TcpClient::connect[" << name_ << "] - Reconnecting to "
             << connector_->serverAddress().toIpPort();
    connector_->restart();
  }
}

TcpClient在构造函数中设置Connector的新连接到来时的回调函数为TcpClient::newConnection, 该函数接收 connect 成功后的新 TCP 连接 socket, 使用该 socket new 一个 TcpConnection并让TcpClient中的connection_成员指向他,

判断连接建立成功

Connector connect 成功返回后, 调用Connector::connecting, 注册了该 socket 的可写事件, 一个新 TCP 连接 socket, 刚建立好, 他是可写的, 这时就会调用可写回调Connector::handleWrite, 在该函数中又会调用TcpClient在构造函数中设置Connector的新连接到来时的回调函数TcpClient::newConnection, 该函数接收 connect 成功后的新 TCP 连接 socket, 使用该 socket new 一个 TcpConnection并让TcpClient中的connection_成员指向他,

连接发生错误时, socket 是可读可写的, 需要用 getsockopt 检查是否出错, 这也是Connector::handleWrite中做的事