说了这么多，我们来以flamingo的服务器程序的网络框架设计为例来验证上述介绍的理论。flamingo的网络框架是基于陈硕的muduo库，改成C 11的版本，并修改了一些bug。在此感谢原作者陈硕。flamingo的源码可以在这里下载：https://github.com/baloonwj/flamingo，打不开github的可以移步csdn：http://download.csdn.net/detail/analogous_love/9805797。
上文介绍的核心线程函数的while循环位于eventloop.cpp中：
代码语言：javascript复制void EventLoop::loop()
{
assert(!looping_);
assertInLoopThread();
looping_ = true;
quit_ = false; // FIXME: what if someone calls quit() before loop() ?
LOG_TRACE << "EventLoop " << this << " start looping";
while (!quit_)
{
activeChannels_.clear();
pollReturnTime_ = poller_->poll(kPollTimeMs, &activeChannels_);
iteration_;
if (Logger::logLevel() <= Logger::TRACE)
{
printActiveChannels();
}
// TODO sort channel by priority
eventHandling_ = true;
for (ChannelList::iterator it = activeChannels_.begin();
it != activeChannels_.end(); it)
{
currentActiveChannel_ = *it;
currentActiveChannel_->handleEvent(pollReturnTime_);
}
currentActiveChannel_ = NULL;
eventHandling_ = false;
doPendingFunctors();
if (frameFunctor_)
{
frameFunctor_();
}
}
LOG_TRACE << "EventLoop " << this << " stop looping";
looping_ = false;
} poller_->poll利用epoll分离网络事件，然后接着处理分离出来的网络事件，每一个客户端socket对应一个连接，即一个TcpConnection和Channel通道对象。currentActiveChannel_->handleEvent(pollReturnTime_)根据是可读、可写、出错事件来调用对应的处理函数，这些函数都是回调函数，程序初始化阶段设置进来的：
代码语言：javascript复制void Channel::handleEvent(Timestamp receiveTime)
{
std::shared_ptr<void> guard;
if (tied_)
{
guard = tie_.lock();
if (guard)
{
handleEventWithGuard(receiveTime);
}
}
else
{
handleEventWithGuard(receiveTime);
}
}
void Channel::handleEventWithGuard(Timestamp receiveTime)
{
eventHandling_ = true;
LOG_TRACE << reventsToString();
if ((revents_ & POLLHUP) && !(revents_ & POLLIN))
{
if (logHup_)
{
LOG_WARN << "Channel::handle_event() POLLHUP";
}
if (closeCallback_) closeCallback_();
}
if (revents_ & POLLNVAL)
{
LOG_WARN << "Channel::handle_event() POLLNVAL";
}
if (revents_ & (POLLERR | POLLNVAL))
{
if (errorCallback_) errorCallback_();
}
if (revents_ & (POLLIN | POLLPRI | POLLRDHUP))
{
//当是侦听socket时，readCallback_指向Acceptor::handleRead
//当是客户端socket时，调用TcpConnection::handleRead
if (readCallback_) readCallback_(receiveTime);
}
if (revents_ & POLLOUT)
{
//如果是连接状态服的socket，则writeCallback_指向Connector::handleWrite()
if (writeCallback_) writeCallback_();
}
eventHandling_ = false;
} 当然，这里利用了Channel对象的“多态性”，如果是普通socket，可读事件就会调用预先设置的回调函数；但是如果是侦听socket，则调用Aceptor对象的handleRead()来接收新连接：
代码语言：javascript复制void Acceptor::handleRead()
{
loop_->assertInLoopThread();
InetAddress peerAddr;
//FIXME loop until no more
int connfd = acceptSocket_.accept(&peerAddr);
if (connfd >= 0)
{
// string hostport = peerAddr.toIpPort();
// LOG_TRACE << "Accepts of " << hostport;
//newConnectionCallback_实际指向TcpServer::newConnection(int sockfd, const InetAddress& peerAddr)
if (newConnectionCallback_)
{
newConnectionCallback_(connfd, peerAddr);
}
else
{
sockets::close(connfd);
}
}
else
{
LOG_SYSERR << "in Acceptor::handleRead";
// Read the section named "The special problem of
// accept()ing when you can't" in libev's doc.
// By Marc Lehmann, author of livev.
if (errno == EMFILE)
{
::close(idleFd_);
idleFd_ = ::accept(acceptSocket_.fd(), NULL, NULL);
::close(idleFd_);
idleFd_ = ::open("/dev/null", O_RDONLY | O_CLOEXEC);
}
}
} 主循环里面的业务逻辑处理对应：
代码语言：javascript复制doPendingFunctors();
if (frameFunctor_)
{
frameFunctor_();
} void EventLoop::doPendingFunctors()
{
std::vector<Functor> functors;
callingPendingFunctors_ = true;
{
std::unique_lock<std::mutex> lock(mutex_);
functors.swap(pendingFunctors_);
}
for (size_t i = 0; i < functors.size(); i)
{
functors[i]();
}
callingPendingFunctors_ = false;
} 这里增加业务逻辑是增加执行任务的函数指针的，增加的任务保存在成员变量pendingFunctors_中，这个变量是一个函数指针数组（vector对象），执行的时候，调用每个函数就可以了。上面的代码先利用一个栈变量将成员变量pendingFunctors_里面的函数指针换过来，接下来对这个栈变量进行操作就可以了，这样减少了锁的粒度。因为成员变量pendingFunctors_在增加任务的时候，也会被用到，设计到多个线程操作，所以要加锁，增加任务的地方是：
代码语言：javascript复制void EventLoop::queueInLoop(const Functor& cb)
{
{
std::unique_lock<std::mutex> lock(mutex_);
pendingFunctors_.push_back(cb);
}
if (!isInLoopThread() || callingPendingFunctors_)
{
wakeup();
}
} 而frameFunctor_就更简单了，就是通过设置一个函数指针就可以了。当然这里有个技巧性的东西，即增加任务的时候，为了能够立即执行，使用唤醒机制，通过往一个fd里面写入简单的几个字节，来唤醒epoll，使其立刻返回，因为此时没有其它的socke有事件，这样接下来就执行刚才添加的任务了。
我们看一下数据收取的逻辑：
代码语言：javascript复制void TcpConnection::handleRead(Timestamp receiveTime)
{
loop_->assertInLoopThread();
int savedErrno = 0;
ssize_t n = inputBuffer_.readFd(channel_->fd(), &savedErrno);
if (n > 0)
{
//messageCallback_指向CTcpSession::OnRead(const std::shared_ptr<TcpConnection>& conn, Buffer* pBuffer, Timestamp receiveTime)
messageCallback_(shared_from_this(), &inputBuffer_, receiveTime);
}
else if (n == 0)
{
handleClose();
}
else
{
errno = savedErrno;
LOG_SYSERR << "TcpConnection::handleRead";
handleError();
}
} 将收到的数据放到接收缓冲区里面，将来我们来解包：
代码语言：javascript复制void ClientSession::OnRead(const std::shared_ptr<TcpConnection>& conn, Buffer* pBuffer, Timestamp receivTime)
{
while (true)
{
//不够一个包头大小
if (pBuffer->readableBytes() < (size_t)sizeof(msg))
{
LOG_INFO << "buffer is not enough for a package header, pBuffer->readableBytes()=" << pBuffer->readableBytes() << ", sizeof(msg)=" << sizeof(msg);
return;
}
//不够一个整包大小
msg header;
memcpy(&header, pBuffer->peek(), sizeof(msg));
if (pBuffer->readableBytes() < (size_t)header.packagesize sizeof(msg))
return;
pBuffer->retrieve(sizeof(msg));
std::string inbuf;
inbuf.append(pBuffer->peek(), header.packagesize);
pBuffer->retrieve(header.packagesize);
if (!Process(conn, inbuf.c_str(), inbuf.length()))
{
LOG_WARN << "Process error, close TcpConnection";
conn->forceClose();
}
}// end while-loop
} 先判断接收缓冲区里面的数据是否够一个包头大小，如果够再判断够不够包头指定的包体大小，如果还是够的话，接着在Process函数里面处理该包。
再看看发送数据的逻辑：
代码语言：javascript复制void TcpConnection::sendInLoop(const void* data, size_t len)
{
loop_->assertInLoopThread();
ssize_t nwrote = 0;
size_t remaining = len;
bool faultError = false;
if (state_ == kDisconnected)
{
LOG_WARN << "disconnected, give up writing";
return;
}
// if no thing in output queue, try writing directly
if (!channel_->isWriting() && outputBuffer_.readableBytes() == 0)
{
nwrote = sockets::write(channel_->fd(), data, len);
if (nwrote >= 0)
{
remaining = len - nwrote;
if (remaining == 0 && writeCompleteCallback_)
{
loop_->queueInLoop(std::bind(writeCompleteCallback_, shared_from_this()));
}
}
else // nwrote < 0
{
nwrote = 0;
if (errno != EWOULDBLOCK)
{
LOG_SYSERR << "TcpConnection::sendInLoop";
if (errno == EPIPE || errno == ECONNRESET) // FIXME: any others?
{
faultError = true;
}
}
}
}
assert(remaining <= len);
if (!faultError && remaining > 0)
{
size_t oldLen = outputBuffer_.readableBytes();
if (oldLen remaining >= highWaterMark_
&& oldLen < highWaterMark_
&& highWaterMarkCallback_)
{
loop_->queueInLoop(std::bind(highWaterMarkCallback_, shared_from_this(), oldLen remaining));
}
outputBuffer_.append(static_cast<const char*>(data) nwrote, remaining);
if (!channel_->isWriting())
{
channel_->enableWriting();
}
}
} 如果剩余的数据remaining大于则调用channel_->enableWriting();开始监听可写事件，可写事件处理如下：
代码语言：javascript复制void TcpConnection::handleWrite()
{
loop_->assertInLoopThread();
if (channel_->isWriting())
{
ssize_t n = sockets::write(channel_->fd(),
outputBuffer_.peek(),
outputBuffer_.readableBytes());
if (n > 0)
{
outputBuffer_.retrieve(n);
if (outputBuffer_.readableBytes() == 0)
{
channel_->disableWriting();
if (writeCompleteCallback_)
{
loop_->queueInLoop(std::bind(writeCompleteCallback_, shared_from_this()));
}
if (state_ == kDisconnecting)
{
shutdownInLoop();
}
}
}
else
{
LOG_SYSERR << "TcpConnection::handleWrite";
// if (state_ == kDisconnecting)
// {
// shutdownInLoop();
// }
}
}
else
{
LOG_TRACE << "Connection fd = " << channel_->fd()
<< " is down, no more writing";
}
} 如果发送完数据以后调用channel_->disableWriting();移除监听可写事件。
很多读者可能一直想问，文中不是说解包数据并处理逻辑是业务代码而非网络通信的代码，你这里貌似都混在一起了，其实没有，这里实际的业务代码处理都是框架曾提供的回调函数里面处理的，具体怎么处理，由框架使用者——业务层自己定义。
总结起来，实际上就是一个线程函数里一个loop那么点事情，不信你再看我曾经工作上的一个交易系统项目代码：
代码语言：javascript复制void CEventDispatcher::Run()
{
m_bShouldRun = true;
while(m_bShouldRun)
{
DispatchIOs();
SyncTime();
CheckTimer();
DispatchEvents();
}
} void CEpollReactor::DispatchIOs()
{
DWORD dwSelectTimeOut = SR_DEFAULT_EPOLL_TIMEOUT;
if (HandleOtherTask())
{
dwSelectTimeOut = 0;
}
struct epoll_event ev;
CEventHandlerIdMap::iterator itor = m_mapEventHandlerId.begin();
for(; itor!=m_mapEventHandlerId.end(); itor )
{
CEventHandler *pEventHandler = (CEventHandler *)(*itor).first;
if(pEventHandler == NULL){
continue;
}
ev.data.ptr = pEventHandler;
ev.events = 0;
int nReadID, nWriteID;
pEventHandler->GetIds(&nReadID, &nWriteID);
if (nReadID > 0)
{
ev.events |= EPOLLIN;
}
if (nWriteID > 0)
{
ev.events |= EPOLLOUT;
}
epoll_ctl(m_fdEpoll, EPOLL_CTL_MOD, (*itor).second, &ev);
}
struct epoll_event events[EPOLL_MAX_EVENTS];
int nfds = epoll_wait(m_fdEpoll, events, EPOLL_MAX_EVENTS, dwSelectTimeOut/1000);
for (int i=0; i<nfds; i )
{
struct epoll_event &evref = events[i];
CEventHandler *pEventHandler = (CEventHandler *)evref.data.ptr;
if ((evref.events|EPOLLIN)!=0 && m_mapEventHandlerId.find(pEventHandler)!=m_mapEventHandlerId.end())
{
pEventHandler->HandleInput();
}
if ((evref.events|EPOLLOUT)!=0 && m_mapEventHandlerId.find(pEventHandler)!=m_mapEventHandlerId.end())
{
pEventHandler->HandleOutput();
}
}
} void CEventDispatcher::DispatchEvents()
{
CEvent event;
CSyncEvent *pSyncEvent;
while(m_queueEvent.PeekEvent(event))
{
int nRetval;
if(event.pEventHandler != NULL)
{
nRetval = event.pEventHandler->HandleEvent(event.nEventID, event.dwParam, event.pParam);
}
else
{
nRetval = HandleEvent(event.nEventID, event.dwParam, event.pParam);
}
if(event.pAdd != NULL) //同步消息
{
pSyncEvent=(CSyncEvent *)event.pAdd;
pSyncEvent->nRetval = nRetval;
pSyncEvent->sem.UnLock();
}
}
} 再看看蘑菇街开源的TeamTalk的源码（代码下载地址：https://github.com/baloonwj/TeamTalk）：
代码语言：javascript复制void CEventDispatch::StartDispatch(uint32_t wait_timeout)
{
fd_set read_set, write_set, excep_set;
timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = wait_timeout * 1000; // 10 millisecond
if(running)
return;
running = true;
while (running)
{
_CheckTimer();
_CheckLoop();
if (!m_read_set.fd_count && !m_write_set.fd_count && !m_excep_set.fd_count)
{
Sleep(MIN_TIMER_DURATION);
continue;
}
m_lock.lock();
memcpy(&read_set, &m_read_set, sizeof(fd_set));
memcpy(&write_set, &m_write_set, sizeof(fd_set));
memcpy(&excep_set, &m_excep_set, sizeof(fd_set));
m_lock.unlock();
int nfds = select(0, &read_set, &write_set, &excep_set, &timeout);
if (nfds == SOCKET_ERROR)
{
log("select failed, error code: %d", GetLastError());
Sleep(MIN_TIMER_DURATION);
continue; // select again
}
if (nfds == 0)
{
continue;
}
for (u_int i = 0; i < read_set.fd_count; i )
{
//log("select return read count=%dn", read_set.fd_count);
SOCKET fd = read_set.fd_array[i];
CBaseSocket* pSocket = FindBaseSocket((net_handle_t)fd);
if (pSocket)
{
pSocket->OnRead();
pSocket->ReleaseRef();
}
}
for (u_int i = 0; i < write_set.fd_count; i )
{
//log("select return write count=%dn", write_set.fd_count);
SOCKET fd = write_set.fd_array[i];
CBaseSocket* pSocket = FindBaseSocket((net_handle_t)fd);
if (pSocket)
{
pSocket->OnWrite();
pSocket->ReleaseRef();
}
}
for (u_int i = 0; i < excep_set.fd_count; i )
{
//log("select return exception count=%dn", excep_set.fd_count);
SOCKET fd = excep_set.fd_array[i];
CBaseSocket* pSocket = FindBaseSocket((net_handle_t)fd);
if (pSocket)
{
pSocket->OnClose();
pSocket->ReleaseRef();
}
}
}
} 由于微信公众号文章字数的限制，本篇文章未完，下一篇是《服务器端编程心得（八）——高性能服务器架构设计总结3——以flamigo服务器代码为例》。
