搭建一個後臺伺服器--服務端（非同步，大併發）
阿新 • • 發佈：2019-02-19
上篇的阻塞模式下伺服器的併發只有幾K，而真正的server 像nginx, apache, yumeiz 輕輕鬆鬆處理幾萬個併發完全不在話下，因此大併發的場合下是不能用阻塞的。
1W的併發是一個分隔點，如果單程序模型下能達到 的話，說明至少在伺服器這塊你已經很厲害了。
伺服器開發就像一門氣功，能不能搞出大併發，容錯性處理得怎麼樣，就是你有沒有內功，內功有多深。
非同步模式是專門為大併發而生，linux下一般用 epoll 來管理事件，下面就開始我們的非同步大併發伺服器實戰吧。
跟阻塞開發一樣，先來看看設計過程：
1.建立事件模型。
2.建立監聽連線並監聽。
3.將監聽連線加入事件模型。
4.當有事件時，判斷事件型別。
5.若事件為監聽連線，則產生客戶連線同時加入事件模型，對客戶連線接收發送。
6.若事件為客戶連線，處理相應IO請求。
為了讓大家一概全貌，我用一個函式實現的( 一個函式寫一個2W併發的伺服器，你試過麼），可讀性可能會差點，但是對付這道面試題是綽綽有餘了。
實際開發過程如下：
先定義一個事件結構，用於對客戶連線進行快取
struct my_event_s
{
int fd;
char recv[64];
char send[64];
int rc_pos;
int sd_pos;
};建立快取物件：
struct epoll_event wait_events[ EPOLL_MAX ]; struct my_event_s my_event[ EPOLL_MAX ];
建立監聽連線：
sock_server = socket( AF_INET, SOCK_STREAM, 0 );
flag = fcntl( sock_server, F_GETFL, 0 );
fcntl( sock_server, F_SETFL, flag | O_NONBLOCK );繫結地址並監聽：
flag = bind( sock_server, ( struct sockaddr* )&addr_server, sizeof( struct sockaddr ) ); if( flag < 0 ) { printf( "your bind is not ok\n" ); close( sock_server ); return 0; } flag = listen( sock_server, 1024 ); if( flag < 0 ) { printf( "your listen is not ok\n"); close( sock_server ); return 0; }
建立事件模型：
epfd = epoll_create( EPOLL_MAX );
if( epfd <= 0 )
{
printf( "event module could not be setup\n");
close( sock_server );
return 0;
}
tobe_event.events = EPOLLIN;
tobe_event.data.fd = sock_server;
epoll_ctl( epfd, EPOLL_CTL_ADD, sock_server, &tobe_event );事件模型處理：
e_num = epoll_wait( epfd, wait_events, EPOLL_MAX, WAIT_TIME_OUT );
if( e_num <= 0 )
{
continue;
}
for( i = 0; i < e_num; ++i )
{監聽處理：
if( sock_server == wait_events[ i ].data.fd )
{ while(1){連線客戶端：
sock_client = accept( sock_server, ( struct sockaddr* )&addr_client, ( socklen_t*)&size );
if( sock_client < 0 )
{
if( errno == EAGAIN )
{
break;
}
if( errno == EINTR )
{
continue;
}
break;
}將客戶端連線設定為非同步：
flag = fcntl( sock_client, F_GETFL, 0 );
fcntl( sock_client, F_SETFL, flag | O_NONBLOCK );將客戶端連線加入到 事件模型：
tobe_event.events = EPOLLIN | EPOLLET;
tobe_event.data.u32 = my_empty_index;
epoll_ctl( epfd, EPOLL_CTL_ADD, sock_client, &tobe_event );++num;
current = time( 0 );
if( current > last )
{
printf( "last sec qps:%d\n", num );
num = 0;
last = current;
}將時間填充到連線快取中：
memcpy( tobe_myevent->send, ¤t, sizeof(time_t) );接收連線內容：
flag = recv( sock_client, tobe_myevent->recv, 64, 0 );
if( flag < 64 )
{
if( flag > 0 )
tobe_myevent->rc_pos += flag;
continue;
}if( tobe_myevent->recv[31] || tobe_myevent->recv[63] )
{
printf( "your recv does follow the protocal\n");
tobe_myevent->fd = 0;
close( sock_client );
continue;
}
flag = send( sock_client, tobe_myevent->send, sizeof( time_t ), 0 );
if( flag < sizeof( time_t ) )
{
tobe_event.events = EPOLLET | EPOLLOUT;
epoll_ctl( epfd, EPOLL_CTL_MOD, sock_client, &tobe_event );
if( flag > 0 )
tobe_myevent->sd_pos += flag;
continue;
}
tobe_myevent->fd = 0;
close( sock_client );後面進行普通連線事件處理，錯誤處理：
if( event_flag & EPOLLHUP )
{
tobe_myevent->fd = 0;
close( sock_client );
continue;
}
else if( event_flag & EPOLLERR )
{
tobe_myevent->fd = 0;
close( sock_client );
continue;
}寫事件：
else if( event_flag & EPOLLOUT )
{
if( tobe_myevent->rc_pos != 64 )
{
continue;
}
if( tobe_myevent->sd_pos >= sizeof( time_t ) )
{
tobe_myevent->fd = 0;
close( sock_client );
continue;
}
flag = send( sock_client, tobe_myevent->send + tobe_myevent->sd_pos, sizeof( time_t ) - tobe_myevent->sd_pos, 0 );
if( flag < 0 )
{
if( errno == EAGAIN )
{
continue;
}
else if( errno == EINTR )
{
continue;
}
tobe_myevent->fd = 0;
close( sock_client );
continue;
}
if( flag >0 )
{
tobe_myevent->sd_pos += flag;
if( tobe_myevent->sd_pos >= sizeof( time_t ) )
{
tobe_myevent->fd = 0;
close( sock_client );
continue;
}
}
}讀事件：
if( event_flag & EPOLLIN )
{
if( tobe_myevent->rc_pos < 64 )
{
flag = recv( sock_client, tobe_myevent->recv + tobe_myevent->rc_pos, 64 - tobe_myevent->rc_pos, 0 );
if( flag <= 0 )
{
continue;
}
tobe_myevent->rc_pos += flag;
if( tobe_myevent->rc_pos < 64 )
{
continue;
}
if( tobe_myevent->recv[31] || tobe_myevent->recv[63] )
{
printf( "your recv does follow the protocal\n");
tobe_myevent->fd = 0;
close( sock_client );
continue;
}
flag = send( sock_client, tobe_myevent->send, sizeof( time_t ), 0 );
if( flag < sizeof( time_t ) )
{
if( flag > 0 )
tobe_myevent->sd_pos += flag;
tobe_event.events = EPOLLET | EPOLLOUT;
tobe_event.data.u32 = wait_events[i].data.u32;
epoll_ctl( epfd, EPOLL_CTL_MOD, sock_client, &tobe_event );
continue;
}
tobe_myevent->fd = 0;
close( sock_client );
}
}