Nginx 网络通信关键分析初步

逃离我推掉我的手 2022-06-18 12:57 205阅读 0赞

Nginx  WEB服务器这里就不多做介绍，本节主要介绍它的网络处理部分关键流程代码。即网络流的IO读，写操作，这里主要采用gdb调试的方式，快速跟踪源代码各个关键部分，至于具体哪个函数作用，请各个读者按照本章节提出的堆栈函数，采用相关源码阅读工具去浏览。

1， 查看Nginx进程  
root     20122     1  0 00:36 ?        00:00:00 nginx: master process ./nginx  
nobody   20123 20122  0 00:36 ?        00:00:00 nginx: worker process   （这个是采用单个工作模块，配制文件决定）

2， 采用gdb调试工具进行跟踪， 查出nginx工作模块的堆栈信息如下

gdb) where  
\#0  0x008317a2 in \_dl\_sysinfo\_int80 () from /lib/ld-linux.so.2  
\#1  0x009142be in epoll\_wait () from /lib/tls/libc.so.6  
\#2  0x0806480d in ngx\_epoll\_process\_events (cycle=0x9cd0178, timer=4294967295, flags=1) at src/event/modules/ngx\_epoll\_module.c:572  
\#3  0x0805c730 in ngx\_process\_events\_and\_timers (cycle=0x9cd0178) at src/event/ngx\_event.c:245  
\#4  0x08062bf7 in ngx\_worker\_process\_cycle (cycle=0x9cd0178, data=0x0) at src/os/unix/ngx\_process\_cycle.c:801  
\#5  0x08060fe8 in ngx\_spawn\_process (cycle=0x9cd0178, proc=0x8062b41 <ngx\_worker\_process\_cycle>, data=0x0,   
    name=0x80a25c6 "worker process", respawn=-3) at src/os/unix/ngx\_process.c:196  
\#6  0x0806249e in ngx\_start\_worker\_processes (cycle=0x9cd0178, n=1, type=-3) at src/os/unix/ngx\_process\_cycle.c:360  
\#7  0x08061e5c in ngx\_master\_process\_cycle (cycle=0x9cd0178) at src/os/unix/ngx\_process\_cycle.c:136  
\#8  0x0804a852 in main (argc=1, argv=0xbfeb9b24) at src/core/nginx.c:405

从这里就可查出Nginx服务器采用的是epoll 的多路复用处理函数。每一层的堆栈信息非常明显，对于整个网络通信服务器基本的流程有个大致了解。具体得如何去分析源码

得靠这里提供的关键堆栈信息，结合SourceInsigh之类的工具进行分析

3，  读取网络流信息堆栈如下：

\#0  ngx\_unix\_recv (c=0x9ce5b58, buf=0x9cd8ce8 "繨\\227", size=1024) at src/os/unix/ngx\_recv.c:132  
\#1  0x0806deee in ngx\_http\_read\_request\_header (r=0x9cd8a50) at src/http/ngx\_http\_request.c:1153  
\#2  0x0806d72d in ngx\_http\_process\_request\_line (rev=0x9cfdab0) at src/http/ngx\_http\_request.c:730  
\#3  0x0806d64f in ngx\_http\_init\_request (rev=0x9cfdab0) at src/http/ngx\_http\_request.c:518  
\#4  0x08064988 in ngx\_epoll\_process\_events (cycle=0x9cd0178, timer=60000, flags=Variable "flags" is not available.  
) at src/event/modules/ngx\_epoll\_module.c:678  
\#5  0x0805c730 in ngx\_process\_events\_and\_timers (cycle=0x9cd0178) at src/event/ngx\_event.c:245  
\#6  0x08062bf7 in ngx\_worker\_process\_cycle (cycle=0x9cd0178, data=0x0) at src/os/unix/ngx\_process\_cycle.c:801  
\#7  0x08060fe8 in ngx\_spawn\_process (cycle=0x9cd0178, proc=0x8062b41 <ngx\_worker\_process\_cycle>, data=0x0,   
    name=0x80a25c6 "worker process", respawn=-3) at src/os/unix/ngx\_process.c:196  
\#8  0x0806249e in ngx\_start\_worker\_processes (cycle=0x9cd0178, n=1, type=-3) at src/os/unix/ngx\_process\_cycle.c:360  
\#9  0x08061e5c in ngx\_master\_process\_cycle (cycle=0x9cd0178) at src/os/unix/ngx\_process\_cycle.c:136  
\#10 0x0804a852 in main (argc=1, argv=0xbfeb9b24) at src/core/nginx.c:405

分析的关键函数流程 ngx\_epoll\_process\_events -->ngx\_http\_init\_request -->ngx\_http\_process\_request\_line-->ngx\_http\_read\_request\_header-->ngx\_unix\_recv

即根据http协议先读取HTTP头，紧跟着读出http 请求协议的一行。