nginx系列第二篇：nginx源码调试

第一篇将nginx源码从下载到运行进行了说明，这一节继续讲解如何调试nginx源代码。本人使用vscode进行调试，选择vscode是因为其比较轻巧，python/C++/C/js等开发都可以，适用性强。

众所周知，nginx是多进程应用程序，master默认启动是守护进程方式启动。所以调试master进程和work进程的方式不同。下面就进入正题。

1.修改编译参数，保证生成可以调试的程序

gcc编译debug程序的两个常用参数：

-g: 创建调试符号表，符号表包含了程序中使用的变量名称的列表。关闭所有的优化机制，以便程序执行过程中严格按照原来的C代码进行。

-O0: 编译不做任何优化，这是默认的编译选项。 

./configure --prefix=/home/baidu123/Downloads/nginx-1.22.1/nginx/bin --with-http_ssl_module --with-stream --with-cc-opt='-O0 -g'
sudo make CFLAGS="-g -oO"
sudo make install

 编译成功见如下目录结构：

 2.调试master进程

(1) 在 conf/nginx.conf 配置文件中添加配置项：daemon off; 如下图所示：

 (2) 启动文件launch.json配置如下：

 "version": "0.2.0",
  "configurations": [
      {
          "name": "debug_master", 
          "type": "cppdbg",
          "request": "launch",
          "program": "${workspaceFolder}/nginx/bin/sbin/nginx", 
          "args": [
              "-c", "${workspaceFolder}/nginx/bin/conf/nginx.conf"
          ],
          "stopAtEntry": false,
          "cwd": "${workspaceFolder}", 
          "environment": [],
          "externalConsole": false,
          "MIMode": "gdb",
          "setupCommands": [
              {
                  "description": "Enable pretty-printing for gdb",
                  "text": "-enable-pretty-printing",
                  "ignoreFailures": true
              }
          ]
      }
  ]
}

 效果如下：

 3.调试work进程

启动文件launch.json配置如下：

{
  // Use IntelliSense to learn about possible attributes.
  // Hover to view descriptions of existing attributes.
  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
  "version": "0.2.0",
  "configurations": [
      { 
          "name": "debug_worker",
          "type": "cppdbg",
          "request": "attach",
          "program": "${workspaceFolder}/nginx/bin/sbin/nginx",
          "processId": "28759",  
          "MIMode": "gdb",
          "setupCommands": [
              {
                  "description": "Enable pretty-printing for gdb",
                  "text": "-enable-pretty-printing",
                  "ignoreFailures": true
              }
          ]
      }
  ]
}

 注意：此处是以gdb attach的方式来调试运行中的进程，需要先使用ps查看nginx woker进程的pid，然后再attach上去，如上图显示work进程id为28759，launch.json文件中的processId也要是28759。

work进程调试效果如下：

在右侧可以看到函数调用栈帧信息

 

疑问：

我在如下两个函数设置断点：

static void

ngx_http_wait_request_handler(ngx_event_t *rev)；

ngx_int_t

ngx_http_parse_request_line(ngx_http_request_t *r, ngx_buf_t *b)；

 

1.刷新网页调用堆栈如下

//先停顿388行
ngx_http_wait_request_handler(ngx_event_t * rev) (/home/baidu123/Downloads/nginx-1.22.1/src/http/ngx_http_request.c:388)
ngx_epoll_process_events(ngx_cycle_t * cycle, ngx_msec_t timer, ngx_uint_t flags) (/home/baidu123/Downloads/nginx-1.22.1/src/event/modules/ngx_epoll_module.c:901)
ngx_process_events_and_timers(ngx_cycle_t * cycle) (/home/baidu123/Downloads/nginx-1.22.1/src/event/ngx_event.c:248)
ngx_worker_process_cycle(ngx_cycle_t * cycle, void * data) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:721)
ngx_spawn_process(ngx_cycle_t * cycle, ngx_spawn_proc_pt proc, void * data, char * name, ngx_int_t respawn) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process.c:199)
ngx_start_worker_processes(ngx_cycle_t * cycle, ngx_int_t n, ngx_int_t type) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:344)
ngx_master_process_cycle(ngx_cycle_t * cycle) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:130)
main(int argc, char * const * argv) (/home/baidu123/Downloads/nginx-1.22.1/src/core/nginx.c:383)

//后停顿135行
ngx_http_parse_request_line(ngx_http_request_t * r, ngx_buf_t * b) (/home/baidu123/Downloads/nginx-1.22.1/src/http/ngx_http_parse.c:135)
ngx_http_process_request_line(ngx_event_t * rev) (/home/baidu123/Downloads/nginx-1.22.1/src/http/ngx_http_request.c:1085)
ngx_http_wait_request_handler(ngx_event_t * rev) (/home/baidu123/Downloads/nginx-1.22.1/src/http/ngx_http_request.c:503)
ngx_epoll_process_events(ngx_cycle_t * cycle, ngx_msec_t timer, ngx_uint_t flags) (/home/baidu123/Downloads/nginx-1.22.1/src/event/modules/ngx_epoll_module.c:901)
ngx_process_events_and_timers(ngx_cycle_t * cycle) (/home/baidu123/Downloads/nginx-1.22.1/src/event/ngx_event.c:248)
ngx_worker_process_cycle(ngx_cycle_t * cycle, void * data) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:721)
ngx_spawn_process(ngx_cycle_t * cycle, ngx_spawn_proc_pt proc, void * data, char * name, ngx_int_t respawn) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process.c:199)
ngx_start_worker_processes(ngx_cycle_t * cycle, ngx_int_t n, ngx_int_t type) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:344)
ngx_master_process_cycle(ngx_cycle_t * cycle) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:130)
main(int argc, char * const * argv) (/home/baidu123/Downloads/nginx-1.22.1/src/core/nginx.c:383)

2.nginx内部自动执行，只停顿到388行

ngx_http_wait_request_handler(ngx_event_t * rev) (/home/baidu123/Downloads/nginx-1.22.1/src/http/ngx_http_request.c:388)
ngx_event_expire_timers() (/home/baidu123/Downloads/nginx-1.22.1/src/event/ngx_event_timer.c:94)
ngx_process_events_and_timers(ngx_cycle_t * cycle) (/home/baidu123/Downloads/nginx-1.22.1/src/event/ngx_event.c:261)
ngx_worker_process_cycle(ngx_cycle_t * cycle, void * data) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:721)
ngx_spawn_process(ngx_cycle_t * cycle, ngx_spawn_proc_pt proc, void * data, char * name, ngx_int_t respawn) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process.c:199)
ngx_start_worker_processes(ngx_cycle_t * cycle, ngx_int_t n, ngx_int_t type) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:344)
ngx_master_process_cycle(ngx_cycle_t * cycle) (/home/baidu123/Downloads/nginx-1.22.1/src/os/unix/ngx_process_cycle.c:130)
main(int argc, char * const * argv) (/home/baidu123/Downloads/nginx-1.22.1/src/core/nginx.c:383)