Home > Article > Backend Development > nginx source code (4) main process
Continued from above.
nginx runs on the console as a single process. Read the main method in core/nginx.c. The preceding code is all initialization code. If you don’t read it carefully, you will easily fall into the devil’s ring. Directly find the definition of ngx_single_process_cycle, in os/unix/ngx_process_cycle.c.
Add the following code in the first for loop:
<code><span>for</span> (i = <span>0</span>; ngx_modules[i]; i++) { <span>char</span> * p = NULL; <span>if</span> (ngx_modules[i]->commands != NULL) { p = ngx_modules[i]->commands->name.data; } <span>if</span> (ngx_modules[i]->init_process) { <span>if</span> (ngx_modules[i]->init_process(cycle) == NGX_ERROR) { <span>/* fatal */</span><span>exit</span>(<span>2</span>); } <span>printf</span>(<span>"[ngx_process_cycle] module ctx_index=%d index=%d name=%s init process\n"</span>, ngx_modules[i]->ctx_index, ngx_modules[i]->index, p); } <span>else</span> { <span>printf</span>(<span>"[ngx_process_cycle] module ctx_index=%d index=%d name=%s\n"</span>, ngx_modules[i]->ctx_index, ngx_modules[i]->index, p); } } <span>printf</span>(<span>"[ngx_process_cycle] for ngx_modules init done\n"</span>);</code>
The function is to print which modules and related indexes and names are currently in nginx.
In the second for loop, it is mainly the ngx_process_events method. After searching, we found that this is a macro, and then this macro is a global variable. Because we loaded the epoll module, it is in event/modules/ngx_epoll_module.c
Found the code in:
<code>ngx_event_actions = ngx_epoll_module_ctx.actions;</code>
Found that the ngx_process_events method is actually the ngx_epoll_process_events method in the actions in the ngx_epoll_module_ctx module. Find the place where the epoll_wait method is called in this method, and add the following code:
<code><span>printf</span>(<span>"[ngx_epoll_module] epoll wait\n"</span>); events = epoll_wait(ep, event_list, nevents, timer); <span>printf</span>(<span>"[ngx_epoll_module] epoll wait ---\n"</span>);</code>
Remake running results:
[main] to start ngx_single_process_cycle
[ngx_process_cycle] module ctx_index=0 index=0 name=daemon
[ngx_process_cycle] module ctx_index=0 index=1 name=error_log
[ngx_process_cycle] module ctx_index=0 index=2 name=include
[ngx_process_cycle] module ctx_index=0 index=3 name=events
[ngx_process_cycle] module ctx_index=0 index=4 name=connections init process
[ngx_process_cycle] module ctx_index=1 index=5 name=rtsig_signo
[ngx_process_cycle] module ctx_index=2 index=6 name=epoll_events
[ngx_process_cycle] module ctx_index=0 index=7 name=http
[ngx_process_cycle] module ctx_index=0 index=8 name=server
[ngx_process_cycle] module ctx_index=1 index=9 name=log_format
[ngx_process_cycle] module ctx_index=2 index=10 name=(null)
[ngx_process_cycle] module ctx_index=3 index=11 name=index
[ngx_process_cycle] module ctx_index=4 index=12 name=allow
[ngx_process_cycle] module ctx_index=5 index=13 name=rewrite
[ngx_process_cycle] module ctx_index=6 index=14 name=proxy_pass
[ngx_process_cycle] module ctx_index=7 index=15 name=(null)
[ngx_process_cycle] module ctx_index=8 index=16 name=(null)
[ngx_process_cycle] module ctx_index=9 index=17 name=(null)
[ngx_process_cycle] module ctx_index=10 index=18 name=(null)
[ngx_process_cycle] module ctx_index=11 index=19 name=gzip
[ngx_process_cycle] module ctx_index=12 index=20 name=charset_map
[ngx_process_cycle] module ctx_index=13 index=21 name=userid
[ngx_process_cycle] module ctx_index=14 index=22 name=expires
[ngx_process_cycle] module ctx_index=15 index=23 name=output_buffers
[ngx_process_cycle] module ctx_index=16 index=24 name=(null)
[ngx_process_cycle] module ctx_index=17 index=25 name=(null)
[ngx_process_cycle] for ngx_modules init done
[ngx_epoll_module] epoll wait
^C[ngx_epoll_module] epoll wait —
Found a total of 25 modules, only the connections module has the init_process method, and some module names are empty. Finally, the program enters the epoll module and is blocked at the epoll_wait call. The subsequent print statement is executed only after CTRL+C is launched.
Here you can take a closer look at nginx’s definition of modules. When looking at the code, it is easy to find that the actual types used in nginx all end with _t. If this type is defined as a structure, the actual types end with _s. , nginx_module_s is defined in the core/ngx_conf_file.h file:
<code><span>struct</span> ngx_module_s { ngx_uint_t ctx_index; ngx_uint_t index; <span>void</span> *ctx; ngx_command_t *commands; ngx_uint_t type; ngx_int_t (*init_module)(ngx_cycle_t *cycle); ngx_int_t (*init_process)(ngx_cycle_t *cycle); <span>#if 0</span> ngx_int_t (*init_thread)(ngx_cycle_t *cycle); <span>#endif</span> };</code>
There are two index numbers, as well as commands and 3 functions. The specific meaning will be used later.
There are two other structures ngx_event_module_t and ngx_event_actions_t; the latter is a member of the former; the former is the nginx event module, but it is abstract and will have different types on a certain platform, here it is epoll.
ngx_event_module_t is as follows:
<code>typedef struct { ngx_str_t <span>*name</span>; void <span>*(</span><span>*create_conf</span>)(ngx_cycle_t <span>*cycle</span>); char <span>*(</span><span>*init_conf</span>)(ngx_cycle_t <span>*cycle</span>, void <span>*conf</span>); ngx_event_actions_t actions; } ngx_event_module_t;</code>
epoll instance is as follows:
<code>ngx_event_module_t ngx_epoll_module_ctx = { &epoll_name, ngx_epoll_create_conf, <span>/* create configuration */</span> ngx_epoll_init_conf, <span>/* init configuration */</span> { ngx_epoll_add_event, <span>/* add an event */</span> ngx_epoll_del_event, <span>/* delete an event */</span> ngx_epoll_add_event, <span>/* enable an event */</span> ngx_epoll_del_event, <span>/* disable an event */</span> ngx_epoll_add_connection, <span>/* add an connection */</span> ngx_epoll_del_connection, <span>/* delete an connection */</span><span>NULL</span>, <span>/* process the changes */</span> ngx_epoll_process_events, <span>/* process the events */</span> ngx_epoll_init, <span>/* init the events */</span> ngx_epoll_done, <span>/* done the events */</span> } };</code>
It happens that the actions members in ngx_event_module_t are defined in ngx_epoll_module_ctx as some functions related to epoll, and the previous ngx_process_events are concatenated by the following two lines of code:
In event/ngx_event.h
<code><span>#<span>define</span> ngx_process_events ngx_event_actions.process_events</span></code>
event/modules/ngx_epoll_module.c
<code><span> ngx_event_actions </span>=<span> ngx_epoll_module_ctx.actions;</span></code>
ngx_event_actions is defined as a global variable in event/ngx_event.c:
<code>ngx_event_actions_t ngx_event_actions;</code>
Next, let’s take a look at the use of epoll in nginx.
to be continued …
The above introduces the main process of nginx source code (4), including various aspects. I hope it will be helpful to friends who are interested in PHP tutorials.