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.