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nginx源码分析—core模块callback

导读:作者:阿波链接:http://blog.csdn.net/livelylittlefish/article/details/7262750Content0. 序1. Core模块的配置结构2. create_conf分析3. init_conf分析4. 小结0. 序在源码分析—全局变量ngx_cycle的初始化>中,简单介绍了如何调用core模块的callback,并简单列出其定义及其初始化,本文...。。。

作者:阿波
链接:http://blog.csdn.net/livelylittlefish/article/details/7262750

Content
0. 序
1. Core模块的配置结构
2. create_conf分析
3. init_conf分析
4. 小结

0. 序

源码分析—全局变量ngx_cycle的初始化>中,简单介绍了如何调用core模块的callback,并简单列出其定义及其初始化,本文将重点阐述callback做什么。

1. Core模块的配置结构

如前文所述,core模块的callback有两个create_conf()init_conf(),从名字就可以看出,一个创建配置结构,另一个初始化该配置结构。core模块的配置结构如下,存放配置文件中的核心指令,如deamonmaster等。

./src/core/ngx_cycle.h

typedef struct {     ngx_flag_t               daemon;     ngx_flag_t               master;     ngx_msec_t               timer_resolution;     ngx_int_t                worker_processes;     ngx_int_t                debug_points;     ngx_int_t                rlimit_nofile;     ngx_int_t                rlimit_sigpending;     off_t                    rlimit_core;     int                      priority;     ngx_uint_t               cpu_affinity_n;     u_long                  *cpu_affinity;     char                    *username;            /* 用户名 */     ngx_uid_t                user;                /* user ID */     ngx_gid_t                group;               /* group ID*/     ngx_str_t                working_directory;   /*  */     ngx_str_t                lock_file;           /* 用户名 */     ngx_str_t                pid;     ngx_str_t                oldpid;              /* 以'.oldbin'结尾 */     ngx_array_t              env;     char                   **environment;#if (NGX_THREADS)     ngx_int_t                worker_threads;     size_t                   thread_stack_size;#endif} ngx_core_conf_t;

2. create_conf分析

create_conf只是指针,CORE模块的create_conf指向ngx_core_module_init_conf()函数,该函数创建ngx_core_conf_t配置结构。

static void *ngx_core_module_create_conf(ngx_cycle_t *cycle){    ngx_core_conf_t  *ccf;    ccf = ngx_pcalloc(cycle->pool, sizeof(ngx_core_conf_t));    if (ccf == NULL) {        return NULL;    }    /*     * set by ngx_pcalloc()     *     *     ccf->pid = NULL;     *     ccf->oldpid = NULL;     *     ccf->priority = 0;     *     ccf->cpu_affinity_n = 0;     *     ccf->cpu_affinity = NULL;     */    ccf->daemon = NGX_CONF_UNSET;    ccf->master = NGX_CONF_UNSET;    ccf->timer_resolution = NGX_CONF_UNSET_MSEC;    ccf->worker_processes = NGX_CONF_UNSET;    ccf->debug_points = NGX_CONF_UNSET;    ccf->rlimit_nofile = NGX_CONF_UNSET;    ccf->rlimit_core = NGX_CONF_UNSET;    ccf->rlimit_sigpending = NGX_CONF_UNSET;    ccf->user = (ngx_uid_t) NGX_CONF_UNSET_UINT;    ccf->group = (ngx_gid_t) NGX_CONF_UNSET_UINT;#if (NGX_THREADS)    ccf->worker_threads = NGX_CONF_UNSET;    ccf->thread_stack_size = NGX_CONF_UNSET_SIZE;#endif    if (ngx_array_init(&ccf->env, cycle->pool, 1, sizeof(ngx_str_t))        != NGX_OK)    {        return NULL;    }    return ccf;}

该函数很简单,即将配置结构的各个字段初始化为未设置的值。如下。

#define NGX_CONF_UNSET       -1#define NGX_CONF_UNSET_UINT  (ngx_uint_t) -1#define NGX_CONF_UNSET_PTR   (void *) -1#define NGX_CONF_UNSET_SIZE  (size_t) -1#define NGX_CONF_UNSET_MSEC  (ngx_msec_t) -1

3. init_conf分析

init_conf才是真正的初始化该结构。

(1) 初始化daemon、master等

直接赋值。

(2) 初始化pid、oldpid

调用ngx_conf_full_name()函数初始化pid,实际上就是在pid字符串前加上NGX_PREFIX获取pid全路径,NGX_PREFIX定义如下。

#ifndef NGX_PREFIX#define NGX_PREFIX  "/usr/local/nginx/"#endif

例如,ngx_conf_full_name()被调用前ccf->pid的内容如下。

(gdb) p ccf->pid $2 = {  len = 14,   data = 0x4727ff "logs/nginx.pid"}

ngx_conf_full_name()被调用后ccf->pid的内容如下。

(gdb) p ccf->pid $3 = {  len = 31,   data = 0x6cce78 "/usr/local/nginx/logs/nginx.pid"}

(3)初始化username,user,group

该初始化通过调用系统函数getpwnam()getgrnam()完成。相关数据结构如下。

The getpwnam() function returns a pointer to a structure containing the broken-out fields of the record in the password database (e.g., the local password file /etc/passwd, NIS, and LDAP) that matches the username name.
       The passwd structure is defined in as follows:
           struct passwd {
               char   *pw_name;       /* username */
               char   *pw_passwd;     /* user password */
               uid_t   pw_uid;        /* user ID */
               gid_t   pw_gid;        /* group ID */
               char   *pw_gecos;      /* user information */
               char   *pw_dir;        /* home directory */
               char   *pw_shell;      /* shell program */
           };

The getgrnam() function returns a pointer to a structure containing the broken-out fields of the record in the group database (e.g., the local group file /etc/group, NIS, and LDAP) that matches the group name name.
      The group structure is defined in as follows:
           struct group {
               char   *gr_name;       /* group name */
               char   *gr_passwd;     /* group password */
               gid_t   gr_gid;        /* group ID */
               char  **gr_mem;        /* group members */
           };

获得的数据如下。

(gdb) p *pwd$5 = {  pw_name = 0x6b82a0 "nobody",   pw_passwd = 0x6b82a7 "x",   pw_uid = 99,   pw_gid = 99,   pw_gecos = 0x6b82af "Nobody",   pw_dir = 0x6b82b6 "/",   pw_shell = 0x6b82b8 "/sbin/nologin"}(gdb) p *grp$6 = {  gr_name = 0x6c3bf0 "nobody",   gr_passwd = 0x6c3bf7 "x",   gr_gid = 99,   gr_mem = 0x6c3c00}

(4) 初始化lock_file

同初始化pid,调用ngx_conf_full_name()函数初始化lock_file,即在lock_file字符串前加上NGX_PREFIX获取其全路径,其全路径如下。

(gdb) p ccf->lock_file $6 = {  len = 32,   data = 0x6ccebf "/usr/local/nginx/logs/nginx.lock"}

(5) 初始化ngx_cycle->lock_file

ngx_cycle->lock_file的初始化是复制ccf->lock_file的内容并在其后链接".accept"。

(6) ngx_cpymem与ngx_memcpy

ngx_cpymem(dst,src,n):将src内容拷贝n个到dst,且返回地址dst+n

ngx_memcpy(dst,src,n):将src内容拷贝n个到dst

(7) 配置结构初始化后的内容

跟踪调试即可获得ngx_core_module这个CORE模块的配置结构,如下。

(gdb) p *ccf$12 = {  daemon = 1,   master = 1,   timer_resolution = 0,   worker_processes = 1,   debug_points = 0,   rlimit_nofile = -1,   rlimit_sigpending = -1,   rlimit_core = -1,   priority = 0,   cpu_affinity_n = 0,   cpu_affinity = 0x0,   username = 0x47280e "nobody",   user = 99,   group = 99,   working_directory = {    len = 0,     data = 0x0  },   lock_file = {    len = 32,     data = 0x6ccebf "/usr/local/nginx/logs/nginx.lock"  },   pid = {    len = 31,     data = 0x6cce78 "/usr/local/nginx/logs/nginx.pid"  },   oldpid = {    len = 39,     data = 0x6cce98 "/usr/local/nginx/logs/nginx.pid.oldbin"  },   env = {    elts = 0x6b12a0,     nelts = 0,     size = 16,     nalloc = 1,     pool = 0x6b0280  },   environment = 0x0}

4. 小结

本文主要分析core模块的callback,后文继续分析配置文件解析等。

阅读、分析优秀的开源代码,一定要亲自操刀运行、调试,才能深刻理解调用路径,数据流向。当然笔者还没有开始分析nginx的核心功能代码,我想那将是非常享受的代码之旅。

 

Reference

# man getpwnam

# man getgrnam

(编辑: livelylittlefish)

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