nginx源码阅读(二).初始化:main函数及ngx_init_cycle函数

前言

在分析源码时,我们可以先把握主干,然后其他部分再挨个分析就行了。接下来我们先看看nginx的main函数干了些什么。

main函数

这里先介绍一些下面会遇到的变量类型:

ngx_int_t: typedef intptr_t ngx_int_t; 64位机器上,intptr_t为long int, 即typedef long int intptr_t;在32位机器上,intptr_t为int,即typedef int intptr_t。

ngx_log_t: typedef struct ngx_log_s ngx_log_t,struct ngx_log_s存储了日志文件的各种信息

ngx_cycle_t是很重要的结构体,等下列出它的定义。

ngx_core_conf_t是core模块存储配置项的结构体。

ngx_core_conf_t是core模块存储配置项的结构体。

/* src/core/nginx.c */

int ngx_cdecl
main(int argc, char *const *argv)
{
    ngx_int_t         i;
    ngx_log_t        *log;
    ngx_cycle_t      *cycle, init_cycle;
    ngx_core_conf_t  *ccf;

#if (NGX_FREEBSD)
    ngx_debug_init();
#endif

    if (ngx_strerror_init() != NGX_OK) {
        return 1;
    }

    //处理参数,设置对应的标识位等
    if (ngx_get_options(argc, argv) != NGX_OK) {
        return 1;
    }

    //根据标识位显示版本、测试配置等
    if (ngx_show_version) {
        ngx_write_stderr("nginx version: " NGINX_VER NGX_LINEFEED);

        if (ngx_show_help) {
            ngx_write_stderr(
                "Usage: nginx [-?hvVtq] [-s signal] [-c filename] "
                             "[-p prefix] [-g directives]" NGX_LINEFEED
                             NGX_LINEFEED
                "Options:" NGX_LINEFEED
                "  -?,-h         : this help" NGX_LINEFEED
                "  -v            : show version and exit" NGX_LINEFEED
                "  -V            : show version and configure options then exit"
                                   NGX_LINEFEED
                "  -t            : test configuration and exit" NGX_LINEFEED
                "  -q            : suppress non-error messages "
                                   "during configuration testing" NGX_LINEFEED
                "  -s signal     : send signal to a master process: "
                                   "stop, quit, reopen, reload" NGX_LINEFEED
#ifdef NGX_PREFIX
                "  -p prefix     : set prefix path (default: "
                                   NGX_PREFIX ")" NGX_LINEFEED
#else
                "  -p prefix     : set prefix path (default: NONE)" NGX_LINEFEED
#endif
                "  -c filename   : set configuration file (default: "
                                   NGX_CONF_PATH ")" NGX_LINEFEED
                "  -g directives : set global directives out of configuration "
                                   "file" NGX_LINEFEED NGX_LINEFEED
                );
        }

        if (ngx_show_configure) {
            ngx_write_stderr(
#ifdef NGX_COMPILER
                "built by " NGX_COMPILER NGX_LINEFEED
#endif
#if (NGX_SSL)
#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
                "TLS SNI support enabled" NGX_LINEFEED
#else
                "TLS SNI support disabled" NGX_LINEFEED
#endif
#endif
                "configure arguments:" NGX_CONFIGURE NGX_LINEFEED);
        }

        if (!ngx_test_config) {
            return 0;
        }
    }

    /* TODO */ ngx_max_sockets = -1;
    //初始化并更新时间
    ngx_time_init();

#if (NGX_PCRE)
    ngx_regex_init();
#endif

    //获取nginx的进程号
    ngx_pid = ngx_getpid();

    //初始化日志
    log = ngx_log_init(ngx_prefix);
    if (log == NULL) {
        return 1;
    }

    /* STUB */
#if (NGX_OPENSSL)
    ngx_ssl_init(log);
#endif

    /*
     * init_cycle->log is required for signal handlers and
     * ngx_process_options()
     */

    /* 初始化ngx_cycle
     * #define ngx_memzero(buf, n)
          (void) memset(buf, 0, n)
     */
    ngx_memzero(&init_cycle, sizeof(ngx_cycle_t));
    init_cycle.log = log;
    ngx_cycle = &init_cycle;

    //分配内存池
    init_cycle.pool = ngx_create_pool(1024, log);
    if (init_cycle.pool == NULL) {
        return 1;
    }

    //将命令行参数保存到init_cycle结构体中
    if (ngx_save_argv(&init_cycle, argc, argv) != NGX_OK) {
        return 1;
    }

    //用运行nginx时可能携带的目录参数来初始化cycle
    if (ngx_process_options(&init_cycle) != NGX_OK) {
        return 1;
    }

    //提取当前操作系统的一些信息
    if (ngx_os_init(log) != NGX_OK) {
        return 1;
    }

    /*
     * ngx_crc32_table_init() requires ngx_cacheline_size set in ngx_os_init()
     */

    //初始化一个循环冗余校验的表
    //后续的循环冗余校验可以直接查表
    if (ngx_crc32_table_init() != NGX_OK) {
        return 1;
    }

    //这个函数是为了执行不重启服务升级nginx做准备
    //通过环境变量NGINX_VAR将老的nginx进程需要监听的端口传给新的nginx进程,这样就可以读取平滑升级的信息了
    if (ngx_add_inherited_sockets(&init_cycle) != NGX_OK) {
        return 1;
    }

    //对所有模块进行编号
    //ngx_modules数组在编译时已经生成了
    ngx_max_module = 0;
    for (i = 0; ngx_modules[i]; i++) {
        ngx_modules[i]->index = ngx_max_module++;
    }

    //大部分的初始化工作都在ngx_init_cycle中进行
    cycle = ngx_init_cycle(&init_cycle);
    if (cycle == NULL) {
        if (ngx_test_config) {
            ngx_log_stderr(0, "configuration file %s test failed",
                           init_cycle.conf_file.data);
        }

        return 1;
    }

    if (ngx_test_config) {
        if (!ngx_quiet_mode) {
            ngx_log_stderr(0, "configuration file %s test is successful",
                           cycle->conf_file.data);
        }

        return 0;
    }

    if (ngx_signal) {
        return ngx_signal_process(cycle, ngx_signal);
    }

    ngx_os_status(cycle->log);

    ngx_cycle = cycle;

    //获取存储ngx_core_module模块感兴趣的配置项的结构体指针
    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);

    //#define NGX_PROCESS_SINGLE     0  
    //#define NGX_PROCESS_MASTER     1  
    //#define NGX_PROCESS_SIGNALLER  2  
    //#define NGX_PROCESS_WORKER     3  
    //#define NGX_PROCESS_HELPER     4  
    //ccf-master若设置为on(1),并且ngx_process设置为单进程模式时
    //此时由master进程设置的模式为准,为NGX_PROCESS_MASTER
    if (ccf->master && ngx_process == NGX_PROCESS_SINGLE) {
        ngx_process = NGX_PROCESS_MASTER;
    }

#if !(NGX_WIN32)

    //完成对信号的注册等工作
    if (ngx_init_signals(cycle->log) != NGX_OK) {
        return 1;
    }

    //若没有继承sockets,并且设置了守护进程标识位
    //则创建守护进程
    if (!ngx_inherited && ccf->daemon) {
        if (ngx_daemon(cycle->log) != NGX_OK) {
            return 1;
        }

        ngx_daemonized = 1;
    }

    if (ngx_inherited) {
        ngx_daemonized = 1;
    }

#endif
    //创建进程记录文件
    if (ngx_create_pidfile(&ccf->pid, cycle->log) != NGX_OK) {
        return 1;
    }

    if (cycle->log->file->fd != ngx_stderr) {

        if (ngx_set_stderr(cycle->log->file->fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
                          ngx_set_stderr_n " failed");
            return 1;
        }
    }

    if (log->file->fd != ngx_stderr) {
        if (ngx_close_file(log->file->fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                          ngx_close_file_n " built-in log failed");
        }
    }

    ngx_use_stderr = 0;

    //进入进程主循环
    //单进程方式运行nginx
    if (ngx_process == NGX_PROCESS_SINGLE) {
        ngx_single_process_cycle(cycle);

    } else {
    //以master-worker方式运行nginx
        ngx_master_process_cycle(cycle);
    }
    return 0;
}

main函数的代码逻辑大概就是这样,下面介绍一下ngx_cycle_t结构体,然后分析下ngx_init_cycle函数。