nginx module和初始化流程

module

数据结构

struct ngx_module_s {
    ngx_uint_t            ctx_index;//所属模块的索引
    ngx_uint_t            index;//全部模块中的索引

    ngx_uint_t            spare0;
    ngx_uint_t            spare1;
    ngx_uint_t            spare2;
    ngx_uint_t            spare3;//保留

    ngx_uint_t            version;

    void                 *ctx;//具体模块类型中的上下文
    ngx_command_t        *commands;//包含的命令
    ngx_uint_t            type;//是哪种模块

    ngx_int_t           (*init_master)(ngx_log_t *log);//初始化master

    ngx_int_t           (*init_module)(ngx_cycle_t *cycle);//初始化module

    ngx_int_t           (*init_process)(ngx_cycle_t *cycle);//初始化服务
    ngx_int_t           (*init_thread)(ngx_cycle_t *cycle);//初始化线程
    void                (*exit_thread)(ngx_cycle_t *cycle);//退出线程
    void                (*exit_process)(ngx_cycle_t *cycle);//退出服务

    void                (*exit_master)(ngx_cycle_t *cycle);//退出master

    uintptr_t             spare_hook0;
    uintptr_t             spare_hook1;
    uintptr_t             spare_hook2;
    uintptr_t             spare_hook3;
    uintptr_t             spare_hook4;
    uintptr_t             spare_hook5;
    uintptr_t             spare_hook6;
    uintptr_t             spare_hook7;//保留
};

module的数据结构特别的简单就不单独说了，来看具体的启动流程为后面的分析做准备。

函数的入口在nginx.c里面的main函数

 ngx_debug_init();//调试初始化

    if (ngx_strerror_init() != NGX_OK) {//把系统的错误保存在ngx_sys_errlist
        return 1;
    }
    if (ngx_get_options(argc, argv) != NGX_OK) { //解析命令参数
        return 1;
    }

 if (ngx_show_version) {
        ngx_write_stderr("nginx version: " NGINX_VER_BUILD NGX_LINEFEED);

        if (ngx_show_help) {
            ngx_write_stderr(
                "Usage: nginx [-?hvVtTq] [-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" //除了version外还可以显示操作系统和configure阶段等相关信息
                                   NGX_LINEFEED
                "  -t            : test configuration and exit" NGX_LINEFEED  //不启动nginx进程，只是测试配置文件是否有错误
                "  -T            : test configuration, dump it and exit"
                                   NGX_LINEFEED
                "  -q            : suppress non-error messages "
                                   "during configuration testing" NGX_LINEFEED //通过-t测试配置文件是否错误的时候,nginx -t -q可以把error级别以下的日志不输出的屏幕
                "  -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  //指定安装目录  
#else
                "  -p prefix     : set prefix path (default: NONE)" NGX_LINEFEED
#endif
                "  -c filename   : set configuration file (default: "
                                   NGX_CONF_PATH ")" NGX_LINEFEED //指定配置文件
                "  -g directives : set global directives out of configuration "
                                   "file" NGX_LINEFEED NGX_LINEFEED
                );
        }

        if (ngx_show_configure) {

#ifdef NGX_COMPILER
            ngx_write_stderr("built by " NGX_COMPILER NGX_LINEFEED);
#endif

#if (NGX_SSL)
            if (SSLeay() == SSLEAY_VERSION_NUMBER) {
                ngx_write_stderr("built with " OPENSSL_VERSION_TEXT
                                 NGX_LINEFEED);
            } else {
                ngx_write_stderr("built with " OPENSSL_VERSION_TEXT
                                 " (running with ");
                ngx_write_stderr((char *) (uintptr_t)
                                 SSLeay_version(SSLEAY_VERSION));
                ngx_write_stderr(")" NGX_LINEFEED);
            }
#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
            ngx_write_stderr("TLS SNI support enabled" NGX_LINEFEED);
#else
            ngx_write_stderr("TLS SNI support disabled" NGX_LINEFEED);
#endif
#endif

            ngx_write_stderr("configure arguments:" NGX_CONFIGURE NGX_LINEFEED);
        }

        if (!ngx_test_config) {
            return 0;
        }
    }

    ngx_time_init(); //初始化nginx环境的当前时间
#if (NGX_PCRE)
    ngx_regex_init();//初始化regex 主要是设置内存函数
#endif
    ngx_pid = ngx_getpid();//获取进程信息

/*
  这个时候还米有读取配置文件，所以不知道日志的存放的位置，如果这个时候要记录一些初始化的错误信息，也需要一个存储的位置，所以就使用的默认的
*/
    log = ngx_log_init(ngx_prefix);
    if (log == NULL) {
        return 1;
    }
#if (NGX_OPENSSL)
    ngx_ssl_init(log);
#endif

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

//初始化init_cycle 然后分配内存分配器
    ngx_memzero(&init_cycle, sizeof(ngx_cycle_t));
    init_cycle.log = log;
    ngx_cycle = &init_cycle;

    init_cycle.pool = ngx_create_pool(1024, log);
    if (init_cycle.pool == NULL) {
        return 1;
    }
    if (ngx_save_argv(&init_cycle, argc, argv) != NGX_OK) {
        return 1;
    }
    if (ngx_process_options(&init_cycle) != NGX_OK) {//设置配置文件路径
        return 1;
    }
    if (ngx_os_init(log) != NGX_OK) {//操作系统相关的初始化
        return 1;
    }
    /*
     * ngx_crc32_table_init() requires ngx_cacheline_size set in ngx_os_init()
     */

    if (ngx_crc32_table_init() != NGX_OK) {
        return 1;
    }
 if (ngx_add_inherited_sockets(&init_cycle) != NGX_OK) {
        return 1;
    }// 函数通过环境变量NGINX完成socket的继承
    ngx_max_module = 0;
    for (i = 0; ngx_modules[i]; i++) {
        ngx_modules[i]->index = ngx_max_module++;
    }//设置module的index

 cycle = ngx_init_cycle(&init_cycle);//开始对cycle进行初始化

//进入到ngx_init_cycle函数
    ngx_timezone_update();

    /* force localtime update with a new timezone */

    tp = ngx_timeofday();
    tp->sec = 0;

    ngx_time_update();


    log = old_cycle->log;

  pool = ngx_create_pool(NGX_CYCLE_POOL_SIZE, log);//创建pool
    if (pool == NULL) {
        return NULL;
    }
    pool->log = log;

    cycle = ngx_pcalloc(pool, sizeof(ngx_cycle_t));//分配新的cycle内存
    if (cycle == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    cycle->pool = pool;
    cycle->log = log;
    cycle->old_cycle = old_cycle;

    cycle->conf_prefix.len = old_cycle->conf_prefix.len;//配置信息拷贝
    cycle->conf_prefix.data = ngx_pstrdup(pool, &old_cycle->conf_prefix);
    if (cycle->conf_prefix.data == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    cycle->prefix.len = old_cycle->prefix.len;
    cycle->prefix.data = ngx_pstrdup(pool, &old_cycle->prefix);
    if (cycle->prefix.data == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    cycle->conf_file.len = old_cycle->conf_file.len;
    cycle->conf_file.data = ngx_pnalloc(pool, old_cycle->conf_file.len + 1);
    if (cycle->conf_file.data == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }
    ngx_cpystrn(cycle->conf_file.data, old_cycle->conf_file.data,
                old_cycle->conf_file.len + 1);

    cycle->conf_param.len = old_cycle->conf_param.len;
    cycle->conf_param.data = ngx_pstrdup(pool, &old_cycle->conf_param);
    if (cycle->conf_param.data == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }
//对路径数组和打开文件列表的一些拷贝和初始化
   n = old_cycle->paths.nelts ? old_cycle->paths.nelts : 10;

    cycle->paths.elts = ngx_pcalloc(pool, n * sizeof(ngx_path_t *));
    if (cycle->paths.elts == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    cycle->paths.nelts = 0;
    cycle->paths.size = sizeof(ngx_path_t *);
    cycle->paths.nalloc = n;

    /*
    // 这里都把内存池给赋值给对象的内存池属性， 因为在内存和资源管理方面，nginx委托内存池统一管理， 这里可以通过具体的对象找到
    它用的内存池对象， 方便实现内存和资源方面的管理。  
    */
    cycle->paths.pool = pool;


    if (ngx_array_init(&cycle->config_dump, pool, 1, sizeof(ngx_conf_dump_t))
        != NGX_OK)
    {
        ngx_destroy_pool(pool);
        return NULL;
    }

    if (old_cycle->open_files.part.nelts) {
        n = old_cycle->open_files.part.nelts;
        for (part = old_cycle->open_files.part.next; part; part = part->next) {
            n += part->nelts;
        }

    } else {
        n = 20;
    }

    if (ngx_list_init(&cycle->open_files, pool, n, sizeof(ngx_open_file_t))
        != NGX_OK)
    {
        ngx_destroy_pool(pool);
        return NULL;
    }

//对共享内存的个数拷贝
    if (old_cycle->shared_memory.part.nelts) {
        n = old_cycle->shared_memory.part.nelts;
        for (part = old_cycle->shared_memory.part.next; part; part = part->next)
        {
            n += part->nelts;
        }

    } else {
        n = 1;
    }

//对共享内存初始化
    if (ngx_list_init(&cycle->shared_memory, pool, n, sizeof(ngx_shm_zone_t)) 
        != NGX_OK)
    {
        ngx_destroy_pool(pool);
        return NULL;
    }

//对listening数组的初始化
 n = old_cycle->listening.nelts ? old_cycle->listening.nelts : 10;

    cycle->listening.elts = ngx_pcalloc(pool, n * sizeof(ngx_listening_t));
    if (cycle->listening.elts == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    cycle->listening.nelts = 0;
    cycle->listening.size = sizeof(ngx_listening_t);
    cycle->listening.nalloc = n;
    cycle->listening.pool = pool;

    ngx_queue_init(&cycle->reusable_connections_queue);

    cycle->conf_ctx = ngx_pcalloc(pool, ngx_max_module * sizeof(void *));//分配上下文信息的存储数组，对每一个模块都进行了分配
    if (cycle->conf_ctx == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    if (gethostname(hostname, NGX_MAXHOSTNAMELEN) == -1) {
        ngx_log_error(NGX_LOG_EMERG, log, ngx_errno, "gethostname() failed");
        ngx_destroy_pool(pool);
        return NULL;
    }

    /* on Linux gethostname() silently truncates name that does not fit */
    hostname[NGX_MAXHOSTNAMELEN - 1] = '\0';
    cycle->hostname.len = ngx_strlen(hostname);

    cycle->hostname.data = ngx_pnalloc(pool, cycle->hostname.len);
    if (cycle->hostname.data == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    ngx_strlow(cycle->hostname.data, (u_char *) hostname, cycle->hostname.len);

//调用所有的NGX_CORE_MODULE create_conf 分配配置存储空间
    for (i = 0; ngx_modules[i]; i++) {
        if (ngx_modules[i]->type != NGX_CORE_MODULE) {
            continue;
        }

        module = ngx_modules[i]->ctx;

        if (module->create_conf) {
            rv = module->create_conf(cycle);
            if (rv == NULL) {
                ngx_destroy_pool(pool);
                return NULL;
            }
            
            cycle->conf_ctx[ngx_modules[i]->index] = rv;//保存在index对应的位置
        }
    }

    senv = environ;

    ngx_memzero(&conf, sizeof(ngx_conf_t));
    /* STUB: init array ? */
    conf.args = ngx_array_create(pool, 10, sizeof(ngx_str_t));//用来保存没一行的信息 
    if (conf.args == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    conf.temp_pool = ngx_create_pool(NGX_CYCLE_POOL_SIZE, log);
    if (conf.temp_pool == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }


    //这时候的conf指向的是cycle
//配置conf的上下文环境
    conf.ctx = cycle->conf_ctx; //结合上一篇文章的配置寻找方法可以很清晰的发现是怎么回事啦
    conf.cycle = cycle;
    conf.pool = pool;
    conf.log = log;
    conf.module_type = NGX_CORE_MODULE;
    conf.cmd_type = NGX_MAIN_CONF;

    if (ngx_conf_param(&conf) != NGX_CONF_OK) { //这时候的conf指向的是cycle 对params进行解析
        environ = senv;
        ngx_destroy_cycle_pools(&conf);
        return NULL;
    }

    if (ngx_conf_parse(&conf, &cycle->conf_file) != NGX_CONF_OK) {//这时候的conf指向的是cycle 进入 cmd handler 模式 命令与handler一一对应 然后进入模块block再递归进行 进行配置解析
        environ = senv;
        ngx_destroy_cycle_pools(&conf);
        return NULL;
    }
//配置解析结束
 if (ngx_test_config && !ngx_quiet_mode) {//-t
        ngx_log_stderr(0, "the configuration file %s syntax is ok",
                       cycle->conf_file.data);
    }

    /*
    调用所有NGX—CORE—MODULE核心模块的init_ conf方法。这一步骤的目的在于让所有核心模块在解析完配置项后可以做综合性处理， 一般来说是对为被初始化的值进行下默认值的配置
    */
    for (i = 0; ngx_modules[i]; i++) {
        if (ngx_modules[i]->type != NGX_CORE_MODULE) {
            continue;
        }

        module = ngx_modules[i]->ctx;

        if (module->init_conf) {
            if (module->init_conf(cycle, cycle->conf_ctx[ngx_modules[i]->index])
                == NGX_CONF_ERROR)
            {
                environ = senv;
                ngx_destroy_cycle_pools(&conf);
                return NULL;
            }
        }
    }
    if (ngx_process == NGX_PROCESS_SIGNALLER) {//sign就收工了
        return cycle;
    }
ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);//获取解析完成后 完成了init后的配置

 if (ngx_test_config) {//-t

        if (ngx_create_pidfile(&ccf->pid, log) != NGX_OK) {
            goto failed;
        }

    } else if (!ngx_is_init_cycle(old_cycle)) {

        /*
         * we do not create the pid file in the first ngx_init_cycle() call
         * because we need to write the demonized process pid
         */

        old_ccf = (ngx_core_conf_t *) ngx_get_conf(old_cycle->conf_ctx,
                                                   ngx_core_module);
        if (ccf->pid.len != old_ccf->pid.len
            || ngx_strcmp(ccf->pid.data, old_ccf->pid.data) != 0)
        {
            /* new pid file name */

            if (ngx_create_pidfile(&ccf->pid, log) != NGX_OK) {
                goto failed;
            }

            ngx_delete_pidfile(old_cycle);
        }
    }

    if (ngx_test_lockfile(cycle->lock_file.data, log) != NGX_OK) {
        goto failed;
    }

    //创建在nginx.conf中涉及到文件路径的文件夹
    if (ngx_create_paths(cycle, ccf->user) != NGX_OK) {
        goto failed;
    }

    if (ngx_log_open_default(cycle) != NGX_OK) {//设置默认log文件
        goto failed;
    }


    /* open the new files */

    part = &cycle->open_files.part;
    file = part->elts;

    for (i = 0; /* void */ ; i++) {

        if (i >= part->nelts) {
            if (part->next == NULL) {
                break;
            }
            part = part->next;
            file = part->elts;
            i = 0;
        }

        if (file[i].name.len == 0) {
            continue;
        }

        file[i].fd = ngx_open_file(file[i].name.data,
                                   NGX_FILE_APPEND,
                                   NGX_FILE_CREATE_OR_OPEN,
                                   NGX_FILE_DEFAULT_ACCESS);

        ngx_log_debug3(NGX_LOG_DEBUG_CORE, log, 0,
                       "log: %p %d \"%s\"",
                       &file[i], file[i].fd, file[i].name.data);

        if (file[i].fd == NGX_INVALID_FILE) {
            ngx_log_error(NGX_LOG_EMERG, log, ngx_errno,
                          ngx_open_file_n " \"%s\" failed",
                          file[i].name.data);
            goto failed;
        }

#if !(NGX_WIN32)
        if (fcntl(file[i].fd, F_SETFD, FD_CLOEXEC) == -1) {
            ngx_log_error(NGX_LOG_EMERG, log, ngx_errno,
                          "fcntl(FD_CLOEXEC) \"%s\" failed",
                          file[i].name.data);
            goto failed;
        }
#endif
    }
    cycle->log = &cycle->new_log;
    pool->log = &cycle->new_log;
 /*  走到这里的时候，所有的配置已经解析完毕，如果配置"zone" proxy_cache_path fastcgi_cache_path等需要创建共享内存，则在下面依次创建对应的共享内存  */

 /* create shared memory */
    part = &cycle->shared_memory.part;
    shm_zone = part->elts;
    //ngx_cycle_t结构体的shared_mem ory链表中将会开始初始化用于进程间通信的共享内存。
    for (i = 0; /* void */ ; i++) {
        if (i >= part->nelts) { //在热启动nginx的时候才会执行下面的相关代码，默认i和part->nelts都等于0
            if (part->next == NULL) {
                break;
            }
            part = part->next;
            shm_zone = part->elts;
            i = 0;
        }

        if (shm_zone[i].shm.size == 0) {
            ngx_log_error(NGX_LOG_EMERG, log, 0,
                          "zero size shared memory zone \"%V\"",
                          &shm_zone[i].shm.name);
            goto failed;
        }

        shm_zone[i].shm.log = cycle->log;

        opart = &old_cycle->shared_memory.part;
        oshm_zone = opart->elts;

        for (n = 0; /* void */ ; n++) {

            if (n >= opart->nelts) {
                if (opart->next == NULL) {
                    break;
                }
                opart = opart->next;
                oshm_zone = opart->elts;
                n = 0;
            }

            if (shm_zone[i].shm.name.len != oshm_zone[n].shm.name.len) {
                continue;
            }

            if (ngx_strncmp(shm_zone[i].shm.name.data,
                            oshm_zone[n].shm.name.data,
                            shm_zone[i].shm.name.len) //
                != 0)
            {
                continue;
            }

            if (shm_zone[i].tag == oshm_zone[n].tag
                && shm_zone[i].shm.size == oshm_zone[n].shm.size
                && !shm_zone[i].noreuse)
            {
                shm_zone[i].shm.addr = oshm_zone[n].shm.addr;
#if (NGX_WIN32)
                shm_zone[i].shm.handle = oshm_zone[n].shm.handle;
#endif

                if (shm_zone[i].init(&shm_zone[i], oshm_zone[n].data)
                    != NGX_OK)
                {
                    goto failed;
                }

                goto shm_zone_found;
            }

            ngx_shm_free(&oshm_zone[n].shm);

            break;
        }

        if (ngx_shm_alloc(&shm_zone[i].shm) != NGX_OK) {
            goto failed;
        }

        if (ngx_init_zone_pool(cycle, &shm_zone[i]) != NGX_OK) {
            goto failed;
        }

        if (shm_zone[i].init(&shm_zone[i], NULL) != NGX_OK) {
            goto failed;
        }

    shm_zone_found:

        continue;
    }

 /* handle the listening sockets */
/*
    listen所有在配置文件里面配置的端口
*/

 if (old_cycle->listening.nelts) {
        ls = old_cycle->listening.elts; //旧的listen,如热启动继承过来的sock,
        for (i = 0; i < old_cycle->listening.nelts; i++) {
            ls[i].remain = 0;
        }

        nls = cycle->listening.elts; //从配置文件nginx.conf中listen的server ip和端口获取到的信息
        for (n = 0; n < cycle->listening.nelts; n++) {

            for (i = 0; i < old_cycle->listening.nelts; i++) {
                if (ls[i].ignore) {
                    continue;
                }

                if (ls[i].remain) {
                    continue;
                }

                if (ngx_cmp_sockaddr(nls[n].sockaddr, nls[n].socklen,
                                     ls[i].sockaddr, ls[i].socklen, 1)
                    == NGX_OK)
                {
                    nls[n].fd = ls[i].fd;
                    nls[n].previous = &ls[i];
                    ls[i].remain = 1;

                    if (ls[i].backlog != nls[n].backlog) {
                        nls[n].listen = 1;
                    }

#if (NGX_HAVE_DEFERRED_ACCEPT && defined SO_ACCEPTFILTER)

                    /*
                     * FreeBSD, except the most recent versions,
                     * could not remove accept filter
                     */
                    nls[n].deferred_accept = ls[i].deferred_accept;

                    if (ls[i].accept_filter && nls[n].accept_filter) {
                        if (ngx_strcmp(ls[i].accept_filter,
                                       nls[n].accept_filter)
                            != 0)
                        {
                            nls[n].delete_deferred = 1;
                            nls[n].add_deferred = 1;
                        }

                    } else if (ls[i].accept_filter) {
                        nls[n].delete_deferred = 1;

                    } else if (nls[n].accept_filter) {
                        nls[n].add_deferred = 1;
                    }
#endif

#if (NGX_HAVE_DEFERRED_ACCEPT && defined TCP_DEFER_ACCEPT)

                    if (ls[i].deferred_accept && !nls[n].deferred_accept) {
                        nls[n].delete_deferred = 1;

                    } else if (ls[i].deferred_accept != nls[n].deferred_accept)
                    {
                        nls[n].add_deferred = 1;
                    }
#endif

#if (NGX_HAVE_REUSEPORT)
                    if (nls[n].reuseport && !ls[i].reuseport) {
                        nls[n].add_reuseport = 1;
                    }
#endif

                    break;
                }
            }

            if (nls[n].fd == (ngx_socket_t) -1) {
                nls[n].open = 1;
#if (NGX_HAVE_DEFERRED_ACCEPT && defined SO_ACCEPTFILTER)
                if (nls[n].accept_filter) {
                    nls[n].add_deferred = 1;
                }
#endif
#if (NGX_HAVE_DEFERRED_ACCEPT && defined TCP_DEFER_ACCEPT)
                if (nls[n].deferred_accept) {
                    nls[n].add_deferred = 1;
                }
#endif
            }
        }

    } else {
        ls = cycle->listening.elts;
        for (i = 0; i < cycle->listening.nelts; i++) {
            ls[i].open = 1;
#if (NGX_HAVE_DEFERRED_ACCEPT && defined SO_ACCEPTFILTER)
            if (ls[i].accept_filter) {
                ls[i].add_deferred = 1;
            }
#endif
#if (NGX_HAVE_DEFERRED_ACCEPT && defined TCP_DEFER_ACCEPT)
            if (ls[i].deferred_accept) {
                ls[i].add_deferred = 1;
            }
#endif
        }
    }

    if (ngx_open_listening_sockets(cycle) != NGX_OK) {// create bind listen
        goto failed;
    }
    if (!ngx_test_config) {
        ngx_configure_listening_sockets(cycle);//配置sock 重新listen
    }


    /* commit the new cycle configuration */

    if (!ngx_use_stderr) {
        (void) ngx_log_redirect_stderr(cycle);
    }

    for (i = 0; ngx_modules[i]; i++) {//调用module的init方法
        if (ngx_modules[i]->init_module) {
            if (ngx_modules[i]->init_module(cycle) != NGX_OK) {
                /* fatal */
                exit(1);
            }
        }
    }

/* close and delete stuff that lefts from an old cycle */

    /* free the unnecessary shared memory */

    opart = &old_cycle->shared_memory.part;
    oshm_zone = opart->elts;

    for (i = 0; /* void */ ; i++) {

        if (i >= opart->nelts) {
            if (opart->next == NULL) {
                goto old_shm_zone_done;
            }
            opart = opart->next;
            oshm_zone = opart->elts;
            i = 0;
        }

        part = &cycle->shared_memory.part;
        shm_zone = part->elts;

        for (n = 0; /* void */ ; n++) {

            if (n >= part->nelts) {
                if (part->next == NULL) {
                    break;
                }
                part = part->next;
                shm_zone = part->elts;
                n = 0;
            }

            if (oshm_zone[i].shm.name.len == shm_zone[n].shm.name.len
                && ngx_strncmp(oshm_zone[i].shm.name.data,
                               shm_zone[n].shm.name.data,
                               oshm_zone[i].shm.name.len)
                == 0)
            {
                goto live_shm_zone;
            }
        }

        ngx_shm_free(&oshm_zone[i].shm);

    live_shm_zone:

        continue;
    }

old_shm_zone_done:


    /* close the unnecessary listening sockets */

    ls = old_cycle->listening.elts;
    for (i = 0; i < old_cycle->listening.nelts; i++) {

        if (ls[i].remain || ls[i].fd == (ngx_socket_t) -1) {
            continue;
        }

        if (ngx_close_socket(ls[i].fd) == -1) {
            ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
                          ngx_close_socket_n " listening socket on %V failed",
                          &ls[i].addr_text);
        }

#if (NGX_HAVE_UNIX_DOMAIN)

        if (ls[i].sockaddr->sa_family == AF_UNIX) {
            u_char  *name;

            name = ls[i].addr_text.data + sizeof("unix:") - 1;

            ngx_log_error(NGX_LOG_WARN, cycle->log, 0,
                          "deleting socket %s", name);

            if (ngx_delete_file(name) == NGX_FILE_ERROR) {
                ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_socket_errno,
                              ngx_delete_file_n " %s failed", name);
            }
        }

#endif
    }


    /* close the unnecessary open files */

    part = &old_cycle->open_files.part;
    file = part->elts;

    for (i = 0; /* void */ ; i++) {

        if (i >= part->nelts) {
            if (part->next == NULL) {
                break;
            }
            part = part->next;
            file = part->elts;
            i = 0;
        }

        if (file[i].fd == NGX_INVALID_FILE || file[i].fd == ngx_stderr) {
            continue;
        }

        if (ngx_close_file(file[i].fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_EMERG, log, ngx_errno,
                          ngx_close_file_n " \"%s\" failed",
                          file[i].name.data);
        }
    }

 ngx_destroy_pool(conf.temp_pool);
//如果是第一次加载，则满足ngx_is_init_cycle。如果是reload热启动，则原来的nginx进程的ngx_process == NGX_PROCESS_MASTER    
    if (ngx_process == NGX_PROCESS_MASTER || ngx_is_init_cycle(old_cycle)) { 

        /*
         * perl_destruct() frees environ, if it is not the same as it was at
         * perl_construct() time, therefore we save the previous cycle
         * environment before ngx_conf_parse() where it will be changed.
         */
        env = environ;
        environ = senv;

        ngx_destroy_pool(old_cycle->pool);
        cycle->old_cycle = NULL;

        environ = env;

        return cycle;
    }


    if (ngx_temp_pool == NULL) {
        ngx_temp_pool = ngx_create_pool(128, cycle->log);
        if (ngx_temp_pool == NULL) {
            ngx_log_error(NGX_LOG_EMERG, cycle->log, 0,
                          "could not create ngx_temp_pool");
            exit(1);
        }

        n = 10;
        ngx_old_cycles.elts = ngx_pcalloc(ngx_temp_pool,
                                          n * sizeof(ngx_cycle_t *));
        if (ngx_old_cycles.elts == NULL) {
            exit(1);
        }
        ngx_old_cycles.nelts = 0;
        ngx_old_cycles.size = sizeof(ngx_cycle_t *);
        ngx_old_cycles.nalloc = n;
        ngx_old_cycles.pool = ngx_temp_pool;

        ngx_cleaner_event.handler = ngx_clean_old_cycles;
        ngx_cleaner_event.log = cycle->log;
        ngx_cleaner_event.data = &dumb;
        dumb.fd = (ngx_socket_t) -1;
    }

    ngx_temp_pool->log = cycle->log;

    old = ngx_array_push(&ngx_old_cycles);
    if (old == NULL) {
        exit(1);
    }
    *old = old_cycle;

    if (!ngx_cleaner_event.timer_set) {
        ngx_add_timer(&ngx_cleaner_event, 30000, NGX_FUNC_LINE);
        ngx_cleaner_event.timer_set = 1;
    }

  return cycle;
//回到 main

    if (ngx_signal) { //加了-S参数
        return ngx_signal_process(cycle, ngx_signal);
    }

  ngx_os_status(cycle->log);

    ngx_cycle = cycle;

    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);

    if (ccf->master && ngx_process == NGX_PROCESS_SINGLE) { //在这里会把进程模式设置为MASTER模式
        ngx_process = NGX_PROCESS_MASTER;
    }
#if !(NGX_WIN32)

    if (ngx_init_signals(cycle->log) != NGX_OK) {
        return 1;
    }

    if (!ngx_inherited && ccf->daemon) {//启动daemon
        if (ngx_daemon(cycle->log) != NGX_OK) {
            return 1;
        }

        ngx_daemonized = 1;
    }

    if (ngx_inherited) {
        ngx_daemonized = 1;
    }

#endif

 if (ngx_create_pidfile(&ccf->pid, cycle->log) != NGX_OK) {
        return 1;
    }

    if (ngx_log_redirect_stderr(cycle) != NGX_OK) {
        return 1;
    }

    if (log->file->fd != ngx_stderr) {
        //前面的log = ngx_log_init(ngx_prefix);
        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;

//对于module会调用 init_process方法 然后进入事件循环
    if (ngx_process == NGX_PROCESS_SINGLE) { //
        ngx_single_process_cycle(cycle);
        
    } else { //一般都是走到这里，master方式
        ngx_master_process_cycle(cycle);

  }

到这里启动结束。 后面来看下daemon master worker

只要的流程就是 初始化系统信息 创建core_module的conf 递归解析文件 侦听端口 然后对共享内存处理 确认使用的process方式。
补一个ngx_cycle

struct ngx_cycle_s {
    void                  ****conf_ctx; //配置上下文数组()
    ngx_pool_t               *pool; //内存池

    ngx_log_t                *log; //日志
    ngx_log_t                 new_log;

    ngx_uint_t                log_use_stderr;  /* unsigned  log_use_stderr:1; */

    ngx_connection_t        **files; //连接文件
    ngx_connection_t         *free_connections; //空闲链接
    ngx_uint_t                free_connection_n; //空闲链接个数

    ngx_queue_t               reusable_connections_queue; //reusable 链接队列

    ngx_array_t               listening; //listen数组
    ngx_array_t               paths;// 路径数组
    ngx_list_t                open_files;//打开文件列表
    ngx_list_t                shared_memory;//共享内存链表

    ngx_uint_t                connection_n; //链接的个数
    ngx_uint_t                files_n; //打开文件的个数

    ngx_connection_t         *connections; //链接
    ngx_event_t              *read_events; //读事件
    ngx_event_t              *write_events;//写事件

    ngx_cycle_t              *old_cycle;//old

    ngx_str_t                 conf_file; //配置文件
    ngx_str_t                 conf_param;//配置文件参数
    ngx_str_t                 conf_prefix;//配置文件前缀
    ngx_str_t                 prefix;//前缀
    ngx_str_t                 lock_file;//锁文件
    ngx_str_t                 hostname;//主机名
};