nginx源码分析―全局变量ngx_cycle的初始化

发布时间：2014-09-05 16:34:17作者：知识屋

作者：阿波

链接：http://blog.csdn.net/livelylittlefish/article/details/7247080

Content
0.序
1. ngx_cycle_t结构
2. ngx_init_cycle()分析
3.注意问题
3.1如何调用CORE模块的callback函数？
3.2 open_files链表中的文件名何时初始化？
4.小结

0.序

Nginx的大部分初始化工作主要围绕一个类型为ngx_cycle_t类型的全局变量(cycle)展开。本文重点介绍全局变量ngx_cycle的初始化。
实现文件：./src/core/ngx_cycle.c。.表示nginx-1.0.4代码目录，本文为/usr/src/nginx-1.0.4。

1. ngx_cycle_t结构

该结构在./src/core/ngx_cycle.h文件中定义，如下。
[cpp] view plaincopy
struct ngx_cycle_s {
    void                  ****conf_ctx; //配置上下文数组(含所有模块)
    ngx_pool_t               *pool;      //内存池

    ngx_log_t                *log;       //日志
    ngx_log_t                 new_log;

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

    ngx_queue_t               reusable_connections_queue; //再利用连接队列

    ngx_array_t               listening;     //监听数组
    ngx_array_t               pathes;        //路径数组
    ngx_list_t                open_files;    //打开文件链表
    ngx_list_t                shared_memory; //共享内存链表

    ngx_uint_t                connection_n; //连接个数
    ngx_uint_t                files_n;      //打开文件个数

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

    ngx_cycle_t              *old_cycle;     //old cycle指针

    ngx_str_t                 conf_file;     //配置文件
    ngx_str_t                 conf_param;    //配置参数
    ngx_str_t                 conf_prefix;   //配置前缀
    ngx_str_t                 prefix;        //前缀
    ngx_str_t                 lock_file;     //锁文件
    ngx_str_t                 hostname;      //主机名
};
该结构体的大小是确定的，sizeof(ngx_cycle_t)=224。
其中，
pathes数组元素结构为ngx_path_t；
open_files链表元素结构为ngx_open_file_t；
shared_memory链表元素结构为ngx_shm_zone_t；
listening数组元素结构为ngx_listening_t，该数组用来存放监听套接字。
各种数据结构关系图如下。

2. ngx_init_cycle()分析

初始化过程如下。
调用ngx_timezone_update()更新时区，调用ngx_time_update()更新时间
创建大小为NGX_CYCLE_POOL_SIZE=16384B的内存池，并从中分配ngx_cycle_t结构
简单初始化，如记录pool指针、log指针
初始化配置前缀、前缀、配置文件、配置参数等字符串
初始化pathes数组
初始化open_files链表
初始化shared_memory链表
初始化listening数组
初始化resuable_connections_queue队列
从pool为conf_ctx分配空间
初始化hostname字符串
调用core模块的create_conf()
配置文件解析
调用core模块的init_conf()
遍历open_files链表中的每一个文件并打开
创建共享内存并初始化(新旧shared_memory链表的比较，相同的共享内存保留，旧的不同的共享内存被释放，新的被创建)
(尝试5遍)遍历listening数组并打开所有侦听sockets(socket()->setsockopt()->bind()->listen())
提交新的cycle配置，并调用所有模块的init_module(实际上只有ngx_event_core_module模块定义了该callback，即只有ngx_event_module_init()被调用)
关闭或删除残留在old_cycle中的资源
释放多余的共享内存
关闭多余的侦听sockets
关闭多余的打开文件
具体请参考附录代码，不需要细究每一步实现，重要的是要搞清楚其初始化流程。
简要的函数调用图如下。图的自动生成，可参考<用Graphviz可视化函数调用-使用开源软件来简化复杂调用结构>。

初始化过程中全局结构ngx_cycle结构图如下。

3.注意问题

3.1如何调用CORE模块的callback函数？

即如可调用core模块的create_conf()和init_conf()？

(1) callback定义
file: ./src/core/ngx_conf_file.h
[cpp] view plaincopy
typedef struct {          //定义core模块上下文类型
    ngx_str_t             name;            //模块名，即ngx_core_module_ctx结构体对象的ngx_string("core")
    void               *(*create_conf)(ngx_cycle_t *cycle);           //创建配置的callback
    char               *(*init_conf)(ngx_cycle_t *cycle, void *conf); //初始化配置的callback
} ngx_core_module_t;
(2) callback初始化
静态初始化ngx_core_module_ctx和ngx_core_module结构。在编译期间就已确定CORE模块的callback了。
file: ./src/core/nginx.c
[cpp] view plaincopy
static ngx_core_module_t ngx_core_module_ctx = { //定义ngx_core_module模块上下文,改方式属于静态初始化
    ngx_string("core"),
    ngx_core_module_create_conf,
    ngx_core_module_init_conf
};

ngx_module_t ngx_core_module = {          //定义ngx_core_module模块,也是静态初始化
    NGX_MODULE_V1,
    &ngx_core_module_ctx,                  /* module context */
    ngx_core_commands,                     /* module directives */
    NGX_CORE_MODULE,                       /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};
静态初始化ngx_core_commands结构。
file: ./src/core/nginx.c
[cpp] view plaincopy
static ngx_command_t ngx_core_commands[] = { //静态初始化core模块的命令

    { ngx_string("daemon"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      0,
      offsetof(ngx_core_conf_t, daemon),
      NULL },

    { ngx_string("master_process"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      0,
      offsetof(ngx_core_conf_t, master),
      NULL },

    { ngx_string("timer_resolution"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_msec_slot,
      0,
      offsetof(ngx_core_conf_t, timer_resolution),
      NULL },

    { ngx_string("pid"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      0,
      offsetof(ngx_core_conf_t, pid),
      NULL },

    { ngx_string("lock_file"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      0,
      offsetof(ngx_core_conf_t, lock_file),
      NULL },

    { ngx_string("worker_processes"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_num_slot,
      0,
      offsetof(ngx_core_conf_t, worker_processes),
      NULL },

    /* ... 省略中间的定义*/

#if (NGX_THREADS)

    { ngx_string("worker_threads"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_num_slot,
      0,
      offsetof(ngx_core_conf_t, worker_threads),
      NULL },

    { ngx_string("thread_stack_size"),
      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_size_slot,
      0,
      offsetof(ngx_core_conf_t, thread_stack_size),
      NULL },

#endif

      ngx_null_command
};
3.2 open_files链表中的文件名何时初始化？
在初始化open_files链表之后遍历该链表并打开文件之前，并未看到向open_files链表中写入文件名。那么，何时写入open_files链表的？
——在ngx_conf_open_file函数中写入。
具体请参考源代码。打开文件后，open_files链表就保存了ngx_open_file_t结构的数据，具体请参考该结构定义。
4.小结
本文主要分析ngx_cycle的初始化，后文继续分析其中调用的CORE模块的callback和配置文件解析等。

Appendix: ngx_init_cycle()代码
[cpp] view plaincopy
ngx_cycle_t *
ngx_init_cycle(ngx_cycle_t *old_cycle)
{
    void                *rv;
    char               **senv, **env;
    ngx_uint_t           i, n;
    ngx_log_t           *log;
    ngx_time_t          *tp;
  ngx_conf_t           conf;
    ngx_pool_t          *pool;
    ngx_cycle_t         *cycle, **old;
    ngx_shm_zone_t      *shm_zone, *oshm_zone;
    ngx_list_part_t     *part, *opart;
    ngx_open_file_t     *file;
    ngx_listening_t     *ls, *nls;
    ngx_core_conf_t     *ccf, *old_ccf;
    ngx_core_module_t   *module;
    char                 hostname[NGX_MAXHOSTNAMELEN];

    ngx_timezone_update(); /*更新时区*/

    /* force localtime update with a new timezone */

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

    ngx_time_update(); /*更新时间*/

    log = old_cycle->log;

    pool = ngx_create_pool(NGX_CYCLE_POOL_SIZE, log); /*创建大小为16384B的内存池*/
    if (pool == NULL) {
        return NULL;
    }
    pool->log = log;

    cycle = ngx_pcalloc(pool, sizeof(ngx_cycle_t)); /*在该内存池上分配大小为224B的空间存放ngx_cycle_t结构*/
    if (cycle == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    /* 以下的初始化就是为了填满上述分配的ngx_cycle_t结构*/

    cycle->pool = pool; /*一些简单的初始化*/
    cycle->log = log;
    cycle->new_log.log_level = NGX_LOG_ERR;
    cycle->old_cycle = old_cycle;

    /** 以下对配置前缀、前缀、配置文件、配置参数等字符串进行初始化
        注意：此处对conf_prefix, prefix, conf_file, conf_param的初始化均是从old_cycle同名字段拷贝而来，
        而old_cycle中的这些字段的初始化是在main函数中调用ngx_init_cycle()函数前调用ngx_process_options()完成
    */
    cycle->conf_prefix.len = old_cycle->conf_prefix.len;
    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;
    }

    /* 以下初始化pathes数组(实际上，在计算出n后，可以调用ngx_array_init()进行初始化) */

    /*先初始化pathes数组元素个数*/
    n = old_cycle->pathes.nelts ? old_cycle->pathes.nelts : 10;

    /*为pathes数组分配空间(从pool指向的内存池)*/
    cycle->pathes.elts = ngx_pcalloc(pool, n * sizeof(ngx_path_t *));
    if (cycle->pathes.elts == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

     /*初始化pathes数组的各字段*/
    cycle->pathes.nelts = 0;
    cycle->pathes.size = sizeof(ngx_path_t *); /*该字段为pathes数组中每个元素的大小*/
    cycle->pathes.nalloc = n;
    cycle->pathes.pool = pool;

    /* 以下初始化open_files链表*/

     /*先初始化open_files链表中所有元素个数*/
    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; /*若改链表中没有元素，则默认赋值为20*/
    }

    /*初始化open_files链表(将从pool指向的内存池分配数组元素空间并进行链表字段的初始化)*/
    if (ngx_list_init(&cycle->open_files, pool, n, sizeof(ngx_open_file_t))
        != NGX_OK)
    {
        ngx_destroy_pool(pool);
        return NULL;
    }

    /* 以下初始化shared_memory链表*/

    /*先初始化shared_memory链表元素个数*/
    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; /*若改链表中没有元素，则默认赋值为1*/
    }

    /*初始化shared_memory链表(将从pool指向的内存池分配数组元素空间并进行链表字段的初始化)*/
    if (ngx_list_init(&cycle->shared_memory, pool, n, sizeof(ngx_shm_zone_t))
        != NGX_OK)
    {
        ngx_destroy_pool(pool);
        return NULL;
    }

    /* 以下初始化listening数组(实际上，在计算出n后，可以调用ngx_array_init()进行初始化) */

    /*先初始化listening数组元素个数*/
    n = old_cycle->listening.nelts ? old_cycle->listening.nelts : 10;

    /*为listening数组分配空间(从pool指向的内存池)*/
    cycle->listening.elts = ngx_pcalloc(pool, n * sizeof(ngx_listening_t));
    if (cycle->listening.elts == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

     /*初始化listening数组的各字段*/
    cycle->listening.nelts = 0;
    cycle->listening.size = sizeof(ngx_listening_t);
    cycle->listening.nalloc = n;
    cycle->listening.pool = pool;

     /*初始化reusable_connections_queue队列*/
    ngx_queue_init(&cycle->reusable_connections_queue);

     /*从pool为conf_ctx分配空间*/
    cycle->conf_ctx = ngx_pcalloc(pool, ngx_max_module * sizeof(void *));
    if (cycle->conf_ctx == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    /* 以下初始化hostname字符串*/

    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core模块的create_conf() */
    for (i = 0; ngx_modules[i]; i++) {
        if (ngx_modules[i]->type != NGX_CORE_MODULE) { /* 仅处理CORE模块*/
            continue;
        }

        module = ngx_modules[i]->ctx; /*即ngx_core_module_ctx结构*/

        if (module->create_conf) {    /*create_conf是core模块的callback*/
            rv = module->create_conf(cycle); /*即调用ngx_core_module_create_conf*/
            if (rv == NULL) {
                ngx_destroy_pool(pool);
                return NULL;
            }
            cycle->conf_ctx[ngx_modules[i]->index] = rv; /*保存该配置结构*/
        }
    }

    senv = environ;

    /*初始化conf.args数组, 10*8=80B*/
    ngx_memzero(&conf, sizeof(ngx_conf_t));
    /* STUB: init array ? */
    conf.args = ngx_array_create(pool, 10, sizeof(ngx_str_t));
    if (conf.args == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    /*创建大小为16384B的内存池, 由conf.temp_pool记录*/
    conf.temp_pool = ngx_create_pool(NGX_CYCLE_POOL_SIZE, log);
    if (conf.temp_pool == NULL) {
        ngx_destroy_pool(pool);
        return NULL;
    }

    /*初始化conf的其他字段，conf是一个局部对象(ngx_conf_t结构体)*/
    conf.ctx = cycle->conf_ctx;
    conf.cycle = cycle;
    conf.pool = pool;
    conf.log = log;
    conf.module_type = NGX_CORE_MODULE;
    conf.cmd_type = NGX_MAIN_CONF;

#if 0
    log->log_level = NGX_LOG_DEBUG_ALL;
#endif

    /*配置参数*/
    if (ngx_conf_param(&conf) != NGX_CONF_OK) {
        environ = senv;
        ngx_destroy_cycle_pools(&conf);
        return NULL;
    }

    /*配置文件解析*/
    if (ngx_conf_parse(&conf, &cycle->conf_file) != NGX_CONF_OK) {
        environ = senv;
        ngx_destroy_cycle_pools(&conf);
        return NULL;
    }

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

    /* 调用core模块的init_conf() */
    for (i = 0; ngx_modules[i]; i++) {
        if (ngx_modules[i]->type != NGX_CORE_MODULE) { /* 仅处理CORE模块*/
            continue;
        }

        module = ngx_modules[i]->ctx; /*即ngx_core_module_ctx结构*/

        if (module->init_conf) {      /*init_conf是core模块的callback*/
            if (module->init_conf(cycle, cycle->conf_ctx[ngx_modules[i]->index])
                == NGX_CONF_ERROR)    /*即调用ngx_core_module_init_conf*/
            {
                environ = senv;
                ngx_destroy_cycle_pools(&conf);
                return NULL;
            }
        }
    }

    if (ngx_process == NGX_PROCESS_SIGNALLER) {
        return cycle;
    }

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

    if (ngx_test_config) {

        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) { /*创建pid文件*/
                goto failed;
            }

            ngx_delete_pidfile(old_cycle);
        }
    }

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

    if (ngx_create_pathes(cycle, ccf->user) != NGX_OK) {
        goto failed;
    }

    if (cycle->new_log.file == NULL) {
        cycle->new_log.file = ngx_conf_open_file(cycle, &error_log); /* 该函数向open_files链表写入数据*/
        if (cycle->new_log.file == NULL) {
            goto failed;
        }
    }

    /* open the new files */

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

    /* 该循环遍历open_files链表*/
    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;
        }

        /* 打开当前文件file[i] */
        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;

    /* create shared memory */

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

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

        if (i >= part->nelts) {
            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;
        }

        if (shm_zone[i].init == NULL) {
            /* unused shared zone */
            continue;
        }

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

        /* 与旧的shared_memory一一比较，将相同的保留，不相同的释放*/
        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].shm.size == oshm_zone[n].shm.size) {
                shm_zone[i].shm.addr = oshm_zone[n].shm.addr;

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

                goto shm_zone_found; /* 相同的共享内存被保留*/
            }

            /* 与&cycle->shared_memory不相同的共享内存被释放*/
            ngx_shm_free(&oshm_zone[n].shm);

            break;
        }

        /* 以下创建共享内存并初始化*/
        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 */

    if (old_cycle->listening.nelts) { /* 旧listening数组有元素时*/
        ls = old_cycle->listening.elts;
        for (i = 0; i < old_cycle->listening.nelts; i++) {
            ls[i].remain = 0;
        }

        /* 新旧listening数组比较*/
        nls = cycle->listening.elts;
        for (n = 0; n < cycle->listening.nelts; n++) {

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

                /* 主要比较新旧listening数组元素的sockaddr字段，并根据比较结果对sockets相关字段赋值*/
                if (ngx_cmp_sockaddr(nls[n].sockaddr, ls[i].sockaddr) == NGX_OK)
                {
                    nls[n].fd = ls[i].fd;
                    nls[n].previous = &ls[i];
                    ls[i].remain = 1;

                    if (ls[n].backlog != nls[i].backlog) {
                        nls[n].listen = 1;
                    }
                    /* 中间省略一些代码*/
                    break;
                }
            }

            if (nls[n].fd == -1) {
                nls[n].open = 1;
            }
        }

    } else { /* 旧listening数组没有元素时*/
        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
        }
    }

    /* 遍历listening数组并打开socket */
    if (ngx_open_listening_sockets(cycle) != NGX_OK) {
        goto failed;
    }

    if (!ngx_test_config) {
        ngx_configure_listening_sockets(cycle);
    }

    /* commit the new cycle configuration */

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

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

    pool->log = cycle->log;

    /* 调用所有模块的init_module，实际上只有ngx_event_core_module模块使用了该callback */
    for (i = 0; ngx_modules[i]; i++) {
        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 */
    /* 中间省略一些代码*/

old_shm_zone_done:

    /* 中间省略一些代码*/

    /* close the unnecessary open files */

    /* 中间省略一些代码*/

    ngx_destroy_pool(conf.temp_pool); /* 销毁临时内存池*/

    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,
                          "can 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; /*在定时器事件中被调用来清理资源*/
        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); /*设定清理定时器,每30000ms清理一次*/
        ngx_cleaner_event.timer_set = 1;
    }

    return cycle;

failed:

    /* 中间省略一些代码*/

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