在nginx在启动过程，ngx_init_cycle这个函数最初始工作。变量的初始化存储在ngx_cycle_t这个结构体中，为了深入了解这个函数都做了那些初始化工作，就化时间研究了一下。并写下来以便以后參考。
1ngx_cycle_t
关于这个结构体前面已经简介过，这里不再赘述。
2ngx_init_cycle
ngx_cycle_t * ngx_init_cycle(ngx_cycle_t *old_cycle);
先看一下这个old_cycle參数从哪里来的：
ngx_cycle_t *cycle, init_cycle;
init_cycle.pool = ngx_create_pool(1024, log);//创建内存池
if (init_cycle.pool == NULL) {
return 1;
} ......
...... if (ngx_process_options(&init_cycle) != NGX_OK) {
return 1;
} cycle = ngx_init_cycle(&init_cycle);
可见在调用ngx_int_cycle之前，这个old_cycle已经保存了一些參数。这些參数包含：prefix,conf_prefix,conf_file, conf_para。主要在ngx_process_options这个函数中初始化old_cycle。这个函数比較简单，看一下代码：
static ngx_int_t
ngx_process_options(ngx_cycle_t *cycle)
{
u_char *p;
size_t len; if (ngx_prefix) {
len = ngx_strlen(ngx_prefix);
p = ngx_prefix; if (!ngx_path_separator(*p)) {
p = ngx_pnalloc(cycle->pool, len + 1);
if (p == NULL) {
return NGX_ERROR;
} ngx_memcpy(p, ngx_prefix, len);
p[len++] = '/';
} cycle->conf_prefix.len = len;
cycle->conf_prefix.data = p;
cycle->prefix.len = len;
cycle->prefix.data = p; } else { #ifndef NGX_PREFIX p = ngx_pnalloc(cycle->pool, NGX_MAX_PATH);
if (p == NULL) {
return NGX_ERROR;
} if (ngx_getcwd(p, NGX_MAX_PATH) == 0) {//得到当前的工作文件夹
ngx_log_stderr(ngx_errno, "[emerg]: " ngx_getcwd_n " failed");
return NGX_ERROR;
} len = ngx_strlen(p); p[len++] = '/'; cycle->conf_prefix.len = len;
cycle->conf_prefix.data = p;//配置文件夹
cycle->prefix.len = len;
cycle->prefix.data = p;//安装文件夹 #else #ifdef NGX_CONF_PREFIX
ngx_str_set(&cycle->conf_prefix, NGX_CONF_PREFIX);//配置文件相对于安装的文件夹
#else
ngx_str_set(&cycle->conf_prefix, NGX_PREFIX);
#endif
ngx_str_set(&cycle->prefix, NGX_PREFIX); #endif
} if (ngx_conf_file) {
cycle->conf_file.len = ngx_strlen(ngx_conf_file);
cycle->conf_file.data = ngx_conf_file; } else {
ngx_str_set(&cycle->conf_file, NGX_CONF_PATH);
} if (ngx_conf_full_name(cycle, &cycle->conf_file, 0) != NGX_OK) {
return NGX_ERROR;
} for (p = cycle->conf_file.data + cycle->conf_file.len - 1;
p > cycle->conf_file.data;
p--)
{
if (ngx_path_separator(*p)) {
cycle->conf_prefix.len = p - ngx_cycle->conf_file.data + 1;
cycle->conf_prefix.data = ngx_cycle->conf_file.data;
break;
}
} if (ngx_conf_params) {
cycle->conf_param.len = ngx_strlen(ngx_conf_params);
cycle->conf_param.data = ngx_conf_params;
} if (ngx_test_config) {
cycle->log->log_level = NGX_LOG_INFO;
} return NGX_OK;
}
如今開始进入关键:ngx_init_cycle,依照运行步骤来进行
2.1调用ngx_timezone_update()、ngx_timeofday() 、ngx_time_update(0,0)做时间校准
ngx_timezone_update();
/* force localtime update with a new timezone */
tp = ngx_timeofday();
tp->sec = 0;
ngx_time_update();
2.2创建一个新的ngx_cycle_t变量cycle，而且初始化其大部分的成员字段。有一些是从传入的old_cycle直接拷贝过来的，这些字段包含：log,conf_prefix,prefix,conf_file,conf_param，初始化pathes数组、初始化open_files链表、初始化shared_memory链表、初始化listening数组等等。
cycle = ngx_pcalloc(pool, sizeof(ngx_cycle_t));//返回的新的cycle。以后这个cycle就是全局的
if (cycle == NULL) {
ngx_destroy_pool(pool);
return NULL;
} cycle->pool = pool;//全局cycle的内存池
cycle->log = log;//全局log
cycle->new_log.log_level = NGX_LOG_ERR;
cycle->old_cycle = old_cycle;//old_cycle cycle->conf_prefix.len = old_cycle->conf_prefix.len;//在nginx.c的ngx_process_options中获得
cycle->conf_prefix.data = ngx_pstrdup(pool, &old_cycle->conf_prefix);
if (cycle->conf_prefix.data == NULL) {//配置文件路径为NULL
ngx_destroy_pool(pool);
return NULL;
} cycle->prefix.len = old_cycle->prefix.len;//在nginx.c的ngx_process_options中获得
cycle->prefix.data = ngx_pstrdup(pool, &old_cycle->prefix);
if (cycle->prefix.data == NULL) {//安装文件夹为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) {//配置文件相对于安装文件夹的路径为NULL
ngx_destroy_pool(pool);
return NULL;
}
ngx_cpystrn(cycle->conf_file.data, old_cycle->conf_file.data,
old_cycle->conf_file.len + 1);//拷贝配置文件相对于安装文件夹的路径 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) {//配置參数
ngx_destroy_pool(pool);
return NULL;
} n = old_cycle->pathes.nelts ? old_cycle->pathes.nelts : 10;//Nginx的操作文件夹个数 cycle->pathes.elts = ngx_pcalloc(pool, n * sizeof(ngx_path_t *));//数组申请内存
if (cycle->pathes.elts == NULL) {
ngx_destroy_pool(pool);
return NULL;
} cycle->pathes.nelts = 0;
cycle->pathes.size = sizeof(ngx_path_t *);
cycle->pathes.nalloc = n;
cycle->pathes.pool = pool; /*计算open_files的个数*/
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;
}
//初始化open_files链表。
if (ngx_list_init(&cycle->open_files, pool, n, sizeof(ngx_open_file_t))
!= NGX_OK)
{
ngx_destroy_pool(pool);
return NULL;
} /*依据old_cycle的shared_memory单链表来初始化cycle的单链表*/
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;
}
//ngx_list_init主要是初始链表的elts,并为其申请内存
if (ngx_list_init(&cycle->shared_memory, pool, n, sizeof(ngx_shm_zone_t))
!= NGX_OK)
{
ngx_destroy_pool(pool);
return NULL;
} n = old_cycle->listening.nelts ? old_cycle->listening.nelts : 10;//默认listening的大小为10
/*初始化listening数组*/
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; //初始化双向链表。主要存储着可反复用的连接ngx_connection_t
ngx_queue_init(&cycle->reusable_connections_queue); //初始化conf_ctx,ngx_max_module是nginx中总的模块数
cycle->conf_ctx = ngx_pcalloc(pool, ngx_max_module * sizeof(void *));
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 */
//初始化hostname
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;
}
//主机名所有是小写
ngx_strlow(cycle->hostname.data, (u_char *) hostname, cycle->hostname.len);
2.3调用全部NGX_CORE_MODULE的create_conf构建配置结构体。并保存在conf_ctx数组里面
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;
}
//返回的配置结构指针放到conf_ctx数组中，偏移位置为ngx_module_t.index
cycle->conf_ctx[ngx_modules[i]->index] = rv;
}
}
senv = environ;
/*初始化暂时变量ngx_conf_t conf*/
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;
}
conf.temp_pool = ngx_create_pool(NGX_CYCLE_POOL_SIZE, log);
if (conf.temp_pool == NULL) {
ngx_destroy_pool(pool);
return NULL;
}
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;//
2.4从命令行和配置文件里把全部配置更新到cycle的conf_ctx中:首先调用ngx_conf_param把命令行中的指令（-g directives）转换为配置结构并把指针增加到cycle.conf_ctx中;接着调用ngx_conf_parse(..,filename)把配置文件里的指令转换为配置结构并把指针增加到cycle.conf_ctx中。
if (ngx_conf_param(&conf) != NGX_CONF_OK) {//src/core/ngx_conf_file.c
environ = senv;
ngx_destroy_cycle_pools(&conf);
return NULL;
}
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);
}
2.5调用全部核心模块的init函数初始化全部核心模块的配置结构体
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) {//调用模块的init_conf初始化全部核心模块的配置结构体
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) {
return cycle;
}
2.6获得核心模块ngx_core_dodule的配置结构，然后调用ngx_create_pidfile创建pid文件
ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);
if (ngx_test_config) {
//创建进程pid文件
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
*/
//得到old_ccf配置结构体
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);
}
}
2.7调用ngx_test_lockfile(filename,log)，ngx_create_pathes(cycle,user)，接着打开errorlog文件并赋值给cycle->new_log.file
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);
if (cycle->new_log.file == NULL) {
goto failed;
}
}
2.8打开新文件，在第2步的时候提到cycle->open_files这个链表是空的。仅仅是给它预先分配了空间，并没有数据。这里之所以可能会有文件被打开，预计是前面读配置文件的时候，调用各个钩子的过程中，填充了这个链表，把ngx_open_file_t结构变量填充进来（结构体中包括要打开文件的路径信息），接着改动一下cycle的成员：cycle->log = &cycle->new_log;pool->log = &cycle->new_log;
2.9创建共享内存，和open_files类似，在第2步的时候cycle－>share_memory也初始化为一个空的链表。也是预分配了空间，假设此时链表中已经被填充了ngx_shm_zone_t结构变量（当中包括须要共享内存的尺寸和标识等信息）。那么这里就会分配共享内存，而且调用合适的初始化钩子初始化分配的共享内存，每块共享内存都会有name标识。这里也会做一些排重，已经分配的就不会再去分配。从对open_files和share_memory的处理过程能够看出，nginx在资源管理上是集中分配的，请求资源的时候分配说明性的结构变量，然后在恰当的时机才去真正分配资源。
2.10处理listening sockets，cycle->listening是ngx_listening_t结构的数组。把cycle->listening于old_cycle->listening进行比較。设置cycle->listening的一些状态信息。接着调用ngx_open_listening_sockets(cycle)启动cycle->listening中的全部监听socket，循环调用socket,bind,listen完毕服务端监听socket的启动。接着调用ngx_configure_listening_sockets(cycle)配置监听socket。会依据ngx_listening_t中的状态信息设置socket的读写缓存和TCP_DEFER_ACCEPT。
if (old_cycle->listening.nelts) {//假设old_cycle中已经有套接字句柄
ls = old_cycle->listening.elts;
for (i = 0; i < old_cycle->listening.nelts; i++) {
ls[i].remain = 0;//正常关闭应经打开的监听port
}
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) {//标识位为1表示跳过设置ngx_lisenting_t中的套接字。
continue; //为0表示正常初始化套接字
}
/********************************************************************************************************/
//有个问题:nls[n].sockaddr是什么时候初始化的
/********************************************************************************************************/
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;//不关闭已经打开的套接字
if (ls[n].backlog != nls[i].backlog) {
nls[n].listen = 1;//套接字已监听
}
#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[n].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
break;
}
}
if (nls[n].fd == -1) {
nls[n].open = 1;
}
}
} 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
}
}
/*
这里有个问题:cycle->listening中的每一个成员ngx_listening_t的sockaddr在哪里初始化的
由于ngx_open_listening_sockets函数会用这个变量来创建新的套接字
*/
//启动cycle->listening中的全部监听socket，循环调用socket,bind,listen完毕服务端监听socket的启动
if (ngx_open_listening_sockets(cycle) != NGX_OK) {
goto failed;
}
if (!ngx_test_config) {//接着调用ngx_configure_listening_sockets(cycle)配置监听socket
ngx_configure_listening_sockets(cycle);
这个阶段还有个问题没解决（见凝视）？？？？？？？？？？？？？？？。
2.11调用全部模块的init_module方法，仅仅有ngx_event_core_module定义了init_module。
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);
}
}
}
2.12关闭或者删除一些残留在old_cycle中的资源。首先释放不用的共享内存，接着关闭不使用的监听socket，再关闭不使用的打开文件，最后把old_cycle放入ngx_old_cycles中，这是一个ngx_cycle_t *的数组，最后设定一个定时器。定期回调ngx_cleaner_event清理ngx_old_cycles。这里设置了30000ms清理一次。
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;
//初始化ngx_cleaner_event事件
ngx_cleaner_event.handler = ngx_clean_old_cycles;//注意这个handler
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;
//将ngx_cleaner_event事件加入到定时器，定时清理old_cycle
if (!ngx_cleaner_event.timer_set) {
ngx_add_timer(&ngx_cleaner_event, 30000);//30000毫秒
ngx_cleaner_event.timer_set = 1;
}
http://blog.csdn.net/xiaoliangsky/article/details/39996563
以下附上一张图：
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图片来源http://blog.csdn.net/lengzijian/article/details/7575813#plain
參考资料：
http://blog.csdn.net/lengzijian/article/details/7575813#plain
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