作者:阿波
链接:/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。
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_tfree_connection_n; //空闲连接个数ngx_queue_treusable_connections_queue; //再利用连接队列ngx_array_tlistening;//监听数组ngx_array_tpathes; //路径数组ngx_list_topen_files; //打开文件链表ngx_list_tshared_memory; //共享内存链表ngx_uint_tconnection_n; //连接个数ngx_uint_tfiles_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。
main()调用ngx_init_cycle()后,全局变量ngx_cycle的内容如下。可对比上图查看。
(gdb) p *ngx_cycle$3 = {conf_ctx = 0x6b1060, pool = 0x6b0280, log = 0x6b02e8, new_log = {log_level = 4, file = 0x6b0558, connection = 0, handler = 0, data = 0x0, action = 0x0}, files = 0x0, free_connections = 0x0, free_connection_n = 0, reusable_connections_queue = {prev = 0x6b0330, next = 0x6b0330}, listening = {elts = 0x6b0930, nelts = 1, size = 184, nalloc = 10, pool = 0x6b0280}, pathes = {elts = 0x6b04d8, nelts = 5, size = 8, nalloc = 10, pool = 0x6b0280}, open_files = {last = 0x6b0398, part = {elts = 0x6b0528, nelts = 2, next = 0x0---Type <return> to continue, or q <return> to quit---}, size = 48, nalloc = 20, pool = 0x6b0280}, shared_memory = {last = 0x6b03d0, part = {elts = 0x6b08e8, nelts = 0, next = 0x0}, size = 72, nalloc = 1, pool = 0x6b0280}, connection_n = 1024, files_n = 0, connections = 0x0, read_events = 0x0, write_events = 0x0, old_cycle = 0x0, conf_file = {len = 32, data = 0x6b04b7 "/usr/local/nginx/conf/nginx.conf"}, conf_param = {len = 0, data = 0x6b04d8 "\240{l"}, conf_prefix = {len = 22, data = 0x6b0490 "/usr/local/nginx/conf//usr/local/nginx//usr/local/nginx/conf/nginx.conf"}, prefix = {len = 17, data = 0x6b04a6 "/usr/local/nginx//usr/local/nginx/conf/nginx.conf"}, lock_file = {---Type <return> to continue, or q <return> to quit---len = 33, data = 0x6ccee0 "/usr/local/nginx/logs/nginx.lock.accept"}, hostname = {len = 4, data = 0x6b11c0 "yu30"}}
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
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callbackchar*(*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
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
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 },#endifngx_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
省略,可自行研究。
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