Ubuntu 下 nginx-1.24.0 源码分析 - ngx_init_cycle 函数

声明在 src/core/ngx_cycle.h

ngx_cycle_t *ngx_init_cycle(ngx_cycle_t *old_cycle);

实现在 src/core/ngx_cycle.c

ngx_cycle_t *
ngx_init_cycle(ngx_cycle_t *old_cycle)
{void                *rv;char               **senv;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();/* 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);if (pool == NULL) {return NULL;}pool->log = log;cycle = ngx_pcalloc(pool, sizeof(ngx_cycle_t));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;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->error_log.len = old_cycle->error_log.len;cycle->error_log.data = ngx_pnalloc(pool, old_cycle->error_log.len + 1);if (cycle->error_log.data == NULL) {ngx_destroy_pool(pool);return NULL;}ngx_cpystrn(cycle->error_log.data, old_cycle->error_log.data,old_cycle->error_log.len + 1);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;}n = old_cycle->paths.nelts ? old_cycle->paths.nelts : 10;if (ngx_array_init(&cycle->paths, pool, n, sizeof(ngx_path_t *))!= NGX_OK){ngx_destroy_pool(pool);return NULL;}ngx_memzero(cycle->paths.elts, n * sizeof(ngx_path_t *));if (ngx_array_init(&cycle->config_dump, pool, 1, sizeof(ngx_conf_dump_t))!= NGX_OK){ngx_destroy_pool(pool);return NULL;}ngx_rbtree_init(&cycle->config_dump_rbtree, &cycle->config_dump_sentinel,ngx_str_rbtree_insert_value);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;}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;}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;if (ngx_array_init(&cycle->listening, pool, n, sizeof(ngx_listening_t))!= NGX_OK){ngx_destroy_pool(pool);return NULL;}ngx_memzero(cycle->listening.elts, n * sizeof(ngx_listening_t));ngx_queue_init(&cycle->reusable_connections_queue);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 */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);if (ngx_cycle_modules(cycle) != NGX_OK) {ngx_destroy_pool(pool);return NULL;}for (i = 0; cycle->modules[i]; i++) {if (cycle->modules[i]->type != NGX_CORE_MODULE) {continue;}module = cycle->modules[i]->ctx;if (module->create_conf) {rv = module->create_conf(cycle);if (rv == NULL) {ngx_destroy_pool(pool);return NULL;}cycle->conf_ctx[cycle->modules[i]->index] = rv;}}senv = environ;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;#if 0log->log_level = NGX_LOG_DEBUG_ALL;
#endifif (ngx_conf_param(&conf) != NGX_CONF_OK) {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);}for (i = 0; cycle->modules[i]; i++) {if (cycle->modules[i]->type != NGX_CORE_MODULE) {continue;}module = cycle->modules[i]->ctx;if (module->init_conf) {if (module->init_conf(cycle,cycle->conf_ctx[cycle->modules[i]->index])== NGX_CONF_ERROR){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) {goto failed;}ngx_delete_pidfile(old_cycle);}}if (ngx_test_lockfile(cycle->lock_file.data, log) != NGX_OK) {goto failed;}if (ngx_create_paths(cycle, ccf->user) != NGX_OK) {goto failed;}if (ngx_log_open_default(cycle) != NGX_OK) {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;/* 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;}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;
#endifif (shm_zone[i].init(&shm_zone[i], oshm_zone[n].data)!= NGX_OK){goto failed;}goto shm_zone_found;}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 */if (old_cycle->listening.nelts) {ls = old_cycle->listening.elts;for (i = 0; i < old_cycle->listening.nelts; i++) {ls[i].remain = 0;}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;}if (ls[i].remain) {continue;}if (ls[i].type != nls[n].type) {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].inherited = ls[i].inherited;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;}
#endifbreak;}}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) {goto failed;}if (!ngx_test_config) {ngx_configure_listening_sockets(cycle);}/* commit the new cycle configuration */if (!ngx_use_stderr) {(void) ngx_log_redirect_stderr(cycle);}pool->log = cycle->log;if (ngx_init_modules(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) {continue;}if (ngx_strncmp(oshm_zone[i].shm.name.data,shm_zone[n].shm.name.data,oshm_zone[i].shm.name.len)!= 0){continue;}if (oshm_zone[i].tag == shm_zone[n].tag&& oshm_zone[i].shm.size == shm_zone[n].shm.size&& !oshm_zone[i].noreuse){goto live_shm_zone;}break;}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);if (ngx_process == NGX_PROCESS_MASTER || ngx_is_init_cycle(old_cycle)) {ngx_destroy_pool(old_cycle->pool);cycle->old_cycle = NULL;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;if (ngx_array_init(&ngx_old_cycles, ngx_temp_pool, n,sizeof(ngx_cycle_t *))!= NGX_OK){exit(1);}ngx_memzero(ngx_old_cycles.elts, n * sizeof(ngx_cycle_t *));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_cleaner_event.timer_set = 1;}return cycle;failed:if (!ngx_is_init_cycle(old_cycle)) {old_ccf = (ngx_core_conf_t *) ngx_get_conf(old_cycle->conf_ctx,ngx_core_module);if (old_ccf->environment) {environ = old_ccf->environment;}}/* rollback the new cycle configuration */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].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);}}/* free the newly created 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.addr == NULL) {continue;}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){goto old_shm_zone_found;}break;}ngx_shm_free(&shm_zone[i].shm);old_shm_zone_found:continue;}if (ngx_test_config) {ngx_destroy_cycle_pools(&conf);return NULL;}ls = cycle->listening.elts;for (i = 0; i < cycle->listening.nelts; i++) {if (ls[i].fd == (ngx_socket_t) -1 || !ls[i].open) {continue;}if (ngx_close_socket(ls[i].fd) == -1) {ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,ngx_close_socket_n " %V failed",&ls[i].addr_text);}}ngx_destroy_cycle_pools(&conf);return NULL;
}

---

ngx_init_cycle 是 Nginx 核心模块中的一个关键函数，
负责初始化 Nginx 的运行环境。
它基于传入的旧周期（old_cycle）创建一个新的周期（cycle），
并完成一系列复杂的初始化工作，
包括配置文件解析、共享内存分配、监听套接字设置等。

---

函数签名

ngx_cycle_t *ngx_init_cycle(ngx_cycle_t *old_cycle)

作用

• 接收一个指向旧周期（old_cycle）的指针。

• 返回一个新创建的周期（cycle）指针，表示初始化后的运行时环境。

• 如果初始化失败，返回 NULL。

• 新周期会继承旧周期的部分信息（如路径、配置文件路径等），同时根据新的配置进行更新。

---

   ngx_timezone_update();/* force localtime update with a new timezone */tp = ngx_timeofday();tp->sec = 0;ngx_time_update();

ngx_timezone_update()更新进程的时区缓存
ngx_timeofday() 获取当前时间缓存对象 tp。
tp->sec = 0 强制标记时间缓存为“已失效”。
ngx_time_update() 重新计算当前时间并更新缓存。

tp->sec = 0; 的作用是强制标记当前时间缓存为无效，从而确保在调用 ngx_time_update() 时会重新调用系统函数来获取最新的时间戳。
如果没有强制刷新时间缓存（即 tp->sec != 0），ngx_time_update() 可能不会真正调用系统函数，而是直接使用缓存值

---

   log = old_cycle->log;

 从旧的 Nginx 运行周期（old_cycle）中继承日志对象（log），并将其赋值给当前的局部变量 log

新周期初始化时，尚未解析新的配置文件，无法确定新的日志路径或级别。
若直接使用新配置的日志可能失败（如路径无效），导致错误信息无法记录。
复用旧日志配置，新周期完全初始化前,确保初始化阶段的日志记录可靠。

---

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

创建一个内存池（memory pool），用于管理 Nginx 运行周期（cycle）中的内存分配

NGX_CYCLE_POOL_SIZE
这是一个宏定义，表示内存池的初始大小。

log 是一个指向日志对象的指针，用于记录内存池操作中的错误或调试信息。

---

   cycle = ngx_pcalloc(pool, sizeof(ngx_cycle_t));if (cycle == NULL) {ngx_destroy_pool(pool);return NULL;}

从内存池分配一个新的 ngx_cycle_t 结构（核心运行时上下文）

---

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

 cycle->pool = pool;
关联新内存池到新周期。
所有后续内存分配均通过此池进行，确保统一管理。

 cycle->log = log;
设置新周期的日志对象。
确保新周期的所有操作使用继承的日志配置，直到新配置生效。

 cycle->old_cycle = old_cycle;
保存旧周期指针到新周期。
在平滑重启或重新配置时，新周期需要访问旧周期的资源（如监听套接字、共享内存）。
资源复用：通过 old_cycle 复用旧资源（如 SO_REUSEPORT 套接字），实现零停机更新。
渐进式释放：旧周期资源在新周期稳定后逐步清理，避免服务中断。

---

   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;}

复制配置文件前缀（conf_prefix）

从旧周期复制 conf_prefix，用于定位配置文件
平滑重启：保持配置路径一致，避免重新解析路径导致的延迟。

ngx_pstrdup

---

    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;}

从旧周期复制 prefix（如 /usr/local/nginx/），用于解析相对路径

---

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

继承错误日志路径：复制旧周期的错误日志文件路径
日志连续性：初始化阶段使用旧日志配置，避免日志记录中断
字符串安全性：通过 ngx_cpystrn 确保字符串以 \0 结尾

---

   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);

继承配置文件路径：复制旧周期的配置文件路径

---

    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) {ngx_destroy_pool(pool);return NULL;}

继承命令行配置参数：复制通过 -g 参数传递的配置

---

    n = old_cycle->paths.nelts ? old_cycle->paths.nelts : 10;

确定 paths 数组的初始容量 n。

若旧周期（old_cycle）存在路径配置，则继承其大小；否则预分配 10 个元素。

paths 用于存储 Nginx 运行时路径（如临时文件目录）。旧周期可能已包含路径信息（如 client_body_temp_path），新周期需复用或初始化。

资源复用：继承旧周期的容量，避免重复计算路径数量。
预分配优化：默认值 10 是经验值，平衡内存占用与扩容开销。

---

    ngx_memzero(cycle->paths.elts, n * sizeof(ngx_path_t *));

将 paths 数组的前 n 个元素清零（初始化为 NULL）

ngx_array_init 分配的内存未初始化，可能包含脏数据。路径指针需显式置空，避免后续误判

确保数组初始状态明确（所有元素为 NULL）

---

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

初始化数组 config_dump，用于存储配置转储条目

使用内存池 pool 分配内存，初始容量为 1，每个元素大小为 ngx_conf_dump_t

若初始化失败（返回 NGX_ERROR），销毁内存池并终止初始化。

Ubuntu 下 nginx-1.24.0 源码分析 - ngx_conf_dump_t-CSDN博客

---

    ngx_rbtree_init(&cycle->config_dump_rbtree, &cycle->config_dump_sentinel,ngx_str_rbtree_insert_value);

初始化红黑树 config_dump_rbtree，用于快速查找和去重

根节点为 config_dump_rbtree，哨兵节点为 config_dump_sentinel。
使用 ngx_str_rbtree_insert_value 作为插入回调，按字符串键排序。
 

Ubuntu 下 nginx-1.24.0 源码分析 - ngx_rbtree_init-CSDN博客

Ubuntu 下 nginx-1.24.0 源码分析 - ngx_str_rbtree_insert_value-CSDN博客

ngx_array_t config_dump	存储配置条目	动态数组，存储 ngx_conf_dump_t 结构体
ngx_rbtree_t config_dump_rbtree	索引配置条目，加速查找与去重	红黑树键值为配置名称（ngx_str_t），节点数据指向 config_dump 数组素

                
        

以 ngx_conf_dump_t.name（配置块名称）作为红黑树的键，通过 ngx_str_rbtree_insert_value 回调按字符串排序。

功能分离：
数组存储数据，红黑树管理索引，职责清晰。

---