Nginx学习之六-nginx核心进程模型
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一、Nginx整体架构
正常执行中的nginx会有多个进程,最基本的有master process(监控进程,也叫做主进程)和woker process(工作进程),还可能有cache相关进程。
一个较为完整的整体框架结构如图所示:
二、核心进程模型
启动nginx的主进程将充当监控进程,而由主进程fork()出来的子进程则充当工作进程。
nginx也可以单进程模型执行,在这种进程模型下,主进程就是工作进程,没有监控进程。
Nginx的核心进程模型框图如下:
master进程
监控进程充当整个进程组与用户的交互接口,同时对进程进行监护。它不需要处理网络事件,不负责业务的执行,只会通过管理worker进程来实现重启服务、平滑升级、更换日志文件、配置文件实时生效等功能。
master进程全貌图(来自阿里集团数据平台博客):
master进程中for(::)无限循环内有一个关键的sigsuspend()函数调用,该函数调用是的master进程的大部分时间都处于挂起状态,直到master进程收到信号为止。
master进程通过检查一下7个标志位来决定ngx_master_process_cycle方法的运行:
sig_atomic_t ngx_reap;
sig_atomic_t ngx_terminate;
sig_atomic_t ngx_quit;
sig_atomic_t ngx_reconfigure;
sig_atomic_t ngx_reopen;
sig_atomic_t ngx_change_binary;
sig_atomic_t ngx_noaccept;
进程中接收到的信号对Nginx框架的意义:
信号对应进程中的全局标志位变量意义QUITngx_quit优雅地关闭整个服务TERM或INTngx_terminate强制关闭整个服务USR1ngx_reopen重新打开服务中的所有文件WINCHngx_noaccept所有子进程不再接受处理新的连接,实际相当于对所有子进程发送QUIT信号USR2ngx_change_binary平滑升级到新版本的Nginx程序HUPng_reconfigure重读配置文件CHLDngx_reap有子进程以外结束,需要监控所有子进程
还有一个标志位会用到:ngx_restart,它仅仅是在master工作流程中作为标志位使用,与信号无关。
核心代码(ngx_process_cycle.c):
- void
- ngx_master_process_cycle(ngx_cycle_t *cycle)
- {
- char *title;
- u_char *p;
- size_t size;
- ngx_int_t i;
- ngx_uint_t n, sigio;
- sigset_t set;
- struct itimerval itv;
- ngx_uint_t live;
- ngx_msec_t delay;
- ngx_listening_t *ls;
- ngx_core_conf_t *ccf;
- //信号处理设置工作
- sigemptyset(&set);
- sigaddset(&set, SIGCHLD);
- sigaddset(&set, SIGALRM);
- sigaddset(&set, SIGIO);
- sigaddset(&set, SIGINT);
- sigaddset(&set, ngx_signal_value(NGX_RECONFIGURE_SIGNAL));
- sigaddset(&set, ngx_signal_value(NGX_REOPEN_SIGNAL));
- sigaddset(&set, ngx_signal_value(NGX_NOACCEPT_SIGNAL));
- sigaddset(&set, ngx_signal_value(NGX_TERMINATE_SIGNAL));
- sigaddset(&set, ngx_signal_value(NGX_SHUTDOWN_SIGNAL));
- sigaddset(&set, ngx_signal_value(NGX_CHANGEBIN_SIGNAL));
- if (sigprocmask(SIG_BLOCK, &set, NULL) == -1) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- "sigprocmask() failed");
- }
- sigemptyset(&set);
- size = sizeof(master_process);
- for (i = 0; i < ngx_argc; i++) {
- size += ngx_strlen(ngx_argv[i]) + 1;
- }
- title = ngx_pnalloc(cycle->pool, size);
- p = ngx_cpymem(title, master_process, sizeof(master_process) - 1);
- for (i = 0; i < ngx_argc; i++) {
- *p++ = ' ';
- p = ngx_cpystrn(p, (u_char *) ngx_argv[i], size);
- }
- ngx_setproctitle(title);
- ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);
- //其中包含了fork产生子进程的内容
- ngx_start_worker_processes(cycle, ccf->worker_processes,
- NGX_PROCESS_RESPAWN);
- //Cache管理进程与cache加载进程的主流程
- ngx_start_cache_manager_processes(cycle, 0);
- ngx_new_binary = 0;
- delay = 0;
- sigio = 0;
- live = 1;
- for ( ;; ) {//循环
- if (delay) {
- if (ngx_sigalrm) {
- sigio = 0;
- delay *= 2;
- ngx_sigalrm = 0;
- }
- ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
- "termination cycle: %d", delay);
- itv.it_interval.tv_sec = 0;
- itv.it_interval.tv_usec = 0;
- itv.it_value.tv_sec = delay / 1000;
- itv.it_value.tv_usec = (delay % 1000 ) * 1000;
- if (setitimer(ITIMER_REAL, &itv, NULL) == -1) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- "setitimer() failed");
- }
- }
- ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "sigsuspend");
- sigsuspend(&set);//master进程休眠,等待接受信号被激活
- ngx_time_update();
- ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
- "wake up, sigio %i", sigio);
- //标志位为1表示需要监控所有子进程
- if (ngx_reap) {
- ngx_reap = 0;
- ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "reap children");
- live = ngx_reap_children(cycle);//管理子进程
- }
- //当live标志位为0(表示所有子进程已经退出)、ngx_terminate标志位为1或者ngx_quit标志位为1表示要退出master进程
- if (!live && (ngx_terminate || ngx_quit)) {
- ngx_master_process_exit(cycle);//退出master进程
- }
- //ngx_terminate标志位为1,强制关闭服务,发送TERM信号到所有子进程
- if (ngx_terminate) {
- if (delay == 0) {
- delay = 50;
- }
- if (sigio) {
- sigio--;
- continue;
- }
- sigio = ccf->worker_processes + 2 /* cache processes */;
- if (delay > 1000) {
- ngx_signal_worker_processes(cycle, SIGKILL);
- } else {
- ngx_signal_worker_processes(cycle,
- ngx_signal_value(NGX_TERMINATE_SIGNAL));
- }
- continue;
- }
- //ngx_quit标志位为1,优雅的关闭服务
- if (ngx_quit) {
- ngx_signal_worker_processes(cycle,
- ngx_signal_value(NGX_SHUTDOWN_SIGNAL));//向所有子进程发送quit信号
- ls = cycle->listening.elts;
- for (n = 0; n < cycle->listening.nelts; n++) {//关闭监听端口
- if (ngx_close_socket(ls[n].fd) == -1) {
- ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_socket_errno,
- ngx_close_socket_n " %V failed",
- &ls[n].addr_text);
- }
- }
- cycle->listening.nelts = 0;
- continue;
- }
- //ngx_reconfigure标志位为1,重新读取配置文件
- //nginx不会让原来的worker子进程再重新读取配置文件,其策略是重新初始化ngx_cycle_t结构体,用它来读取新的额配置文件
- //再创建新的额worker子进程,销毁旧的worker子进程
- if (ngx_reconfigure) {
- ngx_reconfigure = 0;
- //ngx_new_binary标志位为1,平滑升级Nginx
- if (ngx_new_binary) {
- ngx_start_worker_processes(cycle, ccf->worker_processes,
- NGX_PROCESS_RESPAWN);
- ngx_start_cache_manager_processes(cycle, 0);
- ngx_noaccepting = 0;
- continue;
- }
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reconfiguring");
- //初始化ngx_cycle_t结构体
- cycle = ngx_init_cycle(cycle);
- if (cycle == NULL) {
- cycle = (ngx_cycle_t *) ngx_cycle;
- continue;
- }
- ngx_cycle = cycle;
- ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx,
- ngx_core_module);
- //创建新的worker子进程
- ngx_start_worker_processes(cycle, ccf->worker_processes,
- NGX_PROCESS_JUST_RESPAWN);
- ngx_start_cache_manager_processes(cycle, 1);
- /* allow new processes to start */
- ngx_msleep(100);
- live = 1;
- //向所有子进程发送QUIT信号
- ngx_signal_worker_processes(cycle,
- ngx_signal_value(NGX_SHUTDOWN_SIGNAL));
- }
- //ngx_restart标志位在ngx_noaccepting(表示正在停止接受新的连接)为1的时候被设置为1.
- //重启子进程
- if (ngx_restart) {
- ngx_restart = 0;
- ngx_start_worker_processes(cycle, ccf->worker_processes,
- NGX_PROCESS_RESPAWN);
- ngx_start_cache_manager_processes(cycle, 0);
- live = 1;
- }
- //ngx_reopen标志位为1,重新打开所有文件
- if (ngx_reopen) {
- ngx_reopen = 0;
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reopening logs");
- ngx_reopen_files(cycle, ccf->user);
- ngx_signal_worker_processes(cycle,
- ngx_signal_value(NGX_REOPEN_SIGNAL));
- }
- //平滑升级Nginx
- if (ngx_change_binary) {
- ngx_change_binary = 0;
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "changing binary");
- ngx_new_binary = ngx_exec_new_binary(cycle, ngx_argv);
- }
- //ngx_noaccept为1,表示所有子进程不再处理新的连接
- if (ngx_noaccept) {
- ngx_noaccept = 0;
- ngx_noaccepting = 1;
- ngx_signal_worker_processes(cycle,
- ngx_signal_value(NGX_SHUTDOWN_SIGNAL));
- }
- }
- }
ngx_start_worker_processes函数:
- static void
- ngx_start_worker_processes(ngx_cycle_t *cycle, ngx_int_t n, ngx_int_t type)
- {
- ngx_int_t i;
- ngx_channel_t ch;
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "start worker processes");
- ch.command = NGX_CMD_OPEN_CHANNEL;
- //循环创建n个worker子进程
- for (i = 0; i < n; i++) {
- //完成fok新进程的具体工作
- ngx_spawn_process(cycle, ngx_worker_process_cycle,
- (void *) (intptr_t) i, "worker process", type);
- //全局数组ngx_processes就是用来存储每个子进程的相关信息,如:pid,channel,进程做具体事情的接口指针等等,这些信息就是用结构体ngx_process_t来描述的。
- ch.pid = ngx_processes[ngx_process_slot].pid;
- ch.slot = ngx_process_slot;
- ch.fd = ngx_processes[ngx_process_slot].channel[0];
- /*在ngx_spawn_process创建好一个worker进程返回后,master进程就将worker进程的pid、worker进程在ngx_processes数组中的位置及channel[0]传递给前面已经创建好的worker进程,然后继续循环开始创建下一个worker进程。刚提到一个channel[0],这里简单说明一下:channel就是一个能够存储2个整型元素的数组而已,这个channel数组就是用于socketpair函数创建一个进程间通道之用的。master和worker进程以及worker进程之间都可以通过这样的一个通道进行通信,这个通道就是在ngx_spawn_process函数中fork之前调用socketpair创建的。*/
- ngx_pass_open_channel(cycle, &ch);
- }
- }
ngx_spawn_process函数:
- //参数解释:
- //cycle:nginx框架所围绕的核心结构体
- //proc:子进程中将要执行的工作循环
- //data:参数
- //name:子进程名字
- ngx_pid_t
- ngx_spawn_process(ngx_cycle_t *cycle, ngx_spawn_proc_pt proc, void *data,
- char *name, ngx_int_t respawn)
- {
- u_long on;
- ngx_pid_t pid;
- ngx_int_t s;
- if (respawn >= 0) {
- s = respawn;
- } else {
- for (s = 0; s < ngx_last_process; s++) {
- if (ngx_processes[s].pid == -1) {
- break;
- }
- }
- if (s == NGX_MAX_PROCESSES) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
- "no more than %d processes can be spawned",
- NGX_MAX_PROCESSES);
- return NGX_INVALID_PID;
- }
- }
- if (respawn != NGX_PROCESS_DETACHED) {
- /* Solaris 9 still has no AF_LOCAL */
- //创建父子进程间通信的套接字对(基于TCP)
- if (socketpair(AF_UNIX, SOCK_STREAM, 0, ngx_processes[s].channel) == -1)
- {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- "socketpair() failed while spawning \"%s\"", name);
- return NGX_INVALID_PID;
- }
- ngx_log_debug2(NGX_LOG_DEBUG_CORE, cycle->log, 0,
- "channel %d:%d",
- ngx_processes[s].channel[0],
- ngx_processes[s].channel[1]);
- //设置为非阻塞模式
- if (ngx_nonblocking(ngx_processes[s].channel[0]) == -1) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- ngx_nonblocking_n " failed while spawning \"%s\"",
- name);
- ngx_close_channel(ngx_processes[s].channel, cycle->log);
- return NGX_INVALID_PID;
- }
- if (ngx_nonblocking(ngx_processes[s].channel[1]) == -1) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- ngx_nonblocking_n " failed while spawning \"%s\"",
- name);
- ngx_close_channel(ngx_processes[s].channel, cycle->log);
- return NGX_INVALID_PID;
- }
- on = 1;
- if (ioctl(ngx_processes[s].channel[0], FIOASYNC, &on) == -1) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- "ioctl(FIOASYNC) failed while spawning \"%s\"", name);
- ngx_close_channel(ngx_processes[s].channel, cycle->log);
- return NGX_INVALID_PID;
- }
- if (fcntl(ngx_processes[s].channel[0], F_SETOWN, ngx_pid) == -1) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- "fcntl(F_SETOWN) failed while spawning \"%s\"", name);
- ngx_close_channel(ngx_processes[s].channel, cycle->log);
- return NGX_INVALID_PID;
- }
- if (fcntl(ngx_processes[s].channel[0], F_SETFD, FD_CLOEXEC) == -1) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- "fcntl(FD_CLOEXEC) failed while spawning \"%s\"",
- name);
- ngx_close_channel(ngx_processes[s].channel, cycle->log);
- return NGX_INVALID_PID;
- }
- if (fcntl(ngx_processes[s].channel[1], F_SETFD, FD_CLOEXEC) == -1) {
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- "fcntl(FD_CLOEXEC) failed while spawning \"%s\"",
- name);
- ngx_close_channel(ngx_processes[s].channel, cycle->log);
- return NGX_INVALID_PID;
- }
- ngx_channel = ngx_processes[s].channel[1];
- } else {
- ngx_processes[s].channel[0] = -1;
- ngx_processes[s].channel[1] = -1;
- }
- ngx_process_slot = s;
- //创建子进程
- pid = fork();
- switch (pid) {
- case -1:
- ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
- "fork() failed while spawning \"%s\"", name);
- ngx_close_channel(ngx_processes[s].channel, cycle->log);
- return NGX_INVALID_PID;
- case 0:
- ngx_pid = ngx_getpid();
- proc(cycle, data);
- break;
- default:
- break;
- }
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "start %s %P", name, pid);
- ngx_processes[s].pid = pid;
- ngx_processes[s].exited = 0;
- if (respawn >= 0) {
- return pid;
- }
- ngx_processes[s].proc = proc;
- ngx_processes[s].data = data;
- ngx_processes[s].name = name;
- ngx_processes[s].exiting = 0;
- switch (respawn) {
- case NGX_PROCESS_NORESPAWN:
- ngx_processes[s].respawn = 0;
- ngx_processes[s].just_spawn = 0;
- ngx_processes[s].detached = 0;
- break;
- case NGX_PROCESS_JUST_SPAWN:
- ngx_processes[s].respawn = 0;
- ngx_processes[s].just_spawn = 1;
- ngx_processes[s].detached = 0;
- break;
- case NGX_PROCESS_RESPAWN:
- ngx_processes[s].respawn = 1;
- ngx_processes[s].just_spawn = 0;
- ngx_processes[s].detached = 0;
- break;
- case NGX_PROCESS_JUST_RESPAWN:
- ngx_processes[s].respawn = 1;
- ngx_processes[s].just_spawn = 1;
- ngx_processes[s].detached = 0;
- break;
- case NGX_PROCESS_DETACHED:
- ngx_processes[s].respawn = 0;
- ngx_processes[s].just_spawn = 0;
- ngx_processes[s].detached = 1;
- break;
- }
- if (s == ngx_last_process) {
- ngx_last_process++;
- }
- return pid;
- }
worker进程
worker进程的主要任务是完成具体的任务逻辑。其主要关注点是与客户端或后端真实服务器(此时nginx作为中间代理)之间的数据可读/可写等I/O交互事件,所以工作进程的阻塞点是在像select()、epoll_wait()等这样的I/O多路复用函数调用处,以等待发生数据可读/写事件。当然也可能被新收到的进程信号中断。
master进程如何通通知worker进程去做某些工作呢?采用的是信号。
当收到信号时,信号处理函数ngx_signal_handler()就会执行。
对于worker进程的工作方法ngx_worker_process_cycle来说,它主要关注4个全局标志位:
sig_atomic_t ngx_terminate;//强制关闭进程
sig_atomic_t ngx_quit;//优雅地关闭进程(有唯一一段代码会设置它,就是接受到QUIT信号。ngx_quit只有在首次设置为1,时,才会将ngx_exiting置为1)
ngx_uint_t ngx_exiting;//退出进程标志位
sig_atomic_t ngx_reopen;//重新打开所有文件
其中ngx_terminate、ngx_quit 、ngx_reopen都将由ngx_signal_handler根据接受到的信号来设置。ngx_exiting标志位仅由ngx_worker_cycle方法在退出时作为标志位使用。
核心代码(ngx_process_cycle.c):
- static void
- ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data)
- {
- ngx_int_t worker = (intptr_t) data;
- ngx_uint_t i;
- ngx_connection_t *c;
- ngx_process = NGX_PROCESS_WORKER;
- //子进程初始化
- ngx_worker_process_init(cycle, worker);
- ngx_setproctitle("worker process");
- //这里有一段多线程条件下的代码。由于nginx并不支持多线程,因此删除掉了
- //循环
- for ( ;; ) {
- //ngx_exiting标志位为1,进程退出
- if (ngx_exiting) {
- c = cycle->connections;
- for (i = 0; i < cycle->connection_n; i++) {
- if (c[i].fd != -1 && c[i].idle) {
- c[i].close = 1;
- c[i].read->handler(c[i].read);
- }
- }
- if (ngx_event_timer_rbtree.root == ngx_event_timer_rbtree.sentinel)
- {
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");
- ngx_worker_process_exit(cycle);
- }
- }
- ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "worker cycle");
- ngx_process_events_and_timers(cycle);//处理事件的方法
- //强制结束进程
- if (ngx_terminate) {
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");
- ngx_worker_process_exit(cycle);
- }
- //优雅地退出进程
- if (ngx_quit) {
- ngx_quit = 0;
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0,
- "gracefully shutting down");
- ngx_setproctitle("worker process is shutting down");
- if (!ngx_exiting) {
- ngx_close_listening_sockets(cycle);
- //设置ngx_exiting 标志位
- ngx_exiting = 1;
- }
- }
- //重新打开所有文件
- if (ngx_reopen) {
- ngx_reopen = 0;
- ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reopening logs");
- ngx_reopen_files(cycle, -1);
- }
- }
- }
转自:http://blog.csdn.net/chosen0ne/article/details/7736625
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