nginx核心进程模型

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
QUIT	ngx_quit	优雅地关闭整个服务
TERM或INT	ngx_terminate	强制关闭整个服务
USR1	ngx_reopen	重新打开服务中的所有文件
WINCH	ngx_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
USR2	ngx_change_binary	平滑升级到新版本的Nginx程序
HUP	ng_reconfigure	重读配置文件
CHLD	ngx_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）：

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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
.fd) == -1) {

ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_socket_errno,

ngx_close_socket_n " %V failed",

&ls
.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：

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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：

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//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）：

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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);

}

}

}