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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:
201601040001
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:
201601040002
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):
201601040003
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):
[cpp]
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));
}
}
}

[/cpp]
ngx_start_worker_processes函数:
[cpp]
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);
}
}

[/cpp]
ngx_spawn_process函数:
[cpp]
//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;
}

[/cpp]
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):
[cpp]
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);
}
}
}

[/cpp]

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