nginx源码分析--master和worker进程模型

2016/08/05 11:18
阅读数 311

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):

 

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);
    }
  }
}
展开阅读全文
加载中
点击引领话题📣 发布并加入讨论🔥
打赏
0 评论
0 收藏
0
分享
返回顶部
顶部