Nginx之监控进程和工作进程

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1. 函数调用分析

在开启 master 的情况下，多进程模型的下的入口函数为 ngx_master_process_cycle，如下：

int mian() { ... if (ngx_process == NGX_PROCESS_SINGLE) { /* 单进程模型下的入口函数 */ ngx_single_process_cycle(cycle); } else { /* 多进程模型下的入口函数 */ ngx_master_process_cycle(cycle); } return 0; }

Nginx 核心进程模型框图

1.1 ngx_master_process_cycle：

static ngx_cycle_t ngx_exit_cycle; static ngx_log_t ngx_exit_log; static ngx_open_file_t ngx_exit_log_file;/* * 参数意义： * - cycle是当前进程ngx_cycle_t的结构体指针 * * 执行意义： * 进入master进程的工作循环 */ 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; /* 将下列信号添加到 set 信号集中 */ 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)); /* * sigprocmask(int how, const sigset_t *set, sigset_t *oldset); * 函数既可以修改进程的信号掩码，又可获取现有掩码，或者两者皆可。 * - SIG_BLOCK：将set指向信号集内的指定信号添加到信号掩码中。换言之，将信号掩码 * 设置为其当前值和set的并集。 * - SIG_UNBLOCK：将set指向信号集中的指定信号从信号掩码中移除。即使要接触阻塞的信号当前 * 并未处于阻塞状态，也不会返回错误。 * - SIG_SETMASK：将set指向的信号集赋给信号掩码。 */ /* 临时阻塞上面所示信号，防止其信号处理器将某些关键代码片段的执行中断，然后下面调用 * sigsuspend()解除对信号的阻塞，然后暂停执行，直至有信号到达. */ 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); if (title == NULL) { /* fatal */ exit(2); } 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); } /* 设置监控进程的名字 */ ngx_setproctitle(title); ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module); /* 该函数用于fork()产生子进程，该函数的主体是一个无限for( ;; )循环，持续不断地处理 * 客户端的服务请求，而主进程继续执行ngx_master_process_cycle()函数，也就是作为监控 * 进程执行主体for(;;)循环，这也是一个无限循环，直到进程终止才退出. */ ngx_start_worker_processes(cycle, ccf->worker_processes, NGX_PROCESS_RESPAWN); ngx_start_cache_manager_processes(cycle, 0); ngx_new_binary = 0; delay = 0; sigio = 0; live = 1; for ( ;; ) { if (delay) { if (ngx_sigalrm) { sigio = 0; delay *= 2; ngx_sigalrm = 0; } ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "termination cycle: %M", 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(const sigset_t *mask); * 该函数将以mask所指向的信号集来替换进程的信号掩码，然后挂起进程的执行， * 直到其捕获到信号，并从信号处理器中返回。一旦处理器返回，sigsuspend() * 会将进程信号掩码恢复为调用前的值。 */ /* 该函数使得监控进程的大部分时间都处于挂起等待状态，直到监控进程接收到信号为止。 * 当监控进程接收到信号时，信号处理函数ngx_signal_handler()就会被执行。*/ sigsuspend(&set); ngx_time_update(); ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "wake up, sigio %i", sigio); /* 有子进程退出? */ if (ngx_reap) { ngx_reap = 0; ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "reap children"); live = ngx_reap_children(cycle); } /* 进程要退出或终止? */ if (!live && (ngx_terminate || ngx_quit)) { ngx_master_process_exit(cycle); } /* 进程要终止? * 结束比较粗暴，不过它通过使用SIGKILL信号能保证在一段 * 时间后必定被结束掉. */ 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; } /* 进程要退出? * 该结束比较优雅，会让Nginx监控进程做一些清理工作且等待 * 子进程也完全清理并退出之后才终止. */ if (ngx_quit) { ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_SHUTDOWN_SIGNAL)); ls = cycle->listening.elts; for (n = 0; n < cycle->listening.nelts; n++) { 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; } /* 重新加载配置? */ if (ngx_reconfigure) { ngx_reconfigure = 0; 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"); 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); 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; ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_SHUTDOWN_SIGNAL)); } 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; } 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)); } 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); } if (ngx_noaccept) { ngx_noaccept = 0; ngx_noaccepting = 1; ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_SHUTDOWN_SIGNAL)); } } }

1.2 ngx_start_worker_processes

/* * 参数含义： * - cycle: 是当前进程的ngx_cycle_t结构体指针 * - n: 是启动子进程的个数 * - type: 是启动方式，取值范围有以下5个： * - NGX_PROCESS_RESPAWN * - NGX_PROCESS_NORESPAWN * - NGX_PROCESS_JUST_SPAWN * - NGX_PROCESS_JUST_RESPAWN * - NGX_PROCESS_DETACHED * type的值将会影响ngx_process_t结构体的respawn、detached、just_spawn标志位的值. * * 执行意义： * 启动n个worker子进程，并设置好每个子进程与master父进程之间使用socketpair系统调用 * 建立起来的socket句柄通信机制. */ 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"); ngx_memzero(&ch, sizeof(ngx_channel_t)); ch.command = NGX_CMD_OPEN_CHANNEL; for (i = 0; i < n; i++) { ngx_spawn_process(cycle, ngx_worker_process_cycle, (void *) (intptr_t) i, "worker process", type); ch.pid = ngx_processes[ngx_process_slot].pid; // 子进程的id号 ch.slot = ngx_process_slot; // 子进程的相关信息在全局数组ngx_processes中的下标 // 父进程使用的socket描述符 ch.fd = ngx_processes[ngx_process_slot].channel[0]; /* 父进程fork()生成一个新子进程后，就会立即调用该函数ngx_pass_open_channel() * 把这个子进程的相关信息告知给其前面已生成的子进程. */ ngx_pass_open_channel(cycle, &ch); } }

1.3 ngx_spawn_process

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 { /* 遍历所有存活的子进程，找到一个空闲的下标值 */ 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 */ /* 采用socketpair()函数创造一对未命名的UNIX域套接字来进行Linux下具有 * 亲缘关系的进程之间的双向通信. */ /* * 在fork()之前，先调用了socketpair()创建了一对socket描述符存放在变量 * ngx_processes[s].channel内(其中s标志在ngx_processes数组内第一个可用 * 元素的下标，比如最开始产生第一个工作进程时，可用元素的下标s为0)，而 * 在fork()之后，由于子进程继承了父进程的资源，那么父子进程就都有了这一对 * socket描述符，而Nginx将channel[0]给父进程使用，channel[1]给子进程使用， * 这样分别错开地使用不同socket描述符，即可以实现父子进程之间的双向通信. */ 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: master socket:%d, worker socket:%d", ngx_processes[s].channel[0], ngx_processes[s].channel[1]); 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; } /* 记录子进程使用的socket描述符 */ ngx_channel = ngx_processes[s].channel[1]; } else { ngx_processes[s].channel[0] = -1; ngx_processes[s].channel[1] = -1; } /* 记录该子进程的相关信息在全局数组中的下标 */ ngx_process_slot = s; 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(); // 获取该子进程的进程id号 proc(cycle, data); break; default: break; } ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "start child %s pid:%P", name, pid); ngx_processes[s].pid = pid; // 记录子进程的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; }

1.4 ngx_worker_process_cycle

/* * 参数意义： * - cycle是当前进程的ngx_cycle_t结构体指针，这里还未开始使用data参数，所以data一般为NULL * * 执行意义： * 进入worker进程工作的循环 */ static void ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data) { ngx_int_t worker = (intptr_t) data; ngx_process = NGX_PROCESS_WORKER; ngx_worker = worker; /* 子进程的启动初始化函数 */ ngx_worker_process_init(cycle, worker); /* 设置子进程的进程名 */ ngx_setproctitle("worker process"); for ( ;; ) { if (ngx_exiting) { if (ngx_event_no_timers_left() == NGX_OK) { 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"); /* 最重要的函数：监听并处理事件 */ ngx_process_events_and_timers(cycle); if (ngx_terminate) { ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting"); ngx_worker_process_exit(cycle); } 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_exiting = 1; ngx_set_shutdown_timer(cycle); ngx_close_listening_sockets(cycle); ngx_close_idle_connections(cycle); } } if (ngx_reopen) { ngx_reopen = 0; ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reopening logs"); ngx_reopen_files(cycle, -1); } } }