master 进程的守护过程

2015-01-08 20:45:06   最后更新: 2015-01-20 15:18:21   访问数量:1113




接下来,master 进程就要正式开始发挥他作为一个 daemon 进程的责任了,陷入循环,等待信号发生,做出相应处理

ngx_new_binary = 0; delay = 0; sigio = 0; live = 1; for ( ;; ) { // 设定定时器,worker 定时退出 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; // 设定精确的定时功能,以系统时间计算 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"); // 等待信号 // 信号的默认处理函数是 ngx_init_signals 中设定的 ngx_signal_handler 函数 sigsuspend(&set); // 更新时间 ngx_time_update(); ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "wake up, sigio %i", sigio); // SIGCHLD 信号响应 if (ngx_reap) { ngx_reap = 0; ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "reap children"); // 有 worker 异常退出,重启 worker live = ngx_reap_children(cycle); } // 收到 NGX_CMD_TERMINATE 命令 或 SIGTERM 信号 或 SIGINT 信号 // 或 NGX_CMD_QUIT 命令 或 SIGQUIT 信号 if (!live && (ngx_terminate || ngx_quit)) { // 退出 master ngx_master_process_exit(cycle); } // 收到 NGX_CMD_TERMINATE 命令 或 SIGTERM 信号 或 SIGINT 信号 // 给所有进程发送 NGX_TERMINATE_SIGNAL 信号,然后等待 // 如果超时,再次发送 SIGKILL 信号强制退出 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; } // 收到 NGX_CMD_QUIT 命令 或 SIGQUIT 信号 if (ngx_quit) { // 给所有 worker 发送 SIGQUIT 信号 ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_SHUTDOWN_SIGNAL)); // 关闭所有监听 socket 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; } // 收到 SIGHUP 信号 if (ngx_reconfigure) { ngx_reconfigure = 0; // 重启 worker,不需要重新初始化配置 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"); // 重新初始化配置 cycle = ngx_init_cycle(cycle); if (cycle == NULL) { cycle = (ngx_cycle_t *) ngx_cycle; continue; } // 重启 worker 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)); } // worker 需要重启 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; } // 收到 SIGUSR1 信号,重新打开 log 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)); } // 收到 SIGUSR2 信号,热代码替换 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); } // 收到SIGWINCH信号不在接受请求,worker退出,master不退出 if (ngx_noaccept) { ngx_noaccept = 0; ngx_noaccepting = 1; ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_SHUTDOWN_SIGNAL)); } }

 

这里的代码还是比较容易理解的,添加了大量的注释帮助理解

 

使用了 setitimer 设置了定时功能,虽然 alerm 与 sigsuspend 调用同样可以实现相同功能,但是 setitimer 可以实现更加精准的定时功能

关于 setitimer 的用法可以参看:

基于 setitimer 实现的精确计时 sleep

当子进程退出后,会给守护进程发送 SIGCHLD 信号,在默认的信号处理函数 ngx_signal_handler 中,将 ngx_reap 置为 1

随即会执行下面的方法:

// SIGCHLD 信号响应 if (ngx_reap) { ngx_reap = 0; ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "reap children"); // 有 worker 异常退出,重启 worker live = ngx_reap_children(cycle); }

 

// static ngx_uint_t ngx_reap_children(ngx_cycle_t *cycle) // 重启子进程 {{{ static ngx_uint_t ngx_reap_children(ngx_cycle_t *cycle) { ngx_int_t i, n; ngx_uint_t live; ngx_channel_t ch; ngx_core_conf_t *ccf; ngx_memzero(&ch, sizeof(ngx_channel_t)); ch.command = NGX_CMD_CLOSE_CHANNEL; ch.fd = -1; live = 0; for (i = 0; i < ngx_last_process; i++) { ngx_log_debug7(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "child: %d %P e:%d t:%d d:%d r:%d j:%d", i, ngx_processes[i].pid, ngx_processes[i].exiting, ngx_processes[i].exited, ngx_processes[i].detached, ngx_processes[i].respawn, ngx_processes[i].just_spawn); if (ngx_processes[i].pid == -1) { continue; } // 进程已退出则重启 if (ngx_processes[i].exited) { if (!ngx_processes[i].detached) { // 关闭与已退出进程通信的 fd ngx_close_channel(ngx_processes[i].channel, cycle->log); ngx_processes[i].channel[0] = -1; ngx_processes[i].channel[1] = -1; ch.pid = ngx_processes[i].pid; ch.slot = i; // 通知其他子进程关闭与已退出进程通信的fd for (n = 0; n < ngx_last_process; n++) { if (ngx_processes[n].exited || ngx_processes[n].pid == -1 || ngx_processes[n].channel[0] == -1) { continue; } ngx_log_debug3(NGX_LOG_DEBUG_CORE, cycle->log, 0, "pass close channel s:%i pid:%P to:%P", ch.slot, ch.pid, ngx_processes[n].pid); /* TODO: NGX_AGAIN */ // 向子进程发送数据 ngx_write_channel(ngx_processes[n].channel[0], &ch, sizeof(ngx_channel_t), cycle->log); } } // 重启需要重启的已退出进程 if (ngx_processes[i].respawn && !ngx_processes[i].exiting && !ngx_terminate && !ngx_quit) { if (ngx_spawn_process(cycle, ngx_processes[i].proc, ngx_processes[i].data, ngx_processes[i].name, i) == NGX_INVALID_PID) { ngx_log_error(NGX_LOG_ALERT, cycle->log, 0, "could not respawn %s", ngx_processes[i].name); continue; } ch.command = NGX_CMD_OPEN_CHANNEL; ch.pid = ngx_processes[ngx_process_slot].pid; ch.slot = ngx_process_slot; ch.fd = ngx_processes[ngx_process_slot].channel[0]; // 向其他子进程广播新创建进程信息 ngx_pass_open_channel(cycle, &ch); live = 1; continue; } if (ngx_processes[i].pid == ngx_new_binary) { ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module); if (ngx_rename_file((char *) ccf->oldpid.data, (char *) ccf->pid.data) == NGX_FILE_ERROR) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno, ngx_rename_file_n " %s back to %s failed " "after the new binary process \"%s\" exited", ccf->oldpid.data, ccf->pid.data, ngx_argv[0]); } ngx_new_binary = 0; if (ngx_noaccepting) { ngx_restart = 1; ngx_noaccepting = 0; } } if (i == ngx_last_process - 1) { ngx_last_process--; } else { ngx_processes[i].pid = -1; } } else if (ngx_processes[i].exiting || !ngx_processes[i].detached) { live = 1; } } return live; } // }}}

 

在这一过程中,守护进程首先关闭与已退出子进程通信的域套接字 fd,然后向其他子进程广播相应消息

然后执行 ngx_spawn_process 函数重新启动子进程,并广播新的域套接字 fd

当收到 NGX_CMD_TERMINATE 命令或 SIGTERM 或 SIGINT 或 SIGQUIT 信号后,master 进程随即退出

// 收到 NGX_CMD_TERMINATE 命令 或 SIGTERM 信号 或 SIGINT 信号 // 或 NGX_CMD_QUIT 命令 或 SIGQUIT 信号 if (!live && (ngx_terminate || ngx_quit)) { // 退出 master ngx_master_process_exit(cycle); }

 

// static void ngx_master_process_exit(ngx_cycle_t *cycle) // master 的退出 {{{ static void ngx_master_process_exit(ngx_cycle_t *cycle) { ngx_uint_t i; // 删除 pid 文件 ngx_delete_pidfile(cycle); ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exit"); // 执行模块退出回调函数 for (i = 0; ngx_modules[i]; i++) { if (ngx_modules[i]->exit_master) { ngx_modules[i]->exit_master(cycle); } } // 关闭套接字 ngx_close_listening_sockets(cycle); /* * Copy ngx_cycle->log related data to the special static exit cycle, * log, and log file structures enough to allow a signal handler to log. * The handler may be called when standard ngx_cycle->log allocated from * ngx_cycle->pool is already destroyed. */ ngx_exit_log = *ngx_log_get_file_log(ngx_cycle->log); ngx_exit_log_file.fd = ngx_exit_log.file->fd; ngx_exit_log.file = &ngx_exit_log_file; ngx_exit_log.next = NULL; ngx_exit_log.writer = NULL; ngx_exit_cycle.log = &ngx_exit_log; ngx_exit_cycle.files = ngx_cycle->files; ngx_exit_cycle.files_n = ngx_cycle->files_n; ngx_cycle = &ngx_exit_cycle; // 销毁内存池 ngx_destroy_pool(cycle->pool); // 退出进程 exit(0); } // }}}

 

主要进行了以下操作:

  1. 删除 pid 配置文件
  2. 执行退出模块的回调函数结束所有模块
  3. 关闭套接字
  4. 最后销毁进程池
  5. 退出进程

需要注意的是,在上述操作中 worker 并没有退出

于是接下来对信号进行判断

// 收到 NGX_CMD_TERMINATE 命令 或 SIGTERM 信号 或 SIGINT 信号 // 给所有进程发送 NGX_TERMINATE_SIGNAL 信号,然后等待 // 如果超时,再次发送 SIGKILL 信号强制退出 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; } // 收到 NGX_CMD_QUIT 命令 或 SIGQUIT 信号 if (ngx_quit) { // 给所有 worker 发送 SIGQUIT 信号 ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_SHUTDOWN_SIGNAL)); // 关闭所有监听 socket 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; }

 

只有当收到 NGX_CMD_TERMINATE 命令或 SIGTERM 或 SIGINT 信号时才会结束所有的子进程

之后关闭所有监听套接字,结束工作

产生 SIGHUP 信号的三种原因:

  1. 中断关闭,会话首进程,及所有后台进程会收到该信号(默认操作为退出)
  2. 会话首进程退出后,会话中每个进程会收到该信号(默认操作为退出)
  3. 父进程退出时,如果子进程已经收到过 SIGSTOP 或 SIGTSTP 信号,则子进程将收到 SIGHUP 信号

由于 master 已经脱离终端,所以不会收到 SIGHUP,SIGHUP 信号被重用为重启 worker,重新初始化配置信号

if (ngx_reconfigure) { ngx_reconfigure = 0; // 重启 worker,不需要重新初始化配置 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"); // 重新初始化配置 cycle = ngx_init_cycle(cycle); if (cycle == NULL) { cycle = (ngx_cycle_t *) ngx_cycle; continue; } // 重启 worker 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)); }

 

 






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