了解core模块之前还应改学习ngx_start_worker_processes函数,今天我就来详细学一下这个方法,主要内容来自于http://blog.sina.com.cn/s/blog_677be95b0100iivk.html。
nginx的进程启动过程是在ngx_master_process_cycle(src/os/unix/ngx_process_cycle.c)中完成的(单进程是通过ngx_single_process_cycle完成,这里只分析多进程的情况),在ngx_master_process_cycle中,会根据配置文件的worker_processes值创建多个子进程,即一个master进程和多个worker进程。进程之间、进程与外部之间保持通信,进程之间是通过socketpair进行通信的,socketpair是一对全双工的无名socket,可以当作管道使用,和管道不同的是,每条socket既可以读也可以写,而管道只能用于写或者用于读;进程与外部之间是通过信号通信的。
master进程主要进行一些全局性的初始化工作和管理worker的工作;事件处理是在worker中进行的。
进程启动的过程中,有一些重要的全局数据会被设置,最重要的是进程表ngx_processes,master每创建一个worker都会把一个设置好的ngx_process_t结构变量放入ngx_processes中,进程表长度为1024,刚创建的进程存放在ngx_process_slot位置,ngx_last_process是进程表中最后一个存量进程的下一个位置,ngx_process_t是进程在nginx中的抽象:
src/os/unix/ngx_process.h typedef void (*ngx_spawn_proc_pt) (ngx_cycle_t *cycle, void *data); typedef struct { ngx_pid_t pid; //进程id int status; //进程状态 ngx_socket_t channel[2]; //socketpair创建的socket句柄 ngx_spawn_proc_pt proc; //进程执行函数 void *data; //执行函数的参数 char *name; //名称 unsigned respawn:1; //重新创建 unsigned just_spawn:1; //第一次创建的 unsigned detached:1; //分离的 unsigned exiting:1; //正在退出的 unsigned exited:1; //退出过的 } ngx_process_t;
进程间通信是利用socketpair创建的一对socket进行的,通信中传输的是ngx_channel_t结构变量:
ypedef struct { ngx_uint_t command; ngx_pid_t pid; //发送方进程id ngx_int_t slot; //发送方进程表中偏移 ngx_fd_t fd; //发送给对方的句柄 } ngx_channel_t;(src/os/unix/ngx_channel.h) /*command是要发送的命令,有5种: #define NGX_CMD_OPEN_CHANNEL 1 #define NGX_CMD_CLOSE_CHANNEL 2 #define NGX_CMD_QUIT 3 #define NGX_CMD_TERMINATE 4 #define NGX_CMD_REOPEN 5 */
进程的启动过程是比较重要的一个环节,为了把这个过程分析透彻,下面会多采用首先分析ngx_master_process_cycle函数,可以分解为以下各步骤:
1、master设置一些需要处理的信号,这些信号包括
SIGCHLD,SIGALRM,SIGIO,SIGINT,NGX_RECONFIGURE_SIGNAL(SIGHUP),NGX_REOPEN_SIGNAL(SIGUSR1),
NGX_NOACCEPT_SIGNAL(SIGWINCH),NGX_TERMINATE_SIGNAL(SIGTERM),NGX_SHUTDOWN_SIGNAL(SIGQUIT),
NGX_CHANGEBIN_SIGNAL(SIGUSR2);
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));
2、调用ngx_setproctilte设置进程标题,title = "master process" + ngx_argv[0] + ... + ngx_argv[ngx_argc-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);
3、调用ngx_start_worker_processes(cycle, ccf->worker_processes, NGX_PROCESS_RESPAWN)启动worker进程;
ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module); ngx_start_worker_processes(cycle, ccf->worker_processes, NGX_PROCESS_RESPAWN);
4、调用ngx_start_cache_manager_processes(cycle, 0)启动文件cache管理进程,有些模块需要文件cache,比如fastcgi模块,这些模块会把文件cache路径添加到cycle->paths中,文件cache管理进程会定期调用这些模块的文件cache处理钩子处理一下文件cache;
ngx_start_cache_manager_processes(cycle, 0);
注释代码的方式分析。5、master循环处理信号量。
src/os/unix/ngx_process_cycle.c delay = 0; sigio = 0; live = 1; for ( ;; ) { //delay用来设置等待worker推出的时间,master接受了退出信号后, //首先发送退出信号给worker,而worker退出需要一些时间 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; //设置定时器 //以系统真实时间来计算,送出SIGALRM信号 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"); //等待信号量 sigsuspend(&set); ngx_time_update(); ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "wake up, sigio %i", sigio); //收到了SIGCHLD信号,有worker退出(ngx_reap == 1) if (ngx_reap) { ngx_reap = 0; ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "reap children"); //处理所有worker,如果有worker异常退出,则重启 //这个worker,如果所有的worker都退出了,则返回0 live = ngx_reap_children(cycle); } //如果worker都退出了 //并且收到了NGX_CMD_TERMINATE命令或者SIGTERM信号或SIGINT信号(ngx_terminate ==1) //或NGX_CMD_QUIT命令或SIGQUIT信号(ngx_quit == 1),则master退出 if (!live && (ngx_terminate || ngx_quit)) { ngx_master_process_exit(cycle); } //收到了NGX_CMD_TERMINATE命令或者SIGTERM信号或SIGINT信号(ngx_terminate ==1) //通知所有worker退出,并且等待worker退出 if (ngx_terminate) { if (delay == 0) { //设置延时 delay = 50; } if (sigio) { sigio--; continue; } sigio = ccf->worker_processes + 2 /* cache processes */; if (delay > 1000) { //延时已到,给所有worker发送SIGKILL信号,强制杀死worker ngx_signal_worker_processes(cycle, SIGKILL); } else { //给所有worker发送SIGTERM信号,通知worker退出 ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_TERMINATE_SIGNAL)); } continue; } //NGX_CMD_QUIT命令或SIGQUIT信号(ngx_quit == 1) if (ngx_quit) { //给所有的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; //代码已被替换,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); live = 1; ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_SHUTDOWN_SIGNAL)); } //当ngx_noaccepting==1时,会把ngx_restart设为1,重启worker 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)); } //收到SIGUSER2,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)); } }
下一节,继续讲子进程创建,和所做的操作。