Nginx source Code Analysis-Main process-multi-process implementation

By default, Nginx is a multi-process run mode. Nginx and memcached are not the same, is a multi-process mode. Maximum benefits of using multi-process mode:

1. Resource independence for each process

2. No need to add a variety of cumbersome locks

Flowchart of Nginx Multi-process implementation

Nginx Multi-process specific implementation 1. Ngx_master_process_cycle into multi-process mode

The Ngx_master_process_cycle method mainly does two things:

1. The main process for signal monitoring and processing

2. Turn on sub-processes

/** * Nginx Multi-process operation mode */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;/* Sets the signal */sigemptyset (&set) that can be received, 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;} /* Save process title */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_CP YSTRN (P, (U_char *) ngx_argv[i], size);} Ngx_setproctitle (title);/* Get core configuration ngx_core_conf_t */CCF = (ngx_core_conf_t *) ngx_get_conf (Cycle->conf_ctx, Ngx_ Core_module);/* Start worker process-the core function of multi-process start */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;/* main thread loop */for (;;) { /* delay is used to set the time to wait for the worker to launch, after master accepts the exit signal, * First sends the exit signal to the worker, and the worker exits takes some time */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;IF (Setitimer ( Itimer_real, &AMP;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");/* Wait for the signal to arrive, block function */sigsuspend (&set); ngx_time _update (); Ngx_log_debug1 (ngx_log_debug_event, Cycle->log, 0, "Wake Up, Sigio%i", Sigio);/* received a SIGCHLD signal, a worker exited (  Ngx_reap = = 1) */if (ngx_reap) {ngx_reap = 0;ngx_log_debug0 (ngx_log_debug_event, Cycle->log, 0, "reap children"); live = Ngx_reap_children (cycle);} if (!live && (ngx_terminate | | ngx_quit)) {ngx_master_process_exit (cycle);} /* Abort process */if (ngx_terminate) {if (delay = = 0) {delay = 50;} if (Sigio) {sigio--;continue;} Sigio = ccf->worker_processes + 2 */cache processes */;if (Delay >) {ngx_signal_worker_processes (cycle, Sigkil L);} else {ngx_signal_worker_processes (Cycle,ngx_signal_value (ngx_terminate_signal));} Continue;} /* Exit Process */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;} /* Receive SIGHUP signal reinitialization configuration */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, live = 1;ngx_signal_worker_processes (Cycle,ngx_signal_value (ngx_ Shutdown_signal));} /* When Ngx_noaccepting==1, Ngx_restart is set to 1, restart 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;} /* Receive the SIGUSR1 signal, reopen the log file */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));} /* SIGUSER2, Hot code replacement */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);} /* Receive SIGWINCH signal not accepting request, worker exits, Master does not exit */if (ngx_noaccept) {ngx_noaccept = 0;ngx_noaccepting = 1;ngx_signal_worker_ Processes (Cycle,ngx_signal_value (ngx_shutdown_signal));}}

2. Ngx_start_worker_processes Create a worker process

Creates n sub-processes by looping. Each child process has a separate memory space.

The number of child processes is determined by Nginx configuration: ccf->worker_processes

/** * Create worker process */static void ngx_start_worker_processes (ngx_cycle_t *cycle, ngx_int_t n,ngx_int_t type) {ngx_int_t i;ngx_ch annel_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;/* cycle Create worker process  default ccf->worker_processes=8 process, depending on the number of CPUs   */for (i = 0; i < n; i++) {/* Open worker Process  (Ngx_worker_process_cycle callback function, mainly for processing each worker thread) */ngx_spawn_process (cycle, ngx_worker_process_cycle, ( void *) (intptr_t) I, "worker process", type); ch.pid = Ngx_processes[ngx_process_slot].pid;ch.slot = Ngx_process_slot; CH.FD = Ngx_processes[ngx_process_slot].channel[0];ngx_pass_open_channel (cycle, &ch);}}

3. ngx_spawn_process Fork Work Process

The Ngx_spawn_process method is mainly used to fork out each work process. The main view is the code of the fork process.

    /* Fork a sub-process *    /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:/    * If the PID fork succeeds, call the Ngx_worker_process_cycle method *        /Ngx_pid = Ngx_getpid ();        Proc (cycle, data);        break;    Default: Break        ;    }

4. Callback function for ngx_worker_process_cycle child process

Ngx_worker_process_cycle is the callback function for the child process, and the work of all child processes begins with this method.

Nginx's process is ultimately event-driven, and all of this will eventually invoke the ngx_process_events_and_timers event-driven core function.

/** * Subprocess callback function * The logical processing of each process starts with this method */static void Ngx_worker_process_cycle (ngx_cycle_t *cycle, void *data) {ngx_int_t Worke R = (intptr_t) data;ngx_process = Ngx_process_worker;ngx_worker = worker;/* worker process initialization */ngx_worker_process_init (cycle, Workers); Ngx_setproctitle ("worker process");/* process loop */for (;;) {/* Determines whether the status is exited, and if exiting, the socket connection handle */if (ngx_exiting) {ngx_event_cancel_timers () will need to be emptied, 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");/* Event-driven core function */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 Exit */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_close_listening_sockETS (cycle); ngx_close_idle_connections (cycle);}} /* If it is reboot */if (ngx_reopen) {Ngx_reopen = 0;ngx_log_error (ngx_log_notice, Cycle->log, 0, "reopening logs"); Ngx_reopen_ Files (cycle,-1);}}}

5. Ngx_worker_process_init Worker Process Initialization

/** * worker process initialization */static void Ngx_worker_process_init (ngx_cycle_t *cycle, ngx_int_t worker) {sigset_t set;ngx_int_t N;ngx_u int_t i;ngx_cpuset_t *cpu_affinity;struct rlimit rlmt;ngx_core_conf_t *ccf;ngx_listening_t *ls;/* Configure environment Variables */if (ngx_set_ Environment (cycle, null) = = NULL) {/* fatal */exit (2);} /* Get core configuration */CCF = (ngx_core_conf_t *) ngx_get_conf (cycle->conf_ctx, Ngx_core_module); if (worker >= 0 && ccf- >priority! = 0) {if (setpriority (prio_process, 0, ccf->priority) = =-1) {Ngx_log_error (Ngx_log_alert, cycle-> Log, Ngx_errno, "setpriority (%d) failed", ccf->priority);}} if (ccf->rlimit_nofile! = ngx_conf_unset) {rlmt.rlim_cur = (rlim_t) Ccf->rlimit_nofile;rlmt.rlim_max = (rlim_t) Ccf->rlimit_nofile;if (Setrlimit (rlimit_nofile, &AMP;RLMT) = =-1) {Ngx_log_error (Ngx_log_alert, Cycle->log, NGX _errno, "Setrlimit (Rlimit_nofile,%i) failed", Ccf->rlimit_nofile);}} if (ccf->rlimit_core! = ngx_conf_unset) {rlmt.rlim_cur = (rlim_t) Ccf->rlimit_core;rlmt.rlim_max = (rlim_t) ccf->rlimit_core;if (Setrlimit (Rlimit_core, &AMP;RLMT) = =-1) {Ngx_log_error (Ngx_log_alert, cycle- >log, Ngx_errno, "Setrlimit (Rlimit_core,%O) failed", Ccf->rlimit_core);}} /* Set UID Groupuid */if (geteuid () = = 0) {if (Setgid (ccf->group) = =-1) {Ngx_log_error (Ngx_log_emerg, Cycle->log, NGX _errno, "Setgid (%d) failed", ccf->group);/* Fatal */exit (2);} if (Initgroups (ccf->username, ccf->group) = =-1) {Ngx_log_error (Ngx_log_emerg, Cycle->log, Ngx_errno, " Initgroups (%s,%d) failed ", Ccf->username, Ccf->group);} if (setuid (ccf->user) = =-1) {Ngx_log_error (Ngx_log_emerg, Cycle->log, Ngx_errno, "setuid (%d) failed", ccf-> user);/* Fatal */exit (2);}} /* Set CPU affinity */if (worker >= 0) {cpu_affinity = Ngx_get_cpu_affinity (worker), if (cpu_affinity) {ngx_setaffinity (cpu_ affinity, Cycle->log);}} #if (ngx_have_pr_set_dumpable)/* Allow coredump after setuid () in Linux 2.4.x */if (Prctl (pr_set_dumpable, 1, 0, 0, 0) = = -1) {Ngx_log_error (Ngx_log_alert, CYCle->log, Ngx_errno, "Prctl (pr_set_dumpable) failed");} #endif/* Switch working directory */if (Ccf->working_directory.len) {if (ChDir ((char *) ccf->working_directory.data) = =-1) {Ngx_log _error (Ngx_log_alert, Cycle->log, Ngx_errno, "chdir (\"%s\ ") failed", ccf->working_directory.data);/* Fatal */ Exit (2);}} Sigemptyset (&set);/* Clear All signals */if (Sigprocmask (Sig_setmask, &set, NULL) = =-1) {Ngx_log_error (Ngx_log_alert, Cycle->log, Ngx_errno, "Sigprocmask () failed");} Srandom ((ngx_pid <<) ^ ngx_time ());/* * Disable deleting previous events for the listening sockets because * in t He worker processes there is no events at all at the this point *//* clears Sokcet's listener */ls = cycle->listening.elts;for (i = 0; I < cycle->listening.nelts; i++) {ls[i].previous = NULL;} /* For module initialization */for (i = 0; cycle->modules[i]; i++) {if (cycle->modules[i]->init_process) {if (cycle->modules[i]- >init_process (cycle) = = Ngx_error) {/* fatal */exit (2);}} /** * Channel[1 of other processes] off, own channel[0] off */for (n = 0; n < ngx_last_process; n++) {if (Ngx_processes[n].pid = =-1) {continue;} if (n = = Ngx_process_slot) {continue;} if (ngx_processes[n].channel[1] = =-1) {continue;} if (Close (ngx_processes[n].channel[1]) = =-1) {Ngx_log_error (Ngx_log_alert, Cycle->log, Ngx_errno, "close () channel Failed ");}} if (Close (ngx_processes[ngx_process_slot].channel[0]) = =-1) {Ngx_log_error (Ngx_log_alert, Cycle->log, Ngx_errno, "Close () channel failed");} #if 0ngx_last_process = 0; #endif/** * Register A read event handler for Ngx_channel */if (Ngx_add_channel_event (cycle, Ngx_channel, Ngx_read_ Event,ngx_channel_handler) = = Ngx_error) {/* fatal */exit (2);}}

In the next section, we will explain the Nginx cluster and the load balancing process between processes.

Nginx source Code Analysis-Main process-multi-process implementation