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;
	/* Set the signal to be received */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, "sigprocm
	Ask () failed ");

	} sigemptyset (&set); size = sizeof (Master_procESS);
	for (i = 0; i < NGX_ARGC; i++) {size + Ngx_strlen (Ngx_argv[i]) + 1;
	}/* Save the 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_cpystrn (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-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 eject, 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) * 1000; if (Setitimer (Itimer_real, &AMP;ITV, NULL) = =-1) {Ngx_log_error (Ngx_log_alert, Cycle->log, Ngx_errno, "Seti
			Timer () failed ");

		}} ngx_log_debug0 (Ngx_log_debug_event, Cycle->log, 0, "sigsuspend");

		/* Wait for the signal to arrive, blocking function */sigsuspend (&set);

		Ngx_time_update ();

		NGX_LOG_DEBUG1 (ngx_log_debug_event, Cycle->log, 0, "Wake Up, Sigio%i", Sigio);
			/* received the 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, SIGKILL);
			} 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_lo
				G_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 (100);
			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 SIGUSR1 signal, reopen 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);
			*/* received 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_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;

	/* Loop Create worker process  default ccf->worker_processes=8 process, depending on number of CPUs   */For
	(i = 0; i < n; i++) {/

		* Open worker process  (Ngx_worker_process_cycle callback function, mainly used to process 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.

/** * Child Process 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

	Worker = (intptr_t) data;
	ngx_process = Ngx_process_worker;

	Ngx_worker = worker;

	/* Worker Process Initialization */ngx_worker_process_init (cycle, worker);

	Ngx_setproctitle ("worker process"); /* Process loop */for (;;)

			{/* Determines if the status is exited, and if exiting, the socket handle must be emptied */if (ngx_exiting) {ngx_event_cancel_timers (); 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 it is exited */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 restart */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 initialization of work processes

/** * 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_uint_t i;
	ngx_cpuset_t *cpu_affinity;
	struct Rlimit rlmt;
	ngx_core_conf_t *CCF;

	ngx_listening_t *ls;
	/* Configure environment variable */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) {ng
		X_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, &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, &RLMT) = =-1) {Ngx_log_error (Ngx_log_alert, Cycle->log, Ngx_errno, "Setrlimit (R
		Limit_core,%O) failed ", Ccf->rlimit_core); }}//Set UID Groupuid */if (geteuid () = = 0) {if (Setgid (ccf->group) = =-1) {Ngx_log_error (Ngx_log_emerg, CY
			Cle->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_errn
	O, "Sigprocmask () failed");

	} srandom ((ngx_pid <<) ^ ngx_time ()); /* * Disable deleting previous events for the listening sockets because * in the 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; }/* Initializes the module */for (i = 0; cycle->modules[i]; i++) {if (cycle->modules[i]->init_process) {if (CYCLE-&G
			T;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_processe
		S[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_er
	Rno, "Close () channel failed");
} #if 0 ngx_last_process = 0; #endif/** * Register A read event handler function 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.