apache的启动过程 原代码 分析.doc

1 /server/log.c 这个里面定义了ap_log_error()。2 /include/httpd.h 这个文件里面申明了基本的内容，如文件路径，字符串长度，等等。3 /server/listen.c对于apache的httpd，有很多的技术，有MPM多任务并发处理(采用记分板)，内存池，线程池。1 在main（）有一个for(;)里面调用了ap_mpm_run。但这个循环里好象只执行了一次，而不是一直在循环。2 在ap_mpm_run()里，有一个while (!restart_pending & !shutdown_pending)。这个循环每一秒就往返一次，一直执行，直到进程结束。如果是第一次启动，在这个循环里，会调用一个startup_children();在这里面又有一个循环调用make_child()产生初始数量的子进程。3 在上面的while里，perform_idle_server_maintenance(pconf)会每1秒执行一次，如果你kill -9一个子进程，这个函数就起作用，再重新调用make_child()生成一个子进程。4 如果执行httpd k stop，那么ap_mpm_run()会返回错误，在main（）就会跳出for(;)，进程退出。5 在make_child()里，有一个fork（）调用产生子进程，然后在子进程里调用child_main()进行子进程的初始化处理。linux-lncx:/home/apache/httpd-2.2.11/server # ls main.cmain.clinux-lncx:/home/apache/httpd-2.2.11/server #int main(int argc, const char * const argv) char c; int configtestonly = 0; const char *confname = SERVER_CONFIG_FILE; const char *def_server_root = HTTPD_ROOT; const char *temp_error_log = NULL; const char *error; process_rec *process; server_rec *server_conf; apr_pool_t *pglobal; apr_pool_t *pconf; apr_pool_t *plog; /* Pool of log streams, reset _after_ each read of conf */ apr_pool_t *ptemp; /* Pool for temporary config stuff, reset often */ apr_pool_t *pcommands; /* Pool for -D, -C and -c switches */ apr_getopt_t *opt; apr_status_t rv; module *mod; const char *optarg; APR_OPTIONAL_FN_TYPE(ap_signal_server) *signal_server; AP_MONCONTROL(0); /* turn off profiling of startup */ process = init_process(&argc, &argv); pglobal = process-pool; pconf = process-pconf; ap_server_argv0 = process-short_name;#if APR_CHARSET_EBCDIC if (ap_init_ebcdic(pglobal) != APR_SUCCESS) destroy_and_exit_process(process, 1); #endif apr_pool_create(&pcommands, pglobal); apr_pool_tag(pcommands, pcommands); ap_server_pre_read_config = apr_array_make(pcommands, 1, sizeof(char *); ap_server_post_read_config = apr_array_make(pcommands, 1, sizeof(char *); ap_server_config_defines = apr_array_make(pcommands, 1, sizeof(char *); error = ap_setup_prelinked_modules(process); if (error) ap_log_error(APLOG_MARK, APLOG_STARTUP|APLOG_EMERG, 0, NULL, %s: %s, ap_server_argv0, error); destroy_and_exit_process(process, 1); ap_run_rewrite_args(process); /* Maintain AP_SERVER_BASEARGS list in http_main.h to allow the MPM * to safely pass on our args from its rewrite_args() handler. */ apr_getopt_init(&opt, pcommands, process-argc, process-argv); while (rv = apr_getopt(opt, AP_SERVER_BASEARGS, &c, &optarg) = APR_SUCCESS) char *new; switch (c) case c: new = (char *)apr_array_push(ap_server_post_read_config); *new = apr_pstrdup(pcommands, optarg); break; case C: new = (char *)apr_array_push(ap_server_pre_read_config); *new = apr_pstrdup(pcommands, optarg); break; case d: def_server_root = optarg; break; case D: new = (char *)apr_array_push(ap_server_config_defines); *new = apr_pstrdup(pcommands, optarg); /* Setting -D DUMP_VHOSTS is equivalent to setting -S */ if (strcmp(optarg, DUMP_VHOSTS) = 0) configtestonly = 1; /* Setting -D DUMP_MODULES is equivalent to setting -M */ if (strcmp(optarg, DUMP_MODULES) = 0) configtestonly = 1; break; case e: if (strcasecmp(optarg, emerg) = 0) ap_default_loglevel = APLOG_EMERG; else if (strcasecmp(optarg, alert) = 0) ap_default_loglevel = APLOG_ALERT; else if (strcasecmp(optarg, crit) = 0) ap_default_loglevel = APLOG_CRIT; else if (strncasecmp(optarg, err, 3) = 0) ap_default_loglevel = APLOG_ERR; else if (strncasecmp(optarg, warn, 4) = 0) ap_default_loglevel = APLOG_WARNING; else if (strcasecmp(optarg, notice) = 0) ap_default_loglevel = APLOG_NOTICE; else if (strcasecmp(optarg, info) = 0) ap_default_loglevel = APLOG_INFO; else if (strcasecmp(optarg, debug) = 0) ap_default_loglevel = APLOG_DEBUG; else usage(process); break; case E: temp_error_log = apr_pstrdup(process-pool, optarg); break; case X: new = (char *)apr_array_push(ap_server_config_defines); *new = DEBUG; break; case f: confname = optarg; break; case v: printf(Server version: %sn, ap_get_server_description(); printf(Server built: %sn, ap_get_server_built(); destroy_and_exit_process(process, 0); case V: show_compile_settings(); destroy_and_exit_process(process, 0); case l: ap_show_modules(); destroy_and_exit_process(process, 0); case L: ap_show_directives(); destroy_and_exit_process(process, 0); case t: configtestonly = 1; break; case S: configtestonly = 1; new = (char *)apr_array_push(ap_server_config_defines); *new = DUMP_VHOSTS; break; case M: configtestonly = 1; new = (char *)apr_array_push(ap_server_config_defines); *new = DUMP_MODULES; break; case h: case ?: usage(process); /* bad cmdline option? then we die */ if (rv != APR_EOF | opt-ind argc) usage(process); apr_pool_create(&plog, pglobal); apr_pool_tag(plog, plog); apr_pool_create(&ptemp, pconf); apr_pool_tag(ptemp, ptemp); /* Note that we preflight the config file once * before reading it _again_ in the main loop. * This allows things, log files configuration * for example, to settle down. */ ap_server_root = def_server_root; if (temp_error_log) ap_replace_stderr_log(process-pool, temp_error_log); /*=下面这一段是对配置文件进行处理 =*/ server_conf = ap_read_config(process, ptemp, confname, &ap_conftree); if (!server_conf) destroy_and_exit_process(process, 1); if (ap_run_pre_config(pconf, plog, ptemp) != OK) ap_log_error(APLOG_MARK, APLOG_STARTUP |APLOG_ERR, 0, NULL, Pre-configuration failed); destroy_and_exit_process(process, 1); rv = ap_process_config_tree(server_conf, ap_conftree, process-pconf, ptemp); if (rv = OK) ap_fixup_virtual_hosts(pconf, server_conf); ap_fini_vhost_config(pconf, server_conf); apr_hook_sort_all(); if (configtestonly) ap_run_test_config(pconf, server_conf); ap_log_error(APLOG_MARK, APLOG_STARTUP, 0, NULL, Syntax OK); destroy_and_exit_process(process, 0); /*=上面这一段是对配置文件进行处理=*/ signal_server = APR_RETRIEVE_OPTIONAL_FN(ap_signal_server); if (signal_server) int exit_status; if (signal_server(&exit_status, pconf) != 0) destroy_and_exit_process(process, exit_status); /* If our config failed, deal with that here. */ if (rv != OK) destroy_and_exit_process(process, 1); apr_pool_clear(plog); if ( ap_run_open_logs(pconf, plog, ptemp, server_conf) != OK) ap_log_error(APLOG_MARK, APLOG_STARTUP |APLOG_ERR, 0, NULL, Unable to open logs); destroy_and_exit_process(process, 1); if ( ap_run_post_config(pconf, plog, ptemp, server_conf) != OK) ap_log_error(APLOG_MARK, APLOG_STARTUP |APLOG_ERR, 0, NULL, Configuration Failed); destroy_and_exit_process(process, 1); apr_pool_destroy(ptemp); for (;) apr_hook_deregister_all(); apr_pool_clear(pconf); for (mod = ap_prelinked_modules; *mod != NULL; mod+) ap_register_hooks(*mod, pconf); /* This is a hack until we finish the code so that it only reads * the config file once and just operates on the tree already in * memory. rbb */ ap_conftree = NULL; apr_pool_create(&ptemp, pconf); apr_pool_tag(ptemp, ptemp); ap_server_root = def_server_root;/*=下面这一段是对配置文件进行处理，每次循环都要处理 =*/ server_conf = ap_read_config(process, ptemp, confname, &ap_conftree); if (!server_conf) destroy_and_exit_process(process, 1); if (ap_run_pre_config(pconf, plog, ptemp) != OK) ap_log_error(APLOG_MARK, APLOG_STARTUP |APLOG_ERR, 0, NULL, Pre-configuration failed); destroy_and_exit_process(process, 1); if (ap_process_config_tree(server_conf, ap_conftree, process-pconf, ptemp) != OK) destroy_and_exit_process(process, 1); ap_fixup_virtual_hosts(pconf, server_conf); ap_fini_vhost_config(pconf, server_conf); apr_hook_sort_all(); apr_pool_clear(plog); if (ap_run_open_logs(pconf, plog, ptemp, server_conf) != OK) ap_log_error(APLOG_MARK, APLOG_STARTUP |APLOG_ERR, 0, NULL, Unable to open logs); destroy_and_exit_process(process, 1); if (ap_run_post_config(pconf, plog, ptemp, server_conf) != OK) ap_log_error(APLOG_MARK, APLOG_STARTUP |APLOG_ERR, 0, NULL, Configuration Failed); destroy_and_exit_process(process, 1); /*=上面这一段是对配置文件进行处理，每次循环都要处理 =*/ apr_pool_destroy(ptemp); apr_pool_lock(pconf, 1); ap_run_optional_fn_retrieve(); if (ap_mpm_run(pconf, plog, server_conf) :如果出错，则跳出循环。 break; apr_pool_lock(pconf, 0); for(;)在这里结束。父进程的这个循环，每次都会重新读入配置文件进行处理。然后调用ap_mpm_run()重新生成子进程。 apr_pool_lock(pconf, 0); destroy_and_exit_process(process, 0); return 0; /* Termination ok */int ap_mpm_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s) int index; int remaining_children_to_start; apr_status_t rv; ap_log_pid(pconf, ap_pid_fname); first_server_limit = server_limit; if (changed_limit_at_restart) ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s, WARNING: Attempt to change ServerLimit ignored during restart); changed_limit_at_restart = 0; /* Initialize cross-process accept lock */ ap_lock_fname = apr_psprintf(_pconf, %s.% APR_PID_T_FMT, ap_server_root_relative(_pconf, ap_lock_fname), ap_my_pid); rv = apr_proc_mutex_create(&accept_mutex, ap_lock_fname, ap_accept_lock_mech, _pconf); if (ap_accept_lock_mech = APR_LOCK_SYSVSEM) rv = unixd_set_proc_mutex_perms(accept_mutex); if (!is_graceful) if (ap_run_pre_mpm(s-process-pool, SB_SHARED) != OK) mpm_state = AP_MPMQ_STOPPING; return 1; /* fix the generation number in the global score; we just got a new, * cleared scoreboard */ ap_scoreboard_image-global-running_generation = ap_my_generation; set_signals(); 这里进行信号量设定，对主进程有效，对子进程有没有效？ Apachectl restart,apachectl stop, apachectl graceful，这些命令将会导致 信号处理函数 设定如下的全局变量static int volatile shutdown_pending;static int volatile restart_pending;static int volatile is_graceful;这些变量定义在 prefork.c中。 当这些变量发生改变时，程序的流程将发生相应的变化。 if (one_process) AP_MONCONTROL(1); make_child(ap_server_conf, 0); else if (ap_daemons_max_free ap_daemons_limit) remaining_children_to_start = ap_daemons_limit; if (!is_graceful) startup_children(remaining_children_to_start); remaining_children_to_start = 0; else /* give the system some time to recover before kicking into * exponential mode */ hold_off_on_exponential_spawning = 10; ap_log_error(APLOG_MARK, APLOG_NOTICE, 0, ap_server_conf, %s configured - resuming normal operations, ap_get_server_description(); ap_log_error(APLOG_MARK, APLOG_INFO, 0, ap_server_conf, Server built: %s, ap_get_server_built();#ifdef AP_MPM_WANT_SET_ACCEPT_LOCK_MECH ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf, AcceptMutex: %s (default: %s), apr_proc_mutex_name(accept_mutex), apr_proc_mutex_defname();#endif restart_pending = shutdown_pending = 0; mpm_state = AP_MPMQ_RUNNING; while (!restart_pending & !shutdown_pending) :这里每隔一秒就往返一次。一直进行不停 int child_slot; apr_exit_why_e exitwhy; int status, processed_status; /* this is a memory leak, but Ill fix it later. */ apr_proc_t pid; ap_wait_or_timeout(&exitwhy, &status, &pid, pconf); /* XXX: if it takes longer than 1 second for all our children * to start up and get into IDLE state then we may spawn an * extra child */ if (pid.pid != -1) processed_status = ap_process_child_status(&pid, exitwhy, status); if (processed_status = APEXIT_CHILDFATAL) mpm_state = AP_MPMQ_STOPPING; return 1; /* non-fatal death. note that its gone in the scoreboard. */ child_slot = find_child_by_pid(&pid); if (child_slot = 0) (void) ap_update_child_status_from_indexes(child_slot, 0, SERVER_DEAD, (request_rec *) NULL); if (processed_status = APEXIT_CHILDSICK) /* child detected a resource shortage (ENMFILE, ENOBUFS, etc) * cut the fork rate to the minimum */ idle_spawn_rate = 1; else if (remaining_children_to_start & child_slot ap_daemons_limit) /* were still doing a 1-for-1 replacement of dead * children with new children */ make_child(ap_server_conf, child_slot);如果apachectl graceful，将会执行到这里，在这个循环里每一次都会执行到这里，生成相应的子进程， -remaining_children_to_start; #if APR_HAS_OTHER_CHILD else if (apr_proc_other_child_alert(&pid, APR_OC_REASON_DEATH, status) = APR_SUCCESS) /* handled */#endif else if (is_graceful) /* Great, weve probably just lost a slot in the * scoreboard. Somehow we dont know about this * child. */ ap_log_error(APLOG_MARK, APLOG_WARNING, 0, ap_server_conf, long lost child came home! (pid %ld), (long)pid.pid); /* Dont perform idle maintenance when a child dies, * only do it when theres a timeout. Remember only a * finite number of children can die, and its pretty * pathological for a lot to die suddenly. */ continue; else if (remaining_children_to_start) /* we hit a 1 second timeout in which none of the previous * generation of children needed to be reaped. so assume * theyre all done, and pick up the slack if any is left. */ startup_children(remaining_children_to_start); remaining_children_to_start = 0; /* In any event we really shouldnt do the code below because * few of the servers we just started are in the IDLE state * yet, so wed mistakenly create an extra server. */ continue; perform_idle_server_maintenance