深入学习keepalived之一 keepalived的启动

1.keepalived的启动过程：

    启动健康检查子进程和vrrp子进程。其中_WITH_LVS_，_WITH_VRRP_在configure和configure.in文件中定义。

源码如下：

/* Daemon init sequence */static voidstart_keepalived(void){#ifdef _WITH_LVS_    /* start healthchecker child */    if (daemon_mode & 2 || !daemon_mode)        start_check_child();#endif#ifdef _WITH_VRRP_    /* start vrrp child */    if (daemon_mode & 1 || !daemon_mode)        start_vrrp_child();#endif}

2. 启动健康检查子进程。

/* Register CHECK thread */intstart_check_child(void){#ifndef _DEBUG_    pid_t pid;    int ret;    /* Initialize child process */    pid = fork();    if (pid < 0) {        log_message(LOG_INFO, "Healthcheck child process: fork error(%s)"                   , strerror(errno));        return -1;    } else if (pid) {        checkers_child = pid;        log_message(LOG_INFO, "Starting Healthcheck child process, pid=%d"                   , pid);        /* Start respawning thread */        thread_add_child(master, check_respawn_thread, NULL,                 pid, RESPAWN_TIMER);        return 0;    }    /* Opening local CHECK syslog channel */    openlog(PROG_CHECK, LOG_PID | ((debug & 1) ? LOG_CONS : 0),        (log_facility==LOG_DAEMON) ? LOG_LOCAL2 : log_facility);    /* Child process part, write pidfile */    if (!pidfile_write(checkers_pidfile, getpid())) {        log_message(LOG_INFO, "Healthcheck child process: cannot write pidfile");        exit(0);    }    /* Create the new master thread */    signal_handler_destroy();    thread_destroy_master(master);    master = thread_make_master();    /* change to / dir */    ret = chdir("/");    if (ret < 0) {        log_message(LOG_INFO, "Healthcheck child process: error chdir");    }    /* Set mask */    umask(0);#endif    /* If last process died during a reload, we can get there and we     * don't want to loop again, because we're not reloading anymore.     */    UNSET_RELOAD;    /* Signal handling initialization */    check_signal_init();    /* Start Healthcheck daemon */    start_check();    /* Launch the scheduling I/O multiplexer */    launch_scheduler();    /* Finish healthchecker daemon process */    stop_check();    exit(0);}

debug模式暂且不考虑。

2.1 健康检查信号初始化

/* CHECK Child signal handling */voidcheck_signal_init(void){    signal_handler_init();    signal_set(SIGHUP, sighup_check, NULL);    signal_set(SIGINT, sigend_check, NULL);    signal_set(SIGTERM, sigend_check, NULL);    signal_ignore(SIGPIPE);}/* Handlers intialization */voidsignal_handler_init(void){    int n = pipe(signal_pipe);    assert(!n);    fcntl(signal_pipe[0], F_SETFL, O_NONBLOCK | fcntl(signal_pipe[0], F_GETFL));    fcntl(signal_pipe[1], F_SETFL, O_NONBLOCK | fcntl(signal_pipe[1], F_GETFL));    signal_SIGHUP_handler = NULL;    signal_SIGINT_handler = NULL;    signal_SIGTERM_handler = NULL;    signal_SIGCHLD_handler = NULL;}

2.2 启动健康检查后台程序

/* Daemon init sequence */static voidstart_check(void){    /* Initialize sub-system */    ipvs_start();    init_checkers_queue();#ifdef _WITH_VRRP_    init_interface_queue();    kernel_netlink_init();#endif#ifdef _WITH_SNMP_    if (!reload && snmp)        check_snmp_agent_init();#endif    /* Parse configuration file */    global_data = alloc_global_data();    check_data = alloc_check_data();    init_data(conf_file, check_init_keywords);    if (!check_data) {        stop_check();        return;    }    /* Post initializations */    log_message(LOG_INFO, "Configuration is using : %lu Bytes", mem_allocated);    /* SSL load static data & initialize common ctx context */    if (!init_ssl_ctx()) {        stop_check();        return;    }    /* Processing differential configuration parsing */    if (reload) {        clear_diff_services();        copy_srv_states();    }    /* Initialize IPVS topology */    if (!init_services()) {        stop_check();        return;    }    /* Dump configuration */    if (debug & 4) {        dump_global_data(global_data);        dump_check_data(check_data);    }#ifdef _WITH_VRRP_    /* Initialize linkbeat */    init_interface_linkbeat();#endif    /* Register checkers thread */    register_checkers_thread();}

2.3 启动I/O复用分发调度器

/* Our infinite scheduling loop */voidlaunch_scheduler(void){    thread_t thread;    signal_set(SIGCHLD, thread_child_handler, master);    /*     * Processing the master thread queues,     * return and execute one ready thread.     */    while (thread_fetch(master, &thread)) {        /* Run until error, used for debuging only */#ifdef _DEBUG_        if ((debug & 520) == 520) {            debug &= ~520;            thread_add_terminate_event(master);        }#endif        thread_call(&thread);    }}