prefork.c

Apache官方在今天放出产品系列2.2的最新版本2.2.11的源码包 最流行的HTTP服务器软件之一

        apr_signal(AP_SIG_GRACEFUL, stop_listening);
        child_main(slot);
    }

    ap_scoreboard_image->parent[slot].pid = pid;

    return 0;
}


/* start up a bunch of children */
static void startup_children(int number_to_start)
{
    int i;

    for (i = 0; number_to_start && i < ap_daemons_limit; ++i) {
        if (ap_scoreboard_image->servers[i][0].status != SERVER_DEAD) {
            continue;
        }
        if (make_child(ap_server_conf, i) < 0) {
            break;
        }
        --number_to_start;
    }
}


/*
 * idle_spawn_rate is the number of children that will be spawned on the
 * next maintenance cycle if there aren't enough idle servers.  It is
 * doubled up to MAX_SPAWN_RATE, and reset only when a cycle goes by
 * without the need to spawn.
 */
static int idle_spawn_rate = 1;
#ifndef MAX_SPAWN_RATE
#define MAX_SPAWN_RATE  (32)
#endif
static int hold_off_on_exponential_spawning;

static void perform_idle_server_maintenance(apr_pool_t *p)
{
    int i;
    int to_kill;
    int idle_count;
    worker_score *ws;
    int free_length;
    int free_slots[MAX_SPAWN_RATE];
    int last_non_dead;
    int total_non_dead;

    /* initialize the free_list */
    free_length = 0;

    to_kill = -1;
    idle_count = 0;
    last_non_dead = -1;
    total_non_dead = 0;

    for (i = 0; i < ap_daemons_limit; ++i) {
        int status;

        if (i >= ap_max_daemons_limit && free_length == idle_spawn_rate)
            break;
        ws = &ap_scoreboard_image->servers[i][0];
        status = ws->status;
        if (status == SERVER_DEAD) {
            /* try to keep children numbers as low as possible */
            if (free_length < idle_spawn_rate) {
                free_slots[free_length] = i;
                ++free_length;
            }
        }
        else {
            /* We consider a starting server as idle because we started it
             * at least a cycle ago, and if it still hasn't finished starting
             * then we're just going to swamp things worse by forking more.
             * So we hopefully won't need to fork more if we count it.
             * This depends on the ordering of SERVER_READY and SERVER_STARTING.
             */
            if (status <= SERVER_READY) {
                ++ idle_count;
                /* always kill the highest numbered child if we have to...
                 * no really well thought out reason ... other than observing
                 * the server behaviour under linux where lower numbered children
                 * tend to service more hits (and hence are more likely to have
                 * their data in cpu caches).
                 */
                to_kill = i;
            }

            ++total_non_dead;
            last_non_dead = i;
        }
    }
    ap_max_daemons_limit = last_non_dead + 1;
    if (idle_count > ap_daemons_max_free) {
        /* kill off one child... we use the pod because that'll cause it to
         * shut down gracefully, in case it happened to pick up a request
         * while we were counting
         */
        ap_mpm_pod_signal(pod);
        idle_spawn_rate = 1;
    }
    else if (idle_count < ap_daemons_min_free) {
        /* terminate the free list */
        if (free_length == 0) {
            /* only report this condition once */
            static int reported = 0;

            if (!reported) {
                ap_log_error(APLOG_MARK, APLOG_ERR, 0, ap_server_conf,
                            "server reached MaxClients setting, consider"
                            " raising the MaxClients setting");
                reported = 1;
            }
            idle_spawn_rate = 1;
        }
        else {
            if (idle_spawn_rate >= 8) {
                ap_log_error(APLOG_MARK, APLOG_INFO, 0, ap_server_conf,
                    "server seems busy, (you may need "
                    "to increase StartServers, or Min/MaxSpareServers), "
                    "spawning %d children, there are %d idle, and "
                    "%d total children", idle_spawn_rate,
                    idle_count, total_non_dead);
            }
            for (i = 0; i < free_length; ++i) {
#ifdef TPF
                if (make_child(ap_server_conf, free_slots[i]) == -1) {
                    if(free_length == 1) {
                        shutdown_pending = 1;
                        ap_log_error(APLOG_MARK, APLOG_EMERG, 0, ap_server_conf,
                                    "No active child processes: shutting down");
                    }
                }
#else
                make_child(ap_server_conf, free_slots[i]);
#endif /* TPF */
            }
            /* the next time around we want to spawn twice as many if this
             * wasn't good enough, but not if we've just done a graceful
             */
            if (hold_off_on_exponential_spawning) {
                --hold_off_on_exponential_spawning;
            }
            else if (idle_spawn_rate < MAX_SPAWN_RATE) {
                idle_spawn_rate *= 2;
            }
        }
    }
    else {
        idle_spawn_rate = 1;
    }
}

/*****************************************************************
 * Executive routines.
 */

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 (rv != APR_SUCCESS) {
        ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s,
                     "Couldn't create accept lock (%s) (%d)",
                     ap_lock_fname, ap_accept_lock_mech);
        mpm_state = AP_MPMQ_STOPPING;
        return 1;
    }

#if APR_USE_SYSVSEM_SERIALIZE
    if (ap_accept_lock_mech == APR_LOCK_DEFAULT ||
        ap_accept_lock_mech == APR_LOCK_SYSVSEM) {
#else
    if (ap_accept_lock_mech == APR_LOCK_SYSVSEM) {
#endif
        rv = unixd_set_proc_mutex_perms(accept_mutex);
        if (rv != APR_SUCCESS) {
            ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s,
                         "Couldn't set permissions on cross-process lock; "
                         "check User and Group directives");
            mpm_state = AP_MPMQ_STOPPING;
            return 1;
        }
    }

    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();

    if (one_process) {
        AP_MONCONTROL(1);
        make_child(ap_server_conf, 0);
    }
    else {
    if (ap_daemons_max_free < ap_daemons_min_free + 1)  /* Don't thrash... */
        ap_daemons_max_free = ap_daemons_min_free + 1;

    /* If we're doing a graceful_restart then we're going to see a lot
     * of children exiting immediately when we get into the main loop
     * below (because we just sent them AP_SIG_GRACEFUL).  This happens pretty
     * rapidly... and for each one that exits we'll start a new one until
     * we reach at least daemons_min_free.  But we may be permitted to
     * start more than that, so we'll just keep track of how many we're
     * supposed to start up without the 1 second penalty between each fork.
     */
    remaining_children_to_start = ap_daemons_to_start;
    if (remaining_children_to_start > 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) {
        int child_slot;
        apr_exit_why_e exitwhy;
        int status, processed_status;
        /* this is a memory leak, but I'll 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 it's 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 (E[NM]FILE, ENOBUFS, etc)
                     * cut the fork rate to the minimum
                     */
                    idle_spawn_rate = 1;
                }
                else if (remaining_children_to_start
                    && child_slot < ap_daemons_limit) {
                    /* we're still doing a 1-for-1 replacement of dead
                     * children with new children
                     */
                    make_child(ap_server_conf, child_slot);
                    --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, we've probably just lost a slot in the
                 * scoreboard.  Somehow we don't 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);
            }
            /* Don't perform idle maintenance when a child dies,
             * only do it when there's a timeout.  Remember only a
             * finite number of children can die, and it's 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
             * they're 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 shouldn't do the code below because
             * few of the servers we just started are in the IDLE state
             * yet, so we'd mistakenly create an extra server.
             */
            continue;
        }

        perform_idle_server_maintenance(pconf);
#ifdef TPF
        shutdown_pending = os_check_server(tpf_server_name);
        ap_check_signals();
        sleep(1);
#endif /*TPF */
    }
    } /* one_process */

    mpm_state = AP_MPMQ_STOPPING;

    if (shutdown_pending && !is_graceful) {
        /* Time to shut down:
         * Kill child processes, tell them to call child_exit, etc...
         */
        if (unixd_killpg(getpgrp(), SIGTERM) < 0) {
            ap_log_error(APLOG_MARK, APLOG_WARNING, errno, ap_server_conf, "killpg SIGTERM");
        }
        ap_reclaim_child_processes(1);          /* Start with SIGTERM */

        /* cleanup pid file on normal shutdown */
        {
            const char *pidfile = NULL;
            pidfile = ap_server_root_relative (pconf, ap_pid_fname);
            if ( pidfile != NULL && unlink(pidfile) == 0)
                ap_log_error(APLOG_MARK, APLOG_INFO,
                                0, ap_server_conf,
                                "removed PID file %s (pid=%ld)",
                                pidfile, (long)getpid());
        }

        ap_log_error(APLOG_MARK, APLOG_NOTICE, 0, ap_server_conf,