event.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

                break;
            }
        }

        /* A terminating signal was received. Now join each of the
         * workers to clean them up.
         *   If the worker already exited, then the join frees
         *   their resources and returns.
         *   If the worker hasn't exited, then this blocks until
         *   they have (then cleans up).
         */
        join_workers(ts->listener, threads);
    }

    free(threads);

    clean_child_exit(resource_shortage ? APEXIT_CHILDSICK : 0);
}

static int make_child(server_rec * s, int slot)
{
    int pid;

    if (slot + 1 > ap_max_daemons_limit) {
        ap_max_daemons_limit = slot + 1;
    }

    if (one_process) {
        set_signals();
        ap_scoreboard_image->parent[slot].pid = getpid();
        child_main(slot);
    }

    if ((pid = fork()) == -1) {
        ap_log_error(APLOG_MARK, APLOG_ERR, errno, s,
                     "fork: Unable to fork new process");

        /* fork didn't succeed. Fix the scoreboard or else
         * it will say SERVER_STARTING forever and ever
         */
        ap_update_child_status_from_indexes(slot, 0, SERVER_DEAD, NULL);

        /* In case system resources are maxxed out, we don't want
           Apache running away with the CPU trying to fork over and
           over and over again. */
        apr_sleep(apr_time_from_sec(10));

        return -1;
    }

    if (!pid) {
#ifdef HAVE_BINDPROCESSOR
        /* By default, AIX binds to a single processor.  This bit unbinds
         * children which will then bind to another CPU.
         */
        int status = bindprocessor(BINDPROCESS, (int) getpid(),
                                   PROCESSOR_CLASS_ANY);
        if (status != OK)
            ap_log_error(APLOG_MARK, APLOG_WARNING, errno,
                         ap_server_conf,
                         "processor unbind failed %d", status);
#endif
        RAISE_SIGSTOP(MAKE_CHILD);

        apr_signal(SIGTERM, just_die);
        child_main(slot);

        clean_child_exit(0);
    }
    /* else */
    ap_scoreboard_image->parent[slot].quiescing = 0;
    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->parent[i].pid != 0) {
            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(void)
{
    int i, j;
    int idle_thread_count;
    worker_score *ws;
    process_score *ps;
    int free_length;
    int totally_free_length = 0;
    int free_slots[MAX_SPAWN_RATE];
    int last_non_dead;
    int total_non_dead;
    int active_thread_count = 0;

    /* initialize the free_list */
    free_length = 0;

    idle_thread_count = 0;
    last_non_dead = -1;
    total_non_dead = 0;

    for (i = 0; i < ap_daemons_limit; ++i) {
        /* Initialization to satisfy the compiler. It doesn't know
         * that ap_threads_per_child is always > 0 */
        int status = SERVER_DEAD;
        int any_dying_threads = 0;
        int any_dead_threads = 0;
        int all_dead_threads = 1;

        if (i >= ap_max_daemons_limit
            && totally_free_length == idle_spawn_rate)
            break;
        ps = &ap_scoreboard_image->parent[i];
        for (j = 0; j < ap_threads_per_child; j++) {
            ws = &ap_scoreboard_image->servers[i][j];
            status = ws->status;

            /* XXX any_dying_threads is probably no longer needed    GLA */
            any_dying_threads = any_dying_threads ||
                (status == SERVER_GRACEFUL);
            any_dead_threads = any_dead_threads || (status == SERVER_DEAD);
            all_dead_threads = all_dead_threads &&
                (status == SERVER_DEAD || status == SERVER_GRACEFUL);

            /* 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 (ps->pid != 0) { /* XXX just set all_dead_threads in outer
                                   for loop if no pid?  not much else matters */
                if (status <= SERVER_READY &&
                        !ps->quiescing && ps->generation == ap_my_generation) {
                    ++idle_thread_count;
                }
                if (status >= SERVER_READY && status < SERVER_GRACEFUL) {
                    ++active_thread_count;
                }
            }
        }
        if (any_dead_threads
            && totally_free_length < idle_spawn_rate
            && free_length < MAX_SPAWN_RATE
            && (!ps->pid      /* no process in the slot */
                  || ps->quiescing)) {  /* or at least one is going away */
            if (all_dead_threads) {
                /* great! we prefer these, because the new process can
                 * start more threads sooner.  So prioritize this slot
                 * by putting it ahead of any slots with active threads.
                 *
                 * first, make room by moving a slot that's potentially still
                 * in use to the end of the array
                 */
                free_slots[free_length] = free_slots[totally_free_length];
                free_slots[totally_free_length++] = i;
            }
            else {
                /* slot is still in use - back of the bus
                 */
                free_slots[free_length] = i;
            }
            ++free_length;
        }
        /* XXX if (!ps->quiescing)     is probably more reliable  GLA */
        if (!any_dying_threads) {
            last_non_dead = i;
            ++total_non_dead;
        }
    }

    if (sick_child_detected) {
        if (active_thread_count > 0) {
            /* some child processes appear to be working.  don't kill the
             * whole server.
             */
            sick_child_detected = 0;
        }
        else {
            /* looks like a basket case.  give up.
             */
            shutdown_pending = 1;
            child_fatal = 1;
            ap_log_error(APLOG_MARK, APLOG_ALERT, 0,
                         ap_server_conf,
                         "No active workers found..."
                         " Apache is exiting!");
            /* the child already logged the failure details */
            return;
        }
    }

    ap_max_daemons_limit = last_non_dead + 1;

    if (idle_thread_count > max_spare_threads) {
        /* Kill off one child */
        ap_mpm_pod_signal(pod, TRUE);
        idle_spawn_rate = 1;
    }
    else if (idle_thread_count < min_spare_threads) {
        /* 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 (free_length > idle_spawn_rate) {
                free_length = idle_spawn_rate;
            }
            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, ThreadsPerChild "
                             "or Min/MaxSpareThreads), "
                             "spawning %d children, there are around %d idle "
                             "threads, and %d total children", free_length,
                             idle_thread_count, total_non_dead);
            }
            for (i = 0; i < free_length; ++i) {
                make_child(ap_server_conf, free_slots[i]);
            }
            /* 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;
    }
}

static void server_main_loop(int remaining_children_to_start)
{
    int child_slot;
    apr_exit_why_e exitwhy;
    int status, processed_status;
    apr_proc_t pid;
    int i;

    while (!restart_pending && !shutdown_pending) {
        ap_wait_or_timeout(&exitwhy, &status, &pid, pconf);

        if (pid.pid != -1) {
            processed_status = ap_process_child_status(&pid, exitwhy, status);
            if (processed_status == APEXIT_CHILDFATAL) {
                shutdown_pending = 1;
                child_fatal = 1;
                return;
            }
            else if (processed_status == APEXIT_CHILDSICK) {
                /* tell perform_idle_server_maintenance to check into this
                 * on the next timer pop
                 */
                sick_child_detected = 1;
            }
            /* non-fatal death... note that it's gone in the scoreboard. */
            child_slot = find_child_by_pid(&pid);
            if (child_slot >= 0) {
                for (i = 0; i < ap_threads_per_child; i++)
                    ap_update_child_status_from_indexes(child_slot, i,
                                                        SERVER_DEAD,
                                                        (request_rec *) NULL);

                ap_scoreboard_image->parent[child_slot].pid = 0;
                ap_scoreboard_image->parent[child_slot].quiescing = 0;
                if (processed_status == APEXIT_CHILDSICK) {
                    /* resource shortage, minimize the fork rate */
                    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) == 0) {
                /* 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();
    }
}

int ap_mpm_run(apr_pool_t * _pconf, apr_pool_t * plog, server_rec * s)
{
    int remaining_children_to_start;

    ap_log_pid(pconf, ap_pid_fname);

    first_server_limit = server_limit;
    first_thread_limit = thread_limit;

    if (changed_limit_at_restart) {
        ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s,
                     "WARNING: Attempt to change ServerLimit or ThreadLimit "
                     "ignored during restart");
        changed_limit_at_restart = 0;
    }

    if (!is_graceful) {
        if (ap_run_pre_mpm(s->process->pool, SB_SHARED) != OK) {
            mpm_state = AP_MPMQ_STOPPING;
            return 1;
        }
        /* fix the gen