worker.c

最新apache的源代码

     * any communication with the parent process.
     */
    rv = apr_setup_signal_thread();
    if (rv != APR_SUCCESS) {
        ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf,
                     "Couldn't initialize signal thread");
        clean_child_exit(APEXIT_CHILDFATAL);
    }

    if (ap_max_requests_per_child) {
        requests_this_child = ap_max_requests_per_child;
    }
    else {
        /* coding a value of zero means infinity */
        requests_this_child = INT_MAX;
    }
    
    /* Setup worker threads */

    /* clear the storage; we may not create all our threads immediately, 
     * and we want a 0 entry to indicate a thread which was not created
     */
    threads = (apr_thread_t **)calloc(1, 
                                sizeof(apr_thread_t *) * ap_threads_per_child);
    if (threads == NULL) {
        ap_log_error(APLOG_MARK, APLOG_ALERT, errno, ap_server_conf,
                     "malloc: out of memory");
        clean_child_exit(APEXIT_CHILDFATAL);
    }

    ts = (thread_starter *)apr_palloc(pchild, sizeof(*ts));

    apr_threadattr_create(&thread_attr, pchild);
    /* 0 means PTHREAD_CREATE_JOINABLE */
    apr_threadattr_detach_set(thread_attr, 0);

    ts->threads = threads;
    ts->listener = NULL;
    ts->child_num_arg = child_num_arg;
    ts->threadattr = thread_attr;

    rv = apr_thread_create(&start_thread_id, thread_attr, start_threads,
                           ts, pchild);
    if (rv != APR_SUCCESS) {
        ap_log_error(APLOG_MARK, APLOG_ALERT, rv, ap_server_conf,
                     "apr_thread_create: unable to create worker thread");
        /* let the parent decide how bad this really is */
        clean_child_exit(APEXIT_CHILDSICK);
    }

    mpm_state = AP_MPMQ_RUNNING;

    /* If we are only running in one_process mode, we will want to
     * still handle signals. */
    if (one_process) {
        /* Block until we get a terminating signal. */
        apr_signal_thread(check_signal);
        /* make sure the start thread has finished; signal_threads() 
         * and join_workers() depend on that
         */
        /* XXX join_start_thread() won't be awakened if one of our
         *     threads encounters a critical error and attempts to
         *     shutdown this child
         */
        join_start_thread(start_thread_id);
        signal_threads(ST_UNGRACEFUL); /* helps us terminate a little more
                           * quickly than the dispatch of the signal thread
                           * beats the Pipe of Death and the browsers
                           */
        /* 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);
    }
    else { /* !one_process */
        /* remove SIGTERM from the set of blocked signals...  if one of
         * the other threads in the process needs to take us down
         * (e.g., for MaxRequestsPerChild) it will send us SIGTERM
         */
        unblock_signal(SIGTERM);
        apr_signal(SIGTERM, dummy_signal_handler);
        /* Watch for any messages from the parent over the POD */
        while (1) {
            rv = ap_mpm_pod_check(pod);
            if (rv == AP_NORESTART) {
                /* see if termination was triggered while we slept */
                switch(terminate_mode) {
                case ST_GRACEFUL:
                    rv = AP_GRACEFUL;
                    break;
                case ST_UNGRACEFUL:
                    rv = AP_RESTART;
                    break;
                }
            }
            if (rv == AP_GRACEFUL || rv == AP_RESTART) {
                /* make sure the start thread has finished; 
                 * signal_threads() and join_workers depend on that
                 */
                join_start_thread(start_thread_id);
                signal_threads(rv == AP_GRACEFUL ? ST_GRACEFUL : ST_UNGRACEFUL);
                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 */
    if (ap_scoreboard_image->parent[slot].pid != 0) {
        /* This new child process is squatting on the scoreboard
         * entry owned by an exiting child process, which cannot
         * exit until all active requests complete.
         * Don't forget about this exiting child process, or we
         * won't be able to kill it if it doesn't exit by the
         * time the server is shut down.
         */
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf,
                     "taking over scoreboard slot from %" APR_PID_T_FMT "%s",
                     ap_scoreboard_image->parent[slot].pid,
                     ap_scoreboard_image->parent[slot].quiescing ?
                         " (quiescing)" : "");
        ap_register_extra_mpm_process(ap_scoreboard_image->parent[slot].pid);
    }
    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 && status != SERVER_DEAD &&
                        !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,