Function clientsCron

src/server.cpp:1990–2052

 */
#define CLIENTS_CRON_MIN_ITERATIONS 5
void clientsCron(int iel) {
    /* Try to process at least numclients/g_pserver->hz of clients
     * per call. Since normally (if there are no big latency events) this
     * function is called g_pserver->hz times per second, in the average case we
     * process all the clients in 1 second. */
    int numclients = listLength(g_pserver->clients);
    int iterations = numclients/g_pserver->hz;
    mstime_t now = mstime();

    /* Process at least a few clients while we are at it, even if we need
     * to process less than CLIENTS_CRON_MIN_ITERATIONS to meet our contract
     * of processing each client once per second. */
    if (iterations < CLIENTS_CRON_MIN_ITERATIONS)
        iterations = (numclients < CLIENTS_CRON_MIN_ITERATIONS) ?
                     numclients : CLIENTS_CRON_MIN_ITERATIONS;


    int curr_peak_mem_usage_slot = g_pserver->unixtime % CLIENTS_PEAK_MEM_USAGE_SLOTS;
    /* Always zero the next sample, so that when we switch to that second, we'll
     * only register samples that are greater in that second without considering
     * the history of such slot.
     *
     * Note: our index may jump to any random position if serverCron() is not
     * called for some reason with the normal frequency, for instance because
     * some slow command is called taking multiple seconds to execute. In that
     * case our array may end containing data which is potentially older
     * than CLIENTS_PEAK_MEM_USAGE_SLOTS seconds: however this is not a problem
     * since here we want just to track if "recently" there were very expansive
     * clients from the POV of memory usage. */
    int zeroidx = (curr_peak_mem_usage_slot+1) % CLIENTS_PEAK_MEM_USAGE_SLOTS;
    ClientsPeakMemInput[zeroidx] = 0;
    ClientsPeakMemOutput[zeroidx] = 0;


    while(listLength(g_pserver->clients) && iterations--) {
        client *c;
        listNode *head;
        /* Rotate the list, take the current head, process.
         * This way if the client must be removed from the list it's the
         * first element and we don't incur into O(N) computation. */
        listRotateTailToHead(g_pserver->clients);
        head = (listNode*)listFirst(g_pserver->clients);
        c = (client*)listNodeValue(head);
        if (c->iel == iel)
        {
            fastlock_lock(&c->lock);
            /* The following functions do different service checks on the client.
            * The protocol is that they return non-zero if the client was
            * terminated. */
            if (clientsCronHandleTimeout(c,now)) continue;  // Client free'd so don't release the lock
            if (clientsCronResizeQueryBuffer(c)) goto LContinue;
            if (clientsCronTrackExpansiveClients(c, curr_peak_mem_usage_slot)) goto LContinue;
            if (clientsCronTrackClientsMemUsage(c)) goto LContinue;
            if (closeClientOnOutputBufferLimitReached(c, 0)) continue; // Client also free'd
            if (closeClientOnOverload(c)) continue;
        LContinue:
            fastlock_unlock(&c->lock);
        }