And waits for them. That's pointless.
{
    if (!queue_update_in_progress)
    {
        last_queue_update_start_time.store(time(nullptr));
        queue_update_in_progress = true;
    }
    try
    {
        queue.pullLogsToQueue(getZooKeeper(), queue_updating_task->getWatchCallback());
        last_queue_update_finish_time.store(time(nullptr));
        queue_update_in_progress = false;
    }
    catch (const Coordination::Exception & e)
    {
        tryLogCurrentException(log, __PRETTY_FUNCTION__);
        if (e.code == Coordination::Error::ZSESSIONEXPIRED)
        {
            restarting_thread.wakeup();
            return;
        }
        queue_updating_task->scheduleAfter(QUEUE_UPDATE_ERROR_SLEEP_MS);
    }
    catch (...)
    {
        tryLogCurrentException(log, __PRETTY_FUNCTION__);
        queue_updating_task->scheduleAfter(QUEUE_UPDATE_ERROR_SLEEP_MS);
    }
}
void StorageReplicatedMergeTree::mutationsUpdatingTask()