简单实现MySQL负载低时才继续运行任务，负载高的时候睡眠

public static function runSleep($sec = 10, $echo = null) {
    while (true) {
        $result = NoThingModel::getInstance()->db->select("show status like 'Threads_running'", [], false);
        $result = reset($result);
        if ($result) {
            if ($result->Variable_name == 'Threads_running') {
                if ($result->Value > 10) {
                    if ($echo) {
                        echo "sleep 10\n";
                    }
                    sleep($sec);
                } else {
                    break;
                }
            } else {
                break;
            }
        } else {
            break;
        }
    }
}