protected function expireRequests()
    {
        $now = TimeSupport::now();
        $expiredReqs = [];

        foreach ($this->reqs as $pid=>$request)
        {
            if ($now >= $request->getTimeout())
            {
                $expiredReqs[] = $request;
            }
        }

        foreach ($expiredReqs as $request)
        {
            unset($this->reqs[$request->getPid()]);
        }

        foreach ($expiredReqs as $request)
        {
            $request->cancel(new ThrowableProxy(new TimeoutException("RequestRecord has expired.")));
        }
    }