public function refresh(Client $client)
    {
        $clientId = $client->getId();
        $this->clients[$clientId] = $client;
        $this->removeClientForRequest($clientId, $client->getPreviousRequest());

        $requestId = $client->getRequest();
        if ($requestId  !== null) {
            if (!isset($this->requests[$requestId])) {
                $this->requests[$requestId] = array();
            }
            $this->requests[$requestId][$clientId] = $client;
            $this->clientRequest[$clientId] = $requestId;
        }

        return $this;
    }