public function onClientMessage(MessageInterface $msg, $routing)
    {
        $client = $this->client(array_shift($routing));

        if ($msg instanceof ExecuteRequest) {
            $this->clientRequest($client, $msg);

            return;
        }

        if ($msg instanceof FetchRequest) {
            $this->clientFetch($client, $msg);

            return;
        }

        $this->getLogger()->info('Invalid message type: '.get_class($msg).'.');
    }