public function getConnection($connectionName = 'default')
    {
        if ($this->connections->containsKey($connectionName)) {
            return $this->connections->get($connectionName);
        }

        $configuration = $this->getConfiguration($connectionName);

        $this->connections->set($connectionName,
            $database = (new \OrientDB(
                $configuration->getHost(),
                $configuration->getPort(),
                $configuration->getTimeout()
            ))
        );
        $database->connect(
            $configuration->getUser(),
            $configuration->getPassword()
        );

        return $database;
    }