private function prepareCustomVariables()
    {
        if ($this->validationServiceId != null) {
            $serviceId = $this->validationServiceId;
        } else {
            $serviceId = $this->scopeConfig->getValue(Config::XML_FASTLY_SERVICE_ID);
        }

        $customVars =  [
            // Service ID
            'cd1'   =>  $serviceId,
            // isAPIKeyValid
            'cd2'   =>  ($this->isApiKeyValid()) ? 'yes' : 'no',
            // Website name
            'cd3'   =>  $this->getWebsiteName(),
            // Site domain
            'cd4'   =>  $this->request->getServer('HTTP_HOST'),
            // Site location
            'cd5'   =>  $this->getSiteLocation(),
            // Fastly module version
            'cd6'   =>  $this->helper->getModuleVersion(),
            // Fastly CID
            'cd7'   =>  $this->config->getCID(),
            // Anti spam protection
            'cd8'   =>  'fastlyext'
        ];

        return $customVars;
    }