public function getEnvVar($variable, $sshUrl, $refresh = false, $ttl = 3600)
    {
        $varName = $this->config->get('service.env_prefix') . $variable;
        $cacheKey = 'env-' . $sshUrl . '-' . $varName;
        $cached = $this->cache->fetch($cacheKey);
        if ($refresh || $cached === false) {
            $args = ['ssh'];
            $args = array_merge($args, $this->ssh->getSshArgs());
            $args[] = $sshUrl;
            $args[] = 'echo $' . $varName;
            $cached = $this->shellHelper->execute($args, null, true);
            $this->cache->save($cacheKey, $cached, $ttl);
        }

        return $cached ?: '';
    }