该句使用了由关系代词引导的定语从句，用以详细描述需要识别的对象。
What happened?
Your origin server reported a gateway error. Please contact your hosting provider to troubleshoot the following common causes on your origin web server:
1: Ensure that the origin server responds to requests for the hostname and domain in the visitor’s URL that caused the 502 or 504 error.
2: Check for excessive server loads, crashes, or network failures.
3: Identify applications or services that have timed out or have been blocked.
发生了什么？
您的源服务器报告了网关错误。请联系您的主机服务提供商，排查源站服务器中以下常见原因：
1：确保源服务器能够响应访问者请求中的主机名和域名，以避免触发502或504错误。
2：检查服务器是否存在负载过高、崩溃或网络故障等问题。
3：排查是否有应用程序或服务出现超时，或者被阻止访问的情况。