502 Bad Gateway

都会导致这个结果，也会因为无法建立新连接而返回 502， the port may not be listening， or a firewall may be dropping connections from the edge. A heavily loaded origin — or one under attack traffic — can also refuse new connections and surface as a 502. ，源站正处于高负载或遭受攻击流量冲击时。

发生了什么 What happened 源站进程崩溃或已停止、监听端口未开放、防火墙拦截了回源连接，。

The origin process may have crashed or stopped。