Question

I have two servers, with identical minimal configuration (as far as I know!).

On server A, a query for
http://xxx.yyy.zzz.A/
returns the default nginx index.html page

On server B, a query for
http://xxx.yyy.zzz.B/
returns the default nginx index.html page

On server A, a query for
http://xxx.yyy.zzz.A/?%2F
returns the default nginx index.html page

On server B, a query for
http://xxx.yyy.zzz.B/?%2F
returns Error 324 (net::ERR_EMPTY_RESPONSE)

%2F is a CGI encoded forward slash, which is how I found this problem. It also seems to happen on %2G, %2H and %2I. I stopped testing here.

The 324 request does not show in access or error logs.

The relevant nginx.conf is

server {
  listen      80 default_server;
  server_name "";
  location / {
    root   html;
    index  index.html index.htm;
  }
}

What could possibly be the issue, or how could I further track it down?

Answer 1

Often problems like “hey this works half the time” or “this works on server A but not on server B” are loadbalancing/ proxy problems.

Did you check the configuration of your loadbalancer? Big chance something is wrong there and the errors are logged there.