Unexpected error response

Server NGINX
1

I’m using Nginx as a front end proxy and have some config that checks
for a file called /maintenance.html and shows that if it’s present.

As our app is quite Ajaxy I would like return a 503 status when the
/maintenance.html page is served up so that the client app can do some
smarts to make things a bit more friendly for the end user.

This is the config that I currently have:

recursive_error_pages on;

location / {
  return 503;
  error_page 503 @tryMaintenance;
}

location @tryMaintenance {
  try_files /maintenance.html /tomcat_stopped.html
@resetResposeCodeAndForwardToRevolve;
}
location @resetResposeCodeAndForwardToRevolve {
  return 400;
  error_page 400 = @forwardToRevolve;
}

location @forwardToRevolve {
  proxy_pass http://revolve:2080;
  error_page 502 504 @serverDown;
}

location @serverDown {
  rewrite .* /server_down.html;
}

However when the maintenance.html file is not present I end up getting
the generic Nginx 503 error rather than the request getting forwarded on
to my backend server as I expected.

So I guess my question is - is this a bug or am I simply pushing the
boundaries of what is possible using error_page as a flow control
mechanism?

As an aside if I modify the location @tryMaintenance to the following,
the config does work even though they are basically the same.

location @tryMaintenance {
  try_files /maintenance.html /tomcat_stopped.html =400;
        error_page 400 = @forwardToRevolve;
}

Thanks

Oliver

Posted at Nginx Forum: