Bad Hostname Error?

[Maxim Dounin]

Hello!

On Wed, Dec 14, 2011 at 12:54:28AM +0200, Cabbar Duzayak wrote:

> Hi everyone,
> 
> Every once in a while, requests to my NGINX server are giving 500
> errors as with bad hostname responses for http://:
> 
> Can't connect to sub.mydomain.com:80 (Bad hostname: sub.mydomain.com)
> 
> It turned out to be an issue with the DNS server, i.e. my ubuntu box
> is failing to resolve this sub.mydomain.com address.
> 
> What I don't understand is that why is NGINX making an ns lookup for
> these requests??? Basically, when I make a request to this subdomain,
> it should be resolving the request using the request header and proxy
> it to localhost:81 or serving from local directory. And, I don't see
> any reason to perform an nslookup here?

The message you've provided suggests it's from your browser 
(proxy?), not from nginx.

> My config file is as follows:
> 
> server {
>         listen   80;
>         listen   [::]:80 default ipv6only=on; ## listen for ipv6
> 
>         server_name  sub.mydomain.com;
>         server_tokens off;
> 
>         access_log  /var/log/nginx/access.log;
>         error_log  /var/log/nginx/error.log info;
> 
>         location / {
>                 proxy_pass              http://localhost:81;
>                 proxy_set_header        X-Real-IP $remote_addr;
>                 proxy_set_header        X-Forwarded-For
> $proxy_add_x_forwarded_for;
>                 proxy_set_header        Host $http_host;
>         }
> 
>         location /html {
>                 alias /home/user/html/
>                 expires max;
>         }
> }
> 
> DNS lookups will slow the server down, and trying to understand what
> is going on here
> Thanks...

With such configuration nginx will only do a "localhost" name 
lookup once during configuration parsing.

Maxim Dounin