[emerg]: invalid parameter "backup" error on Ubuntu

[Maxim Dounin]

Hello!

On Tue, Sep 08, 2009 at 11:49:07AM -0400, stefancaunter wrote:

> By hostname do you mean "http://backend" (upstream name) ?
> 
> proxy_pass http://backend;

Directive proxy_pass accepts either upstream name as defined 
earlier via upstream{} block or backend hostname (or ip, or unix 
socket).  In the later case it implicitly creates upstream 
block with single server inside.

Therefore this will work as expected:

http {
    upstream backend {
        server 192.168.0.1:80;
        server 192.168.0.2:80 backup;
    }

    server {
        ...
        location / {
            proxy_pass http://backend;
        }
    }
}

And this will fail claiming it can't use "backup", as nginx will 
interpret "backend" string as hostname that should be resolved via 
DNS and will be confused by "upstream backend { ... }" that comes 
later on:

http {
    server {
        ...
        location / {
            proxy_pass http://backend;
        }
    }

    upstream backend {
        server 192.168.0.1:80;
        server 192.168.0.2:80 backup;
    }
}

Maxim Dounin