It is very simple to add multiple rails apps in your NginX server. Here I’m using an example of 2 rails apps with 3 mongrels serving each app. This is what you need to do in your nginx.conf.

…

upstream mongrel_app1 {
server 127.0.0.1:1000;
server 127.0.0.1:1001;
server 127.0.0.1:1002;
}

upstream mongrel_app2 {
server 127.0.0.1:2000;
server 127.0.0.1:2001;
server 127.0.0.1:2002;
}

Server {

….

if (!-f $request_filename) {
proxy_pass http://mongrel_app1;
break;
}

}

Server {

….

if (!-f $request_filename) {
proxy_pass http://mongrel_app2;
break;
}

}

If you’re not sure about the setting up of the entire rails stack, try this link.