Q: How to make a node app route to different subdomains? I use OpenShift Paas, I got a node.js application which got a custom domain. As  my site logic will got a general public web site, a blog site and an store site I want to have:
example.com
blog.example.com
store.example.com

About domain names this is not a problem, I got godaddy as domain name vendor and I simply added a CNAME record for general site. I think I will add proper aliases to same OpenShift domain name.
What I want so, is to make node within one only app attending each.
Being the JavaScript code about routes this:
self.createRoutes = function() {
        self.routes = { };

        self.routes['/'] = function(req, res) {
            res.setHeader('Content-Type', 'text/html');
            res.send(self.cache_get('index.html') );
        };
    };


    /**
     *  Initialize the server (express) and create the routes and register
     *  the handlers.
     */
    self.initializeServer = function() {
        self.createRoutes();
        self.app = express();
        self.app.use(express.static(__dirname + '/public'));
        //  Add handlers for the app (from the routes).
        for (var r in self.routes) {
            self.app.get(r, self.routes[r]);
        }
    };

Would the configuration be over there? 
Would it be really necessary to have another app (node instance) even if it only will print "Hello World!"?
