Handle subdomains for a Clojure classified web app hosted on Heroku - heroku

Question

I have a classified clojure web app I want to host on Heroku. The domain is registered at Godaddy.
What would be the most effective and efficient way to have multiple subdomains:
newyork.classapp.com
montreal.classapp.com
paris.classapp.com
...
Users, all logic, should be shared across subdomains, so I'd love to have only one code base.
It would be easy to redirect subdomains to first level folder like this:
paris.classapp.com -> classapp.com/paris/
But I want users to keep seeing the subdomain while browsing the site, like this:
paris.classapp.com/cars/blue-car-to-sell
As opposed to this:classapp.com/paris/cars/blue-car-to-sell
What should I do?

Answer 1

Heroku support wildcard subdomains: https://devcenter.heroku.com/articles/custom-domains#wildcard-domains.
You will have in the host header the original domain, which you can use with something like (completely untested):
(GET "/" {{host "host"} :headers} (str "Welcomed to " host))
You could also create your own routing MW (completely untested):
(defn domain-routing [domain-routes-map]
(fn [req]
(when-let [route (get domain-routes-map (get-in req [:headers "host"]))]
(route req))))
And use it with something like:
(defroutes paris
(GET "/" [] "I am in Paris"))
(defroutes new-new-york
(GET "/" [] "I am in New New York"))
(def my-domain-specific-routes
(domain-routing {"paris.example.com" paris "newnewyork.example.com" new-new-york}))
And yet another option is to create a "mod-rewrite" MW that modifies the uri before getting to the Compojure routes:
(defn subdomain-mw [handler]
(fn [req]
(let [new-path (str (subdomain-from-host (get-in req [:headers "host"])
"/"
(:uri req))]
(handler (assoc req :uri new-path))))
(defroutes my-routes
(GET "/:subdomain/" [subdomain] (str "Welcomed to " subdomain))
Pick the one that suits your requirements.