Hosting multiple domains from a single Rails app

Some of our reasons for doing this:

• Simplify the backend: server maintenance, releases, and hosting costs
• Repurpose existing CSS, images, javascript, etc
• Repurpose existing code (avoid complications of git submodules keeping shared code in sync between separate Rails apps)

However, we quickly realized that Rail’s doesn’t really support hosting a separate domain from the same app… at least, not out of the box. What we needed was the ability to use routing rules to specify that requests coming from our new domain, truecostofcredit.com, be directed to specific a Controller.

Fortunately, we came across a couple of extremely useful blog posts that helped solve this problem for us.
First, Jamis Buck gives this excellent clinic on the guts of Rails routing: Under the hood: route recognition in Rails
The most helpful resource for us was this: Rails routing based on hostname

We were able to adapt the code used in the above link for our purposes… allowing us to create custom routes that were conditioned on the domain name. Here’s what ended up in one of our initializers:

#
# This allows us to set up custom routes that depend on the domain or host of the request, ie:
# map.connect '', :controller => 'blah', :action => 'blah', :conditions => {:domain => 'blah'}
#
 
module ActionController
  module Routing
    class RouteSet
      def extract_request_environment(request)
        env = { :method => request.method }
        env[:domain] = request.domain if request.domain
        env[:host] = request.host if request.host          
        env
      end
    end
    class Route
      alias_method :old_recognition_conditions, :recognition_conditions
      def recognition_conditions
        result = old_recognition_conditions
        result << "conditions[:domain] === env[:domain]" if conditions[:domain]
        result << "conditions[:host] === env[:host]" if conditions[:host]        
        result
      end
    end
  end
end

Then, we could use this in our routes.rb in the following way:

  map.connect '', :controller => 'true_cost_calculator', :action => 'new', :conditions=>{ :domain=>'truecostofcredit.com' }

Thus… when someone visits truecostofcredit.com, they are directed to our TrueCostCalculatorController!

We loved this solution. It saved us a ton of time and effort, and kept our codebase nice and clean.