Setting Custom Headers for Assets in Rails on Heroku Cedar

Question

I have a cedar application that uses Rails 4.0 and the asset pipeline. I'd like to set custom headers for all assets from the asset pipeline. How can this be done?

Answer 1

An easy way would be to use a rack plugin, something like this:

class RackAssetFilter
   def initialize app
      @app = app
   end

   def call env
      @status, @headers, @body = @app.call env
      if env['PATH_INFO'].starts_with?( "/assets/" )
         @headers['X-Header-1'] = 'value'
         # ... 
      end
      return [@status, @headers, @body]
   end
end

To enable it, in application.rb:

config.middleware.insert_before( ActionDispatch::Static, RackAssetFilter )

Keep in mind you need to declare or load the RackAssetFilter via require before you insert it into the middleware stack in application.rb