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

Answer 2

Since Rails 5 you can use the config public_file_server.headers in the configuration file of the corresponding environment that you want to apply the desired headers, for example:

    # in config/environments/production.rb
    config.public_file_server.headers = {
     "Cache-Control" => "public, max-age=31536000"
    }

The above snippet will configure the Cache-Control header with public, max-age=31536000 value for you assets in the production environment. You can also set any custom headers.