Subdomain Checker

routes.rb

Rails::Application.routes.draw do
  # Limits the admin site only on the admin subdomain
  constraints subdomain: /^admin/ do
    ActiveAdmin.routes(self)

    # Make resque only available to the admin users & redirect to admin login
    # if trying to access resque without being logged in.
    match('/admin/resque/admin/login' => redirect('/admin/login'))
    authenticate :admin_user do
      mount Resque::Server.new, :at => "/admin/resque"
    end

    devise_for :admin_users, ActiveAdmin::Devise.config
  end
end

subdomain_checker.rb

class SubdomainChecker
  def self.matches?(request)
    Rails.logger.info "SubdomainChecker: Subdomain: '#{request.subdomain}' Host: '#{request.host}'"
    subdomain = request.subdomain
    subdomain.to_s =~ /^((?!www)(?!app)(?!admin).)/
  end  
end