Rails dynamic domain and subdomain routes constraint

domain.rb

# -*- encoding : utf-8 -*-
class Domain < ActiveRecord::Base

  after_save :reload_routes

  def reload_routes
    if self.domain_changed?
      REDIS.set("rails_routes_ts", "expired")
    end
  end
end

routes.rb

# -*- encoding : utf-8 -*-
require 'subdomain'

scope :module => :lms do
	constraints(DomainConstraint.new) do
		#my routes
	end
end	

subdomain.rb

# -*- encoding : utf-8 -*-
class DomainConstraint

  STATIC_DOMAINS = %w{ vodeclic.com vodeclic.net vodeclic.dev }
  STATIC_SUB_DOMAINS = %w{ lms biblio ip c2i epn archimed }
  RESERVED_SUB_DOMAINS = %w{ www business app }

  def initialize
    generate_hosts
  end

  def generate_hosts
    dynamic_domains = Domain.select("DISTINCT domain").map(&:domain).uniq

    sanitized_dynamic_domains = dynamic_domains - domains_for(STATIC_DOMAINS, RESERVED_SUB_DOMAINS)

    domains = domains_for(STATIC_DOMAINS, STATIC_SUB_DOMAINS) | sanitized_dynamic_domains

    @hosts = domains | domains_for(domains, ["mobile"])

    set_timestamp
  end

  def set_timestamp
    REDIS.set("rails_routes_ts", Digest::MD5.hexdigest(@hosts.inspect))
  rescue
    warn "WARNING - Error in set_timestamp method, maybe redis is down? (method:#{__method__} in #{__FILE__}"
  end

  def matches?(request)
    check_if_expired_routes?

    @hosts.include?(request.host)
  rescue
    warn "WARNING - Error detecting Route auth for current domain #{request.host} (method:#{__method__} in #{__FILE__}"
    false
  end

  def domains_for(domains, subdomains)
    subdomains.product(domains).map{ |domain| domain.join "." }
  end

  def check_if_expired_routes?
    if REDIS.get("rails_routes_ts") != Digest::MD5.hexdigest(@hosts.inspect)
      generate_hosts
    end
  rescue
    warn "WARNING - Error in check_if_expired_routes? method, maybe redis is down? (method:#{__method__} in #{__FILE__}"
  end

end