Use IronCache as a Rack::Cache metastore with Rails 3.2 on Heroku

iron_cache_metastore.rb

require 'rack/cache'
require 'rack/cache/storage'
require 'rack/cache/metastore'

require 'iron_cache'

class IronCache::MetaStore < Rack::Cache::MetaStore

  def initialize
    @cache = IronCache::Client.new.cache('metastore')
  end

  def read key
    obj = @cache.get hexdigest(key)
    obj ? Marshal.load(obj.value) : []
  end

  def write key, negotiations
    @cache.put hexdigest(key), Marshal.dump(negotiations)
  end

  def purge key
    @cache.delete hexdigest(key)
  end


  def self.resolve(uri)
    new
  end
end

class Rack::Cache::MetaStore
  if ENV['RAILS_GROUPS'] == 'assets'
    IRCONCACHE = Rack::Cache::MetaStore::Heap
  else
    IRONCACHE = IronCache::MetaStore
  end
end

production.rb

#
#
#
config.action_dispatch.rack_cache = {
  :metastore    => 'ironcache:/',
  :entitystore  => 'file:tmp/cache/rack/body',
  :allow_reload => false
}
#
#
#