    # File lib/action_controller/session/mem_cache_store.rb, line 7
            def initialize(app, options = {})
              # Support old :expires option
              options[:expire_after] ||= options[:expires]

              super

              @default_options = {
                :namespace => 'rack:session',
                :memcache_server => 'localhost:11211'
              }.merge(@default_options)

              @pool = options[:cache] || MemCache.new(@default_options[:memcache_server], @default_options)
              unless @pool.servers.any? { |s| s.alive? }
                raise "#{self} unable to find server during initialization."
              end
              @mutex = Mutex.new

              super
            end