fetch

# File lib/drb/timeridconv.rb, line 38
      def fetch(key, dv=@sentinel)
        synchronize do
          rotate
          obj = peek(key)
          if obj == @sentinel
            return dv unless dv == @sentinel
            raise InvalidIndexError
          end
          @renew[key] = obj # KeepIt
          return obj
        end
      end