def flush(now = false)
      if now || (@flush_counter -= 1) <= 0
        @modified_entries.each do |id, object|
          object.save
        end
        @modified_entries = ::Hash.new
        @flush_counter = @flush_delay
      end
      @flush_times += 1
    end
def flush(now = false)
      if now || (@flush_counter -= 1) <= 0
        @modified_entries.each do |id, object|
          object.save
        end
        @modified_entries = ::Hash.new
        @flush_counter = @flush_delay
      end
      @flush_times += 1
    end
Write all excess modified objects into the backing store. If now is true
 all modified objects will be written.
 @param now [Boolean]