def connect
      if sentinel?
        auto_retry_with_timeout do
          discover_slave
          begin
            connect_without_sentinel
          rescue => e
            @failed ||= []
            f = "#{@options[:host]}:#{@options[:port]}"
            @failed.delete(f)
            @failed.push(f) # 必ず末尾に追加する
            raise e
          else
            @failed.delete("#{@options[:host]}:#{@options[:port]}") if @failed
          end
        end
      else
        connect_without_sentinel
      end
    end
def connect
      if sentinel?
        auto_retry_with_timeout do
          discover_slave
          begin
            connect_without_sentinel
          rescue => e
            @failed ||= []
            f = "#{@options[:host]}:#{@options[:port]}"
            @failed.delete(f)
            @failed.push(f) # 必ず末尾に追加する
            raise e
          else
            @failed.delete("#{@options[:host]}:#{@options[:port]}") if @failed
          end
        end
      else
        connect_without_sentinel
      end
    end
override Redis::Client#connect overwritten by redis-sentinel
 https://github.com/flyerhzm/redis-sentinel/blob/master/lib/redis-sentinel/client.rb#L24