class RedisClient::RubyConnection

def connect
  socket = if @config.path
    UNIXSocket.new(@config.path)
  else
    sock = if SUPPORTS_RESOLV_TIMEOUT
      begin
        Socket.tcp(@config.host, @config.port, connect_timeout: @connect_timeout, resolv_timeout: @connect_timeout)
      rescue Errno::ETIMEDOUT => timeout_error
        timeout_error.message << ": #{@connect_timeout}s"
        raise
      end
    else
      Socket.tcp(@config.host, @config.port, connect_timeout: @connect_timeout)
    end
    # disables Nagle's Algorithm, prevents multiple round trips with MULTI
    sock.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
    enable_socket_keep_alive(sock)
    sock
  end
  if @config.ssl
    socket = OpenSSL::SSL::SSLSocket.new(socket, @config.ssl_context)
    socket.hostname = @config.host
    loop do
      case status = socket.connect_nonblock(exception: false)
      when :wait_readable
        socket.to_io.wait_readable(@connect_timeout) or raise CannotConnectError.with_config("", config)
      when :wait_writable
        socket.to_io.wait_writable(@connect_timeout) or raise CannotConnectError.with_config("", config)
      when socket
        break
      else
        raise "Unexpected `connect_nonblock` return: #{status.inspect}"
      end
    end
  end
  @io = BufferedIO.new(
    socket,
    read_timeout: @read_timeout,
    write_timeout: @write_timeout,
  )
  true
rescue SystemCallError, OpenSSL::SSL::SSLError, SocketError => error
  socket&.close
  raise CannotConnectError, error.message, error.backtrace
end