Lesson 27 · The Connection header - Build an HTTP Client

The Connection header

A client needs to know whether to keep the connection open or close it after a response, and the answer depends on both the Connection header and the HTTP version. Today you encode that full rule.

The goal

Decide whether to close the connection after a response, honoring the version-dependent default and the Connection header.

Start here - the target

TO DO

Scenario: Deciding whether to close the connection

Givenan HTTP/1.1 response with no Connection header

WhenShouldClose is checked

Thenit is false - HTTP/1.1 keeps the connection alive by default

Andan HTTP/1.1 response with Connection "close" gives true; an HTTP/1.0 response with no Connection header gives true (1.0 closes by default); an HTTP/1.0 response with Connection "keep-alive" gives false

Background

Whether a connection stays open after a response depends on two things: the Connection header and the HTTP version. In HTTP/1.1 connections are persistent by default - a server keeps the socket open unless it sends Connection: close. In HTTP/1.0 the default is the opposite: the connection closes after each response unless the server opts in with Connection: keep-alive. Your client has to honor both defaults to know whether it may send another request on the same connection.

So ShouldClose is a small decision tree: if Connection says close, close; else if the response is HTTP/1.1, keep it open; else (HTTP/1.0) close unless Connection says keep-alive. Compare the header value case-insensitively, like every header. This is the flag a real client consults before reusing a connection, and getting the version-dependent default right is what keeps it from hanging on a 1.0 server or needlessly redialing a 1.1 one.

Make it work

// the rule, in order:
//   Connection contains "close"      -> true  (close)
//   version is HTTP/1.1 (or later)   -> false (persistent)
//   version is HTTP/1.0              -> true UNLESS Connection
//                                       contains "keep-alive"
// compare the Connection value case-insensitively.
func (r *Response) ShouldClose() bool {
  // branch on Connection value, then on Version
}

CheckpointDONE

The client applies the full persistence rule to decide whether to reuse or close. Commit and stop here.