Folks,
I have just tried to HEAD a web server, and have come across a few
issues around the use of head-pure-port:
1. What is the point of `head-pure-port'? The HTTP server should not
(must not?) send a body. Which means that once the port is purified,
`head-pure-port' returns nothing. So it was a bit silly of me to
expect anything in the first place (this is before I bumped into
connection persistence); maybe the documentation could ask the
potential user, "Didn't you really want to use `head-impure-port'?"
[So, in fact, I have issues with `head-impure-port']:
2. (port->string (head-impure-port
(string->url "http://www.bbc.co.uk/";)))
takes way too long to potentially preflight a website.
cpu time: 2578 real time: 29767 gc time: 125. This is due to
HTTP keep-alive. For anyone who hits this, may I suggest two
solutions:
- keep-alive can be overridden with '("Connection: Close")
passed as a header in `head-impure-port'
(port->string (head-impure-port
(string->url "http://www.bbc.co.uk/";)
'("Connection: Close")))
- if connection persistence is desirable (which I guess it usually
is), then read the header until an empty line:
(for/list ((p (in-port (curryr read-line 'return-linefeed)
(head-impure-port
(string->url "http://www.bbc.co.uk/";))))
#:break (string=? p ""))
p)
3. Poking around url.rkt, I notice that `http-conn-impure-port' makes
a pipe with a limit of 4096 bytes. http-client.rkt, which is directly
required by url.rkt, defines (but does not provide) `PIPE-SIZE' --
also 4096. Is there any merit in sharing this value between the
files?
Tim
--
Tim Brown <t...@timb.net> ▪ +447771714159
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