Async DNS redux

[Lars Ingebrigtsen <larsi@gnus.org>]

I was reading a blog just now, and apparently CloudFlare has a hickup:

larsi@rusty:~/mgnus$ time host www.thisiscolossal.com
www.thisiscolossal.com is an alias for www.thisiscolossal.com.cdn.cloudflare.net.
www.thisiscolossal.com.cdn.cloudflare.net is an alias for cf-ssl4799-protected-www.thisiscolossal.com.cdn.cloudflare.net.
cf-ssl4799-protected-www.thisiscolossal.com.cdn.cloudflare.net has address 141.101.125.141
cf-ssl4799-protected-www.thisiscolossal.com.cdn.cloudflare.net has address 141.101.126.141
;; connection timed out; no servers could be reached
;; connection timed out; no servers could be reached

real	0m20.134s
user	0m0.012s
sys	0m0.000s

This made using Emacs impossible.  The resolving is totally synchronous,
and there were many pictures from this host.  Every one halting Emacs
for 20 seconds.

I'm going to try to fix up url-retrieve-queue somewhat -- if resolving
failed for host foo, then just remove all entries from the queue that
are trying to do the same.  Hm.  But since it fetches a lot of stuff in
parallel, that may not be trivial.  Uhm...

Anyway, what I wanted to ask was whether anybody has had any further
ideas on async DNS resolving in Emacs?  For stuff like this to work in a
satisfactory manner, we really need a kind of
(dns-resolve "foo.bar" 'callback) call in Emacs.

Does gnulib or anything have anything handy here?  :-)

-- 
(domestic pets only, the antidote for overdose, milk.)
  http://lars.ingebrigtsen.no  *  Sent from my Rome