[Chandler-dev] Use of OPTIONS instead of PROPFIND

[Jared Rhine]

What follows is an inquiry about the advisability and effort of using 
HTTP "OPTIONS" instead of "PROPFIND" for Chandler to determine if a 
given URL is a DAV URL.  The inquiry is primarily directed to Morgen.

I've spent a couple days looking at the server-side of a real-world 
Morse Code driven service looks like.  The standard pattern for a 
synchronization is a 4-transaction HTTP set:

71.202.115.113 - - [16/May/2007:13:45:17 -0700] "PROPFIND 
/pim/collection/723886a6-705d-11db-8ee8-99b22f7fce88?ticket=1zaf4xxac0 
HTTP/1.1" 501 1238 "-" "Chandler/0.7.dev-r14332 (Linux; U; i386; en_US)"

71.202.115.113 - - [16/May/2007:13:45:17 -0700] "HEAD 
/pim/collection/723886a6-705d-11db-8ee8-99b22f7fce88?ticket=1zaf4xxac0 
HTTP/1.1" 200 - "-" "Chandler/0.7.dev-r14332 (Linux; U; i386; en_US)"

71.202.115.113 - - [16/May/2007:13:45:17 -0700] "GET 
/pim/collection/723886a6-705d-11db-8ee8-99b22f7fce88?ticket=1zaf4xxac0 
HTTP/1.1" 200 5533 "-" "Chandler/0.7.dev-r14332 (Linux; U; i386; en_US)"

71.202.115.113 - - [16/May/2007:13:45:17 -0700] "GET 
/mc/collection/723886a6-705d-11db-8ee8-99b22f7fce88 HTTP/1.1" 200 
1243606 "-" "Chandler/0.7.dev-r14332 (Linux; U; i386; en_US)"

So, it's a PROPFIND + HEAD + GET /pim + GET /mc.

The initial PROPFIND operation helps Chandler determine if it's working 
with a DAV-based URL.

Essentially every Chandler-driven PROPFIND against the server will fail. 
  This is per the design.

However, it tweaks a little muscle in my sysadmin head: looking for 5xx 
errors in an access log is one of the primary ways to tell if something 
is breaking on the server.  You better pay attention if that metric 
suddenly spikes.

So I've a mild aversion to a regular, everyday operation generating what 
looks like an exception condition.

All Chandler is trying to do is figure out if the URL is a DAV URL. 
There's already a standard WebDAV mechanism to determine this; it's the 
HTTP OPTIONS method.

I hesitate to even ask the question as what we have now works, and it'd 
be a Morgen task, and Morgen is quite the busy camper these days.  But 
the question is out there now, and I'm guessing I'll get a pretty 
reasonable answer that a good balance of these concerns.

Thoughts?

-- Jared