[wp-trac] [WordPress Trac] #14348: If it's a HEAD request, stop after the head!

[WordPress Trac]

#14348: If it's a HEAD request, stop after the head!
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 Reporter:  mitchoyoshitaka                  |       Owner:
     Type:  enhancement                      |      Status:  new
 Priority:  normal                           |   Milestone:  3.3
Component:  Performance                      |     Version:  3.0
 Severity:  normal                           |  Resolution:
 Keywords:  has-patch 3.3-early 2nd-opinion  |
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Changes (by mbijon):

 * keywords:  has-patch 3.3-early => has-patch 3.3-early 2nd-opinion


Comment:

 It's not only feeds, but do_robots() (called for robots.txt) that get a
 lot of HEAD requests. On this count either attachment:14348.diff or
 template_redirect seem better than template_include.

 I tested using Fiddler to send HEAD requests & compare the two that "seem
 better".

 Any change on this ticket will require some plugin updates, but
 template_redirect seems like the option with better workaround vs
 attachment:14348.diff

 ----

 == Feed Tests ==

 attachment:14348.diff doesn't respond with the expected 302 redirect in
 most feed plugins, instead it sends a 200. Then the time in the 200
 response to HEAD doesn't match the ones in a follow-up 302 > 200 sequence
 sent to a GET.
 * BTW, I checked 5 higher-rated ones & they mainly seem to hook
 send_headers or template_redirect
   * If we use template_redirect then send_headers could be hooked to fix
 any broken plugins. With the other option, any feed plugins would need to
 negate this whole tweak with $exit_on_http_head
 * Also tested the old Feedburner FeedSmith. It breaks because it hooks
 template_redirect
   * This plugin is still out there semi-frequently & isn't likely to get
 updated either


 == Robots Tests ==

 I also tested several robots.txt plugins and they all work as expected
 with either attachment:14348.diff or template_redirect.
 * The only odd thing was one plugin that logs the requester/bot from
 do_robot. Currently it logs both on HEAD & GET requests.
   * Either of the performant fixes limits logging to only GETs (but that's
 what I personally would have expected).
 (FYI that I did this testing on a 3.2.1 setup. Robots.txt requests failed
 with a 404 to either GET/HEAD, from [18776], but I wasn't sure if that was
 due to the plugins not being 3.3 compatible yet. '''Could someone else
 confirm if this might be a bug in do_robots()?''')


 == Caching tests ==

 Caching plugins do play here too, but the two biggest aren't impacted.
 They both handle HEAD requests in their own ways:
 * One responds directly to HEAD based on cached files or an internal GET &
 won't break on either change
 * The other has an odd execution path (& I was too lazy to follow it) but
 in testing it responded to repeat GET/HEAD requests fine whether the
 initially cached request was a HEAD or GET

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Ticket URL: <http://core.trac.wordpress.org/ticket/14348#comment:21>
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