[Zope] Management of HEAD requests

[Tres Seaver]

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On 03/15/2011 08:39 AM, Jesus Cea wrote:
> Using Zope 2.10 here.
> 
> When making a HEAD request, I get the "last-modified" time of the
> script, and an "application/octet-stream" content type. The content
> length is the script length.
> 
> When doing a GET request, I get a "last-modified" time of "now" and a
> "text/html" content type. And the length is correct here.
> 
> As far as I know, the HEAD doesn't reach the script, it is processed
> inside Zope. I would rather prefer to actually process the script but
> give back only the headers.
> 
> That is, my problem is that HEAD and GET of the same object provide
> completely different information about different objects (HEAD gives
> info about the actual script, GET gives info of the script output). This
> could be even a privacy issue, giving out script details people don't
> need to know.
> 
> Is there any way to override this?. Suggestion?
> 
> I have issues, for instance, managing RSS feeds, since some clients do a
> HEAD request instead of a conditional GET, for detecting new entries.
> 
> Thanks in advance, folks.

The default HED implementation is in 'webdav.Resource':  it makes some
assumptions which are not appropriate.  You can override it for your own
content objects:  here is what App.ImageFile does::

    security.declarePublic('HEAD')
    def HEAD(self, REQUEST, RESPONSE):
        """ """
        RESPONSE.setHeader('Content-Type', self.content_type)
        RESPONSE.setHeader('Last-Modified', self.lmh)
        return ''

IMNSHO, there is absolutely no general way for a dynamic application to
satisfy clients that use HEAD instead of conditional get:  the semantics
they rely on are meaningless for dynamically generated content.


Tres.
- -- 
===================================================================
Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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