Mailing List Archive: Management of HEAD requests

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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.

A (mostly) happy user since 1998.

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