Conditional GET (was Re: caching using ETags to vary the content)

Poul-Henning Kamp phk at
Thu Nov 13 11:05:54 CET 2008

In message <491B513D.7010607 at>, Ryan Tomayko writes:
>On 11/12/08 3:19 AM, Ricardo Newbery wrote:

>Right. Sorry about the ambiguity in my original message. I'm asking
>specifically about Varnish using If-Modified-Since/If-None-Match to
>revalidate a stale cache entry with the backend.
>Can anyone say whether the lack of validation is due to a conscious
>design decision as opposed to something that just hasn't been
>implemented due to priority/time/resources?

Both, it hasn't been deemed important enough yet for it to happen.

>I'd be willing to take a crack at some of this if it's something that
>would be considered for inclusion in the project.

It's slightly involved, because presently we don't hold on to a
reference to the object that we might revalidate, so the change is
semi-nasty locking wise.

That said, we're happy to receive patches.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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