Conditional Requests (revisited)

Brian Smith brian at
Mon May 5 21:12:31 CEST 2008

I have several questions regarding conditional requests in Varnish. (I have 
read many messages in the archives already and I've read as much VCL 
documentation as I could find.)

(1) I have a back-end that is very fast for validating ETags and generating 
304 Not Modified, but very slow when it has to return a new response body. 
My understanding is that Varnish will never send conditional requests to the 
backend, and it cannot use a 304 response to update the freshness 
information for an already-cached response. Is that correct? If so, is there 
a way to do that in VCL? Would you be willing to accept patches to implement 
that behavior in the core?

(2) I would like to cache entities with max-age=0 by using the logic from 
(1) above to always revalidate the cached representation with the back-end. 
What is the VCL code for doing this? If this is not possible, would you 
accept a patch to make this possible?


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