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

Ryan Tomayko r at
Wed Nov 12 22:57:17 CET 2008

On 11/12/08 3:19 AM, Ricardo Newbery wrote:
> Unless this has changed with 2.0, varnish will *respond* to if- 
> modified-since (IMS) with a 304 response if there is cached entry that  
> fails this condition, but varnish will neither *pass* the IMS header  
> to the backend (unless you customize the vcl) nor *generate* an IMS to  
> the backend.

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?

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.


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