[Varnish 4] Respecting client's Cache-Control: max-age= as TTL

[Guillaume Quintard]

On github I pointed to the doc explaining how you can return(fetch) to
ignore a cached object, possibly based on ttl, so you already have half the
answer.

The other part of the equation is just converting req.http.cache-control to
a duration and comparing that to obj.ttl. It will be similar to what you
have done on v3.

-- 
Guillaume Quintard

On Jul 31, 2017 18:25, "Martynas Jusevičius" <martynas at atomgraph.com> wrote:

> Hi,
>
> I have been reading quite a bit about Varnish and VCL but found almost no
> examples with Cache-Control coming from the client request [1].
>
> What I want to achieve: if the client sends Cache-Control: max-age=60, TTL
> becomes 60 s. If the cache hit is fresher than 60 s, deliver it, otherwise
> fetch a new response from backend (I hope I'm not misusing the VCL terms
> here) *and* cache it.
>
> I had hacked this together in the vcl_fetch section in Varnish 3.x by
> setting the req.http.Cache-Control max-age value as beresp.ttl, but
> vcl_fetch is gone in Varnish 4.x.
>
> I have received a suggestion to use vcl_hit and/or grace [2], but again --
> no examples...
>
> Could anyone provide some VCL pseudo-code that uses req.http.Cache-Control
> value to override TTL? max-age number parsing not necessary, I have figure
> that out.
>
> Thanks,
>
> Martynas
>
> [1] https://developer.mozilla.org/en-US/docs/Web/HTTP/
> Headers/Cache-Control#Cache_request_directives
> [2] https://github.com/varnishcache/varnish-cache/
> issues/2014#issuecomment-319096566
>
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