Varnish and max-age=0

[Reza Naghibi]

Can you provide the varnishlog for a request which isnt getting cached?

--
Reza Naghibi
Varnish Software

On Thu, Jul 20, 2017 at 2:03 PM, Girouard, Yanick <Yanick.Girouard at stm.info>
wrote:

> Hi Reza,
>
>
>
> Yes we are. Here's the default we apply. Those two subs are called in
> order in vcl_backend_response:
>
>
>
> /* REMOVE CACHE-CONTROL AND SURROGATE-CONTROL FROM BACKEND *
>
> ***********************************************************/
>
> sub stm_backend_resp_unset_cache_control_headers {
>
>                 unset beresp.http.Surrogate-Control;
>
>                 unset beresp.http.Cache-Control;
>
>                 unset beresp.http.Expires;
>
> }
>
>
>
> /* DEFAULT ALL TO: TTL 30MIN + GRACE 15MIN *
>
> *******************************************/
>
> sub stm_backend_resp_expiration_default {
>
>                 set beresp.ttl = 30m;
>
>                 set beresp.grace = 15m;
>
> }
>
>
>
> That doesn't seem to have any impact when the backend responds with a
> Cache-Control: max-age=0 header.
>
>
>
> Any idea?
>
>
>
>
>
> *De :* Reza Naghibi [mailto:reza at varnish-software.com]
> *Envoyé :* jeudi 20 juillet 2017 13:58
> *À :* Girouard, Yanick <Yanick.Girouard at stm.info>
> *Cc :* varnish-misc at varnish-cache.org
> *Objet :* Re: Varnish and max-age=0
>
>
>
> The TTL is calculated before entering vcl_backend_response. So eventhough
> you unset the Cache-Control header, the value of TTL will be calculated
> based on it. Are you setting a new value for beresp.ttl? You need to do
> that:
>
>
>
> sub vcl_backend_response
>
> {
>
>   unset beresp.http.Cache-Control;
>
>   set beresp.ttl = 120s;
>
> }
>
>
> --
> Reza Naghibi
> Varnish Software
>
>
>
> On Thu, Jul 20, 2017 at 1:44 PM, Girouard, Yanick <
> Yanick.Girouard at stm.info> wrote:
>
> Hi,
>
>
>
> We use Varnish to cache for multiple backends and need Varnish to *always*
> control what is cached despite what backends could respond. In other words,
> even if a backend sets Cache-Control headers to never cache its pages, we
> still want Varnish to cache them based on defined rules (i.e. certain URL
> patterns or hosts have different TTLs).
>
>
>
> We have recently realized that one of our backend always set the following
> header: *Cache-Control: max-age=0, private, must-revalidate*
>
>
>
> Our VCL unsets the Cache-Control header in vcl_backend_response and sets
> its own before delivering. By unsetting the Cache-Control header in
> vcl_backend_response I would expect Varnish to ignore the max-age=0 value
> and still cache the page as per our other rules, but it seems that the
> second it sees max-age=*0 *in the response header, that it makrs the
> object as not cacheable.
>
>
>
> Other than by changing the backend's response to never set max-age=0, is
> there a way to force Varnish to cach pages even if it returned max-age=0?
>
>
>
> Is this even by design or is it a bug?
>
>
>
> Thanks,
>
> *Yanick Girouard*
>
>
>
>
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>
>
>
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