Varnish and max-age=0

[Reza Naghibi]

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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