TTL <=0 ?
Johan Hendriks
joh.hendriks at gmail.com
Fri Sep 30 12:45:36 UTC 2022
On 27/09/2022 18:00, Guillaume Quintard wrote:
> One minor addition to Geoff's excellent answer: you may want to try
> this VCL: https://docs.varnish-software.com/tutorials/hit-miss-logging/
> Specially at the beginning it helps knowing what happened to the request.
>
> --
> Guillaume Quintard
>
>
> On Tue, Sep 27, 2022 at 6:33 AM Geoff Simmons <geoff at uplex.de> wrote:
>
> On 9/27/22 15:07, Johan Hendriks wrote:
> > Hello all, varnish tells me that the TTL is smaller or equal to
> 0, but
> > looking at the response headers that is not the case as the
> BerespHeader
> > has Expires: Wed, 27 Sep 2023 12:23:11 GMT which is in 2023!
> >
> > - Begin bereq 8203147 pass
>
> The request was set to pass on the client side; that sets
> bereq.uncacheable=true, which is passed along to the backend side as
> beresp.uncacheable=true.
>
> The Expires response header (and also Cache-Control in your example)
> might at least tell browser caches that they can cache the
> response. But
> Varnish won't cache it.
>
> [...]
> > - BereqHeader Cookie: _sharedid=redacted; cto_bundle=redacted
> [...]
>
> > Am i right that the TTL is <=0 because it sends a cookie to the
> backend?
>
> If you haven't changed this part of builtin.vcl, then yes:
>
> sub vcl_req_cookie {
> if (req.http.Cookie) {
> # Risky to cache by default.
> return (pass);
> }
> }
>
> If a request/response has a property such as a Cookie header, and a
> number of other things that suggest that the response may be
> personalized, then it can't take the chance of caching it by default.
> That can be one of the worst mistakes you can make with a caching
> proxy.
>
> So if you need to be able to cache despite the presence of
> cookies, as
> do many sites these days, you need to write rules for that in VCL.
> Default VCL has to make the safest choice.
>
>
> Best,
> Geoff
> --
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Thank you all, that explains a lot.
regards
Johan
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