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
>     -- 
>     ** * * UPLEX - Nils Goroll Systemoptimierung
>
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Thank you all, that explains a lot.
regards
Johan
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