Preventing Caching in Varnish Based on Backend Response Header

[Uday Kumar]

May I know if there is any way to find the best possible TTL?
I meant to ask for uncacheable objects

*Thanks & Regards,*
*Uday Kumar*


On Tue, Jun 11, 2024 at 4:11 PM Uday Kumar <uday.polu at indiamart.com> wrote:

> Hello Guillaume,
> We have made required changes at our end, but we have doubt on giving
> suitable TTL for uncacheable objects
>
> if (beresp.http.Cache-Control ~ "no-cache") {
>         set beresp.ttl = *doubt*;
>         set beresp.uncacheable = true;
> }
>
> FYI;
> we have ttl of 24hrs for normal objects which are cacheable
>
> May I know if there is any way to find the best possible TTL?
>
> *Thanks & Regards,*
> *Uday Kumar*
>
>
> On Tue, May 28, 2024 at 7:07 PM Uday Kumar <uday.polu at indiamart.com>
> wrote:
>
>> Hello Guillaume,
>> Great to know about this, it should work for us!
>> will check this out
>>
>> *Thanks & Regards,*
>> *Uday Kumar*
>>
>>
>> On Tue, May 28, 2024 at 5:53 PM Guillaume Quintard <
>> guillaume.quintard at gmail.com> wrote:
>>
>>> Hi Uday,
>>>
>>> Sure, the classic practice will do nicely:
>>>
>>> sub vcl_backend_response {
>>>     if (beresp.http.that-specific-header) {
>>>         # TTL should match the time during which that header is unlikely
>>> to change
>>>         # do NOT set it to 0s or less (
>>> https://info.varnish-software.com/blog/hit-for-miss-and-why-a-null-ttl-is-bad-for-you
>>> )
>>>         set beresp.ttl = 2m;
>>>         set beresp.uncacheable = true;
>>>         return (deliver);
>>>     }
>>> }
>>>
>>> The main trick here is beresp.uncacheable, you do not have to return
>>> immediately if you still have modifications/checks to do on that response.
>>>
>>> Would that work for you?
>>>
>>> --
>>> Guillaume Quintard
>>>
>>>
>>> On Tue, May 28, 2024 at 4:55 AM Uday Kumar <uday.polu at indiamart.com>
>>> wrote:
>>>
>>>> Hello all,
>>>>
>>>> We need to prevent caching in Varnish based on a specific header from
>>>> the backend.
>>>>
>>>> Could you please suggest the best approach to achieve this?
>>>>
>>>>
>>>> *Thanks & Regards,*
>>>> *Uday Kumar*
>>>> _______________________________________________
>>>> varnish-misc mailing list
>>>> varnish-misc at varnish-cache.org
>>>> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>>>>
>>>
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