obj.ttl derived?

Kristian Lyngstol kristian at redpill-linpro.com
Mon Sep 14 21:45:34 CEST 2009


On Mon, Sep 14, 2009 at 12:43:20PM -0700, David Birdsong wrote:
> On Mon, Sep 14, 2009 at 12:38 PM, David Birdsong
> <david.birdsong at gmail.com> wrote:
> > awesome, thanks.  this explains poor cache-hit ratio.
> >
> > On Mon, Sep 14, 2009 at 12:22 PM, Kristian Lyngstol
> > <kristian at redpill-linpro.com> wrote:
> >> On Mon, Sep 14, 2009 at 11:57:25AM -0700, David Birdsong wrote:
> >>> How is obj.ttl derived when both Expires and max-age is set by the backends?
> >>>
> >>> We had a case where the backend was setting Expires to 60seconds after
> >>> the request and max-age was 5184000.  Additionally in vcl_fetch:
> >>>
> >>> sub vcl_fetch {
> >>>         if (obj.ttl < 9000s) {
> >>>                 set obj.ttl = 9000s;
> >>>         }
> >>> }
> >>>
> >>> What would obj.ttl be set to given the Expires and max-age contradiction?
> >>
> >> If s-maxage is set, use that as default, otherwise use max-age as default.
> >>
> >> If Expires is sooner than the default, use that.
> >>
> >> So in your example, the ttl should be 60s.
> oh, to clarify...
> 
> would the stanza in vcl_fetch override the obj.ttl which was set by
> the Expire header?
> sub vcl_fetch {
>        if (obj.ttl < 9000s) {
>                set obj.ttl = 9000s;
>        }
> }
> 
> or do I have the order wrong?

Ah, yes, it would, I misread the < as >, sorry about that.

But are you sure you're getting hits at all?

-- 
Kristian Lyngstøl
Redpill Linpro AS
Tlf: +47 21544179
Mob: +47 99014497
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