obj.ttl derived?

Kristian Lyngstol kristian at redpill-linpro.com
Mon Sep 14 22:01:14 CEST 2009

On Mon, Sep 14, 2009 at 12:52:15PM -0700, David Birdsong wrote:

(snip snip)

> > But are you sure you're getting hits at all?
> varnistat shows hitrate around .54 for 10 and 1000 second averages.  N
> expired objects is anywhere between 10-40 second though and varnishd
> has only been running for about 12 hours.  i expect the hit rate to
> drop sharply as peak traffic continues to diminish for the day.

Depending on the content, that might be a very low hit-rate.

> i think a 9000s obj.ttl is a complete mistake on our part. so i've
> followed some of the steps found here
> http://varnish.projects.linpro.no/wiki/VCLExampleLongerCaching
> on 1 of our servers.  i'm going to compare it in a day or so.
> why do you ask though?

It's fairly common to have pages that aren't cached.

If I'm going to give you a single tip right now, it's to look at the output
of: varnishtop -i TxURL

That's a sorted list of what urls Varnish requests from your backend (in
other words: cache misses). Most items should have a 1 or less next to
them. The number represents a decaying average, and you should know why if
you have items there that have double-digit representation.

It should also give you an indication of whether this is a problem with
your TTL or a few pages that aren't cached at all, all though the
pass/hitpass counter in varnishstat will tell you that too.

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