Varnish, long lived cache and purge on change

Darryl Dixon - Winterhouse Consulting darryl.dixon at
Wed Aug 19 01:18:06 CEST 2009

> Then we ran
> out of ram and varnish started causing a ton of swap activity and it
> increased the response times of everything on the site to unusable.
> After poking about i seem to have found the culprit.  When you use
> url.purge
> it seems to keep a record of that and check every object as it is fetched
> to
> see if it was purged or not.  To test this i set a script to purge a lot
> of
> stuff and got the same problem to happen.

Hi Karl,

This is about the fourth thread now on varnish-misc about the perils of
using url.purge :) My suggestion in your case, if managing obj.ttl is too
tough, is to look at breaking out the page with ESI and having shorter
cache times on the portions of the page that will potentially end up
getting updated. This combined with a reasonable grace period for those
parts of the page should alleviate most of the load you might otherwise
experience, and keep response times low and page freshness high.

Darryl Dixon
Winterhouse Consulting Ltd

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