Hit ratio dropped significantly after recent upgrades

[Andrei]

The best thing to do (imo) is to trigger the purges directly in media wiki.
I only did a quick search but they seem to already integrate easily with
Varnish, to send cache purge requests on updates/changes
https://m.mediawiki.org/wiki/Manual:Varnish_caching hope it helps!

On Dec 16, 2016 17:42, "Justin Lloyd" <justinl at arena.net> wrote:

> I actually have the TTL set to 48h now and it seems to work well, but I'm
> not sure if there's anything specific I should do regarding invalidation.
> In general, wikis don't allow for deleting or even changing images; you
> just upload new ones and the wiki software keeps previous versions in the
> revision history. However, I am concerned about invalidating cached images
> when new versions are uploaded so that the previous version is purged from
> the cache, but I'm not sure about the most appropriate way to handle that
> from a Varnish or MediaWiki perspective. If you have any thoughts on that,
> I'd appreciate it.
>
> -----Original Message-----
> From: Dridi Boukelmoune [mailto:dridi at varni.sh]
> Sent: Wednesday, December 14, 2016 7:20 AM
> To: Justin Lloyd <justinl at arena.net>
> Cc: Florian Tham <fgtham at gmail.com>; varnish-misc at varnish-cache.org
> Subject: Re: Hit ratio dropped significantly after recent upgrades
>
> On Wed, Dec 14, 2016 at 2:58 PM, Justin Lloyd <justinl at arena.net> wrote:
> > So after increasing the TTL for thumbnail images to 4 hours, the hit
> ratio got to 65-70%, objects in memory got up to around 150k before
> tapering off (due to lots of expirations starting after 4 hours, as to be
> expected) and slowly dipping back down to around 100k before starting on
> the upswing again. I'm continuing to test increasing the TTL, setting it to
> 24h and we'll see if we have any problems reported as a result in case
> that's too long, but at any rate we definitely appear to have found the
> smoking gun and I know where to tinker to try to better optimize things.
> >
> > I'm not sure why this changed with the upgrades, whether it was
> something in MediaWiki or Varnish, but at least I know where to spend
> cycles on optimizations.
> >
> > Thank you all very much for the help!
>
> Hi,
>
> Thanks for the feedback and glad to see things back to normal.
> Consider sharing your findings with the MediaWiki folks as they will
> likely know better how to deal with the thumbnails.
>
> If images/thumbnails aren't changing often, you can safely increase the
> TTL (ideally directly from MediaWiki) as long as you have an invalidation
> strategy in place.
>
> Cheers
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>
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