varnish nuking agressively all my objects.

[Aurélien Lemaire]

Le 16/09/2011 08:55, Jorge Nerín a écrit :
>
> On Thu, Sep 15, 2011 at 11:29, Aurélien Lemaire <aurelien.lemaire at smile.fr 
> <mailto:aurelien.lemaire at smile.fr>> wrote:
>
>     Good day folks,
>
>     First of all, varnish is an outstanding piece of software that my company
>     and i are addicted to. So thanks to all the coders.
>
>     Here is my problem :
>     I allocated varnish 1G of RAM on a website that can have more than 2 Go of
>     possible cacheable objects . Not to worry though as any proxy-cache system
>     should smartly nuke old objects to make place to new one to live
>     peacefully within its allocated RAM. And that's where Varnish behave
>     unexpectedly : each time it need to nuke SOME objects : it nukes ALMOST
>     ALL of them (often ~80% of my 35k objects) which is quite aggressive ;
>     thus i lost almost all my cache....IRK !
>
>     3 Munin graphs attached to see the problem clearly : big drop each time a
>     nuking happens.
>
>     To make sure my pbr is about varnish nuking system : i increased from 1G
>     to 3G(more than the max possible 2G cacheable objects) on another varnish
>     of this platefom (this website is delivered by multiple front/varnish
>     server all stricly similar and independant) and this issue disappeared (no
>     more nuking : no lost of ~80%of my objects)
>
>     Here is my env :
>     Debian 5.0.8 64 bits on 2.6.32-5-openvz-amd64 kernel
>     Varnish 2.1.3 SVN 5049:5055(debian package 2.1.3-8)
>     200 varnish 's worker threads running constantly (no issue on workers)
>     30req/s average with 60/s in peak
>
>     Daemon run as such :
>     /usr/sbin/varnishd -P /var/run/varnishd.pid -a :80 -T localhost:6082 -S
>     /etc/varnish/secret -f /etc/varnish/serverx.vcl -w 100,1024 -s
>     file,/var/lib/varnish/serverx/varnish_storage.bin,3G
>
>     Here a quick varnishstat -1 :
>
>     Is it normal varnish behaviour ? sounds like a bug to me.
>     Am i missing some tuning (lru_interval)  to soften the nuking algo ?
>     Do you need more info ?
>     helps appreciated here  ;-)
>
>     Regards, Aurelien Lemaire
>
>
> It could be someone downloading a large file (like a ~700Mb iso file) and 
> varnish nuking objects to make room for this file (even if its configured to 
> not cache it).
>
> Try to get a varnishlog trace of the moment the nuking begins.
>
> -- 
> Jorge Nerín
> <jnerin at gmail.com <mailto:jnerin at gmail.com>>
This website does not content any files bigger than a couple of Mb.

Will see what i can do to get the varnishlog during the nuking.

--
aurelien lemaire
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