varnish nuking agressively all my objects.

[Jorge Nerín]

On Thu, Sep 15, 2011 at 11:29, Aurélien Lemaire
<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>
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