Re: [squid-users] Hit-ratio graph: can anyone explain what we see here?

On 25/02/2013 9:08 p.m., Coenraad Loubser wrote:
> Hi All
>
> I'm very curious so as to everyone's casual explanations for what
> could cause the up-and-down pattern visible in this hit-ratio graph:
> http://imm.io/XkQ4
>
> I have my own ideas but will reserve them for the time being so as to
> allow you to share an unbiased opinion first. :-)

* Interaction between browser caches and Squid cache leads to funky
diagrams. All objects which are cacheable by Squid are also cacheable
directly on the client machines. The objects are usually cached at both
places. So popular objects which stay popular can cause cycles of
HIT/MISS as clients caches expire and re-fetch them. The first client
will cause a new copy to be stored in Squid which will cause a peak of
HIT traffic as all other clients expire and HIT on the new Squid opy.
This trails off as the other normal MISS traffic flows in afterwards.

* You can also get cycles if your cache is too small to store all the
popular "hot" objects your clients are wanting. Squid garbage collection
coming around every 1-2 hours purges space to make way for new traffic
and can unwittingly erases some of those HIT objects, causing a drop in
ratio at your MISS rate increases.

* If you are running a reverse-proxy spiders can also hit you in waves
as they all apply similar delay between requests, and they tend to raise
the MISS rate too.

Lots of possibilities. But ...

... what Squid version? (squid -v version line please)

... and what are your ideas?

Amos
Received on Mon Feb 25 2013 - 09:58:17 MST