Processing Power

[James Pearson]

Excerpts from Simon Lennon, OnCommerce Ltd.'s message of 2014-01-27 03:45:20 -0800:
> Hi guys, I was wondering what kind of processing power varnish needs. I 
> am setting up a dedicated environment with a custom built VCL which 
> includes some regexp and the load balancing functionality.
> 
> I was going to setup a dual core server with 96GB of ram, is this enough 
> for a HIGH traffic site, says 10,000 hits a second with very high cache 
> utilization?

As always, testing yourself is the best way to find out.  Although it's
simplistic, I've found Bees with Machine Guns![0] to be useful in load-testing
Varnish.

One thing we noticed recently was that we were getting about 20% of our
requests from clients that didn't support gzip.  Turning off
http_gzip_support[1] helped tick down our CPU usage a bit, although you have to
be ok with Varnish keeping (potentially) two separate cache entries for each
object.

With that setting adjusted, in our testing varnish lookups were the only thing
that caused any appreciable amount of load; our machine (an EC2 m1.large) could
handle hits just fine up until the bandwidth capacity topped out.

 - P

[0]: https://github.com/newsapps/beeswithmachineguns
[1]: https://www.varnish-cache.org/docs/3.0/phk/gzip.html