[rescue] web server loadbalancing...

[Stephen Worotynec]

On Thu, 2 Aug 2001, Bill Bradford wrote:
>
> Already looked at it.  No reliable way to eliminate a system from the
> "pool" if one goes down.
>
This is where the F5 shines..since it is a PC with a modified BSD/OS
kernel, it can use as a rule anything you can script or program on BSD, as
well as the F5 supplied algorithms. It can page a database programmer for
a MySQL error, it can move machines in and out of pools based on response
time, HTTP response code, or the phase of the moon if you wish.

An ASIC-based balancer like the Arrowpoint should be much faster, but the
built-in choices of rulesets had better be to your liking, since they
aren't able to take user-input programs. (caveat: this is when I last
checked - about one year ago, and a newer OS may have changed things.)
As an example, the Arrowpoint was able to check a web server via a single
criteria. So the index page might be fine while the cgis are all giving
Internal Server Error, and it might pass the Arrowpoint's criteria for
being "up". Again, this may be improved in a newer OS version.

Stephen Worotynec
sgw at vex.net