So while benchmarking our web server farm today I found out something really odd. In a mod_proxy (or mod_rewrite with proxy) setup with a backend suite of mod_perl servers where you specify the backends by IP (I'm using mod_rewrite for this, but it doesn't make any difference), mod_proxy does a reverse lookup on the IP for each and every request.
I have no idea why it does this. But Red Hat's own copy of mod_proxy is patched to not do that.
The work around I've found is to put all hosts in /etc/hosts, and revert to using host names. This prevents the DNS traffic at least.
