Use iRules to query number of active connections against a node

Thanks for the replies, both very helpful!

I am aware of the overhead incurred with DNS lookups, but at least the RESOLV::lookup command caches queries. Unfortunately it is a requirement given to us and we have to play ball (it's a very customised environment that necessitates this flexibility as the servers can be passed around between locations using VMotion etc and the IP addresses can change).

Very interested in the possibility of using a perpetual script to update the pool members...how might this be done?

I don't think I can use the LB::mode option as that only applies to pools with pool members. With this setup, I cannot add pool members in, because by doing this it will save the IP addresses of those members and it will not allow the DNS lookups to be acted upon. My solution is currently doing DNS lookups via iRules and sending the requests to the approporiate node programatically with no pool members defined.

Kevin, just one final note - the resolution for each hostname will be a single IP address, but we are load balancing across multiple hostnames. So basically we have a simple setup of two hostnames, each of these need to be resolved to their own IP addresses, and it's the load balancing across each of these resolved IP addresses that I want to match up with a least connections type of algorithm. Hope that makes sense.