Performance based "Priority groups"

Hi there Piotr.

Let me answer your question first, because that's what you are probably waiting for, and let's be the smart guy later... 🙂

Not sure whether there is a GUI solution to your problem but here's my suggestion:

Use a external monitor with following logic: - Monitor script will periodically query the server for it's health. - Another script on the server will run some performance diagnostics, like

uptime

on *nix and will return this to the F5 - Monitor script will evaluate the result, will compute "average pool utilization" and based on your predefined thresholds will automatically adjust priority of other pool members (hence add or remove new members").

Some comments: - The script needs to be "self aware" and store the utilization somewhere, because one running instance of the script will be able to directly get the result only from one pool member (upon invoking the external monitor, only one pool member IP is passed to the script as an argument). - For changing the pool member priority call the tmsh from inside the external monitor script. - Be very careful with the timeouts in the external script, specifically about deadlocks if pool member does not answer sooner than another instance of the monitor is invoked by F5 according to health check Interval settings.

Now, as promised, let's be the smart guy. :-) Are you sure this is the solution to your problem? You know, usually, people do not have spare servers doing nothing and waiting for other servers to being overloaded. If you have spare servers, put them into the primary pool in the first place. Another (enterprise) solution would be to have cluster of servers in something like ESX, and let the ESX manage the number of running nodes based on load. F5 will have all of them in the pool and will not bother about the load.

I'm afraid F5 simply does not covers this (yet), and personally I'm also not a fan of this being managed by F5.

Hope I helped.

Jozef