Monitor virtual server with a lot of pool configured in une Irule

I've made a virtual server HTTP that have no default pool assigned because I assign the pool with an Irule

This Irule is made to reflect the requirement of real server that respond on different port due to domain name an work fine.

when HTTP_REQUEST {

log local0. "TEST - l'HOST is [HTTP::host], l'URI is [HTTP::uri]"

switch -glob [HTTP::host] {

"*domain1.it" -

"*domain2.it" {

log local0. "TEST - l'HOST e' [HTTP::host], inside pool-1"

pool pool-1

}

"*domain3.it" -

"*domain4.it" {

log local0. "TEST - l'HOST e' [HTTP::host], inside pool-2"

pool pool-2

}

etc. etc

}

}

This is the I rule (note the asterisc before the domain is due to satisfy the www or other before).

Now my question is:

The virtual server has no pool specified, what is the best practise to inform the Virtual server that the pool (example pool-2) is out of service?

Note: The pool-1 and pool-2 are the same real server but only on different port.

The real configuration provides about 21 pools always on the same server

Thanks