URL based load balancing. How?

Here's an iRule I use for this type of thing. It uses a "Datagroup" that you can update the http host header to pool mapping to do what you want.

1. Create a Datagroup "HOST_2_POOL_DataGroup" with entries like:

   "expample.com" := "APP_Pool01",
   "subdomain.example.com" := "APP_Pool02",
   

   `

2. Here is the iRule "HTTP-Host-2-Pool-MAP"

   `when HTTP_REQUEST {
   set pool_select_value [class lookup [string tolower [HTTP::host]] HOST_2_POOL_DataGroup]
   if {[active_members $pool_select_value] > 0 } {
       log local0.notice "available pool members"
       pool $pool_select_value
       } else {
           HTTP::respond 503 content "No active pool members in pool"
       }
   }