installing irule editor

Ahh, are you referring to the vim-based iRule editor then in your previous post? I forgot that existed, have never used it.

ltm rule /Common/Apology_Rule {
when HTTP_REQUEST {
    if { [active_members http_pool] < 1 } {
            HTTP::respond 200 content {
                    
                    Apology Page
                    Come back later. It's break time! Signed, the servers.
                    
            }
            TCP::close
    }
   }
  }