HTTP connection limit + cookie insert from BigIP

rule HTTP_session_limit {
when RULE_INIT {
   set ::debug 1
   set ::total_active_clients 0
   set ::max_active_clients 100
   log local0. "rule session_limit initialized: total/max: $::total_active_clients/$::max_active_clients"
}
when HTTP_REQUEST {
   if {$::debug}{ set uri [HTTP::uri]}
   ; test cookie presence
   if {[HTTP::cookie exists "ClientID"]} {
      set need_cookie 0
      set client_id [HTTP::cookie "ClientID"]
      if {$::debug}{ log local0. "client [IP::client_addr] with cookie $client_id -> $uri, count: $::total_active_clients"}
   ; if cookie not present & connection limit not reached, set up client_id
   } else {
      if {$::total_active_clients < $::max_active_clients} {
         set need_cookie 1
         set client_id [format "%08d" [expr { int(100000000 * rand()) }]]
         incr ::total_active_clients
      if {$::debug}{ log local0. "client [IP::client_addr] with no cookie, under connection limit -> $uri, count: $::total_active_clients"}
      ; otherwise redirect
      } else {
         if {$::debug}{ log local0. "client [IP::client_addr] with no cookie over limit, redirected  -> $uri, count: $::total_active_clients"}
         HTTP::redirect "http://sorry.domain.com/"
         return
      }
   }
}
when HTTP_RESPONSE {
   ; insert cookie if needed
   if {$need_cookie == 1} {
      if {$::debug}{ log local0. "client [IP::client_addr] inserting cookie: $client_id"}
      HTTP::cookie insert name "ClientID" value $client_id
   }
}
when CLIENT_CLOSED {
   ; decrement current connection counter for this client_id
   if {$::total_active_clients > 0} {
      incr ::total_active_clients -1
      if {$::debug}{ log local0. "client [IP::client_addr] closing connection with cookie $client_id -> $uri, count: $::total_active_clients"}
  }
}
}