Extract hostname from URL using the edge client

This code works if we have only the ACCESS_ACL_ALLOWED. If I Add the HTTP_REQUEST the access to the application hangs. Don't see any errors in the LTM logs. For the ACCESS_POLICY_AGENT_EVENT, I added an access policy and added and iRule event in there allowing everybody access but I added a log in that section and the access policy doesn't seem to kick in.

when HTTP_REQUEST {
   set ::temphost [HTTP::host]
}
when ACCESS_POLICY_AGENT_EVENT {
   ACCESS::session data set session.custom.host $::temphost
}
when ACCESS_ACL_ALLOWED {
   set user "[ACCESS::session data get "session.logon.last.username"]"
   HTTP::header insert X-UPN $user
}