catch bots

It may be the matchclass thing that prevented it working with HTTP_REQUEST. The CLASS command replaces matchclass. See: matchclass and class

This should do it:

when HTTP_REQUEST

   set user_agent [string tolower [HTTP::header User-Agent]]

   if { [class match $user_agent contains datagroup_crawler] } {

      pool pool_webserver_ch_de_bot

      log local0. "using pool_webserver_ch_de_bot for UA $uagent"

        }
   }