Adding a uri if one doesn't exist

The only way to test this is to include logging statements on the BIG-IP as well as web server logging on the backend server.

when HTTP_REQUEST {
  log local0. "URI: [HTTP::uri]"
  if { [HTTP::uri] equals "/" } {
    log local0. "URI is empty, changing to http://[HTTP::host]/ghi..."
    HTTP::uri "/ghi/"
  } else {
    log local0. "URI is not empty, leaving alone..."
  }
}

Then look in the /var/log/ltm file on the BIG-IP to make sure that the iRule is functioning correctly. If you see that is the case, then you'll have to look at the web server's log (or a packet trace) on the web server to verify the GET request is now "/ghi/". If your webserver is still showing a "GET / ..." then you'll have to contact Technical support as this is very basic functionality and you are using the iRule correctly.

-Joe