If you want to record the JobRouter requests, you have to insert the constant CONST_LOG_REQUEST in the config.php file and set the value to true. So, among others, the URL and the time frame per instance and user will be recorded in a separate file request_<username>_<datum>.log.
If you want to record an Ajax request, set the value to true for the constant CONST_LOG_AJAX_REQUEST. The requests will be recorded analogically, as for CONST_LOG_REQUEST.