If you have enabled Log Streaming, the Log Extras setting allows you to automatically add static and dynamic data to the log streaming record. Dynamic content can be any number of internal variables. For example, header lines sent to a client have the prefix “sent_http_”, so to capture a custom header’s value in the client request (e.g., cdn_session), you would use $sent_http_cdn_session. If you are unsure of how to format dynamic Log Extra values, please contact CDN Support. Any Log Extras you create must be notified to CDN Support before they will begin appearing in the log stream.
From the “Add Settings” list, select “Log Extras” and In the field, add the Log Extras you want the CDN to send with the log.