The access log format is configured to include the field %auth-user-name% however what appears in the log is just a dash (minus sign). I am hoping / expecting to see an authenticated user's login ID.
It occurs to me that it might be trying to display a user NAME as opposed to a user ID. The user ID is certainly known because users log in with it, just how it might know the user's name as well I have not looked into. It may or may not be relevant but we use a custom written authentication realm.
I am tempted to try adding %auth-user-id% to the log format but I do not expect it would be understood.
Just for the hell of it I modified the format to include the user agent, sure enough the user agent string appeared in the log but still no user name.