ArcGIS Server logfile column "user" is empty

[RobertBuckley1]

I am monitoring certain services due to recent problems. I have set the log sensitivity to debug and enable the column "user" to see who is requesting data, but the column is always empty. How can a request come from an non-user?

Could anyone explain this?

[ChrisPy]

Is your arcgis server federated with your portal? That is our setup. I also do not see users against service calls logs or even error logs. I only see user names when I access services directly on desktop software like ArcMap. Perhaps since portal controls access of the service via federation, arcgis server does not capture it especially if anonymous sign in in portal is enabled. Just my thoughts.