Typically, this is set to the domain; though nowadays it is common to set it to a static application specific string (which is probably what hadoop is doing ?) since authorization is fairly limited in scope (allow or deny as a while : no domain specific acls and/or resource/access partitions).

Would be nice if this could be overridden by users via some (hidden for now) env variable - simply to allow for future customization without code change : this is ofcourse not very important given the scope of the PR itself !