I've checked all of the documentation, books and google searches I can
think of....

I have a working topology script.  I have dynamic IP's.  I have an
automated process to update the rack data when a datanode changes IP.

What I don't have is any clue as to when the NN reads this script.  If I
execute it right now with 10.10.10.10 it'll return /dc1/rack3  When I run
hadoop balancer I see /default/rack/10.10.10.10:50010
I really don't want to have to restart the NN for IP changes to be noticed.

Any brilliant insights?

Thanks
Chris