When doing a read in HAService mode, the program would go over the list of NameNodes to look for an ObserverNode to handle it. However, it does so even when there is no ObserverNode at all, and each StandbyNode would throw an exception (when using delegation token). Therefore, we fix it by setting up a period, which means that we only iterate over the list of NameNodes every couple of minutes instead of for any read requests.

We will only change the total number of NameNodes and see that we actually go over the for loop for each read request.