A number of components call reloginFromKeytab() before making requests. For StandbyCheckpointer and SecondaryNameNode, where this can be called frequently, it generates many WARN messages like this:
WARN security.UserGroupInformation: Not attempting to re-login since the last re-login was attempted less than 600 seconds before.
Other than these messages, it doesn't do anything wrong. But it will be nice if it is changed to call checkTGTAndReloginFromKeytab() to avoid the potentially misleading WARN messages.