of usernames which need to be processed. The usernames returned may depend
on the value of
, which gives an indication of the frequency with which this
particular update is run. Implementations which have timestamped events to look at should
be conservative and look back further, in case the previous update(s) failed to run. If
then all relevant usernames should be returned, regardless of
any time-related factors.
Implementations should override
to return a meaningful string that
will be used to refer to the instance in logging.