Renewal was timed against the window in two different ways: the period derived
from it, the sweep interval did not. Shortening the window to watch a renewal in
an end-to-end run would have left the refresher still looking for due accounts
every quarter of an hour, so nothing would have been renewed in time and the
test would have reported the feature broken.
Derive the sweep from the period, within bounds that keep a very short window
from spinning and a normal one from checking less often than is useful, and
allow the window itself to be set through the environment so a run can take
seconds instead of half a day. A value that cannot be parsed or falls outside
the bounds keeps the default, because a window nobody intended is a security
property nobody chose, and an override is logged at warning level since it sets
how long a device keeps passing the check after its key is gone.
Every instance has to be given the same value: the window is part of the nonce,
so instances that disagree reject each other's.
riccardom
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