Session timeout detection can go wrong if the leader system time changes
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Key: ZOOKEEPER-366
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-366
Project: Zookeeper
Issue Type: Bug
Reporter: Benjamin Reed
the leader tracks session expirations by calculating when a session will
timeout and then periodically checking to see what needs to be timed out based
on the current time. this works great as long as the leaders clock progresses
at a steady pace. the problem comes when there are big (session size) changes
in clock, by ntp for example. if time gets adjusted forward, all the sessions
could timeout immediately. if time goes backward sessions that should timeout
may take a lot longer to actually expire.
this is really just a leader issue. the easiest way to deal with this is to
have the leader relinquish leadership if it detects a big jump forward in time.
when a new leader gets elected, it will recalculate timeouts of active sessions.
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