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Benjamin Reed commented on ZOOKEEPER-366: ----------------------------------------- after discussion this on the list, we realized that we can detect a big jump in time change in the session expiration thread. since we expire a bucket of sessions each tick, if we run into the situation where we are going to expire more than one bucket in a row, we know we have jumped forward in time. we can "smooth" the jump by requiring at least a 1/2 ticktime wait between each bucket. > Session timeout detection can go wrong if the leader system time changes > ------------------------------------------------------------------------ > > 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. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.