Flavio Junqueira commented on ZOOKEEPER-790:

Hi VIshal, Thanks for testing as well. The issue you mention about the LOOKING 
state, if I understand correctly, is not about the state of the server, but the 
state reported in the notification. 
If so, then it happens because we always repeat the last message sent. Such 
duplicate messages cause what you have observed, but they are supposed to be 
harmless, in the sense that
I do not expect them to lead to any inconsistency in the ZooKeeper service. 
Instead, it may only cause some periods in which some process believes 
incorrectly to be the leader, but again, 
the service is robust to such scenarios. 

> Last processed zxid set prematurely while establishing leadership
> -----------------------------------------------------------------
>                 Key: ZOOKEEPER-790
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-790
>             Project: Zookeeper
>          Issue Type: Bug
>          Components: quorum
>    Affects Versions: 3.3.1
>            Reporter: Flavio Junqueira
>            Assignee: Flavio Junqueira
>            Priority: Blocker
>             Fix For: 3.3.2, 3.4.0
>         Attachments: ZOOKEEPER-790-3.3.patch, ZOOKEEPER-790-3.3.patch, 
> ZOOKEEPER-790-follower-request-NPE.log, ZOOKEEPER-790.patch, 
> ZOOKEEPER-790.patch, ZOOKEEPER-790.patch, ZOOKEEPER-790.patch, 
> ZOOKEEPER-790.patch, ZOOKEEPER-790.travis.log.bz2, ZOOKEEPER-790.v2.patch
> The leader code is setting the last processed zxid to the first of the new 
> epoch even before connecting to a quorum of followers. Because the leader 
> code sets this value before connecting to a quorum of followers 
> (Leader.java:281) and the follower code throws an IOException 
> (Follower.java:73) if the leader epoch is smaller, we have that when the 
> false leader drops leadership and becomes a follower, it finds a smaller 
> epoch and kills itself.

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