Hi Ted, I think the problem you are seeing is due to this issue:

https://issues.apache.org/jira/browse/ZOOKEEPER-790

which is fixed in 3.3.2.

-Flavio

On Apr 20, 2010, at 11:14 PM, Ted Dunning wrote:

> We have just done an upgrade of ZK to 3.3.0.  Previous to this, ZK  
> has been
> up for about a year with no problems.
>
> On two nodes, we killed the previous instance and started the 3.3.0
> instance.  The first node was a follower and the second a leader.
>
> All went according to plan and no clients seemed to notice  
> anything.  The
> stat command showed connections moving around as expected and all  
> other
> indicators were normal.
>
> When we did the third node, we saw this in the log:
>
> 2010-04-20 14:07:49,010 - FATAL [QuorumPeer:/
> 0.0.0.0:2181:Follower@71] -
> Leader epoch 18 is less than our epoch 19
>
> The third node refused all connections.
>
> We brought down the third node, wiped away its snapshot, restarted  
> and it
> joined without complaint.  Note that the third node
> was originally a follower and had never been a leader during the  
> upgrade
> process.
>
> Does anybody know why this happened?
>
> We are fully upgraded and there was no interruption to normal  
> service, but
> this seems strange.

flavio
junqueira

research scientist

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