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From "FPJ" <fpjunque...@yahoo.com>
Subject RE: Rolling config change considered harmful?
Date Fri, 14 Jun 2013 19:07:57 GMT
Not sure if this helps but here is an example:

- Txn T is acknowledged by A and B (ensemble is {A, B, C})
- Ensemble changes to {B, C, D}
- C and D form a quorum and elect C because it has the highest zxid. 

C won't have T, so the txn gets lost.

Does it make sense?


> -----Original Message-----
> From: Jordan Zimmerman [mailto:jordan@jordanzimmerman.com]
> Sent: 14 June 2013 19:35
> To: user@zookeeper.apache.org
> Subject: Rolling config change considered harmful?
> I'm trying to track a race issue in our ZK usage. In debugging, I've come
> wonder if the way we do rolling config ensemble changes is the culprit.
> does ZK internal leader election work if the list of servers is not
consistent on
> each instance. e.g. Given 3 instances A B C and new instance coming online
> If A and B think the server list is  (A, B, C) but C and D think the
server list is (B,
> C, D) how does ZooKeeper handle leader election?
> -Jordan

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