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From Lei Gao <l...@linkedin.com>
Subject Re: Question on maintaining leader/membership status in zookeeper
Date Fri, 30 Apr 2010 19:45:05 GMT
Hi Ted,

I 100% agree with what you said. But my question is more about what if my zookeeper service
cluster is partitioned from a majority of nodes in my USER CLUSTER.  In this case, the majority
nodes in one network partition can’t select a new leader because zookeeper is out of reach.

Another example will be that if there is an asymmetric network failure where a majority of
nodes from the USER CLUSTER can’t reach the leader while the zookeeper still can. How does
zookeeper handle such situation?

Thanks,

Lei

On 4/30/10 12:24 PM, "Ted Dunning" <ted.dunning@gmail.com> wrote:

There are a variety of situations that can trigger a new leader election and a few that can
cause the cluster to be unable to elect a new leader.  Isolation of just the leader is one
of the situations that will cause a new leader election.  Isolation of nodes into groups smaller
than the quorum will result in the cluster freezing.

On Fri, Apr 30, 2010 at 11:56 AM, Lei Gao <lgao@linkedin.com> wrote:
Hi,

I have a general question on how zookeeper can maintain its view of the user cluster (that
zookeeper manages) that is consistent with the nodes in the user cluster. In other words,
when zookeeper considers the current leader is unavailable, does it really guarantee that
a majority of nodes in the user cluster can’t reach the current leader? The same question
applies to the membership service as well. Because the zookeeper can be partitioned from a
majority of the nodes in the user cluster. How does the zookeeper handle situations like this?

Thanks,

Lei



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