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From Mahadev Konar <maha...@yahoo-inc.com>
Subject Re: Question on maintaining leader/membership status in zookeeper
Date Fri, 30 Apr 2010 20:28:11 GMT
Hi Lei,
 I think you might be confusing Leader Election within ZooKeeper itself with
electing a leader for your application? Is that so?

Leader Election within ZooKeeper is totally internal to zookeeper service
and is not visible to applications.

I am little confused, what your problem statement is? Can you please explain
it from the view point of your application?


On 4/30/10 12:45 PM, "Lei Gao" <lgao@linkedin.com> wrote:

> 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 can¹t
> 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 can¹t 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 can¹t 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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