Hi Lei - The 'user cluster' (by which I think you mean the set of clients of ZooKeeper?) plays no part in leader election. If a majority of ZooKeeper server nodes can talk to each other, a new leader can be elected. Clients of the minority server partition will be disconnected - if they too cannot reach the majority partition then they will not be able to reconnect.
Hope this helps, Henry On 30 April 2010 12:45, Lei Gao <l...@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 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.dunn...@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 <l...@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 > > > -- Henry Robinson Software Engineer Cloudera 415-994-6679