Hi Henry, I am not talking about the leader election within zookeeper cluster. I guess I didn't make the discussion context clear. In my case, I run a cluster that uses zookeeper for doing the leader election. Yes, nodes in my cluster are the clients of zookeeper. Those nodes depend on zookeeper to elect a new leader and figure out what the current leader is. So if the zookeeper (think of it as a stand-alone entity) becomes unavailabe in the way I've described earlier, how can I handle such situation so my cluster can still function while a majority of nodes still connect to each other (but not to the zookeeper)?
Thanks, Lei On 4/30/10 1:10 PM, "Henry Robinson" <he...@cloudera.com> wrote: > 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 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.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 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 >> >> >> >
