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From Alexander Shraer <shra...@gmail.com>
Subject Re: Zookeeper Ensemble Automation
Date Thu, 05 Jan 2017 21:08:21 GMT
Since configuration info is stored in a znode, you could access it using a
simple get operation. The getconfig operation is basically doing just that.
So if you have a 3.5 server and a 3.4 client, the client should be able to
read the list of servers and get notified when the list changes by setting
a watch.

The 3.5 client has an updateServerList operation, which allows to create a
zk handle with one list and later update the list.


On Thu, Jan 5, 2017 at 12:41 PM, Shawn Heisey <apache@elyograg.org> wrote:

> On 1/5/2017 11:19 AM, Washko, Daniel wrote:
> > Thanks for the reply Shawn. I would like to clarify something though.
> > Right now, the Dynamic Reconfiguration of Zookeeper works for
> > Zookeeper – that is adding/removing nodes automatically without having
> > to reconfigure each zookeeper node manually. Once Zookeeper is out of
> > Alpha then Solr will be updated to take advantage of the Dynamic
> > Reconfiguration capability of Zookeeper and auto-discover any changes.
> > Is that correct?
> I am not sure whether my understanding is correct, but if it is, then I
> don't think a zookeeper 3.4.x client (like the one in Solr) will notice
> that the server list (with servers running 3.5.x) has changed.
> Depending on exactly how the membership changed, the SolrCloud instance
> might not be able to maintain a viable ZK quorum.  If it loses quorum,
> SolrCloud goes read-only.
> After ZK 3.5 goes through the beta phase and reaches stable, then Solr
> will get the upgrade, and we will make sure that the dynamic
> reconfiguration works.  It's a feature that we definitely want, though
> we may wait for the second or third stable release before we upgrade to
> be absolutely certain that it's solid.
> There are a couple of questions I do not know the answer to:  1) Whether
> any code changes will be required in Solr to take advantage of dynamic
> reconfiguration after the dependency upgrade.  2) Whether a Solr
> instance with the 3.5 client could be told about only one ZK server,
> then discover the whole cluster and connect to all the servers.  Can a
> more knowledgeable member of this community answer these questions for me?
> Thanks,
> Shawn

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