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From Erick Erickson <>
Subject Re: ZooKeeper issues with AWS
Date Sat, 01 Sep 2018 03:02:37 GMT

Yeah, I understood that you were only killing one ZK at a time.

I think Walter and Shawn are pointing you in the right direction.
On Fri, Aug 31, 2018 at 12:53 PM Shawn Heisey <> wrote:
> On 8/31/2018 12:14 PM, Jack Schlederer wrote:
> > Our working hypothesis is that Solr's JVM is caching the IP addresses for the ZK
hosts' DNS names when it starts up, and doesn't re-query DNS for some reason when it finds
that that IP address is no longer reachable (i.e., when a ZooKeeper node dies and spins up
at a different IP).
> It might be the Solr JVM that's doing this, but it is NOT Solr code.  It
> is ZooKeeper code.
> Solr incorporates the ZooKeeper jar and uses the ZooKeeper API for all
> interaction with ZooKeeper.  There is nothing we can do for this DNS
> problem -- it is a problem that must be raised with the ZooKeeper project.
> As Walter hinted, ZooKeeper 3.4.x is not capable of dynamically
> adding/removing servers to/from the ensemble.  To do this successfully,
> all ZK servers and all ZK clients must be upgraded to 3.5.x.  Solr is a
> ZK client when running in cloud mode.  The 3.5.x version of ZK is
> currently in beta.  When a stable version is released, Solr will have
> its dependency upgraded in the next release.  We do not know if you can
> successfully replace the ZK jar in Solr with a 3.5.x version without
> making changes to the code.
> Thanks,
> Shawn

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