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From Shawn Heisey <>
Subject Re: Solr 7.4 and Zookeeper 3.4.12
Date Fri, 29 Jun 2018 15:38:21 GMT
On 6/28/2018 8:39 PM, Zimmermann, Thomas wrote:
> I was wondering if there was a reason Solr 7.4 is still recommending ZK 3.4.11 as the
major version in the official changelog vs shipping with 3.4.12 despite the known regression
in 3.4.11. Are there any known issues with running 7.4 alongside ZK 3.4.12. We are beginning
a major Solr upgrade project (4.10 to 7.4) and want to stand up the most recent supported
versions of both ZK/Solr as part of the process.

That is NOT a recommendation.

The mention of ZK 3.4.11 in Solr's CHANGES.txt file is simply the 
version of ZK that Solr ships with.  ZK is included with Solr mostly for 
the client functionality.  The regression is in the server code, and 
unless you run the embedded ZK server, which is not recommended for 
production, the ZK library that ships with Solr will not experience the 

I am not aware of anywhere in Solr or its reference guide that makes a 
recommendation about a specific version of ZK.  The reference guide does 
mention version 3.4.11, but that's only because that's the version that 
Solr includes.  The version number in the documentation source code is 
dynamic and will always match the specific version that Solr includes.

The compatibility goals of the ZK project indicate that you can run any 
3.4.x or 3.5.x version of ZK on the server side and be compatible with 
the ZK 3.4.x client that's in Solr.

Look for "Backward Compatibility" on this page:

We have an issue for upgrading the version of ZK in Solr to 3.4.12.  I 
have uploaded a new patch on that issue to try and clear up any 
confusion about what version of ZK is recommended for use with Solr:


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