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From Shawn Heisey <apa...@elyograg.org>
Subject Re: One node crashing in 3.4.11 triggered a full ensemble restart
Date Thu, 03 Oct 2019 12:55:22 GMT
On 10/3/2019 2:45 AM, Norbert Kalmar wrote:
> As for running a mixed version of 3.5 and 3.4 quorum - I'm afraid it will
> not work. From 3.5 we have a check on PROTOCOL_VERSION. 3.4 did not have
> this protocol version, so when the nodes try to communicate it will throw
> an exception. Plus, it is not a goal to keep quorum protocol backward
> compatible, so chances are even without the check it would not work.

This document suggests that a mixed environment of 3.4 and 3.5 will work:

https://cwiki.apache.org/confluence/display/ZOOKEEPER/ReleaseManagement

But you seem to be saying that it won't.

As a committer on the Lucene/Solr project (which uses ZK) I am wondering 
what we can tell our users about upgrading ZK.  I was under the 
impression from the wiki page I linked that they could do a rolling 
upgrade with zero downtime, where they do one ZK server at a time.  Are 
you saying that this is not possible?

The Upgrade FAQ that you linked doesn't say anything about 3.4 and 3.5 
not working together.  The only big gotcha I see there is 
ZOOKEEPER-3056, which has a workaround.

(I think of 4lw whitelisting as just a config problem with a new 
default, not a true upgrade issue)

Thanks,
Shawn

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