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From Tim Ward <tim.w...@featurespace.co.uk>
Subject RE: How to deliberately cause a split brain?
Date Fri, 19 Jun 2020 11:39:53 GMT
From: Michael Han <hanm@apache.org>
> There are different cases for split brain and how to test the monitor code depends on
what signals
> you are using - but most usually, a split brain case can be created by artificially split
two quorum
> out of a single quorum through manual configuration change (e.g. a 7 quorum servers can
be split
> into a 4 quorum with a 3 quorum - just exclude the servers from each config).

Yes, I am coming to the conclusion that one could in effect

(a) build two separate Zookeeper ensembles
(b) point parts of one's application at one ensemble and the rest at the other

and expect the application to misbehave somewhat horribly.

And I've come up with some stuff I can monitor to detect all that in various ways.

*BUT* this detection process would reply on the person who had carefully and cunningly maliciously
mis-configured Zookeeper at the same time *correctly* configuring the monitoring system. How
likely is that, I wonder? So I'm discussing with my customer how much use this feature is
really likely to be in the real world ...

Thanks all for the various comments.

Tim Ward
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