I'm using Zookeeper (3.2.2) for a simple group membership service in the manner that is typically described[1,2]:

I create a znode for the group, and each present group member adds an ephemeral node under the group node. I'm using the cversion of the group node as a "group number". I expected this value to be monotonically increasing, but I'm seeing instances where this isn't the case. According to the programmer's guide, changes to a node will cause the appropriate version number to increase, but it says nothing about decreasing.

Am I misunderstanding something about the way node version numbers work? Is there a better/recommended way to implement a monotonically increasing group number?


[1] http://hadoop.apache.org/zookeeper/docs/r3.2.2/recipes.html
[2] http://eng.kaching.com/2010/01/actually-implementing-group-management.html

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