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From Kevin Webb <kcw...@cs.ucsd.edu>
Subject znode cversion decreasing?
Date Sun, 11 Apr 2010 22:53:01 GMT
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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