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From de Souza Medeiros Andre <andre.medei...@aalto.fi>
Subject Question on Zab's Synchronization phase design
Date Thu, 23 Feb 2012 13:21:20 GMT
Hi all,

I hope this list is appropriate to place my question regarding one of the most recent papers
on ZooKeeper's Zab protocol: http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5958223&tag=1

When Phase II (Synchronization) of the protocol is described, in step f.2.1 there are two
actions performed "atomically": setting f.a to e' and accepting every transaction in the initial
history given by the leader. My question is: what precisely does "atomically" mean? Does it
mean that either none or both are executed? Then, do the core properties depend on the atomic
execution of those actions? I've read the proofs in that paper and apparently the atomic execution
of those actions is not mentioned. How does this relate to Zab protocol in the code? I haven't
yet found a synchronization code that sets f.a (currentEpoch in the code) "atomically" together
with the history (through TRUNC, DIFF, or SNAP messages).

Thanks for the attention,
Andre Medeiros

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