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Zookeeper, mail # user - zab protocol: what happens to uncommitted proposal


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zab protocol: what happens to uncommitted proposal
kishore g 2012-12-13, 06:31
Hi,

I read the docs and presentations online
https://cwiki.apache.org/ZOOKEEPER/zookeeperpresentations.html about the
internals of zab. I am confused about what happens to uncommitted proposals
when new leader is elected after current leader fails. To be precise, these
are the scenarios i am thinking

a) new leader has got a proposal that no other follower has seen, will it
commit this proposal or let it go
b) new leader has got a proposal that majority of nodes have it, will it
commit this or let it go. What happens to other followers, will new leader
ask followers to commit or rollback based on what it does.
c)new leader does not have proposal but one of the followers has it, is
this possible?

>From what i understood the new leader simply commits all proposals that he
has seen irrespective of  what other followers have seen.

Can some one explain what exactly happens, i am more interested in what
happens in the code

thanks,
Kishore G