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Sylvain Lebresne commented on CASSANDRA-5062:
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bq. When Acceptor receives proposal, if it doesn't check R, if Tm > Tn (clock
mismatch) according to paxos it needs to send it's old accepted value
In my solution/proposal, a round is a fully separated Paxos instance (it's not
just a proposal round for instance). Meaning that comparing a proposal
timestamp Tn for Round R with a proposal timestamp Tm for another round R-1
(which is the case you are talking about) makes no sense whatsoever and is thus
never done. And it doesn't break Paxos exactly because we don't mix things from
2 completely separated instance of the raw Paxos algorithm.
> Support CAS
> -----------
>
> Key: CASSANDRA-5062
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5062
> Project: Cassandra
> Issue Type: New Feature
> Components: API, Core
> Reporter: Jonathan Ellis
> Fix For: 2.0
>
> Attachments: half-baked commit 1.jpg, half-baked commit 2.jpg,
> half-baked commit 3.jpg
>
>
> "Strong" consistency is not enough to prevent race conditions. The classic
> example is user account creation: we want to ensure usernames are unique, so
> we only want to signal account creation success if nobody else has created
> the account yet. But naive read-then-write allows clients to race and both
> think they have a green light to create.
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