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Sylvain Lebresne commented on CASSANDRA-5062:
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I'm sorry but you are not reading what I have written. You're example is not a
possible execution of the algorithm in my document. Namely, no proposer will
start proposing on round 2 until it has "learned" the value for round 1. And
value are learn only once the full paxos algorithm has unfolded. This is not at
all what your example, you're incrementing the round as soon as the agree phase
is done basically, which is not what I'm suggesting. Maybe what confuse you is
that what I call "commit" is the act of a proposer asking to acceptors to
accept a given proposal. This is different from what Jonathan calls commit,
which I call "learn". I'm sorry if that's confusing, but at the same time, I
think my naming makes sense in my proposal for a number of reasons (but I'm not
saying Jonathan is wrong in using his own terminology because 1) I don't
understand Jonathan's proposal at this point, so I can't judge if the
terminology is good or not and 2) this is only terminology, it shouldn't care
too much as long as the context makes it clear what is what (and I've written
500 lines of context!)).
> 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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