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Sylvain Lebresne commented on CASSANDRA-5062:
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bq. Basically in the acceptor algorithm you don't seem to handle the case where
C_current.timestamp() < R
Note sure I follow. On the acceptor, if C_current.timestamp() < R, then it
means the message if for a round that hasn't been decided yet (more precisely,
that we haven't learned out). That's the case where we actually do some work
(as the pseudo-code does really).
bq. Also note you don't need to send the column values with proposal
Not true. Even if a proposer has his value "accepted", there is not guarantee
that it will be the one learning it, or even the only one learning it for that
matter. For a given round, the value is decided as soon as a quorum of acceptor
accepts it basically, irrelevant of whether the original proposer of that value
gets the commit acks or not.
bq. Essentially consensus is on the next column value to write
Yes. As as discuss later in my brain dump, we'd likely want to support normal
inserts at least. The actual operation is largely of irrelevant (that's why
it's a blob in the paxos_state table :)).
> 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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