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https://issues.apache.org/jira/browse/CASSANDRA-5062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13593607#comment-13593607
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Cristian Opris commented on CASSANDRA-5062:
-------------------------------------------
More obvious example:
{code}
X Y Z
1. L0 L0 L0
2. P/C(R=1)< P/C(R=1)<
3. L1
4. P/C(R=2)< P/C(R=2)<
5. L2
6. P/C(R=3)< P/C(R=3)<
5. L3
{code}
Z dies, that's fine the values are not lost they survive in Y. However a read
with just Z and Y would need to resolve the last 3 paxos rounds to get the
correct value.
That could work, but what I'm suggesting is to do that at accept (your commit)
time ensuring you always have a quorum that has learned
the latest value.
> 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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