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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5062) Support CAS
Date Thu, 13 Dec 2012 15:44:12 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13531113#comment-13531113
] 

Jonathan Ellis commented on CASSANDRA-5062:
-------------------------------------------

One part I don't have a good answer to yet: how do you deal with timeouts in lock-based CAS
after the lock succeeds?  That is: I acquire the lock, write my new user record, but that
write times out.  Remember that this means "write is in progress," not "write has failed,"
but an in-progress write might well not yet be visible for another client that also tries
to CAS.
                
> 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
>
>
> "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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