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From "Todd Nine (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5062) Support CAS
Date Thu, 13 Dec 2012 16:50:13 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13531169#comment-13531169
] 

Todd Nine commented on CASSANDRA-5062:
--------------------------------------

Can you elaborate on your timeout question with an example?  I think we're on the same page
with this, but wanted to be sure.  There's currently a small window in which a client can
think it has a lock, when it actually doesn't (timeout/2).  This is due to not having any
way for the lock to receive a notification when it's column has reached it's ttl and is removed
because the lock heartbeat failed.  
                
> 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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