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From "Aaron Brown (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2494) Quorum reads are not monotonically consistent
Date Thu, 24 Sep 2015 20:46:04 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14906978#comment-14906978
] 

Aaron Brown commented on CASSANDRA-2494:
----------------------------------------

The relevant code in the patch has changed significantly. Is the monotonic read consistency
guarantee still provided?

> Quorum reads are not monotonically consistent
> ---------------------------------------------
>
>                 Key: CASSANDRA-2494
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2494
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Sean Bridges
>            Assignee: Jonathan Ellis
>            Priority: Minor
>             Fix For: 1.0.0
>
>         Attachments: 2494-v2.txt, 2494.txt
>
>
> As discussed in this thread,
> http://www.mail-archive.com/user@cassandra.apache.org/msg12421.html
> Quorum reads should be consistent.  Assume we have a cluster of 3 nodes (X,Y,Z) and a
replication factor of 3. If a write of N is committed to X, but not Y and Z, then a read from
X should not return N unless the read is committed to at  least two nodes.  To ensure this,
a read from X should wait for an ack of the read repair write from either Y or Z before returning.
> Are there system tests for cassandra?  If so, there should be a test similar to the original
post in the email thread.  One thread should write 1,2,3... at consistency level ONE.  Another
thread should read at consistency level QUORUM from a random host, and verify that each read
is >= the last read.



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