[jira] [Commented] (CASSANDRA-2494) Quorum reads are not monotonically consistent

["Sylvain Lebresne (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-2494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13071654#comment-13071654 ] 

Sylvain Lebresne commented on CASSANDRA-2494:
---------------------------------------------

Ok, I now see what you mean :)
Makes perfect sense.

Comments on the patch:
* There is a number of case where scheduleRepairs may not have been called (if the read for repair timeout and/or we had no or only 1 response or we have the situation were removeDeleted removes everything), so repairResults will be null in those cases. In SP, we should check for it.
* That new wait can extend the rpc timeout to almost twice what it should be. I agree that it is not a huge deal, but by exposing the 'startTime' stored in RepairCallback we can make it so we don't extend it that way.
* Shouldn't we give the same love to range requests, now that we do repairs there too ?

> 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
>
>         Attachments: 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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