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From "Michael Theroux (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4905) Repair should exclude gcable tombstones from merkle-tree computation
Date Tue, 21 May 2013 21:50:22 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4905?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13663449#comment-13663449
] 

Michael Theroux commented on CASSANDRA-4905:
--------------------------------------------

Can anyone comment on the risk of a user (such as myself) backporting this fix and patching
locally?  The code that was changed in the patch looks identical in 1.1.11.  

We have a situation where a column family with lots of deletes running under leveled compaction.
 The validation doesn't take too long, but afterwards we get 2k compaction tasks that takes
several hours to run, when really there shouldn't be any inconsistency.  What I suspect is
happening is as tombstones are getting gc_graced they are compacted away on some nodes and
not others at the time repair is run.  I suspect the majority of the 2k compactions are gc_graced
tombstones getting back in-sync.

I'm setting up a test environment with baseline data, going to reproduce the repair, reset
to baseline, and re-run the repair with this patch to see if this is indeed the issue. This
might take a few days to setup and run.

Cassandra is mission and business critical for us.  Moving to 1.2 will take some time, as
we should setup a test environment, practice migrations and test.  We also use the ByteOrderedPartitioner,
which in general concerns me as its not the most popular use of Cassandra, and maybe a source
of issues as its pounded on less by the general user community.
                
> Repair should exclude gcable tombstones from merkle-tree computation
> --------------------------------------------------------------------
>
>                 Key: CASSANDRA-4905
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4905
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Christian Spriegel
>            Assignee: Sylvain Lebresne
>             Fix For: 1.2.0 beta 3
>
>         Attachments: 4905.txt
>
>
> Currently gcable tombstones get repaired if some replicas compacted already, but some
are not compacted.
> This could be avoided by ignoring all gcable tombstones during merkle tree calculation.
> This was discussed with Sylvain on the mailing list:
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/repair-compaction-and-tombstone-rows-td7583481.html

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