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From "Stefan Podkowinski (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-12888) Incremental repairs broken for MVs and CDC
Date Thu, 10 Nov 2016 12:13:58 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12888?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15653899#comment-15653899
] 

Stefan Podkowinski commented on CASSANDRA-12888:
------------------------------------------------

What also puzzles me is that MVs are getting repaired just as usual tables would, in case
of running repair for a single keyspace. Once CFs have been retrieved for a KS, no filtering
for MVs seem to happen and they'll be repaired just as regular tables. I'm not sure if that's
intentional. There should be really just a single way to repair MVs, either by depending on
keeping them consistent with the base table and exclusively following the mutation based approach
as described in this ticket, or by treating MVs just a regular tables during repairs. However,
in the second case we'd have to make sure to always include all MVs for repaired tables in
a repair session, in order to keep them consistent. 

> Incremental repairs broken for MVs and CDC
> ------------------------------------------
>
>                 Key: CASSANDRA-12888
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12888
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Streaming and Messaging
>            Reporter: Stefan Podkowinski
>            Priority: Critical
>
> SSTables streamed during the repair process will first be written locally and afterwards
either simply added to the pool of existing sstables or, in case of existing MVs or active
CDC, replayed on mutation basis:
> As described in {{StreamReceiveTask.OnCompletionRunnable}}:
> {quote}
> We have a special path for views and for CDC.
> For views, since the view requires cleaning up any pre-existing state, we must put all
partitions through the same write path as normal mutations. This also ensures any 2is are
also updated.
> For CDC-enabled tables, we want to ensure that the mutations are run through the CommitLog
so they can be archived by the CDC process on discard.
> {quote}
> Using the regular write path turns out to be an issue for incremental repairs, as we
loose the {{repaired_at}} state in the process. Eventually the streamed rows will end up in
the unrepaired set, in contrast to the rows on the sender site moved to the repaired set.
The next repair run will stream the same data back again, causing rows to bounce on and on
between nodes on each repair.
> See linked dtest on steps to reproduce. An example for reproducing this manually using
ccm can be found [here|https://gist.github.com/spodkowinski/2d8e0408516609c7ae701f2bf1e515e8]



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