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https://issues.apache.org/jira/browse/CASSANDRA-12888?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15655175#comment-15655175
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Blake Eggleston commented on CASSANDRA-12888:
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bq. How about keeping the streamed sstables, and having a special
mutation.apply path that only writes to the commit log/CDC and apply MVs
That does seem like it would be the simplest way to do it. You'd just need to
skip [this
loop|https://github.com/bdeggleston/cassandra/blob/0a1f1c81e641039ca9fd573d5217b6b6f2ad8fb8/src/java/org/apache/cassandra/db/Keyspace.java#L584-L584].
When those commit log entries get replayed on startup though, you'll have
repaired data leak into unrepaired (or at least be duplicated there), causing
data to be re-streamed on the next repair. You could avoid that with a
'cdc-only' flag on the commit log entry though.
> 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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