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From "victor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-12888) Incremental repairs broken for MVs and CDC
Date Wed, 11 Jan 2017 17:01:09 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12888?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15818832#comment-15818832
] 

victor commented on CASSANDRA-12888:
------------------------------------

Hey Benjamin,

thanks for your feedback. At least you refer to "slow" and "painful", but not "massive failure
/ data loss", right? ;)

Still the measure on the complexity to handle is not clear to me. Is it more complex than
handling "manually denormalized tables"? How much more and in which and in which aspects,
if I may ask? I'm not a Cassandra expert, so I can't say I have deeper understanding of Tables
than MVs. From what I interpret of your comment, MVs seem to be at least more complex to operate
in a production cluster than normal tables. From a developer perspective, they are very appealing
and remove some burden on the code.

Are you aware of any description on how to deal with these "painful" scenarios?

Thanks a lot!

> 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
>            Assignee: Benjamin Roth
>            Priority: Critical
>             Fix For: 3.0.x, 3.x
>
>
> 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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