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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9621) Repair of the SystemDistributed keyspace creates a non-trivial amount of memory pressure
Date Fri, 19 Jun 2015 16:38:01 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14593607#comment-14593607
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Sylvain Lebresne commented on CASSANDRA-9621:
---------------------------------------------

Yes, though that's not only a problem for sequential repairs. That is, I could agree that
the underlying problem is that we flush for every range, but CASSANDRA-9491 only has a (partial)
solution for sequential repair currently. And since a proper solution to that in all case
(including parallel repairs) is probably not coming before the release of 2.2, I'd suggest
implementing this to avoid surprise for people upgrading to 2.2. Not that I feel terribly
strongly, just feels the safer option to me.

> Repair of the SystemDistributed keyspace creates a non-trivial amount of memory pressure
> ----------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-9621
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9621
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Sylvain Lebresne
>            Assignee: Marcus Eriksson
>            Priority: Minor
>             Fix For: 2.2.0 rc2
>
>
> When a repair without any particular option is triggered, the {{SystemDistributed}} keyspace
is repaired for all range, and in particular the {{repair_history}} table. For every range,
that table is written and flushed (as part of normal repair), meaning that every range triggers
the creation of a new 1MB slab region (this also triggers quite a few compactions that also
write and flush {{compaction_progress}} at every start and end).
> I don't know how much of a big deal this will be in practice, but I wonder if it's really
useful to repair the {{repair_*}} tables by default so maybe we could exclude the SystemDistributed
keyspace from default repairs and only repair it if asked explicitly?



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