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From "Sebastian Estevez (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-10979) LCS doesn't do L0 STC on new tables while an L0->L1 compaction is in progress
Date Thu, 07 Jan 2016 22:32:40 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15088274#comment-15088274
] 

Sebastian Estevez commented on CASSANDRA-10979:
-----------------------------------------------

[~krummas] I mentioned this briefly this morning over chat but now we have more information
specifically we observe a large L0 to L1 compaction that blocks L0 STCS compactions, probably
because the remaining L0 sstables overlap compactingL0. You can see in the log above that
{quote}L0 is too far behind, performing size-tiering there first{quote} does not appear. What
do you think?

> LCS doesn't do L0 STC on new tables while an L0->L1 compaction is in progress
> -----------------------------------------------------------------------------
>
>                 Key: CASSANDRA-10979
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10979
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Compaction
>         Environment: 2.1.11 / 4.8.3 DSE.
>            Reporter: Jeff Ferland
>              Labels: compaction, leveled
>             Fix For: 2.1.x
>
>
> Reading code from https://github.com/apache/cassandra/blob/cassandra-2.1/src/java/org/apache/cassandra/db/compaction/LeveledManifest.java
and comparing with behavior shown in https://gist.github.com/autocracy/c95aca6b00e42215daaf,
the following happens:
> Score for L1,L2,and L3 is all < 1 (paste shows 20/10 and 200/100, due to incremental
repair).
> Relevant code from here is
>     if (Sets.intersection(l1overlapping, compacting).size() > 0)
>         return Collections.emptyList();
> Since there will be overlap between what is compacting and L1 (in my case, pushing over
1,000 tables in to L1 from L0 SCTS), I get a pile up of 1,000 smaller tables in L0 while awaiting
the transition from L0 to L1 and destroy my performance.
> Requested outcome is to continue to perform SCTS on non-compacting L0 tables.



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