[jira] [Issue Comment Deleted] (CASSANDRA-5907) Leveled compaction may cause overlap in L1 when L0 compaction get behind

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-5907?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jonathan Ellis updated CASSANDRA-5907:
--------------------------------------

    Comment: was deleted

(was: Hmm.  I don't follow what the linked line has to do with the problem.  (Quite possibly there are multiple problems.)  It looks to me like the bug is that the max-sstables short circuit here

{code}
                if (candidates.size() > MAX_COMPACTING_L0)
                {
                    // limit to only the MAX_COMPACTING_L0 oldest candidates
                    candidates = new HashSet<SSTableReader>(ageSortedSSTables(candidates).subList(0, MAX_COMPACTING_L0));
                    break;
                }
{code}

can chop out some of the overlapping stuff from L1 that we added to {{candidates}} in the previous loop.  (In which case it shouldn't be necessary to have multiple parallel compactions to cause trouble.))
    
> Leveled compaction may cause overlap in L1 when L0 compaction get behind
> ------------------------------------------------------------------------
>
>                 Key: CASSANDRA-5907
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5907
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Yuki Morishita
>            Assignee: Yuki Morishita
>            Priority: Minor
>             Fix For: 1.2.9
>
>
> 1.2 makes LCS run parallel, though if L0 compaction get far behind and concurrent compactions at L0 where each compaction holds maximum number of SSTable to compact at L0(32), it will likely cause overlap in L1. There will be ERROR log as follows:
> {code}
> ERROR [CompactionExecutor:30] 2013-08-19 17:54:29,648 LeveledManifest.java (line 244) At level 1, SSTableReader(path='xxx-Data.db') [DecoratedKey(204853724659241194183955214890519, 30303132343830), DecoratedKey(69227335985728660912035125310473966323, 30393537373332)] overlaps SSTableReader(path='xxx-Data.db') [DecoratedKey(217896711032704014921095870827202, 30333635363932), DecoratedKey(71430242198281555888954138354238066233, 30333035343132)].  This is caused by a bug in Cassandra 1.1.0 .. 1.1.3.  Sending back to L0.  If you have not yet run scrub, you should do so since you may also have rows out-of-order within an sstable
> {code}
> We should send back compacted SSTables to L0 when compacting max SSTables at L0. Also, the above error message is confusing, at version 1.2, we can reduce to WARNing level without mentioning scrub.
> C* 2.0 performs Size-Tiered compaction on L0 when it has max SSTables and sends back compacted SSTable to L0, so I think we don't need to fix this on 2.0.

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