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

["Yuki Morishita (JIRA)" <ji...@apache.org>]

Yuki Morishita created CASSANDRA-5907:
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             Summary: 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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