Nikolai Grigoriev created CASSANDRA-6496:
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Summary: Endless L0 LCS compactions
Key: CASSANDRA-6496
URL: https://issues.apache.org/jira/browse/CASSANDRA-6496
Project: Cassandra
Issue Type: Bug
Components: Core
Environment: Cassandra 2.0.3, Linux, 6 nodes, 5 disks per node
Reporter: Nikolai Grigoriev
I have first described the problem here:
http://stackoverflow.com/questions/20589324/cassandra-2-0-3-endless-compactions-with-no-traffic
I think I have really abused my system with the traffic (mix of reads, heavy
updates and some deletes). Now after stopping the traffic I see the compactions
that are going on endlessly for over 4 days.
For a specific CF I have about 4700 sstable data files right now. The
compaction estimates are logged as "[3312, 4, 0, 0, 0, 0, 0, 0, 0]".
sstable_size_in_mb=256. 3214 files are about 256Mb (+/1 few megs), other files
are smaller or much smaller than that. No sstables are larger than 256Mb. What
I observe is that LCS picks 32 sstables from L0 and compacts them into 32
sstables of approximately the same size. So, what my system is doing for last 4
days (no traffic at all) is compacting groups of 32 sstables into groups of 32
sstables without any changes. Seems like a bug to me regardless of what did I
do to get the system into this state...
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