Details
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Bug
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Status: Resolved
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Urgent
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Resolution: Fixed
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None
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Critical
Description
So seeing a problem in 3.11.0 where SSTables are being lost from the view and not being included in compactions/as candidates for compaction. It seems to get progressively worse until there's only 1-2 SSTables in the view which happen to be the most recent SSTables and thus compactions completely stop for that table.
The SSTables seem to still be included in reads, just not compactions.
The issue can be fixed by restarting C*, as it will reload all SSTables into the view, but this is only a temporary fix. User defined/major compactions still work - not clear if they include the result back in the view but is not a good work around.
This also results in a discrepancy between SSTable count and SSTables in levels for any table using LCS.
Keyspace : xxx Read Count: 57761088 Read Latency: 0.10527088681224288 ms. Write Count: 2513164 Write Latency: 0.018211106398149903 ms. Pending Flushes: 0 Table: xxx SSTable count: 10 SSTables in each level: [2, 0, 0, 0, 0, 0, 0, 0, 0] Space used (live): 894498746 Space used (total): 894498746 Space used by snapshots (total): 0 Off heap memory used (total): 11576197 SSTable Compression Ratio: 0.6956629530569777 Number of keys (estimate): 3562207 Memtable cell count: 0 Memtable data size: 0 Memtable off heap memory used: 0 Memtable switch count: 87 Local read count: 57761088 Local read latency: 0.108 ms Local write count: 2513164 Local write latency: NaN ms Pending flushes: 0 Percent repaired: 86.33 Bloom filter false positives: 43 Bloom filter false ratio: 0.00000 Bloom filter space used: 8046104 Bloom filter off heap memory used: 8046024 Index summary off heap memory used: 3449005 Compression metadata off heap memory used: 81168 Compacted partition minimum bytes: 104 Compacted partition maximum bytes: 5722 Compacted partition mean bytes: 175 Average live cells per slice (last five minutes): 1.0 Maximum live cells per slice (last five minutes): 1 Average tombstones per slice (last five minutes): 1.0 Maximum tombstones per slice (last five minutes): 1 Dropped Mutations: 0
Also for STCS we've confirmed that SSTable count will be different to the number of SSTables reported in the Compaction Bucket's. In the below example there's only 3 SSTables in a single bucket - no more are listed for this table. Compaction thresholds haven't been modified for this table and it's a very basic KV schema.
Keyspace : yyy
Read Count: 30485
Read Latency: 0.06708991307200263 ms.
Write Count: 57044
Write Latency: 0.02204061776873992 ms.
Pending Flushes: 0
Table: yyy
SSTable count: 19
Space used (live): 18195482
Space used (total): 18195482
Space used by snapshots (total): 0
Off heap memory used (total): 747376
SSTable Compression Ratio: 0.7607394576769735
Number of keys (estimate): 116074
Memtable cell count: 0
Memtable data size: 0
Memtable off heap memory used: 0
Memtable switch count: 39
Local read count: 30485
Local read latency: NaN ms
Local write count: 57044
Local write latency: NaN ms
Pending flushes: 0
Percent repaired: 79.76
Bloom filter false positives: 0
Bloom filter false ratio: 0.00000
Bloom filter space used: 690912
Bloom filter off heap memory used: 690760
Index summary off heap memory used: 54736
Compression metadata off heap memory used: 1880
Compacted partition minimum bytes: 73
Compacted partition maximum bytes: 124
Compacted partition mean bytes: 96
Average live cells per slice (last five minutes): NaN
Maximum live cells per slice (last five minutes): 0
Average tombstones per slice (last five minutes): NaN
Maximum tombstones per slice (last five minutes): 0
Dropped Mutations: 0
Apr 27 03:10:39 cassandra[9263]: TRACE o.a.c.d.c.SizeTieredCompactionStrategy Compaction buckets are [[BigTableReader(path='/var/lib/cassandra/data/yyy/yyy-5f7a2d60e4a811e6868a8fd39a64fd59/mc-67168-big-Data.db'), BigTableReader(path='/var/lib/cassandra/data/yyy/yyy-5f7a2d60e4a811e6868a8fd39a64fd59/mc-67167-big-Data.db'), BigTableReader(path='/var/lib/cassandra/data/yyy/yyy-5f7a2d60e4a811e6868a8fd39a64fd59/mc-67166-big-Data.db')]]
Also for every LCS table we're seeing the following warning being spammed (seems to be in line with anticompaction spam):
Apr 26 21:30:09 cassandra[9263]: WARNÂ o.a.c.d.c.LeveledCompactionStrategy Live sstable /var/lib/cassandra/data/xxx/xxx-8c3ef9e0e3fc11e6868a8fd39a64fd59/mc-79024-big-Data.db from level 0 is not on corresponding level in the leveled manifest. This is not a problem per se, but may indicate an orphaned sstable due to a failed compaction not cleaned up properly.
This is a vnodes cluster with 256 tokens per node, and the only thing that seems like it could be causing issues is anticompactions.
CASSANDRA-14079 might be related but doesn't quite describe the same issue, and in this case we're using only a single disk for data. Have yet to reproduce but figured worth reporting here first.
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