Probably overlapping sstables
Which compaction strategy?
> On Jun 19, 2019, at 9:51 PM, Léo FERLIN SUTTON <lfer...@mailjet.com.invalid>
> wrote:
>
> I have used the following command to check if I had droppable tombstones :
> `/usr/bin/sstablemetadata --gc_grace_seconds 259200
> /var/lib/cassandra/data/stats/tablename/md-sstablename-big-Data.db`
>
> I checked every sstable in a loop and had 4 sstables with droppable
> tombstones :
>
> ```
> Estimated droppable tombstones: 0.1558453651124074
> Estimated droppable tombstones: 0.20980847354256815
> Estimated droppable tombstones: 0.30826566640798975
> Estimated droppable tombstones: 0.45150604672159905
> ```
>
> I changed my compaction configuration this morning (via JMX) to force a
> tombstone compaction. These are my settings on this node :
>
> ```
> {
> "max_threshold":"32",
> "min_threshold":"4",
> "unchecked_tombstone_compaction":"true",
> "tombstone_threshold":"0.1",
> "class":"org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy"
> }
> ```
> The threshold is lowed than the amount of tombstones in these sstables and I
> expected the setting `unchecked_tombstone_compaction=True` would force
> cassandra to run a "Tombstone Compaction", yet about 24h later all the
> tombstones are still there.
>
> ## About the cluster :
>
> The compaction backlog is clear and here are our cassandra settings :
>
> Cassandra 3.0.18
> concurrent_compactors: 4
> compaction_throughput_mb_per_sec: 150
> sstable_preemptive_open_interval_in_mb: 50
> memtable_flush_writers: 4
>
>
> Any idea what I might be missing ?
>
> Regards,
>
> Leo
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