Hi,
The overlaps you're seeing on time windows aren't due to automatic
compactions, but to read repairs.
You must be reading at quorum or local_quorum which can perform foreground
read repair in case of digest mismatch.
You can set unchecked_tombstone_compaction to true if you want to perform
single sstable compaction to purge tombstones and a patch has recently been
merged in to allow twcs to delete fully expired data even in case of
overlap between time windows (I can't remember if it's been merged in
3.11.1).
Just so you know, the timestamp considered for time windows is the max
timestamp. You can have old data in recent time windows, but not the
opposite.
Cheers,
Le mar. 16 janv. 2018 à 12:07, Cogumelos Maravilha <
cogumelosmaravi...@sapo.pt> a écrit :
> Hi list,
>
> My settings:
>
> AND compaction = {'class':
> 'org.apache.cassandra.db.compaction.TimeWindowCompactionStrategy',
> 'compaction_window_size': '4', 'compaction_window_unit': 'HOURS',
> 'enabled': 'true', 'max_threshold': '64', 'min_threshold': '2',
> 'tombstone_compaction_interval': '15000', 'tombstone_threshold': '0.2',
> 'unchecked_tombstone_compaction': 'false'}
> AND compression = {'chunk_length_in_kb': '64', 'class':
> 'org.apache.cassandra.io.compress.LZ4Compressor'}
> AND crc_check_chance = 0.0
> AND dclocal_read_repair_chance = 0.0
> AND default_time_to_live = 1555200
> AND gc_grace_seconds = 10800
> AND max_index_interval = 2048
> AND memtable_flush_period_in_ms = 0
> AND min_index_interval = 128
> AND read_repair_chance = 0.0
> AND speculative_retry = '99PERCENTILE';
>
> Running this script:
>
> for f in *Data.db; do
> ls -lrt $f
> output=$(sstablemetadata $f 2>/dev/null)
> max=$(echo "$output" | grep Maximum\ timestamp | cut -d" " -f3 | cut
> -c 1-10)
> min=$(echo "$output" | grep Minimum\ timestamp | cut -d" " -f3 | cut
> -c 1-10)
> date -d @$max +'%d/%m/%Y %H:%M:%S'
> date -d @$min +'%d/%m/%Y %H:%M:%S'
> done
>
> on sstables I'm getting values like these:
>
> -rw-r--r-- 1 cassandra cassandra 12137573577 Jan 14 20:08
> mc-22750-big-Data.db
> 14/01/2018 19:57:41
> 31/12/2017 19:06:48
>
> -rw-r--r-- 1 cassandra cassandra 4669422106 Jan 14 06:55
> mc-22322-big-Data.db
> 12/01/2018 07:59:57
> 28/12/2017 19:08:42
>
> My goal is using TWCS for sstables expired fast because lots of new data
> is coming in. What is the best approach to archive that? Should I
> disable auto compaction?
> Thanks in advance.
>
>
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-----------------
Alexander Dejanovski
France
@alexanderdeja
Consultant
Apache Cassandra Consulting
http://www.thelastpickle.com
