Hi Maik,
Yes when u have old and new data mixed together the old SStable will not be
dropped until new SStable is fully expired.
There are couple of ways for you to reclaim the storage,
1.) If this is one time thing probably, you can manually run some commands
which will rewrite sstables like, nodetool compact, scrub or
garbagecollect
2.) If u think this would be recurring probably u should set
unchecked_tombstone_compaction to true default is false
unchecked_tombstone_compaction (default: false)
The single sstable compaction has quite strict checks for whether it should
be started, this option disables those checks and for some use cases this
might be needed. Note that this does not change anything for the actual
compaction, tombstones are only dropped if it is safe to do so - it might
just rewrite an sstable without being able to drop any tombstones.
In both cases it will trigger numerous compactions make sure u have enough
i/o or throttle ur compaction threads
If u r going to make DDL change - option 2, would recommend u to go through
some more info on how TWCS wrks
http://thelastpickle.com/blog/2016/12/08/TWCS-part1.html
Thanks
Sri Rathan
Hallo,
>
> we work with Cassandra version 3.0.9 and have a problem in a table with
> TWCS. The command “nodetool repair” create always new files with old data.
> This avoid the delete of the old data.
>
> The layout of the Table is following:
>
> cqlsh> desc stat.spa
>
>
>
> CREATE TABLE stat.spa (
>
> region int,
>
> id int,
>
> date text,
>
> hour int,
>
> zippedjsonstring blob,
>
> PRIMARY KEY ((region, id), date, hour)
>
> ) WITH CLUSTERING ORDER BY (date ASC, hour ASC)
>
> AND bloom_filter_fp_chance = 0.01
>
> AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
>
> AND comment = ''
>
> AND compaction = {'class':
> 'org.apache.cassandra.db.compaction.TimeWindowCompactionStrategy',
> 'compaction_window_size': '1', 'compaction_window_unit': 'DAYS',
> 'max_threshold': '100', 'min_threshold': '4',
> 'tombstone_compaction_interval': '86460'}
>
> AND compression = {'chunk_length_in_kb': '64', 'class':
> 'org.apache.cassandra.io.compress.LZ4Compressor'}
>
> AND crc_check_chance = 1.0
>
> AND dclocal_read_repair_chance = 0.0
>
> AND default_time_to_live = 0
>
> AND gc_grace_seconds = 864000
>
> 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';
>
>
>
> Actual the oldest data are from 2017/04/15 and will not remove:
>
>
>
> $ for f in *Data.db; do meta=$(sudo sstablemetadata $f); echo -e "Max:"
> $(date --date=@$(echo "$meta" | grep Maximum\ time | cut -d" " -f3| cut -c
> 1-10) '+%Y/%m/%d %H:%M') "Min:" $(date --date=@$(echo "$meta" | grep
> Minimum\ time | cut -d" " -f3| cut -c 1-10) '+%Y/%m/%d %H:%M') $(echo
> "$meta" | grep droppable) $(echo "$meta" | grep "Repaired at") ' \t ' $(ls
> -lh $f | awk '{print $5" "$6" "$7" "$8" "$9}'); done | sort
>
> Max: 2017/04/15 12:08 Min: 2017/03/31 13:09 Estimated droppable
> tombstones: 1.7731048805815162 Repaired at: 1525685601400 42K May 7
> 19:56 mc-22922-big-Data.db
>
> Max: 2017/04/17 13:49 Min: 2017/03/31 13:09 Estimated droppable
> tombstones: 1.9600207684319835 Repaired at: 1525685601400 116M May
> 7 13:31 mc-15096-big-Data.db
>
> Max: 2017/04/21 13:43 Min: 2017/04/15 13:34 Estimated droppable
> tombstones: 1.9090909090909092 Repaired at: 1525685601400 11K May 7
> 19:56 mc-22921-big-Data.db
>
> Max: 2017/05/23 21:45 Min: 2017/04/21 14:00 Estimated droppable
> tombstones: 1.8360655737704918 Repaired at: 1525685601400 21M May 7
> 19:56 mc-22919-big-Data.db
>
> Max: 2017/06/12 15:19 Min: 2017/04/25 14:45 Estimated droppable
> tombstones: 1.8091397849462365 Repaired at: 1525685601400 19M May 7
> 14:36 mc-17095-big-Data.db
>
> Max: 2017/06/15 15:26 Min: 2017/05/10 14:37 Estimated droppable
> tombstones: 1.76536312849162 Repaired at: 1529612605539 9.3M Jun
> 21 22:31 mc-25372-big-Data.db
>
> …
>
>
>
> After a „nodetool repair“ run, a new big data file is created that include
> old data from 2017/07/31.
>
>
>
> Max: 2018/07/27 18:10 Min: 2017/03/31 13:13 Estimated droppable
> tombstones: 0.08392555471691247 Repaired at: 011G Sep 11 22:02
> mc-39281-big-Data.db
>
> …
>
> Max: 2018/08/16 18:18 Min: 2018/08/06 12:19 Estimated droppable
> tombstones: 0.0 Repaired at: 1534525730510123M Aug 17 23:46
> mc-36847-big-Data.db
>
> Max: 2018/08/17 19:20 Min: 2017/07/31 12:04 Estimated droppable
> tombstones: 0.03385963490004347 Repaired at: 011G Sep 11
> 21:43 mc-39265-big-Data.db
>
> Max: 2018/08/17 19:20 Min: 2018/07/24 12:33 Estimated droppable
> tombstones: 0.0 Repaired at: 1534525730510135M Sep 11 21:44
> mc-39270-big-Data.db
>
> …
>
> Max: 2018/09/06 17:30 Min: 2018/08/28 12:17 Estimated droppable
> tombstones: 0.0
