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Re: Infinite loop of single SSTable compactions


nodetool compactionstats  --- see compacting which table
nodetool cfstats keyspace_name.table_name  --- check partition side, tombstones

go the data file directories:  look the data file size, timestamp,  --- compaction will write to new temp file with _tmplink...,

use sstablemetadata ...   ---- look the largest or oldest one first

of course, other factors may be,  like disk space, etc
also what are compaction_throughput_mb_per_sec in cassandra.yaml

Hope it is helpful.

Thanks,

James




On Wed, Jul 25, 2018 at 4:18 AM, Martin Mačura <m.macura@xxxxxxxxx> wrote:
Hi,
we have a table which is being compacted all the time, with no change in size:

Compaction History:
compacted_at            bytes_in    bytes_out   rows_merged
2018-07-25T05:26:48.101 57248063878 57248063878 {1:11655}

                  2018-07-25T01:09:47.346 57248063878 57248063878
{1:11655}
                                         2018-07-24T20:52:48.652
57248063878 57248063878 {1:11655}

2018-07-24T16:36:01.828 57248063878 57248063878 {1:11655}

                  2018-07-24T12:11:00.026 57248063878 57248063878
{1:11655}
                                         2018-07-24T07:28:04.686
57248063878 57248063878 {1:11655}

2018-07-24T02:47:15.290 57248063878 57248063878 {1:11655}

                  2018-07-23T22:06:17.410 57248137921 57248063878
{1:11655}

We tried setting unchecked_tombstone_compaction to false, had no effect.

The data is a time series, there will be only a handful of cell
tombstones present. The table has a TTL, but it'll be least a month
before it takes effect.

Table properties:
   AND compaction = {'class':
'org.apache.cassandra.db.compaction.TimeWindowCompactionStrategy',
'compaction_window_size': '1', 'compaction_window_unit': 'DAYS',
'max_threshold': '32', 'min_threshold': '4',
'unchecked_tombstone_compaction': 'false'}
   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 = 63072000
   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 = 'NONE';

Thanks for any help


Martin

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