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From "Vitali Djatsuk (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-14647) Reading cardinality from Statistics.db failed
Date Wed, 05 Sep 2018 14:45:00 GMT


Vitali Djatsuk commented on CASSANDRA-14647:

Tested again, and there are no more warning in the log for the whole day. Turned out that
monitoring system is querying all keys via jmx and then filters them based on the configuration

> Reading cardinality from Statistics.db failed
> ---------------------------------------------
>                 Key: CASSANDRA-14647
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Metrics
>         Environment: Clients are doing only writes with Local One, cluster consist of
3 regions with RF3.
> Storage is configured wth jbod/XFS on 10 x 1Tb disks
> IOPS limit for each disk 500 (total 5000 iops)
> Bandwith for each disk 60mb/s (600 total)
> OS is Debian linux.
>            Reporter: Vitali Djatsuk
>            Assignee: Marcus Eriksson
>            Priority: Minor
>             Fix For: 3.0.x
>         Attachments: cassandra_compaction_pending_tasks_7days.png
> There is some issue with sstable metadata which is visible in system.log, the messages
> {noformat}
> WARN  [Thread-6] 2018-07-25 07:12:47,928 - Reading cardinality
from Statistics.db failed for /opt/data/disk5/data/keyspace/table/mc-big-Data.db.{noformat}
> Although there is no such file. 
> The message has appeared after i've changed the compaction strategy from SizeTiered to
Leveled. Compaction strategy has been changed region by region (total 3 regions) and it has
coincided with the double client write traffic increase.
>  I have tried to run nodetool scrub to rebuilt the sstable, but that does not fix the
> So very hard to define the steps to reproduce, probably it will be:
>  # run stress tool with write traffic
>  # under load change compaction strategy from SireTiered to Leveled for the bunch of
>  # add more write traffic
> Reading the code it is said that if this metadata is broken, then "estimating the keys
will be done using index summary". 
>  []

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