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Posted to commits@cassandra.apache.org by "Aleksey Yeschenko (JIRA)" <ji...@apache.org> on 2019/07/02 08:46:00 UTC
[jira] [Commented] (CASSANDRA-14670) Table Metrics Virtual Table
[ https://issues.apache.org/jira/browse/CASSANDRA-14670?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16876784#comment-16876784 ]
Aleksey Yeschenko commented on CASSANDRA-14670:
-----------------------------------------------
Are you guys sure that putting `count` in the partition key is a good idea? The partition key isn't really the right sort of place for mutable components like this, and putting it there makes it impossible to look up by partition key. I see the intention, but this might not be the right solution to the sorting issue - relaxing `ORDER BY` is.
> Table Metrics Virtual Table
> ---------------------------
>
> Key: CASSANDRA-14670
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14670
> Project: Cassandra
> Issue Type: Improvement
> Components: Legacy/CQL, Legacy/Observability
> Reporter: Chris Lohfink
> Assignee: Chris Lohfink
> Priority: Low
> Labels: pull-request-available, virtual-tables
> Fix For: 4.0.x
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Different than CASSANDRA-14572 whose goal is to expose all metrics. This is to expose a few hand tailored tables that are particularly useful in debugging slow Cassandra instances (in my experience). These are useful in finding out which table it is that is having issues if you see a node performing poorly in general. This can kinda be figured out with cfstats sorting and some clever bash-foo but its been a bit of a operational UX pain for me personally for awhile.
> examples:
> {code}
> cqlsh> select * from system_views.max_partition_size limit 5;
> max_partition_size | keyspace_name | table_name
> --------------------+---------------+----------------
> 126934 | system | size_estimates
> 9887 | system_schema | columns
> 9887 | system_schema | tables
> 6866 | system | local
> 258 | keyspace1 | standard1
> (5 rows)
> cqlsh> select * from system_views.local_reads limit 5 ;
> count | keyspace_name | table_name | 99th | max | median | per_second
> -------+---------------+-----------------+-----------+-----------+---------+------------
> 23 | system | local | 186563160 | 186563160 | 1629722 | 3.56101
> 22 | system_schema | tables | 4055269 | 4055269 | 454826 | 3.72452
> 14 | system_schema | columns | 1131752 | 1131752 | 545791 | 2.37015
> 14 | system_schema | dropped_columns | 126934 | 126934 | 88148 | 2.37015
> 14 | system_schema | indexes | 219342 | 219342 | 152321 | 2.37015
> (5 rows)
> cqlsh> select * from system_views.coordinator_reads limit 5;
> count | keyspace_name | table_name | 99th | max | median | per_second
> -------+---------------+------------+------+-----+--------+------------
> 2 | system | local | 0 | 0 | 0 | 0.005324
> 1 | system_auth | roles | 0 | 0 | 0 | 0.002662
> 0 | basic | wide | 0 | 0 | 0 | 0
> 0 | basic | wide3 | 0 | 0 | 0 | 0
> 0 | keyspace1 | counter1 | 0 | 0 | 0 | 0
> (5 rows)
> {code}
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