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https://issues.apache.org/jira/browse/CASSANDRA-14572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17799846#comment-17799846
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Maxim Muzafarov commented on CASSANDRA-14572:
---------------------------------------------
I actually have an update for the last benchmark with the _keyspaces_group_
virtual table! The problem was that during the iteration I was resolving a
metric value for EVERY row, which is a really expensive operation if the metric
type is histogram.
So, when I moved the metric value resolution to the post-filtering everything
became perfect, and now we can get a metric value by partition key really fast
and without GC pressure. I've updated the patch according to the new test
results.
See the screenshot below, select a metric by name with value resolution for
each row and without:
!select keyspaces_group compare with wo.png|width=80%!
!select keyspaces_group without value.png|width=80%!
> Expose all table metrics in virtual table
> -----------------------------------------
>
> Key: CASSANDRA-14572
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14572
> Project: Cassandra
> Issue Type: New Feature
> Components: Legacy/Observability, Observability/Metrics
> Reporter: Chris Lohfink
> Assignee: Maxim Muzafarov
> Priority: Low
> Labels: virtual-tables
> Fix For: 5.x
>
> Attachments: keyspayces_group responses times.png, keyspayces_group
> summary.png, select keyspaces_group compare with wo.png, select
> keyspaces_group without value.png, systemv_views.metrics_dropped_message.png,
> thread_pools benchmark.png
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> While we want a number of virtual tables to display data in a way thats great
> and intuitive like in nodetool. There is also much for being able to expose
> the metrics we have for tooling via CQL instead of JMX. This is more for the
> tooling and adhoc advanced users who know exactly what they are looking for.
> *Schema:*
> Initial idea is to expose data via {{((keyspace, table), metric)}} with a
> column for each metric value. Could also use a Map or UDT instead of the
> column based that can be a bit more specific to each metric type. To that end
> there can be a {{metric_type}} column and then a UDT for each metric type
> filled in, or a single value with more of a Map<Text, Text> style. I am
> purposing the column type though as with {{ALLOW FILTERING}} it does allow
> more extensive query capabilities.
> *Implementations:*
> * Use reflection to grab all the metrics from TableMetrics (see:
> CASSANDRA-7622 impl). This is easiest and least abrasive towards new metric
> implementors... but its reflection and a kinda a bad idea.
> * Add a hook in TableMetrics to register with this virtual table when
> registering
> * Pull from the CassandraMetrics registery (either reporter or iterate
> through metrics query on read of virtual table)
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