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https://issues.apache.org/jira/browse/CASSANDRA-14572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17849386#comment-17849386
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David Capwell commented on CASSANDRA-14572:
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For visibility there is a large conversation in slack about this feature
https://the-asf.slack.com/archives/CK23JSY2K/p1716324924466269
Here are a few of the points
*) the "group" tables expose a "name" that doesn't reflect the "name" in our
metrics, but instead an internal map used for unique metric detection
*) the term "group" maps to "type" for JMX, so causes confusion for users (the
"group" is "org.apache.cassandra.metrics", every instance of group is actually
"type")
*) implementation is O(N) where N is the number of metrics in the JVM
**) new benchmarks were created using tlp-stress and show that these tables are
2-3x slower than other vtables for a freshly started instance with no tables.
*) UX is hard for users and for automation due to it exposing a internal key
that must be parsed (mentally or by tools) rather than showing columns users
would expect
*) histogram metrics return a single double value, this may not be the best UX
for histograms
We have been talking about solutions to these problems and we should create a
ticket to track this, should make sure to link that once its ready
> 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: 5.1
>
> Attachments: flight_recording_1270017199_13.jfr, keyspayces_group
> responses times.png, keyspayces_group summary.png, select keyspaces_group by
> string prefix.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: 8h
> 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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