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https://issues.apache.org/jira/browse/CASSANDRA-14572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17837832#comment-17837832
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Caleb Rackliffe commented on CASSANDRA-14572:
---------------------------------------------

Hi [~mmuzaf].

After merging this to trunk, I've noticed a bit of an issue w/ 
{{o.a.c.distributed.test.ReadRepairTest}} failing sporadically due to OOM in my 
CI environment, and looking at the heap situation, the bulk of it is references 
to {{CassandraMetricsRegistry}}. I am able to stabilize things by just giving 
the tests more heap or by reverting this patch entirely, but I'd also like to 
understand, if possible, the impact we expect this patch to have on persistent 
heap usage.

Thanks!

P.S. If I were to experiment with something like a feature flag for my own 
testing, what would be the easiest place to insert that?

> 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: 7h 50m
>  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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