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https://issues.apache.org/jira/browse/CASSANDRA-14572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17821317#comment-17821317
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Stefan Miklosovic commented on CASSANDRA-14572:
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I like non-processor approach more (PR 3137). I think that the building logic
is complicated enough already and putting more logic on top of that and
generating some classes ... nah. Also, how often do we need to update the code
around this, if ever, that it justifies the generation?
I was playing with -walker branch and I was trying to make e.g.
CounterMetricRow implement RowWalker<CounterMetricRow> so the row would visit
itself with a given visitor but I just hit a dead end on some typing and I gave
up but it is just a matter of trying it harder.
That way, we could logically couple Row with its Walker and we could drop whole
walker package completely. I think it is better if all logic around some metric
is centralized to one class rather than having it at multiple places.
my walker branch with a lot of other polishing etc is here
https://github.com/smiklosovic/cassandra/commits/CASSANDRA-14572-walker/
> 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: 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: 2h 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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