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https://issues.apache.org/jira/browse/CASSANDRA-20250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17926123#comment-17926123
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Dmitry Konstantinov commented on CASSANDRA-20250:
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I have committed a draft version here:
[https://github.com/apache/cassandra/compare/trunk...netudima:cassandra:20250_proto-trunk]
Meter implementation:
[https://github.com/apache/cassandra/compare/trunk...netudima:cassandra:20250_proto-trunk#diff-f04f24b849374e4be4c6d6a3e536578670a4e582bbc30548e5b9b3bc289d4461]
the current version uses global double rate values in
ThreadLocalExponentialMovingAverages: I am thinking about possibility to move
to per-thread rates ticking.
For a full integration it looks like I will have to implement an equivalent of
Timer too (without thread-local logic, just to use my Meter implementation in
it).
Preliminary JMH results:
{code:java}
[java] Benchmark (metricsCount) (polluteCpuCaches) (type)
Mode Cnt Score Error Units
[java] MetersBench.mark 10 true ThreadLocal
avgt 16 484.250 ? 14.694 ns/op
[java] MetersBench.mark 10 true Dropwizard
avgt 16 2792.963 ? 215.250 ns/op {code}
> Provide the ability to disable specific metrics collection
> ----------------------------------------------------------
>
> Key: CASSANDRA-20250
> URL: https://issues.apache.org/jira/browse/CASSANDRA-20250
> Project: Apache Cassandra
> Issue Type: New Feature
> Components: Observability/Metrics
> Reporter: Dmitry Konstantinov
> Assignee: Dmitry Konstantinov
> Priority: Normal
> Attachments: 5.1_profile_cpu.html,
> 5.1_profile_cpu_without_metrics.html, async_profiler_cpu_profiles.zip,
> cpu_profile_insert.html, jmh-result.json, vmstat.log,
> vmstat_without_metrics.log
>
>
> Cassandra has a lot of metrics collected, many of them are collected per
> table, so their instance number is multiplied by number of tables. From one
> side it gives a better observability, from another side metrics are not for
> free, there is an overhead associated with them:
> 1) CPU overhead: in case of simple CPU bound load: I already see like 5.5% of
> total CPU spent for metrics in cpu framegraphs for read load and 11% for
> write load.
> Example: [^cpu_profile_insert.html] (search by "codahale" pattern). The
> framegraph is captured using Async profiler build:
> async-profiler-3.0-29ee888-linux-x64
> 2) memory overhead: we spend memory for entities used to aggregate metrics
> such as LongAdders and reservoirs + for MBeans (String concatenation within
> object names is a major cause of it, for each table+metric name combination a
> new String is created)
>
> The idea of this ticket is to allow an operator to configure a list of
> disabled metrics in cassandra.yaml, like:
> {code:java}
> disabled_metrics:
> - metric_a
> - metric_b
> {code}
> From implementation point of view I see two possible approaches (which can be
> combined):
> # Generic: when a metric is registering if it is listed in disabled_metrics
> we do not publish it via JMX and provide a noop implementation of metric
> object (such as histogram) for it.
> Logging analogy: log level check within log method
> # Specialized: for some metrics the process of value calculation is not for
> free and introduces an overhead as well, in such cases it would be useful to
> check within specific logic using an API (like: isMetricEnabled) do we need
> to do it. Example of such metric:
> ClientRequestSizeMetrics.recordRowAndColumnCountMetrics
> Logging analogy: an explicit 'if (isDebugEnabled())' condition used when a
> message parameter is expensive.
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