Armeria: Limit the cardinality of request metrics

[trustin]

I heard that RestTemplate logs a warning about large cardinality of meter tags and refuses to record the metrics for the tag combinations generated after then. We could also implement something similar.

[trustin]

Related commit: https://github.com/spring-projects/spring-boot/commit/1a9c268b6baecaa44ffb770e736c40960c625cd3
Related issue: https://github.com/spring-projects/spring-boot/issues/11338
Related MeterFilter implementation in Micrometer: https://github.com/micrometer-metrics/micrometer/blob/HEAD@%7B2019-10-03T06:14:12Z%7D/micrometer-core/src/main/java/io/micrometer/core/instrument/config/MeterFilter.java#L207-L231

[trustin]

In Armeria, MetricCollecting{Client,Service} collects the request metrics. We could modify them to count the cardinality and enforce the limitation.

We need to:

• Allow a user specify max cardinality when creating MetricCollecting{Client,Service}.
• Modify MetricCollecting{Client,Service} to respect the max cardinality and warn when the cardinality is too large.
• Add the configuration property for the max cardinality to the Spring Boot integration.

[SooJungDev]

I'll work on it

[trustin]

It's all yours, @SooJungDev!

[heowc]

@SooJungDev @trustin Gentle ping 😉

I'm interested in this. Can I try?
Or can you recommend another issue?

[SooJungDev]

yes, you can try!!@heowc thank you:wink:

[heowc]

@trustin

I've been analyzing the code for a few days, and I have some questions.

We could also implement something similar. (comment)

Does it mean to use Meterfilter? Or does it mean a similar implementation? It seems strange to integrate with spring boot if you mean to implement similarly.

Allow a user to specify max cardinality when creating MetricCollecting{Client,Service}. (comment)

Why should the user set max cardinality in MetricCollecting {Client, Service}? Isn't it a good idea to set it in the registry?

If I'm misunderstanding, please point me in the right path. Thank you. 😄