[Netty 5] Visibility / Metrics

[normanmaurer]

Some visibility may be accomplished via Extensibility however there may also be visibility which is not easily inferred via Extensibility. Do we want to have something like a “Metrics SPI” for these events? Do we take another dependency? Should it be push/pull (see github discussion )?

More investigation is needed but we agreed that it would be nice to not bring in another dependency to the core.

[trustin]

Micrometer was good enough to me. Metric collection is a way more complex topic than logging in terms of API space, so I'd leave it to a third party library. I'd also be happy to see Netty pull SLF4J in as one and only logging API because it's now de facto.

[marcingrzejszczak]

I'm a co-maintainer of Spring Cloud Sleuth and Micrometer projects (together with @shakuzen and @jonatan-ivanov).

Micrometer Observation is part of the Micrometer 1.10 release and Micrometer Tracing is a new project. The idea of Micrometer Observation is that you instrument code once but you get multiple benefits out of it - e.g. you can get tracing, metrics, logging or whatever you see fit).

If there's still interest in adding this feature for Netty 6, we could provide a PR to add support for that using Micrometer Observation so that except for metrics, spans could be created and tracing context propagation could happen too.

if there's still some willingness to have that done in Netty 6, I can contribute this feature. I've done sth similar for Armeria line/armeria#4980

[marcingrzejszczak]

@trustin WDYT about adding Micrometer Observation support as we did for Armeria?

[jonatan-ivanov]

Hey, do you have any thought using the Observation API (above)?
I think its scope is wider than just metrics since it makes it possible to instrument the codebase once and get metrics, tracing, etc. out of it without the need of re-instrumenting using multiple tools.