Support for Prometheus Exemplars

It seems more and more people are interested in using Exemplars with Micrometer and Prometheus (I’m not sure if other backends support it), see:

• https://github.com/micrometer-metrics/micrometer/issues/2627
• SO: How to get spring boot cloud/actuator to support prometheus Exemplars?

Exemplars are metadata attached to metrics (see: Prometheus Exemplars), e.g.: traceId so that you can get an example traceId for your metrics.

This issue is for starting a discussion about this feature and checking the popularity of this possible feature.

Prometheus has Exemplar support for Counter and Histogram, so the subtasks for this issue are:

• https://github.com/micrometer-metrics/micrometer/issues/2811
• https://github.com/micrometer-metrics/micrometer/issues/2812

[jonatan-ivanov]

Hi @jjneely,

Yepp, it is around the corner, we are planning to add it in the next minor release of Micrometer (1.9.0).

Why don’t we have it right now? The exemplar support is quite new in the field: as far as I know (this might have changed) Prometheus is the only backend that supports exemplars and this feature is experimental. OTel Metrics is experimental too so as far as I know, there is no production-ready exemplar support exists as of today (I might be mistaken, please correct me if I’m wrong).

Our plan is to add Exemplar support to Micrometer in 1.9; as you pointed out, Sleuth already has it so after the feature is added to Micrometer the plan is to offer out-of-the-box Exemplar support with Micrometer and Spring Cloud Sleuth (with Prometheus as the backend).

[roadSurfer]

Thanks @jonatan-ivanov, being able to jump from a metric of interest to a trace would be a huge boon. I only have passing familiarity with Sleuth (and, indeed, Micrometer), but I will at least take a look and see how much work is involved.