SOLR-18172 Declare OTEL metrics as BETA in Solr 10

[janhoy]

Update release notes and metrics documents in ref.guide.

Intention is to merge this all the way to branch_10_0 so the ref.guide is updated.

https://issues.apache.org/jira/browse/SOLR-18172

[HoustonPutman]

I would say that we hope to finalize them in an early 10.x release.

[janhoy]

I would say that we hope to finalize them in an early 10.x release.

Yea, that would be the goal. I don't like communicating "hope". What about us instead letting it be undefined until we are ready to GA it, and then remove the disclaimers in docs, and add a release note about metrics now being stable. Then we don't promise too much.

@HoustonPutman Perhaps if we write a short users list mail about this, we can express our hopes in that email instead?

[dsmiley]

can we lock these in for 10.1?

[janhoy]

I'm ready to merge this soon. Here is the email I intend to send to users list:

Subject: [ANNOUNCE] Solr 10.x OpenTelemetry Metrics System Declared BETA

Hi Solr users,

Solr 10.0 introduced a brand new metrics system based on OpenTelemetry (OTEL) instrumentation, replacing the metrics produced by solr-exporter in Solr 9.x. The two systems are not backward compatible.

As we have been working with the new metrics system post-release, we have identified areas that need stabilization before the API can be considered stable. In hindsight, we should have shipped this feature as BETA in 10.0 — we are correcting that now.

The OpenTelemetry-based metrics system is officially designated BETA as of Solr 10.0. Metric names and other details may change in upcoming 10.x minor releases. All such changes will be clearly documented in the release notes.

If you are on Solr 9.x, nothing changes for you. If you have already upgraded to 10.0 and are consuming the new OTEL metrics, please factor this in before treating the metric names as stable.

The Reference Guide will be updated shortly with a BETA disclaimer.

Thank you for your understanding.

The Apache Solr PMC

[epugh]

Thanks for the critical thinking in this topic