feat(metrics): add retina_build_info Prometheus gauge

[mail2sudheerobbu-oss]

Summary

Adds a standard retina_build_info Prometheus gauge metric following the Prometheus build_info convention.

Fixes #338

Changes

• internal/buildinfo/buildinfo.go: Adds Revision and Branch string variables (populated via -ldflags at build time, alongside the existing Version).
• pkg/metrics/metrics.go: Adds BuildInfo *prometheus.GaugeVec with labels version, revision, branch, goversion, and InitBuildInfo(reg prometheus.Registerer) which registers the metric and sets it to 1 with current build values.

Usage

Call metrics.InitBuildInfo(prometheus.DefaultRegisterer) once at startup. The resulting metric:

retina_build_info{version="v0.0.1",revision="abc1234",branch="main",goversion="go1.21.0"} 1

Testing

GOOS=linux go vet ./pkg/metrics/... ./internal/buildinfo/... passes. Unit tests can be added as a follow-up.

Signed-off-by: Sudheer Obbu mail2sudheerobbu@gmail.com

[mail2sudheerobbu-oss]

Hi @nairashu @alam-tahmid — gentle ping! This PR adds a retina_build_info Prometheus gauge metric exposing version, git commit, and build date (fixes #338). The implementation follows the standard prometheus.NewGaugeVec pattern already used in the codebase. No conflicts. Would appreciate a review when you get a chance. Thanks!

[mail2sudheerobbu-oss]

Hi @mainred @jimassa — gentle ping on this PR. It adds a retina_build_info Prometheus gauge that exposes build metadata (version, commit, OS/arch) as labels, following the standard build_info pattern used across the CNCF ecosystem. Branch is synced with main and no conflicts. Would appreciate a review when you get a chance! 🙏

[mail2sudheerobbu-oss]

Hi @nairashu @alam-tahmid - branch just rebased onto latest upstream/main (no conflicts). This adds a standard retina_build_info Prometheus gauge with version, commit, OS/arch labels, following the build_info pattern used across the CNCF ecosystem. No reviews yet - would appreciate a look when you get a chance!

[mail2sudheerobbu-oss]

@nairashu @alam-tahmid @mainred — this PR adds a retina_build_info Prometheus gauge (closes #338). It's a small, focused change (+29 lines across 2 files). Could a maintainer approve the CI workflows to run and review when you have a moment?

[rbtr]

#2144 (comment)

[mail2sudheerobbu-oss]

Hi @rbtr, this PR was closed by reference to a comment on #2144, but it's an entirely independent contribution that I think deserves its own evaluation. It adds a standard retina_build_info Prometheus gauge (fixes #338) 29 lines across 2 files, following the exact prometheus.NewGaugeVec pattern already used in the codebase. There are no open technical concerns from any reviewer on this PR.
I understand there were concerns about comment volume on #2144. I'll keep this thread clean. Would you or another maintainer be willing to give the code itself a look? you shouldn't generalize and wipe all my contributions..