export Membrane Version as Prometheus metric

[rrayst]

Summary by CodeRabbit

• New Features
  • Added version metric to Prometheus output, enabling better visibility into the system version through monitoring dashboards.

[coderabbitai]

📝 Walkthrough

Walkthrough

A version metric was added to Prometheus output by introducing a buildVersionLine(Context ctx) method in PrometheusInterceptor that appends version information, integrated into the response builder with a static import of VERSION.

Changes

Cohort / File(s)	Summary
Prometheus Version Metric core/src/main/java/com/predic8/membrane/core/interceptor/prometheus/PrometheusInterceptor.java	Added buildVersionLine(Context ctx) private method to output membrane_info metric with version data. Integrated into buildPrometheusStyleResponse to ensure version metric appears in Prometheus-style responses. Static import for VERSION added.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

Poem

🐰 A whisker twitch, a metric new,
Version info, shining through,
Prometheus sees what hops about,
No more guessing—membrane shouts! 📊

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'export Membrane Version as Prometheus metric' directly and clearly describes the main change: adding version information as a Prometheus metric to the output.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch prometheus_version

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In
`@core/src/main/java/com/predic8/membrane/core/interceptor/prometheus/PrometheusInterceptor.java`:
- Around line 164-166: buildVersionLine currently appends a mangled version
metric into ctx.count which mixes it with membrane_count TYPE header; change
buildVersionLine to write directly to ctx.sb (not ctx.count), emit a "# TYPE
membrane_info gauge" line before the metric, and use the raw VERSION as the
label value instead of prometheusCompatibleName (but make sure to escape any
backslashes and double-quotes in VERSION) so the metric becomes e.g. "# TYPE
membrane_info gauge\nmembrane_info{version=\"<escaped VERSION>\"} 1\n". Ensure
you only reference prometheusCompatibleName for metric/label names elsewhere and
avoid altering label values here.