docs: pipeline: inputs: node_exporter_metrics: document network interface metric expiration

[eschabell]

Signed-off-by: Eric D. Schabell eric@schabell.org

Summary by CodeRabbit

• Documentation
  • Added documentation for network interface metric expiration in the netdev collector.
  • Clarified that, starting with Fluent Bit 5.1.2, metrics for interfaces absent during a scan on Linux or macOS stop being produced, ending their time series instead of retaining previous values.
  • Linked the netdev collector listing to the new documentation section.
  • Noted that other collectors are unaffected.

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• pipeline/inputs/node-exporter-metrics.md

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📝 Walkthrough

Walkthrough

The netdev collector documentation now links to a section describing metric expiration from Fluent Bit 5.1.2. On Linux and macOS, unobserved interfaces stop producing metrics after a scan.

Changes

Netdev collector documentation

Layer / File(s)	Summary
Document metric expiration pipeline/inputs/node-exporter-metrics.md	The collector table links to a new section. The section documents removal of metrics for interfaces absent from a scan, the resulting time-series behavior, the Fluent Bit 5.1.2 availability, and the Linux/macOS scope.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Merge Risk: ⚪ Minimal · up to a66c6

The netdev documentation now describes interface metric expiration on Linux and macOS from Fluent Bit 5.1.2. No current merge-readiness risk is identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main documentation change: documenting network interface metric expiration for the node_exporter_metrics pipeline input.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[eschabell]

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Actionable comments posted: 1

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Inline comments:
In `@pipeline/inputs/node-exporter-metrics.md`:
- Line 132: Update the documented minimum Fluent Bit version for network
interface metric expiration from 5.1.3 to 5.1.2, preserving the statement that
the feature is available in version 5.1.2 and later.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Team

Run ID: 57f5cad6-9075-44c2-96cb-191f8730157f

📥 Commits

Reviewing files that changed from the base of the PR and between aa409a6 and 997cf7c.

📒 Files selected for processing (1)

• pipeline/inputs/node-exporter-metrics.md

Included review availability: Your plan provides up to 2 included reviews per hour; 0 remain after this review.

[eschabell]

@patrick-stephens ready for review!