in_node_exporter_metrics: expire metrics for networking

[cosmo0920]

This is because network interfaces sometimes absent after VM creation and exit.

The test is now implemented in the existing runtime binary at in_node_exporter_metrics.c and registered at line 314.

Summary:

• Creates a fake /proc/net/dev containing eth0 and veth-stale.
• Confirms both are emitted.
• Rewrites the file without veth-stale.
• Confirms the next snapshot retains eth0 but removes veth-stale.

The existing diskstats test was restored in the same binary. The netdev test is Linux-only, so macOS correctly reports one test; Linux will report two. The CMake registration now supports the binary on both platforms at CMakeLists.txt

Verification:

• cmake --build build --target flb-rt-in_node_exporter_metrics -j8 — passed.
• ctest --test-dir build -R '^flb-rt-in_node_exporter_metrics$' --output-on-failure — passed on macOS (diskstats).
• Linux netdev execution and memory-checker pass — not run because this host is macOS; the Linux-only section passed a forced syntax compilation.

Closes #9400.

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Testing
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Documentation

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Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• Bug Fixes

  • Network device metrics now remove stale label sets when devices are no longer detected, preventing outdated device metrics from persisting across scans.

• Tests

  • Added runtime coverage for disk statistics metric collection.
  • Added Linux coverage verifying that metrics for removed network devices disappear from subsequent snapshots.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-04T07:50:13.613737Z	a41394d	PR opened

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Team

Run ID: 97953410-1cc7-49ad-9488-e4b4cc49b8c1

📥 Commits

Reviewing files that changed from the base of the PR and between 98f3bde and a41394d.

📒 Files selected for processing (4)

• plugins/in_node_exporter_metrics/ne_netdev_darwin.c
• plugins/in_node_exporter_metrics/ne_netdev_linux.c
• tests/runtime/CMakeLists.txt
• tests/runtime/in_node_exporter_metrics.c

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📝 Walkthrough

Walkthrough

The netdev collectors now expire labels for devices absent from a scan. Runtime coverage adds diskstats output validation and a Linux test for stale network-device removal.

Changes

Network metric expiration

Layer / File(s)	Summary
Collector metric expiration plugins/in_node_exporter_metrics/ne_netdev_linux.c, plugins/in_node_exporter_metrics/ne_netdev_darwin.c	The Linux and Darwin collectors expire metric label sets for devices not observed during the current scan.
Runtime test harness tests/runtime/in_node_exporter_metrics.c, tests/runtime/CMakeLists.txt	Runtime output handling, the diskstats scrape test, platform registration, and test-list entries were added.
Stale device validation tests/runtime/in_node_exporter_metrics.c	A Linux test uses temporary procfs data to verify that a removed network device disappears from later metric snapshots.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to a4139

This change removes metrics for network interfaces that disappear between scans and adds runtime coverage for the expected lifecycle. No merge-blocking risk is currently identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 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%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 3 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: expiring stale network metrics in the node exporter metrics plugin. It is concise and specific.
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 3 files. (1 skipped: 1 unsupported.)

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch cosmo0920-expire-metrics-for-networking

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[chatgpt-codex-connector]

💡 Codex Review

fluent-bit/tests/runtime/CMakeLists.txt

Lines 38 to 40 in a41394d

	# Input Plugins
	FLB_RT_TEST(FLB_IN_EVENT_TEST "in_event_test.c")
	# FLB_IN_WINEVTLOG is only enabled on Windows builds

Split the runtime tests into a separate commit

This commit combines the node-exporter plugin implementation with a new runtime test and its CMake registration, while the repository requires plugin changes and tests to be separate commits. Move this registration and in_node_exporter_metrics.c into a tests: runtime: commit, leaving the plugin changes in the component commit.

AGENTS.md reference: AGENTS.md:L174-L179

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