docs: in_process_exporter_metrics: fix defaults, sort tables, add metric details

[eschabell]

• Fix path.procfs default from /proc/ to /proc (matches code)
• Sort Configuration and Available metrics tables alphabetically
• Fix fd, typo in metrics description
• Add new "Prometheus metric names" section documenting all 18 exposed metrics with their types (counter/gauge) and which collector enables them

Fixes #2327.

Summary by CodeRabbit

Release Notes

• Documentation
  • Reorganized and expanded Process Exporter Metrics plugin documentation
  • Added detailed Prometheus metrics naming reference with process and thread-level metrics
  • Enhanced configuration sections with updated defaults and metric groupings

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[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request updates the Process Exporter Metrics plugin documentation by reorganizing configuration sections, updating default paths, and replacing the generic "Available metrics" section with a comprehensive Prometheus-oriented metrics reference. The new documentation includes explicit metric names, enablement status, types, and descriptions for both process-level and thread-level metrics.

Changes

Cohort / File(s)

Summary

Process Exporter Metrics Documentation pipeline/inputs/process-exporter-metrics.md

Reorganized configuration exposition; updated default procfs path from /proc/ to /proc; restructured metrics section with new grouping; replaced generic metrics listing with detailed Prometheus metric names (process_context_switches_total, process_cpu_seconds_total, process_fd_ratio, process_major_page_faults_total, process_memory_bytes, process_minor_page_faults_total, process_num_threads, process_open_filedesc, process_read_bytes_total, process_start_time_seconds, process_states, process_write_bytes_total, and thread-level equivalents); added structured process-level and thread-level metrics sections with explicit enablement mappings (+41/-9 lines)

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Suggested labels

4.2.1

Suggested reviewers

• esmerel
• patrick-stephens

Poem

🐰 A rabbit's celebration of clearer docs:
Configuration sorted, metrics now gleam,
Prometheus names flow like a dream,
Procfs paths polished, tables aligned,
Better documentation, beautifully designed! ✨

🚥 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 accurately describes the main changes: fixing default path, sorting tables, and adding metric details, all of which are reflected in the documentation update.
Linked Issues check	✅ Passed	The pull request addresses all key objectives from issue #2327: sorts configuration and metrics tables, corrects typos, lists previously missing Prometheus metrics, and provides comprehensive metric documentation.
Out of Scope Changes check	✅ Passed	All changes in the pull request are directly related to documentation improvements for the Process Exporter Metrics plugin and are within scope of the linked issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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🧹 Recent nitpick comments

pipeline/inputs/process-exporter-metrics.md (1)

61-61: Consider using a more standard date format.

The date "1970/01/01" uses slash separators, which is less common in technical documentation. Consider using "1970-01-01" (ISO 8601 format) or "Unix epoch" for better consistency with technical standards.

📝 Suggested date format improvement

-| `process_start_time_seconds`        | `start_time`      | gauge   | Start time in seconds since 1970/01/01.            |
+| `process_start_time_seconds`        | `start_time`      | gauge   | Start time in seconds since Unix epoch (1970-01-01). |

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📜 Recent review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 77d150b and 1212e83.

📒 Files selected for processing (1)

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

🔇 Additional comments (3)

pipeline/inputs/process-exporter-metrics.md (3)

29-42: LGTM! Well-organized collector documentation.

The Available metrics table is properly sorted alphabetically and provides clear descriptions for each collector. The descriptions consistently reference /proc as the data source.

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24-24: Verify the default path.procfs value against the fluent-bit plugin source code.

The documentation shows the default as /proc. This claim cannot be verified from the documentation repository alone—the actual plugin implementation exists in the separate fluent/fluent-bit repository. Confirm that this default matches the plugin's source code in src/plugins/in_process_exporter/ or equivalent location.

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43-74: Source code verification unavailable in documentation repository.

This documentation appears internally consistent and properly follows Prometheus conventions for metric types (counters for accumulated work like CPU time and I/O bytes; gauges for current state like memory and file descriptors). The "Enabled by" mappings correctly match the 9 available collectors listed in the configuration section. However, definitive verification that these metric names and types match what the plugin actually exports requires access to the fluent-bit source code repository (plugins/in_process_exporter_metrics), which is not available in this documentation repository.

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[eschabell]

@esmerel a bit of a cleanup!

[eschabell]

Thanks for the review @cosmo0920, merging.