Added documentation of the Routing Metrics & Observability features in fluent bit 4.2 to router docs. Fixes #2205.

[eschabell]

Added documentation of the Routing Metrics & Observability features in fluent bit 4.2 to router docs. Fixes #2205.

Summary by CodeRabbit

• Documentation
  • Expanded routing docs with a new "Context types" section listing available context fields for condition rules (body, metadata, group metadata/attributes, and OpenTelemetry-related attributes) and examples.
  • Added a "Routing metrics" section describing Prometheus-format metrics, label meanings, how to enable/access them via the HTTP endpoint, configuration snippets, and sample outputs.

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[coderabbitai]

Walkthrough

Updated pipeline/router.md to add a "Context types" section enumerating available context fields for condition evaluation and a "Routing metrics" section documenting Prometheus-format routing metrics, labels, and how to access them via the HTTP server.

Changes

Cohort / File(s)

Change Summary

Router documentation pipeline/router.md

Added a "Context types" section listing body, metadata, group_metadata, group_attributes, otel_resource_attributes, otel_scope_attributes, otel_scope_metadata with descriptions; updated condition rule context reference to point to the new section; added "Routing metrics" section describing Prometheus-format metrics, labels, example outputs, and HTTP /metrics access instructions with config snippets.

Sequence Diagram(s)

sequenceDiagram
  %% Styling for readability
  participant Event as Event (log)
  participant Router as Router
  participant Eval as Condition Evaluator\n(using Context types)
  participant Route as Route Decision
  participant Metrics as Metrics Exporter\n(/metrics)

  rect rgb(230, 247, 255)
    Event->>Router: incoming event
    Router->>Eval: evaluate conditions\n(context: body/metadata/group_*/otel_*)
    Eval-->>Router: match / no-match
    Router->>Route: forward to matched route(s)
  end

  rect rgb(255, 247, 230)
    Router->>Metrics: increment routing metrics\n(e.g., routed_total, unmatched_total, dropped_total)
    Metrics-->>/metrics: exposed via HTTP endpoint
  end

  note over Metrics: Metrics use Prometheus format with labels\n(service, pipeline, route, reason)

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Check accuracy of listed context keys and descriptions against implementation.
• Verify Prometheus metric names, label names, and example output match code that exposes /metrics.
• Confirm HTTP server config snippets and example endpoints are correct.

Possibly related PRs

• Add comprehensive documentation for both tag-based routing and the new conditional routing feature. Fixes #2199. #2200 — Expands conditional routing documentation and context usage; closely related to the new "Context types" content.
• Issue #2205 — Feature request for routing metrics & observability; aligns with the added "Routing metrics" section.

Poem

🐰 In tunnels of docs I quietly hop,
I plant context seeds and watch metrics pop.
Routes hum with counters, labels in tune,
Docs bloom like clover beneath the moon. 🥕✨

Pre-merge checks and finishing touches

✅ 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 change: adding documentation for Routing Metrics & Observability features to router docs, and references the linked issue.
Linked Issues check	✅ Passed	The PR addresses all three coding-related requirements from issue #2205: Routing Metrics documentation, Metrics Export via /metrics endpoint, and Context-based Routing with updated router.md sections.
Out of Scope Changes check	✅ Passed	All changes are within scope—only router.md documentation was modified to add Context types and Routing metrics sections as specified in the linked issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

---

📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a9440e2 and a273e87.

📒 Files selected for processing (1)

• pipeline/router.md (2 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• pipeline/router.md

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

pipeline/router.md (1)

250-250: Address the style guide violation flagged by Vale on the use of "below".

Line 250 uses "See context types below," which triggers a style guide warning. Consider rephrasing to avoid directional language, such as "See the Context types section" or "See Context types for details."

-| `context` | Optional. Specifies where to look for the field. See context types below. Defaults to `body`. |
+| `context` | Optional. Specifies where to look for the field. See the Context types section. Defaults to `body`. |

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 60a2d7f and a9440e2.

📒 Files selected for processing (1)

• pipeline/router.md (2 hunks)

🧰 Additional context used

🪛 GitHub Check: runner / vale

pipeline/router.md

[warning] 250-250:
[vale] reported by reviewdog 🐶
[FluentBit.Directional] Verify your use of 'below' with the Style Guide.

Raw Output:
{"message": "[FluentBit.Directional] Verify your use of 'below' with the Style Guide.", "location": {"path": "pipeline/router.md", "range": {"start": {"line": 250, "column": 82}}}, "severity": "INFO"}

🔇 Additional comments (1)

pipeline/router.md (1)

252-264: Context types section is well-documented and addresses PR objectives.

The new "Context types" section clearly documents the seven supported context options with concise descriptions. This directly addresses the PR objective to document context-based routing for dynamic routing decisions. The table format is consistent with existing documentation patterns.

[eschabell]

AI review passed, merging.