processor_journald_otel: handle journald as otel processed logs

[cosmo0920]

Implemented the opt-in native journald_otel processor. I recommend this live upstream: it provides reusable semantic mapping without additional runtime dependencies.

It preserves unknown/malformed fields, separates process resources, and supports input/output placement.

The linked [OpenTelemetry proposal](open-telemetry/opentelemetry-specification#4995) remains unmerged; the documentation explicitly identifies the mapping as provisional.

Verification passed:

• Full build and all nine runtime test groups.
• OTLP integration using synthetic journal records, including fan-out isolation.
• Strict Valgrind: zero errors and zero lost blocks.

Exact integration commands run:

tests/integration/.venv/bin/python -m pytest tests/integration/scenarios/out_opentelemetry/tests/test_out_opentelemetry_001.py -k journald -q
VALGRIND=1 VALGRIND_STRICT=1 tests/integration/.venv/bin/python -m pytest tests/integration/scenarios/out_opentelemetry/tests/test_out_opentelemetry_001.py -k journald -q

Both runs: 2 passed. Changes are uncommitted.

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Testing
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• Run local packaging test showing all targets (including any new ones) build.
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Documentation

• Documentation required for this feature

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

• New Features

  • Added the journald_otel processor to convert systemd journal records into OpenTelemetry Logs format.
  • Maps messages, severity, timestamps, resources, and attributes while preserving unrecognized fields.
  • Added options to control field-name casing and underscore handling.
  • Processor can be enabled through the standard build configuration.

• Tests

  • Added runtime and integration coverage for field mapping, severity conversion, timestamps, metadata handling, and pipeline placement.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-08T06:19:17.343960Z	af1cdd7	PR opened

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: a1ed26e5-0e8a-4e42-b784-f02744d75d91

📥 Commits

Reviewing files that changed from the base of the PR and between f784724 and af1cdd7.

📒 Files selected for processing (8)

• cmake/plugins_options.cmake
• plugins/CMakeLists.txt
• plugins/processor_journald_otel/CMakeLists.txt
• plugins/processor_journald_otel/journald_otel.c
• tests/integration/scenarios/out_opentelemetry/config/out_otel_journald.yaml
• tests/integration/scenarios/out_opentelemetry/tests/test_out_opentelemetry_001.py
• tests/runtime/CMakeLists.txt
• tests/runtime/processor_journald_otel.c

Included review availability: Your plan provides up to 8 included reviews per hour; 6 remain after this review.

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📝 Walkthrough

Walkthrough

Adds the journald_otel processor, enables and registers it in CMake, maps journald fields into OpenTelemetry Logs records, and adds runtime and integration coverage.

Changes

Journald OpenTelemetry processor

Layer / File(s)	Summary
Processor build registration cmake/plugins_options.cmake, plugins/CMakeLists.txt, plugins/processor_journald_otel/CMakeLists.txt, tests/runtime/CMakeLists.txt	Adds the processor build option, plugin registration, source registration, runtime test target, and conditional envelope test definition.
Journald record mapping plugins/processor_journald_otel/journald_otel.c	Adds journald key matching, numeric parsing, deep-copy helpers, OTLP resource and attribute mapping, severity conversion, timestamp handling, per-record groups, conditions, and processor configuration.
Runtime and integration validation tests/runtime/processor_journald_otel.c, tests/integration/scenarios/out_opentelemetry/config/out_otel_journald.yaml, tests/integration/scenarios/out_opentelemetry/tests/test_out_opentelemetry_001.py	Tests field mapping, malformed values, resource isolation, options, conditions, envelope handling, and input or output pipeline placement.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: ⚪ Minimal · up to af1cd

The processor is opt-in and has broad runtime and integration coverage; no concrete merge-blocking risk is established.

Sequence Diagram(s)

sequenceDiagram
  participant HTTPInput
  participant journald_otel
  participant OpenTelemetryOutput
  HTTPInput->>journald_otel: Receive journald-style records
  journald_otel->>journald_otel: Map fields into OTLP records
  journald_otel->>OpenTelemetryOutput: Forward grouped OpenTelemetry Logs
  OpenTelemetryOutput-->>HTTPInput: Emit mapped records to the test endpoint

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 12.90% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 31 functions across 3 files. (5 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the new journald_otel processor and its purpose of handling journald records as OpenTelemetry logs.

Full details: Docstring Coverage

Explanation

Docstring coverage is 12.90% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 31 functions across 3 files. (5 skipped: 5 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-handle-journald-as-otel-processed-logs

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: af1cdd759f

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[cosmo0920]

I tagged the milestone as Fluent Bit Next. Once the otel upstream's implementation gets merged, we'll revisit to determine the milestone.