opentelemetry: allow empty strings for TraceID and SpanID (logs)

[edsiper]

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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
  • Logs with empty trace and span IDs are now accepted; these fields are treated as absent.
• Bug Fixes
  • Validation runs only when trace/span IDs are provided; empty values no longer trigger errors.
  • When present, trace IDs must be 32-char hex and span IDs 16-char hex; non-hex characters are rejected.
• Tests
  • Added coverage ensuring empty trace/span IDs are skipped while the log payload is still processed.

[coderabbitai]

Walkthrough

Updates OpenTelemetry log parsing to treat empty traceId/spanId as absent, bypassing validation and emission. Maintains strict hex and length checks when IDs are non-empty. Adds a test case verifying logs with empty IDs are processed without trace/span metadata.

Changes

Cohort / File(s)	Summary
OpenTelemetry log ID handling src/opentelemetry/flb_opentelemetry_logs.c	Adjusts validation: if traceId/spanId size is 0, treat as absent; otherwise enforce 32/16-char hex respectively. Performs hex checks only when non-empty. Emission gated to valid lengths/hex.
Tests: empty IDs behavior tests/internal/data/opentelemetry/test_cases.json	Adds test case ensuring empty traceId/spanId are ignored and log is emitted without trace/span metadata.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant Ingest as Input Log
  participant Parser as OTEL Log Parser
  participant Validator as ID Validator
  participant Emitter as Encoder/Emitter

  Ingest->>Parser: Log record with traceId/spanId
  Parser->>Validator: Check traceId/spanId
  alt Empty ID
    note over Validator: Size == 0 ➜ treat as absent
    Validator-->>Parser: No ID metadata
  else Non-empty ID
    Validator->>Validator: Length check (traceId=32, spanId=16)
    Validator->>Validator: Hex check (0-9,a-f)
    Validator-->>Parser: Valid or error
  end
  Parser->>Emitter: Emit log (include IDs only if valid & present)
  Emitter-->>Ingest: Output log record

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• opentelemetry: logs: fix packaging length for trace_id and span_id #10767 — Also modifies flb_opentelemetry_logs.c around trace/span ID validation, length handling, and emission gating; closely related logic.

Suggested reviewers

• koleini
• fujimotos

Poem

I hopped through logs with careful eyes,
Where trace and span wore thin disguise;
When strings were void, I let them be,
And carried payloads merrily.
Hexy trails, when bold, I scan—
A tidy burrow, log by span.
(^･ω･^)=☕️

Pre-merge checks and finishing touches

❌ 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%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The title clearly and concisely describes the primary change by indicating that empty strings for TraceID and SpanID in log records are now permitted, using consistent terminology from the codebase and focusing on the main functionality without extraneous detail.

✨ Finishing touches

• 📝 Generate Docstrings

🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch in_opentelemetry_empty_trace_span

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

tests/internal/data/opentelemetry/test_cases.json (1)

1310-1329: Consider adding test cases for partial empty ID scenarios.

While this test case covers both IDs being empty, consider adding test cases for:

1. Empty traceId with valid spanId
2. Valid traceId with empty spanId

These scenarios would ensure the implementation correctly handles mixed empty/non-empty ID combinations.

Would you like me to generate these additional test cases?

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between d985e8e and 27415fc.

📒 Files selected for processing (2)

• src/opentelemetry/flb_opentelemetry_logs.c (4 hunks)
• tests/internal/data/opentelemetry/test_cases.json (1 hunks)

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🔇 Additional comments (3)

src/opentelemetry/flb_opentelemetry_logs.c (2)

162-192: LGTM! Empty trace_id is now correctly treated as absent.

The implementation properly handles empty trace_id strings by treating them as absent (setting to NULL) and skipping validation, while maintaining strict 32-character hex validation for non-empty values. The logic is clear and aligns with the PR objectives.

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200-230: LGTM! Empty span_id is now correctly treated as absent.

The implementation mirrors the trace_id logic, properly handling empty span_id strings by treating them as absent and skipping validation, while maintaining strict 16-character hex validation for non-empty values. The parallel structure with trace_id handling ensures consistency.

tests/internal/data/opentelemetry/test_cases.json (1)

1310-1329: LGTM! Test case correctly verifies empty trace/span ID behavior.

The new test case properly validates that logs with empty traceId and spanId are processed without including trace/span metadata in the output. The expected output correctly shows the log is processed with standard group metadata and log body, while omitting trace_id and span_id from the log_metadata.otlp object.