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Apache OpenTelemetry

OpenTelemetry Java

Baggage header parsing could discard valid members after encountering invalid percent-encoded entries.

Pull Request

Original Issue

  • Baggage header parsing could fail recovery when invalid percent-encoded entries appeared.
  • The parser needed to reject malformed entries without losing valid baggage members.

Root Cause Analysis

  • Parser recovery treated malformed percent encoding too broadly.
  • Valid members were not preserved cleanly after an invalid entry was encountered.

Investigation Process

  • Reduced the failing input to mixed valid and invalid baggage entries.
  • Compared expected parser recovery behavior with actual member preservation.

Fix Implementation

  • Adjusted parser recovery to preserve valid entries while rejecting malformed ones.
  • Kept the behavior narrow so the patch did not change unrelated header parsing semantics.

Regression Tests

  • Added focused tests around invalid percent-encoded baggage members.
  • Validated behavior across Linux, macOS, and Windows CI.

Lessons Learned

  • Parser fixes are often about recovery semantics, not only accepting or rejecting input.
  • A small open-source patch needs a narrow behavioral claim and strong regression coverage.