[Geneva] Fix ETW metadata to allow .NET EventSource subscriptions

[zvorygin]

It's impossible to subscribe to OpenTelemetry EventSource, since data published to the ETW doesn't match manifest/schema inferred from the EtwEventSource Event-annotated methods. Listeners receive errors and truncated data.

Changes

Make manifest schema match the actual data written to the ETW. Changed the internal format to have two fields - buffer size, ad raw data, as .Net EventSource expects(mayb be a breaking change). Verified that Geneva MonitringAgent can ingest the data.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: zvorygin / name: Dmitrii Zvorygin (154067f, f1eae10)
• ✅ login: zvorygin / name: Dmitry Zvorygin (0108f72, 8147dbd, cd5b151)

[github-actions]

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[xiang17]

Looks good to me

[martincostello]

Please add a CHANGELOG entry for this fix.

[Copilot]

Pull request overview

This PR fixes the Geneva ETW transport’s EventSource/ETW metadata mismatch so that .NET EventListener/EventSource subscriptions can successfully parse the emitted payload (preventing listener errors and truncated data).

Changes:

• Adjust ETW payload writing to match the EventSource-inferred manifest schema (length + raw data).
• Add an ETW roundtrip test validating EventListener can receive the full byte[] payload.
• Add an xUnit collection definition to disable parallelization for ETW tests (system-global resource).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
src/OpenTelemetry.Exporter.Geneva/Internal/Transports/EtwDataTransport.cs	Updates EventSource metadata and WriteEventCore payload layout to align ETW data with the generated manifest.
test/OpenTelemetry.Exporter.Geneva.Tests/Internal/Transports/EtwDataTransportTests.cs	Adds a roundtrip ETW/EventListener test to verify the payload is received and decoded correctly.
test/OpenTelemetry.Exporter.Geneva.Tests/EtwCollection.cs	Adds a non-parallel xUnit collection for ETW tests to avoid cross-test interference.

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[zvorygin]

Please add a CHANGELOG entry for this fix.

Added

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.43%. Comparing base (0f90170) to head (8cd3566).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4729      +/-   ##
==========================================
+ Coverage   77.37%   77.43%   +0.05%     
==========================================
  Files         466      466              
  Lines       19764    19766       +2     
==========================================
+ Hits        15292    15305      +13     
+ Misses       4472     4461      -11     

Flag	Coverage Δ
unittests-Exporter.Geneva	56.66% <100.00%> (+0.22%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ter.Geneva/Internal/Transports/EtwDataTransport.cs	86.36% <100.00%> (+1.36%)	⬆️

... and 2 files with indirect coverage changes

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[martincostello]

@zvorygin Please fix the file encoding for EtwCollection.cs and EtwDataTransportTest.cs.