[Geneva] Log error when buffer too small

[martincostello]

Fixes #1152

Changes

Log an error if a metric is too large for the buffer.

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)

[codecov]

Codecov Report

❌ Patch coverage is 70.31250% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.92%. Comparing base (435cf5f) to head (d6978b8).
⚠️ Report is 4 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...eva/Metrics/OtlpProtobuf/OtlpProtobufSerializer.cs	8.33%	11 Missing ⚠️
...eva/Internal/EventHeader/EventHeaderLogExporter.cs	0.00%	5 Missing ⚠️
...va/Internal/GenevaBufferOverflowExceptionHelper.cs	92.00%	2 Missing ⚠️
...a/Metrics/OtlpProtobuf/ProtobufSerializerHelper.cs	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4027      +/-   ##
==========================================
+ Coverage   75.76%   75.92%   +0.16%     
==========================================
  Files         438      439       +1     
  Lines       18002    18038      +36     
==========================================
+ Hits        13639    13696      +57     
+ Misses       4363     4342      -21     

Flag	Coverage Δ
unittests-Exporter.Geneva	55.42% <70.31%> (+0.70%)	⬆️

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

Files with missing lines	Coverage Δ
...ry.Exporter.Geneva/Internal/ExporterEventSource.cs	62.96% <100.00%> (+32.01%)	⬆️
...emetry.Exporter.Geneva/Metrics/MetricSerializer.cs	100.00% <100.00%> (ø)
...a/Metrics/OtlpProtobuf/ProtobufSerializerHelper.cs	98.41% <88.88%> (-1.59%)	⬇️
...va/Internal/GenevaBufferOverflowExceptionHelper.cs	92.00% <92.00%> (ø)
...eva/Internal/EventHeader/EventHeaderLogExporter.cs	14.08% <0.00%> (-0.41%)	⬇️
...eva/Metrics/OtlpProtobuf/OtlpProtobufSerializer.cs	90.51% <8.33%> (+0.55%)	⬆️

... and 1 file with indirect coverage changes

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[Copilot]

Pull request overview

Adds a dedicated error log path for Geneva metric TLV serialization buffer overflows, addressing #1152 by producing a clearer diagnostic event when a metric cannot fit into the fixed-size buffer.

Changes:

• Catch buffer-exhaustion exceptions during TLV metric export and emit a dedicated EventSource error event.
• Add a new ExporterEventSource event (ID 11) for “metric serialization buffer exceeded”.
• Add a unit test validating the new buffer-overflow log behavior and update Geneva exporter changelog.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
test/OpenTelemetry.Exporter.Geneva.Tests/GenevaMetricExporterTests.cs	Adds a new test that forces a serialization buffer overflow and asserts the dedicated error event is emitted.
src/OpenTelemetry.Exporter.Geneva/Metrics/TlvMetricExporter.cs	Adds targeted exception handling to detect buffer overflow and log the new event.
src/OpenTelemetry.Exporter.Geneva/Internal/ExporterEventSource.cs	Introduces a new EventSource event (ID 11) with a clearer buffer-overflow message.
src/OpenTelemetry.Exporter.Geneva/CHANGELOG.md	Documents the new error logging behavior in Unreleased notes.

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[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.