Remove mut self reference from LogExporter::export() method.

[lalitb]

Changes

As discussed here - #2374 (comment)
The changes are minimal, and the stress test for the logs now includes an exporter call over the future, causing a slight regression.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Attention: Patch coverage is 15.78947% with 16 lines in your changes missing coverage. Please review.

Project coverage is 79.4%. Comparing base (957659f) to head (4fff54b).

Files with missing lines	Patch %	Lines
opentelemetry-stdout/src/logs/exporter.rs	0.0%	7 Missing ⚠️
opentelemetry-otlp/src/exporter/tonic/logs.rs	0.0%	5 Missing ⚠️
opentelemetry-appender-tracing/src/layer.rs	0.0%	1 Missing ⚠️
opentelemetry-otlp/src/exporter/http/logs.rs	0.0%	1 Missing ⚠️
opentelemetry-otlp/src/logs.rs	0.0%	1 Missing ⚠️
opentelemetry-sdk/src/logs/log_processor.rs	66.6%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2380   +/-   ##
=====================================
  Coverage   79.4%   79.4%           
=====================================
  Files        123     123           
  Lines      21479   21484    +5     
=====================================
+ Hits       17064   17068    +4     
- Misses      4415    4416    +1     

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[cijothomas]

I think this is the right direction. Our processors are only requiring self and not mut self, so there seems to be no strong reason for exporter methods to require mut self. Also looked at tracing-subscriber - its on_event method is also just requiring self , and it lets layers manage its state via interior mutability.

Requiring mut self would prevent exporters's export() method from being called in parallel. While this is a spec requirement now, we expect to allow exporters to be called parallel in certain situations. Instead of adding another trait for that, it seems okay to use self itself and let exporters handle state via interior mutability, if they need to.

Would love to get more feedback on this, as we are close to declaring stability, so can't make breaking changes after that.

[lalitb]

agree, would prefer to have closer on this sooner, the slight regression seen in stress test can then be evaluated to improve with #2374.