fix: batch size accounting in BatchSpanProcessor when queue is full

[dojiong]

Fixes #

• When the queue is full, spans are dropped but current_batch_size is incremented
• However, when spans are later exported, current_batch_size is still decremented based on the actual number of spans exported

Changes

moving the current_batch_size.fetch_add to only execute when try_send succeeds

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)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: dojiong / name: Lo (f4b856b)
• ✅ login: cijothomas / name: Cijo Thomas (73aeae9)

[codecov]

Codecov Report

❌ Patch coverage is 68.18182% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.1%. Comparing base (42139cb) to head (f4b856b).

Files with missing lines	Patch %	Lines
opentelemetry-sdk/src/trace/span_processor.rs	68.1%	7 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3089   +/-   ##
=====================================
  Coverage   80.1%   80.1%           
=====================================
  Files        126     126           
  Lines      21957   21958    +1     
=====================================
+ Hits       17603   17604    +1     
  Misses      4354    4354           

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[Copilot]

Pull Request Overview

This PR fixes a bug in the BatchSpanProcessor where the current batch size counter was incorrectly incremented even when spans were dropped due to a full queue, leading to inaccurate batch size accounting.

• Moved the batch size increment logic to only execute when spans are successfully queued
• Restructured the span queuing logic to use a match statement for clearer error handling
• Added test verification for correct batch size tracking when spans are dropped

Comments suppressed due to low confidence (1)

opentelemetry-sdk/src/trace/span_processor.rs:569

• There appears to be an extra closing brace. The function should end after the match statement without this additional closing brace.

    }

[lalitb]

Good catch. Thanks for fixing. Just verified the approach in log processor - which looks fine.

please update the Changelog.

[dojiong]

Good catch. Thanks for fixing. Just verified the approach in log processor - which looks fine.

please update the Changelog.

updated