Fix thread-safety issue in LogRecordSharedPool.Rent() #6833

kimjaejung96 · 2026-01-17T05:42:28Z

Changes

This PR fixes a thread-safety issue in LogRecordSharedPool.Rent() where the same LogRecord instance could be rented to multiple threads concurrently under high contention.

Fixed Race Condition: In Rent(), when TryRentCoreRare fails (due to a race), changed the behavior to break the loop and create a new LogRecord instance. Previously, it would continue and retry with a new index, which could lead to a duplicate rental.
Optimized Calculation: Extracted slotIndex calculation to avoid redundant modulo operations.
Added Regression Test: Added RentShouldNeverReturnSameInstanceConcurrently in LogRecordSharedPoolTests.cs to verify the fix.

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)

Fixes open-telemetry#6233 - Change TryRentCoreRare failure handling from 'continue' to 'break' to prevent duplicate LogRecord rentals under high contention - Optimize slotIndex calculation - Add regression test RentShouldNeverReturnSameInstanceConcurrently

linux-foundation-easycla · 2026-01-17T05:42:36Z

The committers listed above are authorized under a signed CLA.

✅ login: Kielek / name: Piotr Kiełkowicz (b45f9c4)
✅ login: kimjaejung96 / name: kimjaejung96 (5d5a38a, 8a8f10b, 9edc7dc)
✅ login: martincostello / name: Martin Costello (5d5a38a)

kimjaejung96 · 2026-01-22T03:21:43Z

Hi.

@alanwest @open-telemetry/dotnet-approvers could you please review this? It addresses the thread-safety issue in LogRecordSharedPool (Fixes #6233).

@TimothyMothra, tagging you as well since this is in the Logs/LogRecord pool area.

Also, this is my first time requesting a review in this repo—if I’m not tagging the right people or there’s a preferred process, please let me know and I’ll follow it.

github-actions · 2026-01-29T03:54:46Z

This PR was marked stale due to lack of activity and will be closed in 7 days. Commenting or pushing will instruct the bot to automatically remove the label. This bot runs once per day.

martincostello

Please update the CHANGELOG with the bug fix details.

martincostello · 2026-01-29T14:48:29Z

test/OpenTelemetry.Tests/Logs/LogRecordSharedPoolTests.cs

+                    if (!inUseRecords.TryAdd(record, Environment.CurrentManagedThreadId))
+                    {
+                        Volatile.Write(ref duplicateDetected, true);
+                        duplicateDetails = $"LogRecord {record.GetHashCode()} rented by thread {inUseRecords[record]} and {Environment.CurrentManagedThreadId}";


If the bug happened again, this might overwrite a race itself. It would be better to add the message to a concurrent collection, then join its contents to construct the failure message.

Thank you for the review, @martincostello!

I've addressed your feedback:

CHANGELOG updated - Added the bug fix entry under the Unreleased section in src/OpenTelemetry/CHANGELOG.md

Test race condition fixed - Changed the duplicate detection logic to use ConcurrentQueue<string> instead of a single string variable. Now all duplicate events are collected safely and joined in the final assertion message.

Changes:

Replaced duplicateDetected (bool) + duplicateDetails (string) with ConcurrentQueue<string> duplicateMessages

Used TryGetValue to safely retrieve the first thread ID

Updated the assertion to Assert.True(duplicateMessages.IsEmpty, ...)

Please let me know if there's anything else that needs to be addressed.

- Add CHANGELOG entry for thread-safety fix in LogRecordSharedPool.Rent() - Use ConcurrentQueue for duplicate detection messages in test to avoid race condition when collecting failure details"

src/OpenTelemetry/CHANGELOG.md

Co-authored-by: Martin Costello <martin@martincostello.com>

codecov · 2026-01-30T08:04:36Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.14%. Comparing base (cfc2d0c) to head (b45f9c4).
⚠️ Report is 7 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6833      +/-   ##
==========================================
- Coverage   87.17%   87.14%   -0.04%     
==========================================
  Files         263      263              
  Lines       12385    12386       +1     
==========================================
- Hits        10797    10794       -3     
- Misses       1588     1592       +4

Flag	Coverage Δ
unittests-Project-Experimental	`87.01% <100.00%> (-0.15%)`	⬇️
unittests-Project-Stable	`87.06% <100.00%> (+<0.01%)`	⬆️

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

Files with missing lines	Coverage Δ
src/OpenTelemetry/Logs/Pool/LogRecordSharedPool.cs	`100.00% <100.00%> (ø)`

... and 1 file with indirect coverage changes

github-actions · 2026-02-07T03:54:08Z

This PR was marked stale due to lack of activity and will be closed in 7 days. Commenting or pushing will instruct the bot to automatically remove the label. This bot runs once per day.

kimjaejung96 · 2026-02-07T05:52:08Z

Hi @martincostello — re-requesting review 🙇
Please let me know if there's anything else I should update.

kimjaejung96 requested a review from a team as a code owner January 17, 2026 05:42

github-actions bot added the pkg:OpenTelemetry Issues related to OpenTelemetry NuGet package label Jan 17, 2026

kimjaejung96 mentioned this pull request Jan 17, 2026

[bug] LogRecordSharedPool isn't thread safe #6233

Open

github-actions bot added the Stale Issues and pull requests which have been flagged for closing due to inactivity label Jan 29, 2026

Kielek removed the Stale Issues and pull requests which have been flagged for closing due to inactivity label Jan 29, 2026

martincostello reviewed Jan 29, 2026

View reviewed changes

kimjaejung96 added 2 commits January 30, 2026 14:05

Address PR review feedback

9edc7dc

- Add CHANGELOG entry for thread-safety fix in LogRecordSharedPool.Rent() - Use ConcurrentQueue for duplicate detection messages in test to avoid race condition when collecting failure details"

Merge upstream/main and resolve CHANGELOG conflict

8a8f10b

martincostello approved these changes Jan 30, 2026

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src/OpenTelemetry/CHANGELOG.md Outdated Show resolved Hide resolved

kimjaejung96 and others added 2 commits January 30, 2026 16:30

Update src/OpenTelemetry/CHANGELOG.md

5d5a38a

Co-authored-by: Martin Costello <martin@martincostello.com>

Merge branch 'main' into fix/6233-logrecordsharedpool-threadsafe

b45f9c4

github-actions bot added the Stale Issues and pull requests which have been flagged for closing due to inactivity label Feb 7, 2026

kimjaejung96 requested a review from martincostello February 7, 2026 05:51

github-actions bot removed the Stale Issues and pull requests which have been flagged for closing due to inactivity label Feb 8, 2026

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Fix thread-safety issue in LogRecordSharedPool.Rent() #6833

Fix thread-safety issue in LogRecordSharedPool.Rent() #6833

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