fix: concurrent session creation race

[cryo-zd]

Change:

This PR guards the duplicate session check with s.mu in func (s *inMemoryService) Create. The omap.Map lookup used to happen before the lock, so concurrent Create calls for the same (app, user, session) may could both pass the "exists" check and insert.

Fix #367

[gemini-code-assist]

Summary of Changes

Hello @cryo-zd, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical concurrency issue within the inMemoryService's session creation mechanism. Previously, concurrent attempts to create identical sessions could bypass the existence check, potentially resulting in inconsistent state. The core change involves strategically placing a mutex lock to ensure thread-safe access during the session lookup, guaranteeing that only one session is created per unique key. A dedicated concurrent test has also been introduced to validate the robustness of this fix.

Highlights

• Race Condition Fix: Resolved a race condition in inMemoryService.Create where concurrent calls could lead to duplicate session creation by moving the mutex lock to guard the session existence check.
• Concurrency Test: Added a new test case, Test_inMemoryService_CreateConcurrentAccess, to specifically verify the fix for concurrent session creation scenarios.

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[gemini-code-assist]

Code Review

This pull request correctly fixes a race condition in inMemoryService.Create by extending the mutex lock to cover both the check for an existing session and the creation of a new one. This ensures that concurrent calls to create the same session are handled atomically. The change also correctly protects updates to app and user state within the same critical section. I've added a suggestion to improve the new concurrency test to assert the logical correctness of the fix, not just the absence of data races.

[baptmont]

Hi @cryo-zd nice catch and thank you for the contribution. The fix looks great but I would modify the test as suggested by gemini.

[cryo-zd]

Hi @cryo-zd nice catch and thank you for the contribution. The fix looks great but I would modify the test as suggested by gemini.

Thanks for your review, I have updated the test as suggested. When you have time, please review the change.