feat(idempotency): enhance thread safety with AsyncLocal context and thread-safe configuration

[hjgraca]

Please provide the issue number

Issue number: #1083

Summary

Changes

This pull request introduces significant improvements to thread safety and concurrency handling in the idempotency library, ensuring correct behavior when AWS Lambda runs with multiple concurrent invocations. The main changes include using thread-local and AsyncLocal storage to isolate per-invocation state, making configuration methods thread-safe and idempotent.. These changes help prevent cross-thread data leakage and race conditions.

Idempotency library improvements:

• Thread-safe Lambda context storage: Replaces a static property with AsyncLocal<ILambdaContext> in Idempotency to ensure each Lambda invocation has its own isolated context, preventing context leaks between concurrent executions. (Idempotency.cs) [1] [2] [3]
• Thread-safe configuration in persistence store: Adds locking and a double-check pattern to BasePersistenceStore.Configure methods, using a lock and a volatile flag to make configuration idempotent and safe for concurrent calls. (BasePersistenceStore.cs) [1] [2] [3]

User experience

Please share what the user experience looks like before and after this change

Checklist

Please leave checklist items unchecked if they do not apply to your change.

• Meets tenets criteria
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented
• PR title follows conventional commit semantics

Is this a breaking change?

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Disclaimer: We value your time and bandwidth. As such, any pull requests created on non-triaged issues might not be successful.

[codecov]

Codecov Report

❌ Patch coverage is 81.13208% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.39%. Comparing base (b0bd80e) to head (e197d1f).
⚠️ Report is 6 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ls.Idempotency/Persistence/BasePersistenceStore.cs	81.63%	6 Missing and 3 partials ⚠️
...c/AWS.Lambda.Powertools.Idempotency/Idempotency.cs	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1084      +/-   ##
===========================================
+ Coverage    78.36%   78.39%   +0.02%     
===========================================
  Files          298      298              
  Lines        12126    12157      +31     
  Branches      1456     1464       +8     
===========================================
+ Hits          9503     9530      +27     
- Misses        2158     2159       +1     
- Partials       465      468       +3     

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[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud