feat: provider wrapper to support state race fix

[toddbaert]

PoC for open-feature/spec#365. This adds a StateManagingProvider interface (opt-in) so providers can own their state and event emissions, fixing the race between SDK-managed state writes and provider-emitted events during/after init. When a provider implements this interface, the SDK reads state directly from the provider and skips its own state writes and event emissions in the init, shutdown, and runtime event paths. Legacy providers that do not implement the interface continue to work exactly as before (SDK manages their state). Not breaking for application-authors or provider-authors.

Companion PoCs:

• JS: feat: provider wrapper to support state race fix js-sdk#1362
• Java: feat: provider wrapper to support state race fix #1892
• Go: feat: provider wrapper to support state race fix go-sdk#487

[gemini-code-assist]

Summary of Changes

Hello, 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 introduces a mechanism for feature providers to manage their own state, rather than the SDK managing it on their behalf. This is achieved through a new StateManagingProvider interface and modifications to the FeatureProviderStateManager to delegate state management when appropriate. This change is intended to address potential race conditions and improve the overall robustness of state management in the OpenFeature SDK.

Highlights

• State Management: Introduces a StateManagingProvider interface to allow providers to manage their own state, rather than relying on the SDK to manage it.
• Provider Wrapper: Modifies FeatureProviderStateManager to check if the delegate provider manages its own state, and if so, defers state management to the delegate.
• Race Condition Fix: Aims to address a potential race condition where the SDK's state management could conflict with a provider's internal state management.

Changelog

• FeatureProviderStateManager.java
  • Delegate state management to providers that implement StateManagingProvider.
• StateManagingProvider.java
  • Introduce StateManagingProvider interface.

Activity

• Introduced StateManagingProvider interface.
• Modified FeatureProviderStateManager to support providers managing their own state.
• Addressed potential race conditions in state management.

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[gemini-code-assist]

Code Review

This pull request introduces a StateManagingProvider interface to allow providers to manage their own state, which helps in fixing potential race conditions with state management. The FeatureProviderStateManager is updated to respect this new interface, delegating state management to the provider if it implements StateManagingProvider. The changes are logical and well-implemented. I have one suggestion to improve code quality by avoiding a call to a deprecated method.

[gemini-code-assist]

The getState() method on FeatureProvider is deprecated. To avoid potential compiler warnings and to make the code clearer, it's better to cast the delegate to StateManagingProvider before calling getState(). This makes it explicit that you are using the non-deprecated method from the StateManagingProvider interface.

Suggested change

	return delegate.getState();
	return ((StateManagingProvider) delegate).getState();

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.63%. Comparing base (d5f7a64) to head (6160338).

Files with missing lines	Patch %	Lines
...v/openfeature/sdk/FeatureProviderStateManager.java	50.00%	2 Missing and 6 partials ⚠️
...n/java/dev/openfeature/sdk/ProviderRepository.java	50.00%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1892      +/-   ##
============================================
+ Coverage     92.25%   92.63%   +0.37%     
- Complexity      653      657       +4     
============================================
  Files            59       59              
  Lines          1589     1602      +13     
  Branches        179      187       +8     
============================================
+ Hits           1466     1484      +18     
+ Misses           76       64      -12     
- Partials         47       54       +7     

Flag	Coverage Δ
unittests	92.63% <50.00%> (+0.37%)	⬆️

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[sonarqubecloud]

Quality Gate passed

Issues
0 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