Add RetryAfter to BrokenCircuitException.

[DL444]

Pull Request

The issue or feature being addressed

Closes #2284

Details on the issue fix or feature implementation

This PR adds RetryAfter property to BrokenCircuitException to indicate time of possible circuit closure.

The implementation stores the time span from the time when the exception is thrown to the time when the circuit breaker should enter half-open state. This can cause inaccuracy if the exception is stowed and consumed at a later time, as the value would become stale. This route is chosen over storing the time of circuit closure because it

• Maintains API consistency with RateLimiterRejectedException, another derived type of ExecutionRejectedException, whose RetryAfter was already defined to return TimeSpan.
• Avoids performing time computation in the exception.
• Avoids demonstrating inconsistent behavior when the value is observed multiple times.

Tests are expanded to cover the new APIs. Specific test policy proposed and implemented:

• Direct tests against the exception types (BrokenCircuitExceptionTests, IsolatedCircuitExceptionTests) are expanded to cover the new API;
• Issue tests are kept as-is because they are supposed to focus on the specific relevant issues.
• Each specs test category (CircuitBreakerSpecs, CircuitBreakerAsyncSpecs, AdvancedCircuitBreakerSpecs, AdvancedCircuitBreakerAsyncSpecs, CircuitBreakerTResultSpecs, CircuitBreakerTResultMixedResultExceptionSpecs, CircuitBreakerTResultAsyncSpecs) implements one test for the value of the new RetryAfter property.
• All other reference sites of the exception in specs tests confirm nullity of the property.

Let me know if either the implementation or the tests need rework.

It is also observed that BrokenCircuitException supports binary serialization on .NET Framework. I'm unfortunately not familiar with its details, and as a deprecated technology, information about it online is scarce. I'm not sure if this change would have any negative implications from a compatibility standpoint.

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have successfully run a local build

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.40%. Comparing base (439cf15) to head (9a93845).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2324      +/-   ##
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+ Coverage   85.39%   85.40%   +0.01%     
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  Files         313      313              
  Lines        7461     7467       +6     
  Branches     1126     1126              
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+ Hits         6371     6377       +6     
  Misses        745      745              
  Partials      345      345              

Flag	Coverage Δ
linux	85.40% <100.00%> (+0.01%)	⬆️
macos	85.37% <100.00%> (+0.01%)	⬆️
windows	85.40% <100.00%> (+0.01%)	⬆️

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[martintmk]

I would keep this feature to Polly.Core only as the Polly V7 should be limited to bug fixes only. Wdyt @martincostello, @peter-csala ?

[peter-csala]

I would keep this feature to Polly.Core only as the Polly V7 should be limited to bug fixes only. Wdyt @martincostello, @peter-csala ?

Yes, that's my understand as well. Your implementation should be limited to V8 only.

[peter-csala]

Also, please don't forget to update the documentation as well: https://github.com/App-vNext/Polly/blob/main/docs/strategies/circuit-breaker.md

[martincostello]

I agree, we should just make this change to Polly.Core.

[DL444]

The source branch is rebased, revised, and force-pushed to incorporate the following requested changes:

• Reverts all changes made to Polly and Polly.Specs projects as new features are no longer accepted for them.
• Expands relevant documentations to cover the new feature.
• Addresses miscellaneous code review comments.

[DL444]

New commits are added to:

• Implement binary serialization support for the new property.
• Refactor exception constructor tests to improve readability.

[github-actions]

Thanks for your contribution @DL444 - the changes from this pull request have been published as part of version 8.5.0 📦, which is now available from NuGet.org 🚀