Fix blocking sleep and incorrect backoff durations in RefreshNowAsync (#196)
Description
Why is this change being made?

RefreshNowAsync uses Thread.Sleep which blocks a thread pool
thread, causing thread pool starvation and ignoring the
CancellationToken.
exceptionCount is never incremented, so exponential backoff never
grows — every retry uses the same base delay.
.Milliseconds (sub-second component only, 0–999) is used instead of
the full TimeSpan, truncating intended ~7s delays to ~400ms.
Environment.TickCount (32-bit signed int) overflows after ~24.9
days, causing incorrect retry timing in long-running services.

What is changing?

Replace Thread.Sleep with await Task.Delay(TimeSpan, CancellationToken) so the wait is non-blocking and cancellable.
Increment exceptionCount in the catch block so backoff actually
grows exponentially.
Use TimeSpan directly instead of extracting .Milliseconds, fixing
the truncated delay durations.
Replace Environment.TickCount arithmetic with DateTime.UtcNow +
TimeSpan for overflow-safe timing.

Related Links

Issue #, if available: N/A


Testing
How was this tested?

Added RefreshNowAsyncRespectsTokenCancellation — verifies
cancellation is immediate (<100ms) during the jitter delay.
Added RefreshNowAsyncAfterExceptionWithExpiredBackoff — covers the
branch where nextRetryTime is in the past (wait is negative),
confirming recovery works.
Added RefreshNowAsyncAfterExceptionWithActiveBackoff — covers the
branch where backoff wait exceeds base jitter, verified via
cancellation.
All 17 existing tests pass.

When testing locally, provide testing artifact(s):

dotnet test — all tests pass including the 3 new ones.


Reviewee Checklist
Update the checklist after submitting the PR

 I have reviewed, tested and understand all changes
If not, why:
 I have filled out the Description and Testing sections above
If not, why:
 Build and Unit tests are passing
If not, why:
 Unit test coverage check is passing
If not, why:
 Integration tests pass locally
If not, why: No integration test suite in this repository.
 I have updated integration tests (if needed)

If not, why: Not applicable — changes are to caching internals, no
integration tests exist.

 I have ensured no sensitive information is leaking (i.e., no
logging of sensitive fields, or otherwise)
If not, why:
 I have added explanatory comments for complex logic, new
classes/methods and new tests
If not, why:
 I have updated README/documentation (if needed)

If not, why: No public API changes; behavioral change (longer jitter
delay) is noted in the PR description.

 I have clearly called out breaking changes (if any)

If not, why: Behavioral change: RefreshNowAsync now waits the
originally intended ~7s jitter (was ~400ms due to the .Milliseconds
bug). This is a correction, not a regression.

Reviewer Checklist
All reviewers please ensure the following are true before reviewing:

Reviewee checklist has been accurately filled out
Code changes align with stated purpose in description
Test coverage adequately validates the changes


By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Co-authored-by: Simon Marty simon.marty0@gmail.com