Investigate and fix test hang for EventProcessorTests.MainProcessingLoop.BackgroundProcessingStopsProcessingAllPartitionsWhenShutdown

[jsquire]

Summary

After investigation, it was determined that the test EventProcessorTests.MainProcessingLoop.BackgroundProcessingStopsProcessingAllPartitionsWhenShutdown has been intermittently hanging during CI runs, most often on the net461 target. Thus far, a local reproduction has not been found. It is suspected that the approach to synchronization used on lines 578, 589, and 637 are the potential root cause.

Scope of Work

• Investigate the test, attempting to locate and devise a fix for the intermittent hang.

• Reenable the test to be run normally.

• When the PR is submitted, use that as the basis to kick off several rounds of the CI build/test to help validate, as local run results are likely misleading.

Success Criteria

• The root cause of the intermittent hang has been found and fixed.

• The test has been reenabled and is included in test runs normally.

• The fix has been validated by at least 3 consecutive successful CI runs against the pull request.

• The existing test suite continues to pass consistently with deterministic results.