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Fix flaky DefaultAcknowledgementSetManagerTests#6720

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lawofcycles wants to merge 1 commit intoopensearch-project:mainfrom
lawofcycles:fix/flaky-default-ack-set-manager-test
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Fix flaky DefaultAcknowledgementSetManagerTests#6720
lawofcycles wants to merge 1 commit intoopensearch-project:mainfrom
lawofcycles:fix/flaky-default-ack-set-manager-test

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@lawofcycles lawofcycles commented Apr 3, 2026

Description

Fix flaky DefaultAcknowledgementSetManagerTests.testExpirations() that intermittently fails with AssertionError: Expected: <0> but: was <1>.

The test asserts that the acknowledgement set monitor size is 0 immediately after a Thread.sleep(), assuming the cleanup thread has already removed the expired set. Under CI load, the cleanup may not have completed in time. The subsequent await() block only checks the result field, not the monitor size, so the stale size is never retried.

This change moves the getSize() == 0 assertion into the await().untilAsserted() block so both conditions are polled together.

CI impact

This fix targets Gradle Build / build workflow (gradle.yml), specifically DefaultAcknowledgementSetManagerTests.testExpirations() in :data-prepper-core:test.

Local verification (10 consecutive runs each):
The race condition is difficult to reproduce with the default TEST_TIMEOUT (400ms) on a local machine. To amplify it, the Thread.sleep in testExpirations was temporarily hardcoded to 20ms (instead of TEST_TIMEOUT * 2 = 800ms), reducing the margin for the cleanup thread to near zero.

  • Before fix (getSize assertion outside await): 0/10 passed
  • After fix (getSize assertion inside await): 10/10 passed

Issues Resolved

Resolves #6719

Check List

  • New functionality includes testing.
  • New functionality has a documentation issue. Please link to it in this PR.
    • New functionality has javadoc added
  • Commits are signed with a real name per the DCO

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

Move the monitor size assertion into the await().untilAsserted() block.
The assertion was placed after Thread.sleep() but before await(),
assuming the cleanup thread had already run. Under CI load, the cleanup
may not have completed in time, causing intermittent failures.

Signed-off-by: Sotaro Hikita <bering1814@gmail.com>
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[BUG] Flaky DefaultAcknowledgementSetManagerTests

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