try to fix async wrapper test

[derrickaw]

Seeing this failure:

Gradle Test Run :sdks:java:core:test > Gradle Test Executor 2 > AsyncWrapperTest > testBufferStopsAcceptingItems FAILED
java.lang.AssertionError: expected:<5> but was:<0>
at org.junit.Assert.fail(Assert.java:89)
at org.junit.Assert.failNotEquals(Assert.java:835)
at org.junit.Assert.assertEquals(Assert.java:647)
at org.junit.Assert.assertEquals(Assert.java:633)
at org.apache.beam.sdk.transforms.AsyncWrapperTest.testBufferStopsAcceptingItems(AsyncWrapperTest.java:678)

here

1. Add polling

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• Update CHANGES.md with noteworthy changes.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI or the workflows README for a list of workflows and how to trigger them.

[github-actions]

Assigning reviewers:

R: @ahmedabu98 for label java.

Note: If you would like to opt out of this review, comment assign to next reviewer.

Available commands:

• stop reviewer notifications - opt out of the automated review tooling
• remind me after tests pass - tag the comment author after tests pass
• waiting on author - shift the attention set back to the author (any comment or push by the author will return the attention set to the reviewers)

The PR bot will only process comments in the main thread (not review comments).

[tkaymak]

Hi @derrickaw, I hit the same AsyncWrapperTest.java:678 failure on Windows and filed #40448. I opened #40449, which takes a deterministic route. It gates BasicDofn with a CountDownLatch and joins all producers before asserting, so the count no longer depends on sleep timing. It also covers the sibling tests that got the same race from #38970. Happy to fold anything from here into it, or close mine if you'd rather go ahead with this one.

[derrickaw]

Hi @derrickaw, I hit the same AsyncWrapperTest.java:678 failure on Windows and filed #40448. I opened #40449, which takes a deterministic route. It gates BasicDofn with a CountDownLatch and joins all producers before asserting, so the count no longer depends on sleep timing. It also covers the sibling tests that got the same race from #38970. Happy to fold anything from here into it, or close mine if you'd rather go ahead with this one.

Hi @tkaymak, I think yours is better. Will defer to yours. Thanks!