merlimat opened a new pull request, #25357:
URL: https://github.com/apache/pulsar/pull/25357
## Flaky test failure
```
java.lang.AssertionError: expected [true] but found [false]
at org.testng.Assert.assertTrue(Assert.java:56)
at
org.apache.pulsar.broker.topiclistlimit.TopicListSizeResultCacheTest.testResultHolder_concurrentRequestsWaitForFirstToComplete(TopicListSizeResultCacheTest.java:132)
```
## Summary
Fix flaky
`TopicListSizeResultCacheTest.testResultHolder_concurrentRequestsWaitForFirstToComplete`
which had two bugs:
1. **Unsynchronized `ArrayList`**: `futures` list was populated from
multiple threads via `futures.add()` without synchronization, causing potential
data corruption and lost adds.
2. **Wrong ordering assumption**: The test assumed `futures.get(0)` was the
"first" request (the one that wins the CAS in `getSizeAsync()` and gets back a
completed future). But thread scheduling is nondeterministic — any thread could
add its future to the list first regardless of which called `getSizeAsync()`
first.
### Fix
- Use `CopyOnWriteArrayList` for thread-safe concurrent adds
- Instead of assuming `futures.get(0)` is the CAS winner, count how many
futures are done (should be exactly 1) and find it via `stream().filter(isDone)`
- Verify all futures complete after `updateSize()` without assuming
index-based ordering
Verified with `invocationCount = 100` — 100/100 pass.
## Documentation
- [x] `doc-not-needed`
(Your PR doesn't need any doc update)
## Matching PR in forked repository
_No response_
### Tip
Add the labels `ready-to-test` and `area/test` to trigger the CI.
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