[PR] [fix][test] Fix thread resource leaks in tests and PrometheusMetricsProvider [pulsar]

["lhotari (via GitHub)" <gi...@apache.org>]

lhotari opened a new pull request, #25487:
URL: https://github.com/apache/pulsar/pull/25487

   ### Motivation
   
   Thread leak detection in CI ([run #24135406928](https://github.com/apache/pulsar/actions/runs/24135406928)) revealed several thread resource leaks across multiple test classes and one production code issue. This PR addresses the most impactful and fixable leaks.
   
   ### Modifications
   
   **Production code fix:**
   - **PrometheusMetricsProvider.stop()**: The `ScheduledExecutorService` created in `start()` was never shut down in `stop()`, leaking `metrics-*` threads. Added `MoreExecutors.shutdownAndAwaitTermination()` call.
   
   **Test code fixes:**
   - **BookKeeperClusterTestCase**: Replaced bare `executor.shutdownNow()` with `MoreExecutors.shutdownAndAwaitTermination()` to ensure cached thread pool threads have time to terminate. This reduced leaked threads in auditor test groups from ~205 to ~27 (remaining are BookKeeper bookie internal threads).
   - **TransactionMetadataStoreProviderTest**: Added `@AfterMethod` to close the `TransactionMetadataStore` which was created in `@BeforeMethod` but never closed, leaking `txn-topic-threads-OrderedExecutor` threads.
   - **AuthenticationProviderAthenzTest**: Added `@AfterClass` to close the `AuthenticationProviderAthenz` instance which was created in `@BeforeClass` but never closed.
   
   ### Verifying this change
   
   This change is already covered by existing tests. Each fix was verified locally by running the affected test with `THREAD_LEAK_DETECTOR_WAIT_MILLIS=10000`:
   - `TestPrometheusMetricsProvider` — no thread leaks after fix (was 5)
   - `AuditorBookieTest` — reduced from 205 to 27 leaked threads (remaining are BK bookie internals)
   - `TransactionMetadataStoreProviderTest` — no thread leaks after fix (was 6)
   - `AuthenticationProviderAthenzTest` — 1 remaining leak from Athenz library singleton (not fixable from Pulsar side)
   
   ### Does this pull request potentially affect one of the following parts:
   
   - [ ] Dependencies (add or upgrade a dependency)
   - [ ] The public API
   - [ ] The schema
   - [ ] The default values of configurations
   - [ ] The threading model
   - [ ] The binary protocol
   - [ ] The REST endpoints
   - [ ] The admin CLI options
   - [ ] The metrics
   - [ ] Anything that affects deployment


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Re: [PR] [fix][test] Fix thread resource leaks in tests and PrometheusMetricsProvider [pulsar]

["merlimat (via GitHub)" <gi...@apache.org>]

merlimat merged PR #25487:
URL: https://github.com/apache/pulsar/pull/25487


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