Fix a flaky test for issue 19916 ClusterShardLimitIT

[liuguoqingfz]

Description

Fix a timing/ack timeout flake: prepareClose(...).get() returns an AcknowledgedResponse that can be false if the close cluster-state update times out waiting for acknowledgements, even though the close may still eventually apply.

Related Issues

Resolves #19916
Related CI test run: https://build.ci.opensearch.org/job/gradle-check/66791/testReport/org.opensearch.cluster.shards/ClusterShardLimitIT/testOpenIndexOverLimit__p0___opensearch_experimental_feature_writable_warm_index_enabled___true___/

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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Summary by CodeRabbit

• Tests
  • Improved cluster shard limit test reliability by implementing polling-based state verification instead of direct acknowledgments.
  • Enhanced test assertions with explicit health checks and busy-wait conditions for better cluster state validation.
  • Updated test method signatures to properly handle exception declarations.

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[coderabbitai]

📝 Walkthrough

Walkthrough

This change fixes a flaky test in ClusterShardLimitIT by replacing synchronous acknowledgement checks with explicit asynchronous polling to reliably wait for index state transitions, adding explicit cluster health verification, and updating method signatures to declare exception handling.

Changes

Cohort / File(s)	Change Summary
Test reliability improvements server/src/internalClusterTest/java/org/opensearch/cluster/shards/ClusterShardLimitIT.java	Replaced AcknowledgedResponse-based index closing with direct close call and busy-wait polling for CLOSED state confirmation; added explicit cluster health check after filling shards; replaced prepareState().get().getState() with prepareState().execute().actionGet().getState(); updated testOpenIndexOverLimit() signature to throw Exception; added imports for TimeUnit and assertThat

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Single file modification focused on test reliability improvements
• Pattern changes involve replacing synchronous checks with polling—straightforward conceptual shift
• Main attention: Verify the polling logic correctly handles timeout scenarios and that health check addition doesn't introduce new race conditions

Suggested labels

bug, flaky-test

Suggested reviewers

• dbwiddis
• andrross
• msfroh
• gbbafna
• cwperks
• sachinpkale
• shwetathareja
• saratvemulapalli

Poem

🐰 A flaky test once danced in the night,
But now with polling, we've set things right!
No rushed acknowledgments, just patient waits—
The state will confirm what the cluster awaits! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically identifies the main change: fixing a flaky test in ClusterShardLimitIT related to issue 19916.
Linked Issues check	✅ Passed	The code changes (asynchronous polling, busy-wait for CLOSED state, explicit health checks) directly address the flaky test issue caused by unreliable AcknowledgedResponse from prepareClose timeout scenarios.
Out of Scope Changes check	✅ Passed	All changes are limited to the ClusterShardLimitIT test file and directly target fixing the flakiness issue; no out-of-scope modifications detected.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description check	✅ Passed	The pull request description provides a clear and concise explanation of the fix, references the related issue (#19916), and confirms compliance with the Apache 2.0 license and DCO requirements.

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✨ Finishing touches

• 📝 Generate docstrings

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[github-actions]

✅ Gradle check result for b129421: SUCCESS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.26%. Comparing base (930ae74) to head (b129421).
⚠️ Report is 54 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #20252      +/-   ##
============================================
+ Coverage     73.20%   73.26%   +0.05%     
- Complexity    71745    71754       +9     
============================================
  Files          5795     5795              
  Lines        328304   328304              
  Branches      47283    47283              
============================================
+ Hits         240334   240517     +183     
+ Misses        68663    68467     -196     
- Partials      19307    19320      +13     

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[opensearch-trigger-bot]

This PR is stalled because it has been open for 30 days with no activity.