Fix flaky OpenSearchTestBasePluginFuncTest (#20955)

[psychbot]

Description

When integTest runs with maxParallelForks > 1, all parallel test JVMs share the same default .gradle-test-kit directory. This can causes a race condition where concurrent tests simultaneously read and write the Groovy DSL compiled script cache (cp_settings), may result in a NoSuchFileException.

Fixing by assigning each test method its own isolated TestKit directory via withTestKitDir() using a subdirectory within the already-unique temporary folder.

Related Issues

Should resolve #20955

java.nio.file.NoSuchFileException: /var/jenkins/workspace/gradle-check/search/buildSrc/build/tmp/integTest/work/.gradle-test-kit/caches/9.4.0/groovy-dsl/02bba72833c5af3120d1ca946c9f6b22/instrumented/cp_settings

Check List

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

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[github-actions]

PR Reviewer Guide 🔍

(Review updated until commit d58a480)

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🧪 No relevant tests

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⚡ No major issues detected

[github-actions]

PR Code Suggestions ✨

Latest suggestions up to d58a480
Explore these optional code suggestions:

Category	Suggestion	Impact
General	Ensure unique test kit directory per test The testKitDir is created once in setup() and shared across all test methods, but if multiple tests run in parallel or the same directory is reused across test runs, it could cause conflicts. Consider using a unique subdirectory per test (e.g., incorporating the spec name or a UUID) to ensure isolation between test executions. buildSrc/src/integTest/groovy/org/opensearch/gradle/fixtures/AbstractGradleFuncTest.groovy [54] -testKitDir = testProjectDir.newFolder('.gradle-test-kit') +testKitDir = testProjectDir.newFolder('.gradle-test-kit-' + UUID.randomUUID().toString()) Suggestion importance[1-10]: 3 __ Why: The testProjectDir is already a unique TemporaryFolder per test (created by the @Rule annotation), so each test already gets its own isolated directory. Adding a UUID suffix would be redundant and adds unnecessary complexity, making the suggestion of low value.	Low

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Previous suggestions

Suggestions up to commit 6a6dd43

Category	Suggestion	Impact
General	Avoid shared test kit directory conflicts The testKitDir is created once in setup() and shared across all test methods via gradleRunner. If multiple gradleRunner calls occur in parallel or across tests sharing state, they may conflict over the same directory. Consider using a unique subdirectory per test or per runner invocation to avoid potential flakiness from shared state. buildSrc/src/integTest/groovy/org/opensearch/gradle/fixtures/AbstractGradleFuncTest.groovy [54] -testKitDir = testProjectDir.newFolder('.gradle-test-kit') +testKitDir = testProjectDir.newFolder('.gradle-test-kit-' + UUID.randomUUID().toString()) Suggestion importance[1-10]: 3 __ Why: The testProjectDir is a @Rule TemporaryFolder which creates a fresh directory per test, so testKitDir is already unique per test. The suggestion addresses a concern that doesn't apply in this context, making it a low-impact change.	Low

[github-actions]

Persistent review updated to latest commit d58a480

[github-actions]

❌ Gradle check result for d58a480: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

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Failed to generate code suggestions for PR

[github-actions]

❌ Gradle check result for d3e110b: null

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for d3e110b: SUCCESS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.25%. Comparing base (85113a4) to head (d3e110b).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #20975      +/-   ##
============================================
- Coverage     73.31%   73.25%   -0.06%     
+ Complexity    72544    72526      -18     
============================================
  Files          5819     5819              
  Lines        331399   331399              
  Branches      47887    47887              
============================================
- Hits         242955   242768     -187     
- Misses        68935    69112     +177     
- Partials      19509    19519      +10     

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