Fix flaky LeafSorterOptimizationTests by improving segment creation r…

[rgsriram]

Description

The test LeafSorterOptimizationTests.testReadOnlyEngineUsesLeafSorter was flaky in CI due to inconsistent segment creation. We fixed it by indexing more documents, disabling merges, adjusting flush frequency, and making assertions handle both single- and multi-segment cases.

Related Issues

Resolves #18898

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]

❌ Gradle check result for 635fd3f: 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?

[github-actions]

❌ Gradle check result for 676e265: 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?

[github-actions]

❌ Gradle check result for a4a15c2: 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?

[github-actions]

❌ Gradle check result for 728f806: 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?

[github-actions]

❌ Gradle check result for 4841617: 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?

[github-actions]

❌ Gradle check result for bf7bd77: 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?

[rgsriram]

@andrross - Could you please help me here?. I am not getting a detection of breaking changes in the local environment. I would like to know what I am missing here.

./gradlew japicmp                                                                                                                                                                                               
=======================================
OpenSearch Build Hamster says Hello!
  Gradle Version        : 8.14.3
  OS Info               : Mac OS X 15.5 (aarch64)
  JDK Version           : 24 (Homebrew JDK)
  JAVA_HOME             : /opt/homebrew/Cellar/openjdk/24.0.2/libexec/openjdk.jdk/Contents/Home
  Random Testing Seed   : E60E942F5983423D
  Crypto Standard       : any-supported
=======================================

BUILD SUCCESSFUL in 6s
35 actionable tasks: 35 up-to-date

[andrross]

@rgsriram I believe the failures here are intermittent failures related to a spotless check:

A problem occurred configuring project ':build-tools'.
> Could not create task ':build-tools:spotlessJava'.
   > java.io.IOException: Failed to load eclipse jdt formatter: java.lang.RuntimeException: java.net.SocketTimeoutException: Connect timed out

Go ahead and push a commit to remove the changelog entry to retry the workflows.

[prudhvigodithi]

@rgsriram I believe the failures here are intermittent failures related to a spotless check:

A problem occurred configuring project ':build-tools'.
> Could not create task ':build-tools:spotlessJava'.
   > java.io.IOException: Failed to load eclipse jdt formatter: java.lang.RuntimeException: java.net.SocketTimeoutException: Connect timed out

Go ahead and push a commit to remove the changelog entry to retry the workflows.

The fix has been merged #19199, @rgsriram re-base should fix this error. Thanks

[github-actions]

❌ Gradle check result for bbb48d4: 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?

[github-actions]

✅ Gradle check result for f5fa030: SUCCESS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.73%. Comparing base (4aff917) to head (f5fa030).
⚠️ Report is 36 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #19191      +/-   ##
============================================
- Coverage     72.88%   72.73%   -0.15%     
+ Complexity    69650    69620      -30     
============================================
  Files          5658     5658              
  Lines        320085   320085              
  Branches      46345    46345              
============================================
- Hits         233296   232829     -467     
- Misses        67886    68408     +522     
+ Partials      18903    18848      -55     

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[rgsriram]

@andrross - Please kindly check.