[CI] CompletionStatsCacheTests testCompletionStatsCache failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-intake #21914 / part1
• elasticsearch-pull-request #68130 / part-1

Reproduction Line:

./gradlew ":server:test" --tests "org.elasticsearch.index.engine.CompletionStatsCacheTests.testCompletionStatsCache" -Dtests.seed=1DE783D89B0B9943 -Dtests.locale=es-EA -Dtests.timezone=America/Anchorage -Druntime.java=24

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: 
Expected: a value greater than <168L>
     but: <168L> was equal to <168L>

Issue Reasons:

• [main] 2 failures in test testCompletionStatsCache (1.0% fail rate in 209 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

This has been muted on branch main

Mute Reasons:

• [main] 2 failures in test testCompletionStatsCache (1.0% fail rate in 209 executions)

Build Scans:

• elasticsearch-intake #21914 / part1
• elasticsearch-pull-request #68130 / part-1

[elasticsearchmachine]

Pinging @elastic/es-search (Team:Search)

[elasticsearchmachine]

Pinging @elastic/es-search-foundations (Team:Search Foundations)

[javanna]

I had a quick look at this, it's to do with completion and it's suspicious that this test started failing right after the Lucene 10.2 upgrade, while it has not failed in a long time before that. Lucene 10.2 loads completions FSTs off heap, which may cause discrepancy. I could not determine from my quick look whether this is the cause of this failre, it's not that evident at least.