[CI] FullClusterRestartIT testRollupAfterRestart {cluster=OLD} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #4523 / openjdk17_7.17.25_java-fips-matrix-bwc
• elasticsearch-periodic #4463 / 7.15.2_bwc

Reproduction Line:

./gradlew ":x-pack:qa:full-cluster-restart:v7.17.25#bwcTest" -Dtests.class="org.elasticsearch.xpack.restart.FullClusterRestartIT" -Dtests.method="testRollupAfterRestart {cluster=UPGRADED}" -Dtests.seed=678A207D9C9D6903 -Dtests.bwc=true -Dtests.locale=da -Dtests.timezone=Pacific/Honolulu -Druntime.java=17 -Dtests.fips.enabled=true

Applicable branches:
8.16

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: null

Issue Reasons:

• [8.16] 2 failures in test testRollupAfterRestart {cluster=OLD} (0.2% fail rate in 853 executions)
• [8.16] 2 failures in pipeline elasticsearch-periodic (15.4% fail rate in 13 executions)

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

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)

[kkrik-es]

@martijnvg I think you looked at similar failures a month ago, any clues?

[martijnvg]

I will take a look.

[kkrik-es]

The following exception is thrown during bulk:

org.elasticsearch.client.WarningFailureException: method [POST], host [http://127.0.0.1:42149], URI [/_bulk], status line [HTTP/1.1 200 OK]
Warnings: [Disabling _field_names is not necessary because it no longer carries a large index overhead. Support for the `enabled` setting will be removed in a future major version. Please remove it from your mappings and templates.]