[CI] MixedClusterClientYamlTestSuiteIT test {p0=indices.create/20_synthetic_source/stored field under object with store_array_source} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-intake #9183 / 8.15.1_bwc-snapshots
• elasticsearch-pull-request #29252 / 8.15.1_bwc-snapshots
• elasticsearch-pull-request #29149 / 8.15.1_bwc-snapshots

Reproduction Line:

./gradlew ":qa:mixed-cluster:v8.15.1#mixedClusterTest" -Dtests.class="org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT" -Dtests.method="test {p0=indices.create/20_synthetic_source/stored field under object with store_array_source}" -Dtests.seed=EA10560D29FDD45E -Dtests.bwc=true -Dtests.locale=ar-SA -Dtests.timezone=Asia/Urumqi -Druntime.java=22

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Failure at [indices.create/20_synthetic_source:1390]: field [hits.hits.1._source.obj] should be null but was [{foo=hello_from_the_other_side}] expected null, but was:<{foo=hello_from_the_other_side}>

Issue Reasons:

• [main] 3 failures in test test {p0=indices.create/20_synthetic_source/stored field under object with store_array_source} (42.9% fail rate in 7 executions)
• [main] 3 failures in step 8.15.1_bwc-snapshots (42.9% fail rate in 7 executions)
• [main] 2 failures in pipeline elasticsearch-pull-request (40.0% fail rate in 5 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] 3 failures in test test {p0=indices.create/20_synthetic_source/stored field under object with store_array_source} (42.9% fail rate in 7 executions)
• [main] 3 failures in step 8.15.1_bwc-snapshots (42.9% fail rate in 7 executions)
• [main] 2 failures in pipeline elasticsearch-pull-request (40.0% fail rate in 5 executions)

Build Scans:

• elasticsearch-intake #9183 / 8.15.1_bwc-snapshots
• elasticsearch-pull-request #29252 / 8.15.1_bwc-snapshots
• elasticsearch-pull-request #29149 / 8.15.1_bwc-snapshots

[elasticsearchmachine]

Pinging @elastic/es-delivery (Team:Delivery)

[mark-vieira]

Looks like this test was just added in #112173. @lkts do you mind taking a look?

[dnhatn]

I think we need to introduce a new cluster feature for the fix and use it in the new test.

[elasticsearchmachine]

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