[CI] MultiClusterSpecIT test {fork.ForkWithStats} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-intake #22265 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #69145 / 9.1.0_bwc-snapshots
• elasticsearch-intake #22260 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #69138 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #69108 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #69099 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #68935 / 9.1.0_bwc-snapshots

Reproduction Line:

./gradlew ":x-pack:plugin:esql:qa:server:multi-clusters:v9.1.0#newToOld" -Dtests.class="org.elasticsearch.xpack.esql.ccq.MultiClusterSpecIT" -Dtests.method="test {fork.ForkWithStats}" -Dtests.seed=9370E2D75C42B527 -Dtests.bwc=true -Dtests.locale=en-CC -Dtests.timezone=Asia/Tashkent -Druntime.java=24

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: 
Data mismatch:
row 4 column 2:a list containing
row 4 column 2:0: expected "100" but was "0"
row 4 column 3:a list containing
row 4 column 3:0: expected "10100" but was "null"
row 4 column 4:a list containing
row 4 column 4:0: expected "10001" but was "null"
row 5 column 2:a list containing
row 5 column 2:0: expected "100" but was "0"
row 5 column 3:a list containing
row 5 column 3:0: expected "10001" but was "null"
Actual:
_fork:keyword | emp_no:integer | x:long | y:integer | z:integer
fork1         | 10048          | null   | null      | null     
fork1         | 10081          | null   | null      | null     
fork2         | 10081          | null   | null      | null     
fork2         | 10087          | null   | null      | null     
fork3         | null           | 0      | null      | null     
fork4         | null           | 0      | null      | null     

Expected:
_fork:keyword | emp_no:integer | x:long | y:integer | z:integer
fork1         | 10048 
[truncated]

Issue Reasons:

• [main] 7 failures in test test {fork.ForkWithStats} (0.9% fail rate in 766 executions)
• [main] 7 failures in step 9.1.0_bwc-snapshots (4.6% fail rate in 152 executions)
• [main] 2 failures in pipeline elasticsearch-intake (4.9% fail rate in 41 executions)
• [main] 5 failures in pipeline elasticsearch-pull-request (4.5% fail rate in 112 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 consecutive failures in step 9.1.0_bwc-snapshots
• [main] 5 failures in test test {fork.ForkWithStats} (0.7% fail rate in 756 executions)
• [main] 5 failures in step 9.1.0_bwc-snapshots (3.4% fail rate in 149 executions)
• [main] 4 failures in pipeline elasticsearch-pull-request (3.6% fail rate in 112 executions)

Build Scans:

• elasticsearch-intake #22260 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #69138 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #69108 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #69099 / 9.1.0_bwc-snapshots
• elasticsearch-pull-request #68935 / 9.1.0_bwc-snapshots

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[ioanatia]

closed with #127309

tracking CCS support for FORK in #121950