**Build scan:**
https://gradle-enterprise.elastic.co/s/3ripydbohdts4/tests/:x-pack:qa:rolling-upgrade:v8.0.1%23oneThirdUpgradedTest/org.elasticsearch.upgrades.MLModelDeploymentsUpgradeIT/testTrainedModelDeployment
**Reproduction line:**
```
./gradlew ':x-pack:qa:rolling-upgrade:v8.0.1#oneThirdUpgradedTest' -Dtests.class="org.elasticsearch.upgrades.MLModelDeploymentsUpgradeIT" -Dtests.method="testTrainedModelDeployment" -Dtests.seed=81B864C9DF6DC290 -Dtests.bwc=true -Dtests.locale=de-CH -Dtests.timezone=Libya -Druntime.java=21
```

**Applicable branches:**
main

**Reproduces locally?:**
Didn't try

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.upgrades.MLModelDeploymentsUpgradeIT&tests.test=testTrainedModelDeployment
**Failure excerpt:**
```
org.elasticsearch.client.ResponseException: method [POST], host [http://127.0.0.1:39891], URI [/_ml/trained_models/upgrade-deployment-test/deployment/_infer], status line [HTTP/1.1 400 Bad Request]
Warnings: [[POST /_ml/trained_models/{model_id}/deployment/_infer] is deprecated! Use [POST /_ml/trained_models/{model_id}/_infer] instead.]
{"error":{"root_cause":[{"type":"action_request_validation_exception","reason":"Validation Failed: 1: at least one document is required ;"}],"type":"action_request_validation_exception","reason":"Validation Failed: 1: at least one document is required ;"},"status":400}

  at __randomizedtesting.SeedInfo.seed([81B864C9DF6DC290:7A602296FEAD7807]:0)
  at org.elasticsearch.client.RestClient.convertResponse(RestClient.java:347)
  at org.elasticsearch.client.RestClient.performRequest(RestClient.java:313)
  at org.elasticsearch.client.RestClient.performRequest(RestClient.java:288)
  at org.elasticsearch.upgrades.MLModelDeploymentsUpgradeIT.infer(MLModelDeploymentsUpgradeIT.java:291)
  at org.elasticsearch.upgrades.MLModelDeploymentsUpgradeIT.assertInfer(MLModelDeploymentsUpgradeIT.java:184)
  at org.elasticsearch.upgrades.MLModelDeploymentsUpgradeIT.testTrainedModelDeployment(MLModelDeploymentsUpgradeIT.java:118)
  at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
  at java.lang.reflect.Method.invoke(Method.java:580)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$8.evaluate(RandomizedRunner.java:946)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$9.evaluate(RandomizedRunner.java:982)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:996)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:48)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:45)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:843)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:490)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.runSingleTest(RandomizedRunner.java:955)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$5.evaluate(RandomizedRunner.java:840)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$6.evaluate(RandomizedRunner.java:891)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$7.evaluate(RandomizedRunner.java:902)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleStoreClassName$1.evaluate(TestRuleStoreClassName.java:38)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleIgnoreTestSuites$1.evaluate(TestRuleIgnoreTestSuites.java:47)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:850)
  at java.lang.Thread.run(Thread.java:1583)

```
x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/inference/assignment/TrainedModelAssignmentTests.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0; you may not use this file except in compliance with the Elastic License
 * 2.0.
 */
package org.elasticsearch.xpack.core.ml.inference.assignment;
import org.elasticsearch.ResourceAlreadyExistsException;
import org.elasticsearch.ResourceNotFoundException;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.common.unit.ByteSizeValue;
import org.elasticsearch.common.util.set.Sets;
import org.elasticsearch.core.Tuple;
import org.elasticsearch.test.AbstractXContentSerializingTestCase;
import org.elasticsearch.xcontent.XContentParser;
import org.elasticsearch.xpack.core.ml.action.StartTrainedModelDeploymentAction;
import org.elasticsearch.xpack.core.ml.action.StartTrainedModelDeploymentTaskParamsTests;
import org.elasticsearch.xpack.core.ml.stats.CountAccumulator;
import java.io.IOException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.stream.Stream;
import static org.hamcrest.Matchers.arrayContainingInAnyOrder;
import static org.hamcrest.Matchers.contains;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.greaterThanOrEqualTo;