**Build scan:**
https://gradle-enterprise.elastic.co/s/xyy3qgfryjs2y/tests/:modules:data-streams:test/org.elasticsearch.datastreams.DataStreamGetWriteIndexTests/testPickingBackingIndicesPredefinedDates

**Reproduction line:**
`./gradlew ':modules:data-streams:test' --tests "org.elasticsearch.datastreams.DataStreamGetWriteIndexTests.testPickingBackingIndicesPredefinedDates" -Dtests.seed=123E35694A81242C -Dtests.locale=da-DK -Dtests.timezone=Asia/Pontianak -Druntime.java=17`

**Applicable branches:**
master

**Reproduces locally?:**
Yes

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.datastreams.DataStreamGetWriteIndexTests&tests.test=testPickingBackingIndicesPredefinedDates

**Failure excerpt:**
```
java.lang.AssertionError: 
Expected: not null
     but: was null

  at __randomizedtesting.SeedInfo.seed([123E35694A81242C:DA947B7805F37533]:0)
  at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
  at org.junit.Assert.assertThat(Assert.java:956)
  at org.junit.Assert.assertThat(Assert.java:923)
  at org.elasticsearch.datastreams.DataStreamGetWriteIndexTests.testPickingBackingIndicesPredefinedDates(DataStreamGetWriteIndexTests.java:93)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-2)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
  at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:568)
  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:44)
  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:375)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:824)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:475)
  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:375)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:831)
  at java.lang.Thread.run(Thread.java:833)

```
modules/data-streams/src/test/java/org/elasticsearch/datastreams/DataStreamGetWriteIndexTests.java
Version.CURRENT
                )
            );
            MetadataFieldMapper dtfm = DataStreamTestHelper.getDataStreamTimestampFieldMapper();
            Mapping mapping = new Mapping(
                root.build(MapperBuilderContext.ROOT),
                new MetadataFieldMapper[] { dtfm },
                Collections.emptyMap()
            );
            MappingLookup mappingLookup = MappingLookup.fromMappers(mapping, List.of(dtfm, dateFieldMapper), List.of(), List.of());
            indicesService = DataStreamTestHelper.mockIndicesServices(mappingLookup);
        }
        MetadataCreateIndexService createIndexService;
        {
            Environment env = mock(Environment.class);
            when(env.sharedDataFile()).thenReturn(null);
            AllocationService allocationService = mock(AllocationService.class);
            when(allocationService.reroute(any(ClusterState.class), any(String.class))).then(i -> i.getArguments()[0]);
            ShardLimitValidator shardLimitValidator = new ShardLimitValidator(Settings.EMPTY, clusterService);
            createIndexService = new MetadataCreateIndexService(
                Settings.EMPTY,
                clusterService,
                indicesService,
                allocationService,
                shardLimitValidator,
                env,
                IndexScopedSettings.DEFAULT_SCOPED_SETTINGS,
                testThreadPool,
                null,
                EmptySystemIndices.INSTANCE,