**Build scan:**
https://gradle-enterprise.elastic.co/s/njctqv4g2k7ly/tests/:modules:dlm:internalClusterTest/org.elasticsearch.dlm.DataLifecycleServiceIT/testErrorRecordingOnRollover

**Reproduction line:**
```
gradlew ':modules:dlm:internalClusterTest' --tests "org.elasticsearch.dlm.DataLifecycleServiceIT.testErrorRecordingOnRollover" -Dtests.seed=7A0C4AB39ECCF42F -Dtests.locale=fr-FR -Dtests.timezone=Universal -Druntime.java=20
```

**Applicable branches:**
main

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

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.dlm.DataLifecycleServiceIT&tests.test=testErrorRecordingOnRollover

**Failure excerpt:**
```
java.lang.AssertionError: 
Expected: null
     but: was "{\"type\":\"exception\",\"reason\":\"Force merge request only had 1 successful shards out of a total of 2\"}"

  at __randomizedtesting.SeedInfo.seed([7A0C4AB39ECCF42F:EF340B4E82C2DA79]: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.dlm.DataLifecycleServiceIT.lambda$testErrorRecordingOnRollover$11(DataLifecycleServiceIT.java:453)
  at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:1158)
  at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:1131)
  at org.elasticsearch.dlm.DataLifecycleServiceIT.testErrorRecordingOnRollover(DataLifecycleServiceIT.java:435)
  at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
  at java.lang.reflect.Method.invoke(Method.java:578)
  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:1623)

```
modules/dlm/src/internalClusterTest/java/org/elasticsearch/dlm/DataLifecycleServiceIT.java
assertThat(getDataStreamResponse.getDataStreams().size(), equalTo(1));
                DataStream dataStream = getDataStreamResponse.getDataStreams().get(0).getDataStream();
                assertThat(dataStream.getName(), equalTo(dataStreamName));
                List<Index> backingIndices = dataStream.getIndices();
                assertThat(backingIndices.size(), equalTo(currentBackingIndexCount + 1));
                String writeIndex = dataStream.getWriteIndex().getName();
                assertThat(writeIndex, backingIndexEqualTo(dataStreamName, currentBackingIndexCount + 1));
                int postDlmSegmentsNewlyRolledOverIndex = getSegmentCount(toBeRolledOverIndex);
                /*
                 * We only expect forcemerge to happen on the 2nd DLM run and later, since on the first there's only the single write
                 * index to be rolled over.
                 */
                if (currentBackingIndexCount > 1) {
                    int postDlmSegmentsForceMergedIndex = getSegmentCount(toBeForceMergedIndex);
                    assertThat(
                        "The segments for " + toBeForceMergedIndex + " were not merged",
                        postDlmSegmentsForceMergedIndex,
                        lessThan(preDlmSegmentsForceMergedIndex)
                    );
                    logger.info("postDlmSegmentsForceMergedIndex: {}", postDlmSegmentsForceMergedIndex);
                }
                
                assertThat(
                    "The segments for " + toBeRolledOverIndex + " were unexpectedly merged",
                    postDlmSegmentsNewlyRolledOverIndex,
                    equalTo(preDlmSegmentsAboutToBeRolledOverIndex)
                );
            });
        }
    }