It seems to fail rarely. I can see a similar failure on Oct25 in master and another on Nov 22 in 7.16

**Build scan:**
https://gradle-enterprise.elastic.co/s/bf3jiz2ojwa5q/tests/:x-pack:plugin:ccr:internalClusterTest/org.elasticsearch.xpack.ccr.RestartIndexFollowingIT/testFollowIndex

**Reproduction line:**
`./gradlew ':x-pack:plugin:ccr:internalClusterTest' --tests "org.elasticsearch.xpack.ccr.RestartIndexFollowingIT.testFollowIndex" -Dtests.seed=515B350E07CA8464 -Dtests.locale=es-EC -Dtests.timezone=America/Belize -Druntime.java=17`

**Applicable branches:**
master

**Reproduces locally?:**
No

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.ccr.RestartIndexFollowingIT&tests.test=testFollowIndex

**Failure excerpt:**
```
java.lang.AssertionError: (No message provided)

  at __randomizedtesting.SeedInfo.seed([515B350E07CA8464:B237FA3C3E72BDEE]:0)
  at org.junit.Assert.fail(Assert.java:86)
  at org.junit.Assert.assertTrue(Assert.java:41)
  at org.junit.Assert.assertTrue(Assert.java:52)
  at org.elasticsearch.xpack.ccr.RestartIndexFollowingIT.setupRemoteCluster(RestartIndexFollowingIT.java:125)
  at org.elasticsearch.xpack.ccr.RestartIndexFollowingIT.testFollowIndex(RestartIndexFollowingIT.java:91)
  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.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:44)
  at org.apache.lucene.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:45)
  at org.apache.lucene.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.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.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.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.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.apache.lucene.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.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)

```
x-pack/plugin/ccr/src/internalClusterTest/java/org/elasticsearch/xpack/ccr/RestartIndexFollowingIT.java
final String source = String.format(Locale.ROOT, "{\"f\":%d}", i);
            leaderClient().prepareIndex("index1").setId(Integer.toString(i)).setSource(source, XContentType.JSON).get();
        }
        assertBusy(
            () -> assertThat(followerClient().prepareSearch("index2").get().getHits().getTotalHits().value, equalTo(firstBatchNumDocs))
        );
        getFollowerCluster().fullRestart();
        ensureFollowerGreen("index2");
        final long secondBatchNumDocs = randomIntBetween(10, 200);
        for (int i = 0; i < secondBatchNumDocs; i++) {
            leaderClient().prepareIndex("index1").setSource("{}", XContentType.JSON).get();
        }
        cleanRemoteCluster();
        getLeaderCluster().fullRestart();
        ensureLeaderGreen("index1");
        
        setupRemoteCluster();
        final long thirdBatchNumDocs = randomIntBetween(10, 200);
        for (int i = 0; i < thirdBatchNumDocs; i++) {
            leaderClient().prepareIndex("index1").setSource("{}", XContentType.JSON).get();
        }
        assertBusy(
            () -> assertThat(
                followerClient().prepareSearch("index2").get().getHits().getTotalHits().value,
                equalTo(firstBatchNumDocs + secondBatchNumDocs + thirdBatchNumDocs)
            )
        );
        cleanRemoteCluster();
        assertAcked(followerClient().execute(PauseFollowAction.INSTANCE, new PauseFollowAction.Request("index2")).actionGet());
        assertAcked(followerClient().admin().indices().prepareClose("index2"));