**Build scan:**
https://gradle-enterprise.elastic.co/s/5g3re76rgzz4o/tests/:x-pack:plugin:searchable-snapshots:internalClusterTest/org.elasticsearch.xpack.searchablesnapshots.cache.full.SearchableSnapshotsPrewarmingIntegTests/testConcurrentPrewarming

**Reproduction line:**
```
./gradlew ':x-pack:plugin:searchable-snapshots:internalClusterTest' --tests "org.elasticsearch.xpack.searchablesnapshots.cache.full.SearchableSnapshotsPrewarmingIntegTests.testConcurrentPrewarming" -Dtests.seed=367AEC923A22F7A8 -Dtests.locale=tr-TR -Dtests.timezone=Etc/GMT+3 -Druntime.java=20
```

**Applicable branches:**
main

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

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.searchablesnapshots.cache.full.SearchableSnapshotsPrewarmingIntegTests&tests.test=testConcurrentPrewarming

**Failure excerpt:**
```
java.lang.AssertionError: 
Expected: <21>
     but: was <20>

  at __randomizedtesting.SeedInfo.seed([367AEC923A22F7A8:7E197EE4537CC3F7]: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.xpack.searchablesnapshots.cache.full.SearchableSnapshotsPrewarmingIntegTests.testConcurrentPrewarming(SearchableSnapshotsPrewarmingIntegTests.java:271)
  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)

```
x-pack/plugin/searchable-snapshots/src/internalClusterTest/java/org/elasticsearch/xpack/searchablesnapshots/cache/full/SearchableSnapshotsPrewarmingIntegTests.java
public class SearchableSnapshotsPrewarmingIntegTests extends ESSingleNodeTestCase {
    private static final int MAX_NUMBER_OF_INDICES = 10;
    @Override
    protected Collection<Class<? extends Plugin>> getPlugins() {
        return List.of(LocalStateSearchableSnapshots.class, TrackingRepositoryPlugin.class);
    }
    @Override
    protected Settings nodeSettings() {
        return Settings.builder()
            .put(super.nodeSettings())
            .put(LicenseSettings.SELF_GENERATED_LICENSE_TYPE.getKey(), "trial")
            .put(SearchableSnapshots.CACHE_FETCH_ASYNC_THREAD_POOL_SETTING + ".max", randomIntBetween(1, 32))
            .put(SearchableSnapshots.CACHE_FETCH_ASYNC_THREAD_POOL_SETTING + ".keep_alive", "1s")
            .put(SearchableSnapshots.CACHE_PREWARMING_THREAD_POOL_SETTING + ".max", randomIntBetween(1, 32))
            .put(SearchableSnapshots.CACHE_PREWARMING_THREAD_POOL_SETTING + ".keep_alive", "1s")
            .put(ThrottlingAllocationDecider.CLUSTER_ROUTING_ALLOCATION_NODE_CONCURRENT_RECOVERIES_SETTING.getKey(), MAX_NUMBER_OF_INDICES)
            .build();
    }
    public void testConcurrentPrewarming() throws Exception {
        final int nbIndices = randomIntBetween(1, MAX_NUMBER_OF_INDICES);
        logger.debug("--> creating [{}] indices", nbIndices);
        final Map<String, Integer> shardsPerIndex = new HashMap<>();
        for (int index = 0; index < nbIndices; index++) {
            final String indexName = "index-" + index;
            final int nbShards = randomIntBetween(1, 5);
            createIndex(indexName, indexSettings(nbShards, 0).build());
            shardsPerIndex.put(indexName, nbShards);
        }
        logger.debug("--> indexing documents");
        final Map<String, Long> docsPerIndex = new HashMap<>();