**Build scan:**
https://gradle-enterprise.elastic.co/s/zy3maqdnytk64/tests/:server:test/org.elasticsearch.action.admin.indices.diskusage.TransportAnalyzeIndexDiskUsageActionTests/testRandomLimitConcurrentRequests

**Reproduction line:**
`./gradlew ':server:test' --tests "org.elasticsearch.action.admin.indices.diskusage.TransportAnalyzeIndexDiskUsageActionTests.testRandomLimitConcurrentRequests" -Dtests.seed=38580122459C0704 -Dtests.locale=mt -Dtests.timezone=Asia/Shanghai -Druntime.java=19`

**Applicable branches:**
8.3

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

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.action.admin.indices.diskusage.TransportAnalyzeIndexDiskUsageActionTests&tests.test=testRandomLimitConcurrentRequests

**Failure excerpt:**
```
java.lang.NullPointerException: Cannot invoke "org.elasticsearch.action.admin.indices.diskusage.IndexDiskUsageStats.getIndexSizeInBytes()" because the return value of "java.util.Map.get(Object)" is null

  at __randomizedtesting.SeedInfo.seed([38580122459C0704:1B67A99AA2E7C41C]:0)
  at org.elasticsearch.action.admin.indices.diskusage.TransportAnalyzeIndexDiskUsageActionTests.testRandomLimitConcurrentRequests(TransportAnalyzeIndexDiskUsageActionTests.java:211)
  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: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:1596)

```
server/src/test/java/org/elasticsearch/action/admin/indices/diskusage/TransportAnalyzeIndexDiskUsageActionTests.java
Semaphore availableRequests = new Semaphore(0);
        AtomicBoolean stopped = new AtomicBoolean();
        TestTransportService transportService = new TestTransportService(threadPool, r -> {
            pendingRequests.add(r);
            availableRequests.release();
        });
        final AtomicLong totalIndexSize = new AtomicLong();
        final Thread handlingThread = new Thread(() -> {
            Map<ShardId, Integer> shardIdToRounds = ConcurrentCollections.newConcurrentMap();
            while (stopped.get() == false && requestFuture.isDone() == false) {
                try {
                    if (availableRequests.tryAcquire(10, TimeUnit.MILLISECONDS) == false) {
                        continue;
                    }
                    if (randomBoolean()) {
                        
                        Map<DiscoveryNode, Integer> perNode = new HashMap<>();
                        for (CapturingRequest r : pendingRequests) {
                            int count = perNode.compute(r.node, (k, v) -> v == null ? 1 : v + 1);
                            assertThat(count, lessThanOrEqualTo(maxConcurrentRequests));
                        }
                    }
                    final List<CapturingRequest> readyRequests = randomSubsetOf(between(1, pendingRequests.size()), pendingRequests);
                    pendingRequests.removeAll(readyRequests);
                    availableRequests.acquireUninterruptibly(readyRequests.size() - 1);
                    for (CapturingRequest r : readyRequests) {
                        ShardId shardId = r.request.shardId();
                        int round = shardIdToRounds.compute(shardId, (k, curr) -> curr == null ? 1 : curr + 1);
                        int maxRound = shardToRoutings.get(shardId).size();
                        if (failedShards.contains(shardId) || (round < maxRound && randomBoolean())) {