Fix [BUG] ClusterMaxMergesAtOnceIT is flaky

CHANGELOG.md

@@ -81,6 +81,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix case-insensitive wildcard + aggregation query crash ([#19489](https://github.com/opensearch-project/OpenSearch/pull/19489))
 - Avoid primary shard failure caused by merged segment warmer exceptions ([#19436](https://github.com/opensearch-project/OpenSearch/pull/19436))
 - Fix pull-based ingestion out-of-bounds offset scenarios and remove persisted offsets ([#19607](https://github.com/opensearch-project/OpenSearch/pull/19607))
+- Fix flaky test ClusterMaxMergesAtOnceIT.testClusterLevelDefaultUpdatesMergePolicy ([#18056](https://github.com/opensearch-project/OpenSearch/issues/18056))
 - Fix issue with updating core with a patch number other than 0 ([#19377](https://github.com/opensearch-project/OpenSearch/pull/19377))
 - [Java Agent] Allow JRT protocol URLs in protection domain extraction ([#19683](https://github.com/opensearch-project/OpenSearch/pull/19683))
 - Fix potential concurrent modification exception when updating allocation filters ([#19701])(https://github.com/opensearch-project/OpenSearch/pull/19701))

server/src/internalClusterTest/java/org/opensearch/index/ClusterMaxMergesAtOnceIT.java

@@ -48,6 +48,7 @@
 import java.util.concurrent.ExecutionException;
 
 import static org.opensearch.indices.IndicesService.CLUSTER_DEFAULT_INDEX_MAX_MERGE_AT_ONCE_SETTING;
+import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertAcked;
 
 @OpenSearchIntegTestCase.ClusterScope(scope = OpenSearchIntegTestCase.Scope.TEST, numDataNodes = 2)
 public class ClusterMaxMergesAtOnceIT extends AbstractSnapshotIntegTestCase {
@@ -64,7 +65,6 @@ public void setUp() throws Exception {
         internalCluster().startClusterManagerOnlyNode();
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/opensearch-project/OpenSearch/issues/18056")
     public void testClusterLevelDefaultUpdatesMergePolicy() throws ExecutionException, InterruptedException {
         String clusterManagerName = internalCluster().getClusterManagerName();
         List<String> dataNodes = new ArrayList<>(internalCluster().getDataNodeNames());
@@ -98,9 +98,11 @@ public void testClusterLevelDefaultUpdatesMergePolicy() throws ExecutionExceptio
 
         // Create index with index level override in settings
         indexName = "log-myindex-3";
-        createIndex(
-            indexName,
-            Settings.builder().put(TieredMergePolicyProvider.INDEX_MERGE_POLICY_MAX_MERGE_AT_ONCE_SETTING.getKey(), 15).build()
+        assertAcked(
+            prepareCreate(
+                indexName,
+                Settings.builder().put(TieredMergePolicyProvider.INDEX_MERGE_POLICY_MAX_MERGE_AT_ONCE_SETTING.getKey(), 15)
+            )
         );
         ensureYellowAndNoInitializingShards(indexName);
         ensureGreen(indexName);