Fix Flaky NodeJoinLeftIT Test (opensearch-project#19059)

Signed-off-by: Atri Sharma <[email protected]>

Author: atris

server/src/internalClusterTest/java/org/opensearch/cluster/coordination/NodeJoinLeftIT.java

@@ -131,17 +131,19 @@ public void setUp() throws Exception {
         ClusterHealthResponse response = client().admin().cluster().prepareHealth().setWaitForNodes(">=3").get();
         assertThat(response.isTimedOut(), is(false));
 
-        // create an index
-        client().admin()
-            .indices()
-            .prepareCreate(indexName)
-            .setSettings(
-                Settings.builder()
-                    .put(IndexMetadata.INDEX_ROUTING_INCLUDE_GROUP_SETTING.getKey() + "color", "blue")
-                    .put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 1)
-                    .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
-            )
-            .get();
+        // create an index only if it doesn't exist
+        if (!client().admin().indices().prepareExists(indexName).get().isExists()) {
+            client().admin()
+                .indices()
+                .prepareCreate(indexName)
+                .setSettings(
+                    Settings.builder()
+                        .put(IndexMetadata.INDEX_ROUTING_INCLUDE_GROUP_SETTING.getKey() + "color", "blue")
+                        .put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 1)
+                        .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
+                )
+                .get();
+        }
     }
 
     @After
@@ -329,6 +331,10 @@ public void testRestartCmNode() throws Exception {
 
         logger.info("-> restarting stopped node");
         internalCluster().startNode(Settings.builder().put("node.name", clusterManager).put(cmNodeSettings).build());
+
+        // Wait for cluster to stabilize before checking node count
+        ensureGreen();
+
         response = client().admin().cluster().prepareHealth().setWaitForNodes("3").get();
         assertThat(response.isTimedOut(), is(false));
     }