distinguish local cluster when name is same as remote

Signed-off-by: Amit Galitzky <amgalitz@amazon.com>

Author: amitgalitz

CHANGELOG.md

@@ -21,6 +21,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
 ### Enhancements
 - Github workflow for changelog verification ([#1413](https://github.com/opensearch-project/anomaly-detection/pull/1413))
 ### Bug Fixes
+- Distinguish local cluster when local name is same as remote ([#1446](https://github.com/opensearch-project/anomaly-detection/pull/1446))
 ### Infrastructure
 ### Documentation
 ### Maintenance

src/main/java/org/opensearch/timeseries/util/CrossClusterConfigUtils.java

@@ -28,7 +28,9 @@ public class CrossClusterConfigUtils {
      * @return The local {@link NodeClient} for the local cluster, or a remote client for a remote cluster.
      */
     public static Client getClientForCluster(String clusterName, Client client, String localClusterName) {
-        return clusterName.equals(localClusterName) ? client : client.getRemoteClusterClient(clusterName);
+        return clusterName.contains("#local") && clusterName.split("#")[0].equals(localClusterName)
+            ? client
+            : client.getRemoteClusterClient(clusterName);
     }
 
     /**
@@ -68,9 +70,9 @@ public static HashMap<String, List<String>> separateClusterIndexes(List<String>
             String clusterName = clusterAndIndex.getKey();
             String indexName = clusterAndIndex.getValue();
 
-            // If the index entry does not have a cluster_name, it indicates the index is on the local cluster.
             if (clusterName.isEmpty()) {
-                clusterName = localClusterName;
+                // Use #local marker to indicate local cluster to avoid clashing if local cluster has the same name as remote cluster
+                clusterName = localClusterName + "#local";
             }
             output.computeIfAbsent(clusterName, k -> new ArrayList<>()).add(indexName);
         }

src/test/java/org/opensearch/timeseries/util/CrossClusterConfigUtilsTests.java

@@ -62,10 +62,22 @@ public void testSeparateClusterIndexesRemoteCluster() {
 
         assertEquals(3, result.size());
         assertEquals(Arrays.asList("index1"), result.get("remoteCluster"));
-        assertEquals(Arrays.asList("index2"), result.get("localCluster"));
+        assertEquals(Arrays.asList("index2"), result.get("localCluster#local"));
         assertEquals(Arrays.asList("index2"), result.get("remoteCluster2"));
     }
 
+    public void testSeparateClusterIndexesWithSameRemoteClusterName() {
+        List<String> indexes = Arrays.asList("opensearch:index1", "index2");
+        ClusterService mockClusterService = mock(ClusterService.class);
+        when(mockClusterService.getClusterName()).thenReturn(new ClusterName("opensearch"));
+
+        HashMap<String, List<String>> result = CrossClusterConfigUtils.separateClusterIndexes(indexes, mockClusterService);
+
+        assertEquals(2, result.size());
+        assertEquals(Arrays.asList("index1"), result.get("opensearch"));
+        assertEquals(Arrays.asList("index2"), result.get("opensearch#local"));
+    }
+
     public void testParseClusterAndIndexName_WithClusterAndIndex() {
         String input = "clusterA:index1";
         Pair<String, String> result = CrossClusterConfigUtils.parseClusterAndIndexName(input);