Ensure that local cluster alias is never treated as remote

server/src/main/java/org/elasticsearch/action/search/SearchTransportService.java

@@ -26,6 +26,7 @@
 import org.elasticsearch.action.support.HandledTransportAction.ChannelActionListener;
 import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.cluster.node.DiscoveryNode;
+import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -401,11 +402,11 @@ public void onFailure(Exception e) {
     /**
      * Returns a connection to the given node on the provided cluster. If the cluster alias is <code>null</code> the node will be resolved
      * against the local cluster.
-     * @param clusterAlias the cluster alias the node should be resolve against
+     * @param clusterAlias the cluster alias the node should be resolved against
      * @param node the node to resolve
      * @return a connection to the given node belonging to the cluster with the provided alias.
      */
-    Transport.Connection getConnection(String clusterAlias, DiscoveryNode node) {
+    Transport.Connection getConnection(@Nullable String clusterAlias, DiscoveryNode node) {
         if (clusterAlias == null) {
             return transportService.getConnection(node);
         } else {

server/src/main/java/org/elasticsearch/action/search/TransportSearchAction.java

@@ -353,16 +353,19 @@ static BiFunction<String, String, Transport.Connection> buildConnectionLookup(St
                                                               BiFunction<String, DiscoveryNode, Transport.Connection> nodeToConnection) {
         return (clusterAlias, nodeId) -> {
             final DiscoveryNode discoveryNode;
+            final boolean remoteCluster;
             if (clusterAlias == null || requestClusterAlias != null) {
                 assert requestClusterAlias == null || requestClusterAlias.equals(clusterAlias);
                 discoveryNode = localNodes.apply(nodeId);
+                remoteCluster = false;
             } else {
                 discoveryNode = remoteNodes.apply(clusterAlias, nodeId);
+                remoteCluster = true;
             }
             if (discoveryNode == null) {
                 throw new IllegalStateException("no node found for id: " + nodeId);
             }
-            return nodeToConnection.apply(clusterAlias, discoveryNode);
+            return nodeToConnection.apply(remoteCluster ? clusterAlias : null, discoveryNode);
         };
     }
 

server/src/main/java/org/elasticsearch/transport/RemoteClusterAware.java

@@ -346,7 +346,7 @@ private static int indexOfPortSeparator(String remoteHost) {
     }
 
     public static String buildRemoteIndexName(String clusterAlias, String indexName) {
-        return clusterAlias != null ? clusterAlias + REMOTE_CLUSTER_INDEX_SEPARATOR + indexName : indexName;
+        return clusterAlias == null || LOCAL_CLUSTER_GROUP_KEY.equals(clusterAlias)
+            ? indexName : clusterAlias + REMOTE_CLUSTER_INDEX_SEPARATOR + indexName;
     }
-
 }

server/src/test/java/org/elasticsearch/action/search/TransportSearchActionSingleNodeTests.java

@@ -0,0 +1,62 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.action.search;
+
+import org.elasticsearch.action.index.IndexRequest;
+import org.elasticsearch.action.index.IndexResponse;
+import org.elasticsearch.action.support.WriteRequest;
+import org.elasticsearch.rest.RestStatus;
+import org.elasticsearch.search.SearchHit;
+import org.elasticsearch.test.ESSingleNodeTestCase;
+
+public class TransportSearchActionSingleNodeTests extends ESSingleNodeTestCase {
+
+    public void testLocalClusterAlias() {
+        IndexRequest indexRequest = new IndexRequest("test");
+        indexRequest.id("1");
+        indexRequest.source("field", "value");
+        indexRequest.setRefreshPolicy(WriteRequest.RefreshPolicy.WAIT_UNTIL);
+        IndexResponse indexResponse = client().index(indexRequest).actionGet();
+        assertEquals(RestStatus.CREATED, indexResponse.status());
+
+        {
+            SearchRequest searchRequest = new SearchRequest("local");
+            SearchResponse searchResponse = client().search(searchRequest).actionGet();
+            assertEquals(1, searchResponse.getHits().getTotalHits().value);
+            SearchHit[] hits = searchResponse.getHits().getHits();
+            assertEquals(1, hits.length);
+            SearchHit hit = hits[0];
+            assertEquals("local", hit.getClusterAlias());
+            assertEquals("test", hit.getIndex());
+            assertEquals("1", hit.getId());
+        }
+        {
+            SearchRequest searchRequest = new SearchRequest("");
+            SearchResponse searchResponse = client().search(searchRequest).actionGet();
+            assertEquals(1, searchResponse.getHits().getTotalHits().value);
+            SearchHit[] hits = searchResponse.getHits().getHits();
+            assertEquals(1, hits.length);
+            SearchHit hit = hits[0];
+            assertEquals("", hit.getClusterAlias());
+            assertEquals("test", hit.getIndex());
+            assertEquals("1", hit.getId());
+        }
+    }
+}

server/src/test/java/org/elasticsearch/transport/RemoteClusterAwareTests.java

@@ -0,0 +1,40 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.transport;
+
+import org.elasticsearch.test.ESTestCase;
+
+public class RemoteClusterAwareTests extends ESTestCase {
+
+    public void testBuildRemoteIndexName() {
+        {
+            String clusterAlias = randomAlphaOfLengthBetween(5, 10);
+            String index = randomAlphaOfLengthBetween(5, 10);
+            String remoteIndexName = RemoteClusterAware.buildRemoteIndexName(clusterAlias, index);
+            assertEquals(clusterAlias + ":" + index, remoteIndexName);
+        }
+        {
+            String index = randomAlphaOfLengthBetween(5, 10);
+            String clusterAlias = randomBoolean() ? null : RemoteClusterAware.LOCAL_CLUSTER_GROUP_KEY;
+            String remoteIndexName = RemoteClusterAware.buildRemoteIndexName(clusterAlias, index);
+            assertEquals(index, remoteIndexName);
+        }
+    }
+}