Fail request if there is a local index that matches the both a remote and local index

core/src/main/java/org/elasticsearch/action/search/RemoteClusterService.java

@@ -88,7 +88,7 @@ public final class RemoteClusterService extends AbstractComponent implements Clo
 
     /**
      * The name of a node attribute to select nodes that should be connected to in the remote cluster.
-     * For instance a node can be configured with <tt>node.node_attr.gateway: true</tt> in order to be eligible as a gateway node between
+     * For instance a node can be configured with <tt>node.attr.gateway: true</tt> in order to be eligible as a gateway node between
      * clusters. In that case <tt>search.remote.node_attribute: gateway</tt> can be used to filter out other nodes in the remote cluster.
      * The value of the setting is expected to be a boolean, <tt>true</tt> for nodes that can become gateways, <tt>false</tt> otherwise.
      */
@@ -177,15 +177,24 @@ public final class RemoteClusterService extends AbstractComponent implements Clo
      *
      * @param perClusterIndices a map to fill with remote cluster indices from the given request indices
      * @param requestIndices the indices in the search request to filter
+     * @param indexExists a predicate that can test if a certain index or alias exists
+     *
      * @return all indices in the requestIndices array that are not remote cluster indices
      */
-    public String[] filterIndices(Map<String, List<String>> perClusterIndices, String[] requestIndices) {
+    public String[] filterIndices(Map<String, List<String>> perClusterIndices, String[] requestIndices, Predicate<String> indexExists) {
         List<String> localIndicesList = new ArrayList<>();
         for (String index : requestIndices) {
             int i = index.indexOf(REMOTE_CLUSTER_INDEX_SEPARATOR);
             if (i >= 0) {
                 String remoteCluster = index.substring(0, i);
                 if (isRemoteClusterRegistered(remoteCluster)) {
+                    if (indexExists.test(index)) {
+                        // we use : as a separator for remote clusters. might conflict if there is an index that is actually named
+                        // remote_cluster_alias:index_name - for this case we fail the request. the user can easily change the cluster alias
+                        // if that happens
+                        throw new IllegalArgumentException("Index " + index + " exists but there is also a remote cluster named: "
+                            + remoteCluster + " can't filter indices");
+                    }
                     String remoteIndex = index.substring(i + 1);
                     List<String> indices = perClusterIndices.get(remoteCluster);
                     if (indices == null) {

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

@@ -122,9 +122,11 @@ public class TransportSearchAction extends HandledTransportAction<SearchRequest,
         final long startTimeInMillis = Math.max(0, System.currentTimeMillis());
         final String[] localIndices;
         final Map<String, List<String>> remoteIndicesByCluster;
+        final ClusterState clusterState = clusterService.state();
         if (remoteClusterService.isCrossClusterSearchEnabled()) {
             remoteIndicesByCluster = new HashMap<>();
-            localIndices = remoteClusterService.filterIndices(remoteIndicesByCluster, searchRequest.indices());
+            localIndices = remoteClusterService.filterIndices(remoteIndicesByCluster, searchRequest.indices(),
+                idx -> indexNameExpressionResolver.hasIndexOrAlias(idx, clusterState));
         } else {
             remoteIndicesByCluster = Collections.emptyMap();
             localIndices = searchRequest.indices();
@@ -132,7 +134,7 @@ public class TransportSearchAction extends HandledTransportAction<SearchRequest,
 
         if (remoteIndicesByCluster.isEmpty()) {
             executeSearch((SearchTask)task, startTimeInMillis, searchRequest, localIndices, Collections.emptyList(),
-                (nodeId) -> null, Collections.emptyMap(), listener);
+                (nodeId) -> null, clusterState, Collections.emptyMap(), listener);
         } else {
             remoteClusterService.collectSearchShards(searchRequest, remoteIndicesByCluster,
                 ActionListener.wrap((searchShardsResponses) -> {
@@ -141,16 +143,16 @@ public class TransportSearchAction extends HandledTransportAction<SearchRequest,
                     Function<String, Transport.Connection> connectionFunction = remoteClusterService.processRemoteShards(
                         searchShardsResponses, remoteShardIterators, remoteAliasFilters);
                     executeSearch((SearchTask)task, startTimeInMillis, searchRequest, localIndices, remoteShardIterators,
-                        connectionFunction, remoteAliasFilters, listener);
+                        connectionFunction, clusterState, remoteAliasFilters, listener);
                 }, listener::onFailure));
         }
     }
 
     private void executeSearch(SearchTask task, long startTimeInMillis, SearchRequest searchRequest, String[] localIndices,
                                List<ShardIterator> remoteShardIterators, Function<String, Transport.Connection> remoteConnections,
-                               Map<String, AliasFilter> remoteAliasMap, ActionListener<SearchResponse> listener) {
+                               ClusterState clusterState, Map<String, AliasFilter> remoteAliasMap,
+                               ActionListener<SearchResponse> listener) {
 
-        ClusterState clusterState = clusterService.state();
         clusterState.blocks().globalBlockedRaiseException(ClusterBlockLevel.READ);
         // TODO: I think startTime() should become part of ActionRequest and that should be used both for index name
         // date math expressions and $now in scripts. This way all apis will deal with now in the same way instead

core/src/test/java/org/elasticsearch/action/search/RemoteClusterServiceTests.java

@@ -144,11 +144,15 @@ public class RemoteClusterServiceTests extends ESTestCase {
                     assertFalse(service.isRemoteClusterRegistered("foo"));
                     Map<String, List<String>> perClusterIndices = new HashMap<>();
                     String[] localIndices = service.filterIndices(perClusterIndices, new String[]{"foo:bar", "cluster_1:bar",
-                        "cluster_2:foo:bar", "cluster_1:test", "cluster_2:foo*", "foo"});
+                        "cluster_2:foo:bar", "cluster_1:test", "cluster_2:foo*", "foo"}, i -> false);
                     assertArrayEquals(new String[]{"foo:bar", "foo"}, localIndices);
                     assertEquals(2, perClusterIndices.size());
                     assertEquals(Arrays.asList("bar", "test"), perClusterIndices.get("cluster_1"));
                     assertEquals(Arrays.asList("foo:bar", "foo*"), perClusterIndices.get("cluster_2"));
+
+                    expectThrows(IllegalArgumentException.class, () ->
+                    service.filterIndices(perClusterIndices, new String[]{"foo:bar", "cluster_1:bar",
+                        "cluster_2:foo:bar", "cluster_1:test", "cluster_2:foo*", "foo"}, i -> "cluster_1:bar".equals(i)));
                 }
             }
         }