Disable cross-cluster functionality for _fleet/_fleet_msearch

Author: pawankartik-elastic

x-pack/plugin/fleet/src/internalClusterTest/java/org/elasticsearch/xpack/fleet/action/FleetSearchRemoteIndicesDisallowedIT.java

@@ -41,5 +41,43 @@ public void testEndpointsShouldRejectRemoteIndices() {
                 Matchers.containsString("Fleet search API does not support remote indices. Found: [" + remoteIndex + "]")
             );
         }
+
+        {
+            Request request = new Request("POST", "/" + remoteIndex + "/_fleet/_fleet_msearch");
+            request.setJsonEntity("{}\n{}\n");
+            ResponseException responseException = expectThrows(ResponseException.class, () -> getRestClient().performRequest(request));
+            assertThat(
+                responseException.getMessage(),
+                Matchers.containsString("Fleet search API does not support remote indices. Found: [" + remoteIndex + "]")
+            );
+        }
+
+        {
+            // This is fine, there are no remote indices.
+            Request request = new Request("POST", "/foo/_fleet/_fleet_msearch");
+            request.setJsonEntity("{\"index\": \"bar*\"}\n{}\n");
+            try {
+                getRestClient().performRequest(request);
+            } catch (Exception r) {
+                throw new AssertionError(r);
+            }
+        }
+
+        {
+            // This is not valid. We shouldn't be passing multiple indices.
+            Request request = new Request("POST", "/foo/_fleet/_fleet_msearch");
+            request.setJsonEntity("{\"index\": \"bar*,baz\"}\n{}\n");
+
+            ResponseException responseException = expectThrows(ResponseException.class, () -> getRestClient().performRequest(request));
+            assertThat(responseException.getMessage(), Matchers.containsString("Fleet search API only supports searching a single index."));
+        }
+
+        {
+            // This is not valid. We shouldn't be passing remote indices.
+            Request request = new Request("POST", "/foo/_fleet/_fleet_msearch");
+            request.setJsonEntity("{\"index\": \"bar*\"}\n{}\n{\"index\": \"remote:index\"}\n{}\n");
+            ResponseException responseException = expectThrows(ResponseException.class, () -> getRestClient().performRequest(request));
+            assertThat(responseException.getMessage(), Matchers.containsString("Fleet search API does not support remote indices. Found:"));
+        }
     }
 }

x-pack/plugin/fleet/src/main/java/org/elasticsearch/xpack/fleet/rest/RestFleetMultiSearchAction.java

@@ -22,6 +22,7 @@
 import org.elasticsearch.rest.action.RestRefCountedChunkedToXContentListener;
 import org.elasticsearch.rest.action.search.RestMultiSearchAction;
 import org.elasticsearch.rest.action.search.RestSearchAction;
+import org.elasticsearch.transport.RemoteClusterService;
 import org.elasticsearch.usage.SearchUsageHolder;
 
 import java.io.IOException;
@@ -106,12 +107,17 @@ protected RestChannelConsumer prepareRequest(RestRequest request, NodeClient cli
                         "Fleet search API param wait_for_checkpoints is only supported with an index to search specified. "
                             + "No index specified."
                     );
-                } else if (indices.length > 1) {
-                    throw new IllegalArgumentException(
-                        "Fleet search API only supports searching a single index. Found: [" + Arrays.toString(indices) + "]."
-                    );
                 }
             }
+            if (indices.length > 1) {
+                throw new IllegalArgumentException(
+                    "Fleet search API only supports searching a single index. Found: [" + Arrays.toString(indices) + "]."
+                );
+            }
+
+            if (RemoteClusterService.isRemoteIndexName(indices[0])) {
+                throw new IllegalArgumentException("Fleet search API does not support remote indices. Found: [" + indices[0] + "].");
+            }
             long[] checkpoints = searchRequest.getWaitForCheckpoints().get("*");
             if (checkpoints != null) {
                 searchRequest.setWaitForCheckpoints(Collections.singletonMap(indices[0], checkpoints));