Pass failures back correctly

Author: pawankartik-elastic

server/src/internalClusterTest/java/org/elasticsearch/indices/cluster/RemoteFieldCapsForceConnectTimeoutIT.java

@@ -19,6 +19,7 @@
 import org.elasticsearch.test.AbstractMultiClustersTestCase;
 import org.elasticsearch.test.transport.MockTransportService;
 import org.elasticsearch.transport.TransportService;
+import org.hamcrest.Matchers;
 
 import java.util.Collection;
 import java.util.List;
@@ -73,7 +74,7 @@ public void testTimeoutSetting() {
             MockTransportService mts = (MockTransportService) cluster(LOCAL_CLUSTER).getInstance(TransportService.class, nodeName);
 
             mts.addConnectBehavior(
-                cluster(REMOTE_CLUSTER_1).getInstance(TransportService.class, randomFrom(cluster(REMOTE_CLUSTER_1).getNodeNames())),
+                cluster(REMOTE_CLUSTER_1).getInstance(TransportService.class, cluster(REMOTE_CLUSTER_1).getNodeNames()[0]),
                 ((transport, discoveryNode, profile, listener) -> {
                     try {
                         latch.await();
@@ -105,6 +106,11 @@ public void testTimeoutSetting() {
             fieldCapsRequest.fields("foo", "bar", "baz");
             var result = safeGet(client().execute(TransportFieldCapabilitiesAction.TYPE, fieldCapsRequest));
 
+            var failures = result.getFailures();
+            assertThat(failures.size(), Matchers.is(1));
+            var message = result.getFailures().getFirst().getException().toString();
+            assertThat(message, Matchers.containsString("org.elasticsearch.ElasticsearchTimeoutException: timed out after [1s/1000ms]"));
+
             latch.countDown();
             result.decRef();
         }

server/src/main/java/org/elasticsearch/action/fieldcaps/TransportFieldCapabilitiesAction.java

@@ -398,13 +398,7 @@ private static void mergeIndexResponses(
                 listener.onResponse(new FieldCapabilitiesResponse(new ArrayList<>(indexResponses.values()), failures));
             }
         } else {
-            // we have no responses at all, maybe because of errors
-            if (indexFailures.isEmpty() == false) {
-                // throw back the first exception
-                listener.onFailure(failures.get(0).getException());
-            } else {
-                listener.onResponse(new FieldCapabilitiesResponse(Collections.emptyList(), Collections.emptyList()));
-            }
+            listener.onResponse(new FieldCapabilitiesResponse(Collections.emptyList(), failures));
         }
     }