Merge pull request #12155 from jaymode/external_test_cluster_settings

allow settings to be passed to client for external test cluster

core/src/test/java/org/elasticsearch/test/ElasticsearchIntegrationTest.java

@@ -1650,7 +1650,11 @@ public abstract class ElasticsearchIntegrationTest extends ElasticsearchTestCase
                 throw new IllegalArgumentException("port is not valid, expected number but was [" + split[1] + "]");
             }
         }
-        return new ExternalTestCluster(createTempDir(), transportAddresses);
+        return new ExternalTestCluster(createTempDir(), externalClusterClientSettings(), transportAddresses);
+    }
+
+    protected Settings externalClusterClientSettings() {
+        return Settings.EMPTY;
     }
 
     protected TestCluster buildTestCluster(Scope scope, long seed) throws IOException {

core/src/test/java/org/elasticsearch/test/ExternalTestCluster.java

@@ -65,9 +65,10 @@ public final class ExternalTestCluster extends TestCluster {
     private final int numDataNodes;
     private final int numMasterAndDataNodes;
 
-    public ExternalTestCluster(Path tempDir, TransportAddress... transportAddresses) {
+    public ExternalTestCluster(Path tempDir, Settings additionalSettings, TransportAddress... transportAddresses) {
         super(0);
         Settings clientSettings = Settings.settingsBuilder()
+                .put(additionalSettings)
                 .put("name", InternalTestCluster.TRANSPORT_CLIENT_PREFIX + EXTERNAL_CLUSTER_PREFIX + counter.getAndIncrement())
                 .put(InternalSettingsPreparer.IGNORE_SYSTEM_PROPERTIES_SETTING, true) // prevents any settings to be replaced by system properties.
                 .put("client.transport.ignore_cluster_name", true)