Deprecate ExternalTestCluster (#101844)

`ExternalTestCluster` doesn't really make sense now that the transport
client is removed. We only use it in the ML integ test suite and it'd be
good to avoid expanding its usage further, so this commit deprecates it
and removes the functionality in `ESIntegTestCase` that might quietly
switch to using it in a new test suite if running with certain system
properties.

Relates #49582

modules/analysis-common/src/internalClusterTest/java/org/elasticsearch/analysis/common/ReloadSynonymAnalyzerIT.java

@@ -17,7 +17,6 @@
 import org.elasticsearch.index.query.QueryBuilders;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.test.ESIntegTestCase;
-import org.elasticsearch.test.InternalTestCluster;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
@@ -44,15 +43,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Arrays.asList(CommonAnalysisPlugin.class);
     }
 
-    /**
-     * This test needs to write to the config directory, this is difficult in an external cluster so we overwrite this to force running with
-     * {@link InternalTestCluster}
-     */
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     public void testSynonymsUpdateable() throws FileNotFoundException, IOException, InterruptedException {
         testSynonymsUpdate(false);
     }

modules/data-streams/src/internalClusterTest/java/org/elasticsearch/datastreams/lifecycle/CrudDataStreamLifecycleIT.java

@@ -36,10 +36,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return List.of(DataStreamsPlugin.class, MockTransportService.TestPlugin.class);
     }
 
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     public void testGetLifecycle() throws Exception {
         DataStreamLifecycle lifecycle = randomLifecycle();
         putComposableIndexTemplate("id1", null, List.of("with-lifecycle*"), null, null, lifecycle);

modules/data-streams/src/internalClusterTest/java/org/elasticsearch/datastreams/lifecycle/DataStreamLifecycleServiceIT.java

@@ -90,10 +90,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return List.of(DataStreamsPlugin.class, MockTransportService.TestPlugin.class);
     }
 
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
         Settings.Builder settings = Settings.builder().put(super.nodeSettings(nodeOrdinal, otherSettings));

modules/data-streams/src/internalClusterTest/java/org/elasticsearch/datastreams/lifecycle/ExplainDataStreamLifecycleIT.java

@@ -62,10 +62,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return List.of(DataStreamsPlugin.class, MockTransportService.TestPlugin.class);
     }
 
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
         Settings.Builder settings = Settings.builder().put(super.nodeSettings(nodeOrdinal, otherSettings));

modules/ingest-common/src/internalClusterTest/java/org/elasticsearch/ingest/common/IngestRestartIT.java

@@ -50,11 +50,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Arrays.asList(IngestCommonPlugin.class, CustomScriptPlugin.class);
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     public static class CustomScriptPlugin extends MockScriptPlugin {
         @Override
         protected Map<String, Function<Map<String, Object>, Object>> pluginScripts() {

modules/parent-join/src/internalClusterTest/java/org/elasticsearch/join/query/ParentChildTestCase.java

@@ -29,11 +29,6 @@
 @ESIntegTestCase.ClusterScope(scope = ESIntegTestCase.Scope.SUITE)
 public abstract class ParentChildTestCase extends ESIntegTestCase {
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Arrays.asList(InternalSettingsPlugin.class, ParentJoinPlugin.class);

modules/reindex/src/internalClusterTest/java/org/elasticsearch/client/documentation/ReindexDocumentationIT.java

@@ -56,11 +56,6 @@ public class ReindexDocumentationIT extends ESIntegTestCase {
     private static final Semaphore ALLOWED_OPERATIONS = new Semaphore(0);
     private static final String INDEX_NAME = "source_index";
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Arrays.asList(ReindexPlugin.class, ReindexCancellationPlugin.class);

modules/transport-netty4/src/internalClusterTest/java/org/elasticsearch/ESNetty4IntegTestCase.java

@@ -19,11 +19,6 @@
 
 public abstract class ESNetty4IntegTestCase extends ESIntegTestCase {
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected boolean addMockTransportService() {
         return false;

qa/smoke-test-http/src/javaRestTest/java/org/elasticsearch/http/HttpSmokeTestCase.java

@@ -41,11 +41,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return List.of(getTestTransportPlugin(), MainRestPlugin.class);
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     public static void assertOK(Response response) {
         assertThat(response.getStatusLine().getStatusCode(), oneOf(200, 201));
     }

server/src/internalClusterTest/java/org/elasticsearch/ingest/IngestStatsNamesAndTypesIT.java

@@ -45,11 +45,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return List.of(CustomIngestTestPlugin.class, CustomScriptPlugin.class);
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @SuppressWarnings("unchecked")
     public void testIngestStatsNamesAndTypes() throws IOException {
         String pipeline1 = org.elasticsearch.core.Strings.format("""

server/src/internalClusterTest/java/org/elasticsearch/persistent/PersistentTasksExecutorFullRestartIT.java

@@ -34,10 +34,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Collections.singletonList(TestPersistentTasksPlugin.class);
     }
 
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     public void testFullClusterRestart() throws Exception {
         PersistentTasksService service = internalCluster().getInstance(PersistentTasksService.class);
         int numberOfTasks = randomIntBetween(1, 10);

server/src/internalClusterTest/java/org/elasticsearch/persistent/PersistentTasksExecutorIT.java

@@ -51,10 +51,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Collections.singletonList(TestPersistentTasksPlugin.class);
     }
 
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Before
     public void resetNonClusterStateCondition() {
         TestPersistentTasksExecutor.setNonClusterStateCondition(true);

server/src/internalClusterTest/java/org/elasticsearch/persistent/decider/EnableAssignmentDeciderIT.java

@@ -36,11 +36,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return singletonList(TestPersistentTasksPlugin.class);
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     /**
      * Test that the {@link EnableAssignmentDecider#CLUSTER_TASKS_ALLOCATION_ENABLE_SETTING} setting correctly
      * prevents persistent tasks to be assigned after a cluster restart.

server/src/internalClusterTest/java/org/elasticsearch/search/fieldcaps/FieldCapabilitiesIT.java

@@ -193,11 +193,6 @@ protected boolean addMockHttpTransport() {
         return false; // enable http
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     public void testFieldAlias() {
         FieldCapabilitiesResponse response = client().prepareFieldCaps().setFields("distance", "route_length_miles").get();
 

test/framework/src/main/java/org/elasticsearch/test/ESIntegTestCase.java

@@ -158,9 +158,7 @@
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
-import java.net.InetAddress;
 import java.net.InetSocketAddress;
-import java.net.URL;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
@@ -1983,46 +1981,7 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Collections.emptyList();
     }
 
-    private ExternalTestCluster buildExternalCluster(String clusterAddresses, String clusterName) throws IOException {
-        String[] stringAddresses = clusterAddresses.split(",");
-        TransportAddress[] transportAddresses = new TransportAddress[stringAddresses.length];
-        int i = 0;
-        for (String stringAddress : stringAddresses) {
-            URL url = new URL("http://" + stringAddress);
-            InetAddress inetAddress = InetAddress.getByName(url.getHost());
-            transportAddresses[i++] = new TransportAddress(new InetSocketAddress(inetAddress, url.getPort()));
-        }
-        return new ExternalTestCluster(
-            createTempDir(),
-            externalClusterClientSettings(),
-            nodePlugins(),
-            getClientWrapper(),
-            clusterName,
-            transportAddresses
-        );
-    }
-
-    protected Settings externalClusterClientSettings() {
-        return Settings.EMPTY;
-    }
-
-    protected boolean ignoreExternalCluster() {
-        return false;
-    }
-
     protected TestCluster buildTestCluster(Scope scope, long seed) throws IOException {
-        String clusterAddresses = System.getProperty(TESTS_CLUSTER);
-        if (Strings.hasLength(clusterAddresses) && ignoreExternalCluster() == false) {
-            if (scope == Scope.TEST) {
-                throw new IllegalArgumentException("Cannot run TEST scope test with " + TESTS_CLUSTER);
-            }
-            String clusterName = System.getProperty(TESTS_CLUSTER_NAME);
-            if (Strings.isNullOrEmpty(clusterName)) {
-                throw new IllegalArgumentException("External test cluster name must be provided");
-            }
-            return buildExternalCluster(clusterAddresses, clusterName);
-        }
-
         final String nodePrefix = switch (scope) {
             case TEST -> TEST_CLUSTER_NODE_PREFIX;
             case SUITE -> SUITE_CLUSTER_NODE_PREFIX;

test/framework/src/main/java/org/elasticsearch/test/ExternalTestCluster.java

@@ -51,7 +51,11 @@
  * External cluster to run the tests against.
  * It is a pure immutable test cluster that allows to send requests to a pre-existing cluster
  * and supports by nature all the needed test operations like wipeIndices etc.
+ *
+ * @deprecated not a realistic test setup since the removal of the transport client, use {@link ESIntegTestCase} for internal-cluster tests
+ *             or {@link org.elasticsearch.test.rest.ESRestTestCase} otherwise.
  */
+@Deprecated(forRemoval = true)
 public final class ExternalTestCluster extends TestCluster {
 
     private static final Logger logger = LogManager.getLogger(ExternalTestCluster.class);

x-pack/plugin/autoscaling/src/internalClusterTest/java/org/elasticsearch/xpack/autoscaling/action/GetAutoscalingCapacityRestCancellationIT.java

@@ -60,11 +60,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Collections.unmodifiableList(result);
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     public void testCapacityRestCancellationAndResponse() throws Exception {
         internalCluster().startMasterOnlyNode();
 

x-pack/plugin/downsample/src/internalClusterTest/java/org/elasticsearch/xpack/downsample/DataStreamLifecycleDownsampleIT.java

@@ -43,10 +43,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return List.of(DataStreamsPlugin.class, LocalStateCompositeXPackPlugin.class, Downsample.class, AggregateMetricMapperPlugin.class);
     }
 
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
         Settings.Builder settings = Settings.builder().put(super.nodeSettings(nodeOrdinal, otherSettings));

x-pack/plugin/eql/src/internalClusterTest/java/org/elasticsearch/xpack/eql/action/RestEqlCancellationIT.java

@@ -139,8 +139,4 @@ public void testRestCancellation() throws Exception {
         expectThrows(CancellationException.class, future::actionGet);
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
 }

x-pack/plugin/ilm/src/internalClusterTest/java/org/elasticsearch/xpack/ilm/ClusterStateWaitThresholdBreachTests.java

@@ -62,11 +62,6 @@ public void refreshDataStreamAndPolicy() {
         managedIndex = "index-" + randomAlphaOfLengthBetween(10, 15).toLowerCase(Locale.ROOT);
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Arrays.asList(LocalStateCompositeXPackPlugin.class, IndexLifecycle.class, Ccr.class);

x-pack/plugin/ilm/src/internalClusterTest/java/org/elasticsearch/xpack/ilm/DataStreamAndIndexLifecycleMixingTests.java

@@ -80,10 +80,6 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
         return List.of(LocalStateCompositeXPackPlugin.class, IndexLifecycle.class, DataStreamsPlugin.class);
     }
 
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
         Settings.Builder settings = Settings.builder().put(super.nodeSettings(nodeOrdinal, otherSettings));

x-pack/plugin/ilm/src/internalClusterTest/java/org/elasticsearch/xpack/ilm/DataTiersMigrationsTests.java

@@ -55,11 +55,6 @@ public void refreshDataStreamAndPolicy() {
         managedIndex = "index-" + randomAlphaOfLengthBetween(10, 15).toLowerCase(Locale.ROOT);
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Arrays.asList(LocalStateCompositeXPackPlugin.class, IndexLifecycle.class);

x-pack/plugin/ilm/src/internalClusterTest/java/org/elasticsearch/xpack/ilm/IndexLifecycleInitialisationTests.java

@@ -109,11 +109,6 @@ protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
         return nodeSettings.build();
     }
 
-    @Override
-    protected boolean ignoreExternalCluster() {
-        return true;
-    }
-
     @Override
     protected Collection<Class<? extends Plugin>> nodePlugins() {
         return Arrays.asList(LocalStateCompositeXPackPlugin.class, IndexLifecycle.class, TestILMPlugin.class);