Fix test memory leak

server/src/main/java/org/elasticsearch/plugins/PluginsService.java

@@ -309,7 +309,7 @@ public <T> List<? extends T> loadServiceProviders(Class<T> service) {
         List<T> result = new ArrayList<>();
 
         for (LoadedPlugin pluginTuple : plugins()) {
-            ServiceLoader.load(service, pluginTuple.loader()).iterator().forEachRemaining(c -> result.add(c));
+            result.addAll(createExtensions(service, pluginTuple.instance));
         }
 
         return Collections.unmodifiableList(result);
@@ -348,11 +348,18 @@ static <T> T createExtension(Class<? extends T> extensionClass, Class<T> extensi
             throw new IllegalStateException("no public " + extensionConstructorMessage(extensionClass, extensionPointType));
         }
 
-        if (constructors.length > 1) {
+        Constructor<T> constructor = constructors[0];
+        // Using modules and SPI requires that we declare the default no-arg constructor apart from our custom
+        // one arg constructor with a plugin.
+        if (constructors.length == 2) {
+            // we prefer the one arg constructor in this case
+            if (constructors[1].getParameterCount() > 0) {
+                constructor = constructors[1];
+            }
+        } else if (constructors.length > 1) {
             throw new IllegalStateException("no unique public " + extensionConstructorMessage(extensionClass, extensionPointType));
         }
 
-        final Constructor<T> constructor = constructors[0];
         if (constructor.getParameterCount() > 1) {
             throw new IllegalStateException(extensionSignatureMessage(extensionClass, extensionPointType, plugin));
         }

server/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java

@@ -531,6 +531,10 @@ public TestExtension() {}
             public TestExtension(TestPlugin plugin) {
 
             }
+
+            public TestExtension(TestPlugin plugin, String anotherArg) {
+
+            }
         }
         IllegalStateException e = expectThrows(
             IllegalStateException.class,

x-pack/plugin/ilm/src/main/java/org/elasticsearch/xpack/ilm/ILMImmutableStateHandlerProvider.java

@@ -10,23 +10,24 @@
 import org.elasticsearch.immutablestate.ImmutableClusterStateHandler;
 import org.elasticsearch.immutablestate.ImmutableClusterStateHandlerProvider;
 
-import java.util.Arrays;
 import java.util.Collection;
-import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * ILM Provider implementation for the {@link ImmutableClusterStateHandlerProvider} service interface
  */
 public class ILMImmutableStateHandlerProvider implements ImmutableClusterStateHandlerProvider {
-    private static final Set<ImmutableClusterStateHandler<?>> handlers = ConcurrentHashMap.newKeySet();
+    private final IndexLifecycle plugin;
 
-    @Override
-    public Collection<ImmutableClusterStateHandler<?>> handlers() {
-        return handlers;
+    public ILMImmutableStateHandlerProvider() {
+        throw new IllegalStateException("Provider must be constructed using PluginsService");
+    }
+
+    public ILMImmutableStateHandlerProvider(IndexLifecycle plugin) {
+        this.plugin = plugin;
     }
 
-    public static void registerHandlers(ImmutableClusterStateHandler<?>... stateHandlers) {
-        handlers.addAll(Arrays.asList(stateHandlers));
+    @Override
+    public Collection<ImmutableClusterStateHandler<?>> handlers() {
+        return plugin.immutableClusterStateHandlers();
     }
 }

x-pack/plugin/ilm/src/main/java/org/elasticsearch/xpack/ilm/IndexLifecycle.java

@@ -27,6 +27,7 @@
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.env.NodeEnvironment;
 import org.elasticsearch.health.HealthIndicatorService;
+import org.elasticsearch.immutablestate.ImmutableClusterStateHandler;
 import org.elasticsearch.index.IndexModule;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.license.XPackLicenseState;
@@ -159,6 +160,7 @@ public class IndexLifecycle extends Plugin implements ActionPlugin, HealthPlugin
     private final SetOnce<SnapshotHistoryStore> snapshotHistoryStore = new SetOnce<>();
     private final SetOnce<IlmHealthIndicatorService> ilmHealthIndicatorService = new SetOnce<>();
     private final SetOnce<SlmHealthIndicatorService> slmHealthIndicatorService = new SetOnce<>();
+    private final SetOnce<ImmutableLifecycleAction> immutableLifecycleAction = new SetOnce<>();
     private final Settings settings;
 
     public IndexLifecycle(Settings settings) {
@@ -268,10 +270,8 @@ public Collection<Object> createComponents(
         components.addAll(Arrays.asList(snapshotLifecycleService.get(), snapshotHistoryStore.get(), snapshotRetentionService.get()));
         ilmHealthIndicatorService.set(new IlmHealthIndicatorService(clusterService));
         slmHealthIndicatorService.set(new SlmHealthIndicatorService(clusterService));
+        immutableLifecycleAction.set(new ImmutableLifecycleAction(xContentRegistry, client, XPackPlugin.getSharedLicenseState()));
 
-        ILMImmutableStateHandlerProvider.registerHandlers(
-            new ImmutableLifecycleAction(xContentRegistry, client, XPackPlugin.getSharedLicenseState())
-        );
         return components;
     }
 
@@ -422,6 +422,10 @@ public List<RestHandler> getRestHandlers(
         return actions;
     }
 
+    List<ImmutableClusterStateHandler<?>> immutableClusterStateHandlers() {
+        return List.of(immutableLifecycleAction.get());
+    }
+
     @Override
     public Collection<HealthIndicatorService> getHealthIndicatorServices() {
         return List.of(ilmHealthIndicatorService.get(), slmHealthIndicatorService.get());