Added tests.

Signed-off-by: dblock <dblock@amazon.com>

server/src/main/java/org/opensearch/extensions/ExtensionsManager.java

@@ -300,7 +300,7 @@ private void registerRequestHandler(DynamicActionRegistry dynamicActionRegistry)
      * Loads a single extension
      * @param extension The extension to be loaded
      */
-    public void loadExtension(Extension extension) throws IOException {
+    public DiscoveryExtensionNode loadExtension(Extension extension) throws IOException {
         validateExtension(extension);
         DiscoveryExtensionNode discoveryExtensionNode = new DiscoveryExtensionNode(
             extension.getName(),
@@ -314,6 +314,12 @@ public void loadExtension(Extension extension) throws IOException {
         extensionIdMap.put(extension.getUniqueId(), discoveryExtensionNode);
         extensionSettingsMap.put(extension.getUniqueId(), extension);
         logger.info("Loaded extension with uniqueId " + extension.getUniqueId() + ": " + extension);
+        return discoveryExtensionNode;
+    }
+
+    public void initializeExtension(Extension extension) throws IOException {
+        DiscoveryExtensionNode node = loadExtension(extension);
+        initializeExtensionNode(node);
     }
 
     private void validateField(String fieldName, String value) throws IOException {
@@ -340,13 +346,11 @@ private void validateExtension(Extension extension) throws IOException {
      */
     public void initialize() {
         for (DiscoveryExtensionNode extension : extensionIdMap.values()) {
-            if (! initializedExtensions.containsKey(extension)) {
-                initializeExtension(extension);
-            }
+            initializeExtensionNode(extension);
         }
     }
 
-    private void initializeExtension(DiscoveryExtensionNode extension) {
+    private void initializeExtensionNode(DiscoveryExtensionNode extension) {
 
         final CompletableFuture<InitializeExtensionResponse> inProgressFuture = new CompletableFuture<>();
         final TransportResponseHandler<InitializeExtensionResponse> initializeExtensionResponseHandler = new TransportResponseHandler<
@@ -386,7 +390,7 @@ public String executor() {
         transportService.getThreadPool().generic().execute(new AbstractRunnable() {
             @Override
             public void onFailure(Exception e) {
-                logger.warn(String.format("Error registering extension: %s", extension.getId()), e);
+                logger.warn("Error registering extension: " + extension.getId(), e);
                 extensionIdMap.remove(extension.getId());
                 if (e.getCause() instanceof ConnectTransportException) {
                     logger.info("No response from extension to request.", e);

server/src/main/java/org/opensearch/extensions/rest/RestActionsRequestHandler.java

@@ -63,7 +63,7 @@ public TransportResponse handleRegisterRestActionsRequest(
     ) throws Exception {
         DiscoveryExtensionNode discoveryExtensionNode = extensionIdMap.get(restActionsRequest.getUniqueId());
         if (discoveryExtensionNode == null) {
-            throw new IllegalStateException(String.format("Missing extension node for %s", restActionsRequest.getUniqueId()));
+            throw new IllegalStateException("Missing extension node for " + restActionsRequest.getUniqueId());
         }
         RestHandler handler = new RestSendToExtensionAction(
             restActionsRequest,

server/src/main/java/org/opensearch/extensions/rest/RestInitializeExtensionAction.java

@@ -159,8 +159,7 @@ public RestChannelConsumer prepareRequest(RestRequest request, NodeClient client
             extAdditionalSettings
         );
         try {
-            extensionsManager.loadExtension(extension);
-            extensionsManager.initialize();
+            extensionsManager.initializeExtension(extension);
         } catch (CompletionException e) {
             Throwable cause = e.getCause();
             if (cause instanceof TimeoutException) {

server/src/test/java/org/opensearch/extensions/ExtensionsManagerTests.java

@@ -36,6 +36,7 @@
 import org.opensearch.core.common.transport.TransportAddress;
 import org.opensearch.core.indices.breaker.NoneCircuitBreakerService;
 import org.opensearch.core.transport.TransportResponse;
+import org.opensearch.discovery.InitializeExtensionRequest;
 import org.opensearch.env.Environment;
 import org.opensearch.env.EnvironmentSettingsResponse;
 import org.opensearch.extensions.ExtensionsSettings.Extension;
@@ -67,7 +68,6 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Set;
-import java.util.concurrent.ExecutorService;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Collectors;
 
@@ -78,6 +78,7 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
@@ -410,36 +411,37 @@ public void testInitialize() throws Exception {
                 )
             );
 
-            // Test needs to be changed to mock the connection between the local node and an extension. Assert statment is commented out for
-            // now.
+            // Test needs to be changed to mock the connection between the local node and an extension.
             // Link to issue: https://github.com/opensearch-project/OpenSearch/issues/4045
             // mockLogAppender.assertAllExpectationsMatched();
         }
     }
 
-    public void testInitializeExtensionTwice() throws Exception {
+    public void testInitializeExtension() throws Exception {
         ExtensionsManager extensionsManager = new ExtensionsManager(Set.of(), identityService);
-        initialize(extensionsManager);
-
-        ThreadPool mockThreadPool = spy(threadPool);
-        ExecutorService mockExecutorService = mock(ExecutorService.class);
-        when(mockThreadPool.generic()).thenReturn(mockExecutorService);
 
-        TransportService transportService = new TransportService(
-            Settings.EMPTY,
-            mock(Transport.class),
-            mockThreadPool,
-            TransportService.NOOP_TRANSPORT_INTERCEPTOR,
-            x -> null,
-            null,
-            Collections.emptySet(),
-            NoopTracer.INSTANCE
+        TransportService mockTransportService = spy(
+            new TransportService(
+                Settings.EMPTY,
+                mock(Transport.class),
+                threadPool,
+                TransportService.NOOP_TRANSPORT_INTERCEPTOR,
+                x -> null,
+                null,
+                Collections.emptySet(),
+                NoopTracer.INSTANCE
+            )
         );
 
+        doNothing().when(mockTransportService).connectToExtensionNode(any(DiscoveryExtensionNode.class));
+
+        doNothing().when(mockTransportService)
+            .sendRequest(any(DiscoveryExtensionNode.class), anyString(), any(InitializeExtensionRequest.class), any());
+
         extensionsManager.initializeServicesAndRestHandler(
             actionModule,
             settingsModule,
-            transportService,
+            mockTransportService,
             clusterService,
             settings,
             client,
@@ -458,8 +460,7 @@ public void testInitializeExtensionTwice() throws Exception {
             null
         );
 
-        extensionsManager.loadExtension(firstExtension);
-        extensionsManager.initialize();
+        extensionsManager.initializeExtension(firstExtension);
 
         Extension secondExtension = new Extension(
             "secondExtension",
@@ -473,12 +474,18 @@ public void testInitializeExtensionTwice() throws Exception {
             null
         );
 
-        extensionsManager.loadExtension(secondExtension);
-        extensionsManager.initialize();
+        extensionsManager.initializeExtension(secondExtension);
 
-        // When execution is mocked, the successful registration callback is not called and the extension is never added to
-        // registered extensions.
-        // verify(mockExecutorService, times(2)).execute(any());
+        ThreadPool.terminate(threadPool, 3, TimeUnit.SECONDS);
+
+        verify(mockTransportService, times(2)).connectToExtensionNode(any(DiscoveryExtensionNode.class));
+
+        verify(mockTransportService, times(2)).sendRequest(
+            any(DiscoveryExtensionNode.class),
+            anyString(),
+            any(InitializeExtensionRequest.class),
+            any()
+        );
     }
 
     public void testHandleRegisterRestActionsRequest() throws Exception {
@@ -515,20 +522,20 @@ public void testHandleRegisterRestActionsRequestRequiresDiscoveryNode() throws E
         );
     }
 
-    public void testHandleRegisterTwoRestActionsRequest() throws Exception {
+    public void testHandleRegisterRestActionsRequestMultiple() throws Exception {
 
         ExtensionsManager extensionsManager = new ExtensionsManager(Set.of(), identityService);
         initialize(extensionsManager);
 
         List<String> actionsList = List.of("GET /foo foo", "PUT /bar bar", "POST /baz baz");
         List<String> deprecatedActionsList = List.of("GET /deprecated/foo foo_deprecated", "It's deprecated!");
         for (int i = 0; i < 2; i++) {
-            String uniqueIdStr = String.format("uniqueid-%d", i);
+            String uniqueIdStr = "uniqueid-%d" + i;
 
             Set<Setting<?>> additionalSettings = extAwarePlugin.getExtensionSettings().stream().collect(Collectors.toSet());
             ExtensionScopedSettings extensionScopedSettings = new ExtensionScopedSettings(additionalSettings);
             Extension firstExtension = new Extension(
-                String.format("Extension %s", i),
+                "Extension %s" + i,
                 uniqueIdStr,
                 "127.0.0.0",
                 "9300",