Added createComponent to Extension interface

build.gradle

@@ -48,7 +48,7 @@ publishing {
 repositories {
     mavenLocal()
     // Remove the commented code below once TransportService is published to maven
-    //maven { url "https://aws.oss.sonatype.org/content/repositories/snapshots" }
+    maven { url "https://aws.oss.sonatype.org/content/repositories/snapshots" }
     maven { url "https://d1nvenhzbhpy0q.cloudfront.net/snapshots/lucene/"}
     mavenCentral()
 }
@@ -65,6 +65,7 @@ dependencies {
     implementation 'org.opensearch.client:opensearch-rest-client:2.0.0'
     implementation 'org.opensearch.client:opensearch-java:2.0.0'
     implementation "io.netty:netty-all:4.1.73.Final"
+    implementation "org.apache.lucene:lucene-core:9.4.0-snapshot-ddf0d0a"
     testCompileOnly ("junit:junit:4.13.2") {
         exclude module : 'hamcrest'
         exclude module : 'hamcrest-core'

src/main/java/org/opensearch/sdk/BaseExtension.java

@@ -0,0 +1,43 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+package org.opensearch.sdk;
+
+import java.util.Collection;
+import java.util.Collections;
+
+import org.opensearch.cluster.service.ClusterService;
+import org.opensearch.env.Environment;
+import org.opensearch.threadpool.ThreadPool;
+
+public abstract class BaseExtension implements Extension {
+    protected SDKClient client;
+    protected ClusterService clusterService;
+    protected ThreadPool threadPool;
+    protected Environment environment;
+
+    /**
+     * Empty constructor to fulfill abstract class requirements
+     */
+    protected BaseExtension() {
+
+    }
+
+    public Collection<Object> createComponents(
+        SDKClient client,
+        ClusterService clusterService,
+        ThreadPool threadPool,
+        Environment environment
+    ) {
+        this.client = client;
+        this.clusterService = clusterService;
+        this.threadPool = threadPool;
+        this.environment = environment;
+
+        return Collections.emptyList();
+    }
+}

src/main/java/org/opensearch/sdk/Extension.java

@@ -11,8 +11,14 @@
 import java.io.IOException;
 import java.net.URL;
 import java.util.Collections;
+import java.util.Collection;
 import java.util.List;
 
+import org.opensearch.client.OpenSearchClient;
+import org.opensearch.cluster.service.ClusterService;
+import org.opensearch.env.Environment;
+import org.opensearch.threadpool.ThreadPool;
+
 import org.opensearch.common.settings.Setting;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -48,6 +54,21 @@ default List<Setting<?>> getSettings() {
         return Collections.emptyList();
     }
 
+    /**
+     * Returns components added by this extension.
+     *
+     * @param client A client to make requests to the system
+     * @param clusterService A service to allow watching and updating cluster state
+     * @param threadPool A service to allow retrieving an executor to run an async action
+     * @param environment the environment for path and setting configurations
+     */
+    public Collection<Object> createComponents(
+        OpenSearchClient client,
+        ClusterService clusterService,
+        ThreadPool threadPool,
+        Environment environment
+    );
+
     /**
      * Helper method to read extension settings from a YAML file.
      *

src/main/java/org/opensearch/sdk/ExtensionsRunner.java

@@ -149,7 +149,10 @@ private ExtensionsRunner(Extension extension) throws IOException {
         // save custom settings
         this.customSettings = extension.getSettings();
         // initialize the transport service
-        this.initializeExtensionTransportService(this.getSettings());
+        ThreadPool threadPool = new ThreadPool(this.getSettings());
+        this.initializeExtensionTransportService(this.getSettings(), threadPool);
+        // Create components
+        extension.createComponents(new SDKClient(), null, threadPool, null);
         // start listening on configured port and wait for connection from OpenSearch
         this.startActionListener(0);
     }
@@ -330,9 +333,7 @@ public Netty4Transport getNetty4Transport(Settings settings, ThreadPool threadPo
      * @param settings  The transport settings to configure.
      * @return The initialized TransportService object.
      */
-    public TransportService initializeExtensionTransportService(Settings settings) {
-
-        ThreadPool threadPool = new ThreadPool(settings);
+    public TransportService initializeExtensionTransportService(Settings settings, ThreadPool threadPool) {
 
         Netty4Transport transport = getNetty4Transport(settings, threadPool);
 
@@ -554,10 +555,7 @@ public void sendActionListenerOnFailureRequest(TransportService transportService
             transportService.sendRequest(
                 opensearchNode,
                 ExtensionsOrchestrator.REQUEST_EXTENSION_ACTION_LISTENER_ON_FAILURE,
-                new ExtensionRequest(
-                    ExtensionsOrchestrator.RequestType.REQUEST_EXTENSION_ACTION_LISTENER_ON_FAILURE,
-                    failureException.toString()
-                ),
+                new ExtensionActionListenerOnFailureRequest(failureException.toString()),
                 listenerHandler
             );
         } catch (Exception e) {
@@ -662,7 +660,8 @@ public static void main(String[] args) throws IOException {
         ExtensionsRunner extensionsRunner = new ExtensionsRunner();
 
         // initialize the transport service
-        extensionsRunner.initializeExtensionTransportService(extensionsRunner.getSettings());
+        ThreadPool threadPool = new ThreadPool(extensionsRunner.getSettings());
+        extensionsRunner.initializeExtensionTransportService(extensionsRunner.getSettings(), threadPool);
         // start listening on configured port and wait for connection from OpenSearch
         extensionsRunner.startActionListener(0);
     }

src/main/java/org/opensearch/sdk/sample/helloworld/HelloWorldExtension.java

@@ -10,6 +10,7 @@
 import java.io.IOException;
 import java.util.List;
 
+import org.opensearch.sdk.BaseExtension;
 import org.opensearch.sdk.Extension;
 import org.opensearch.sdk.ExtensionRestHandler;
 import org.opensearch.sdk.ExtensionSettings;
@@ -25,7 +26,7 @@
  * <p>
  * To execute, pass an instatiated object of this class to {@link ExtensionsRunner#run(Extension)}.
  */
-public class HelloWorldExtension implements Extension {
+public class HelloWorldExtension extends BaseExtension {
 
     /**
      * Optional classpath-relative path to a yml file containing extension settings.
@@ -40,7 +41,8 @@ public class HelloWorldExtension implements Extension {
     /**
      * Instantiate this extension, initializing the connection settings and REST actions.
      */
-    public HelloWorldExtension() {
+    public HelloWorldExtension() throws IOException {
+        super();
         try {
             this.settings = initializeSettings();
         } catch (IOException e) {