Fix TransportPPLQueryAction

Signed-off-by: Lantao Jin <ltjin@amazon.com>

Author: LantaoJin

plugin/src/main/java/org/opensearch/sql/plugin/SQLPlugin.java

@@ -95,6 +95,7 @@
 import org.opensearch.sql.opensearch.setting.OpenSearchSettings;
 import org.opensearch.sql.opensearch.storage.OpenSearchDataSourceFactory;
 import org.opensearch.sql.opensearch.storage.script.CompoundedScriptEngine;
+import org.opensearch.sql.plugin.config.EngineExtensionsHolder;
 import org.opensearch.sql.plugin.config.OpenSearchPluginModule;
 import org.opensearch.sql.plugin.rest.RestPPLGrammarAction;
 import org.opensearch.sql.plugin.rest.RestPPLQueryAction;
@@ -158,7 +159,7 @@ public String description() {
   @Override
   public void loadExtensions(ExtensionLoader loader) {
     this.executionEngineExtensions = loader.loadExtensions(ExecutionEngine.class);
-    if (!executionEngineExtensions.isEmpty()) {
+    if (executionEngineExtensions != null && !executionEngineExtensions.isEmpty()) {
       LOGGER.info(
           "Loaded {} execution engine extension(s): {}",
           executionEngineExtensions.size(),
@@ -305,12 +306,15 @@ public Collection<Object> createComponents(
     ScheduledAsyncQueryJobRunner.getJobRunnerInstance()
         .loadJobResource(client, clusterService, threadPool, asyncQueryExecutorService);
 
+    EngineExtensionsHolder extensionsHolder = new EngineExtensionsHolder(executionEngineExtensions);
+
     return ImmutableList.of(
         dataSourceService,
         asyncQueryExecutorService,
         clusterManagerEventListener,
         pluginSettings,
-        directQueryExecutorService);
+        directQueryExecutorService,
+        extensionsHolder);
   }
 
   @Override

plugin/src/main/java/org/opensearch/sql/plugin/config/EngineExtensionsHolder.java

@@ -0,0 +1,16 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.sql.plugin.config;
+
+import java.util.List;
+import org.opensearch.sql.executor.ExecutionEngine;
+
+/**
+ * Holds execution engine engines loaded via SPI. Returned from {@code SQLPlugin.createComponents()}
+ * so that OpenSearch's Guice injector can inject it into transport actions like {@code
+ * TransportPPLQueryAction}.
+ */
+public record EngineExtensionsHolder(List<ExecutionEngine> engines) {}

plugin/src/main/java/org/opensearch/sql/plugin/config/OpenSearchPluginModule.java

@@ -45,7 +45,7 @@ public class OpenSearchPluginModule extends AbstractModule {
 
   private final List<ExecutionEngine> executionEngineExtensions;
 
-  /** Default constructor for when no extensions are available. */
+  /** Default constructor for when no engines are available. */
   public OpenSearchPluginModule() {
     this(List.of());
   }

plugin/src/main/java/org/opensearch/sql/plugin/transport/TransportPPLQueryAction.java

@@ -33,6 +33,7 @@
 import org.opensearch.sql.monitor.profile.QueryProfiling;
 import org.opensearch.sql.opensearch.executor.OpenSearchQueryManager;
 import org.opensearch.sql.opensearch.setting.OpenSearchSettings;
+import org.opensearch.sql.plugin.config.EngineExtensionsHolder;
 import org.opensearch.sql.plugin.config.OpenSearchPluginModule;
 import org.opensearch.sql.ppl.PPLService;
 import org.opensearch.sql.ppl.domain.PPLQueryRequest;
@@ -65,11 +66,12 @@ public TransportPPLQueryAction(
       NodeClient client,
       ClusterService clusterService,
       DataSourceServiceImpl dataSourceService,
-      org.opensearch.common.settings.Settings clusterSettings) {
+      org.opensearch.common.settings.Settings clusterSettings,
+      EngineExtensionsHolder extensionsHolder) {
     super(PPLQueryAction.NAME, transportService, actionFilters, TransportPPLQueryRequest::new);
 
     ModulesBuilder modules = new ModulesBuilder();
-    modules.add(new OpenSearchPluginModule());
+    modules.add(new OpenSearchPluginModule(extensionsHolder.engines()));
     modules.add(
         b -> {
           b.bind(NodeClient.class).toInstance(client);