[Extensions] Add ExtensionAwarePlugin extension point to add custom settings for extensions

CHANGELOG.md

@@ -94,6 +94,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Provide mechanism to configure XContent parsing constraints (after update to Jackson 2.15.0 and above) ([#7550](https://github.com/opensearch-project/OpenSearch/pull/7550))
 - Support to clear filecache using clear indices cache API ([#7498](https://github.com/opensearch-project/OpenSearch/pull/7498))
 - Create NamedRoute to map extension routes to a shortened name ([#6870](https://github.com/opensearch-project/OpenSearch/pull/6870))
+- [Extensions] Add ExtensionAwarePlugin extension point to add custom settings for extensions ([#7526](https://github.com/opensearch-project/OpenSearch/pull/7526))
 
 ### Dependencies
 - Bump `com.netflix.nebula:gradle-info-plugin` from 12.0.0 to 12.1.3 (#7564)

server/src/main/java/org/opensearch/common/settings/Setting.java

@@ -132,6 +132,11 @@ public enum Property {
          */
         Deprecated,
 
+        /**
+         * Extension scope
+         */
+        ExtensionScope,
+
         /**
          * Node scope
          */

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

@@ -0,0 +1,34 @@
+/*
+ * 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.extensions;
+
+import org.opensearch.common.settings.AbstractScopedSettings;
+import org.opensearch.common.settings.Setting;
+import org.opensearch.common.settings.Setting.Property;
+import org.opensearch.common.settings.SettingUpgrader;
+import org.opensearch.common.settings.Settings;
+
+import java.util.Collections;
+import java.util.Set;
+
+/**
+ * Encapsulates all valid extension level settings.
+ *
+ * @opensearch.internal
+ */
+public final class ExtensionAdditionalSettings extends AbstractScopedSettings {
+
+    public ExtensionAdditionalSettings(final Set<Setting<?>> settingsSet) {
+        this(settingsSet, Collections.emptySet());
+    }
+
+    public ExtensionAdditionalSettings(final Set<Setting<?>> settingsSet, final Set<SettingUpgrader<?>> settingUpgraders) {
+        super(Settings.EMPTY, settingsSet, settingUpgraders, Property.ExtensionScope);
+    }
+}

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

@@ -17,9 +17,11 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
 import java.util.concurrent.TimeUnit;
@@ -39,6 +41,7 @@
 import org.opensearch.cluster.ClusterSettingsResponse;
 import org.opensearch.cluster.node.DiscoveryNode;
 import org.opensearch.cluster.service.ClusterService;
+import org.opensearch.common.settings.Setting;
 import org.opensearch.core.util.FileSystemUtils;
 import org.opensearch.common.io.stream.StreamInput;
 import org.opensearch.common.settings.Settings;
@@ -116,6 +119,7 @@
     private CustomSettingsRequestHandler customSettingsRequestHandler;
     private TransportService transportService;
     private ClusterService clusterService;
+    private Set<Setting<?>> additionalSettings;
     private Settings environmentSettings;
     private AddSettingsUpdateConsumerRequestHandler addSettingsUpdateConsumerRequestHandler;
     private NodeClient client;
@@ -124,9 +128,10 @@
      * Instantiate a new ExtensionsManager object to handle requests and responses from extensions. This is called during Node bootstrap.
      *
      * @param extensionsPath  Path to a directory containing extensions.
+     * @param additionalSettings  Additional settings to read in from extensions.yml
      * @throws IOException  If the extensions discovery file is not properly retrieved.
      */
-    public ExtensionsManager(Path extensionsPath) throws IOException {
+    public ExtensionsManager(Path extensionsPath, Set<Setting<?>> additionalSettings) throws IOException {
         logger.info("ExtensionsManager initialized");
         this.extensionsPath = extensionsPath;
         this.initializedExtensions = new HashMap<String, DiscoveryExtensionNode>();
@@ -135,6 +140,11 @@
         // will be initialized in initializeServicesAndRestHandler which is called after the Node is initialized
         this.transportService = null;
         this.clusterService = null;
+        if (additionalSettings == null) {
+            this.additionalSettings = new HashSet<>();
+        } else {
+            this.additionalSettings = additionalSettings;
+        }
         this.client = null;
         this.extensionTransportActionsHandler = null;
 
@@ -629,6 +639,17 @@
                         }
                     }
 
+                    ExtensionAdditionalSettings extAdditionalSettings = new ExtensionAdditionalSettings(additionalSettings);
+                    Set<String> additionalSettingsKeys = additionalSettings.stream().map(s -> s.getKey()).collect(Collectors.toSet());
+                    Map<String, ?> additionalSettingsMap = extensionMap.entrySet()
+                        .stream()
+                        .filter(kv -> additionalSettingsKeys.contains(kv.getKey()))
+                        .collect(Collectors.toMap(map -> map.getKey(), map -> map.getValue()));
+
+                    Settings.Builder output = Settings.builder();
+                    output.loadFromMap(additionalSettingsMap);
+                    extAdditionalSettings.applySettings(output.build());
+
                     // Create extension read from yml config
                     readExtensions.add(
                         new Extension(
@@ -639,7 +660,8 @@
                             extensionMap.get("version").toString(),
                             extensionMap.get("opensearchVersion").toString(),
                             extensionMap.get("minimumCompatibleVersion").toString(),
-                            extensionDependencyList
+                            extensionDependencyList,
+                            extAdditionalSettings
                         )
                     );
                 } catch (IOException e) {

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

@@ -44,6 +44,7 @@ public static class Extension {
         private String opensearchVersion;
         private String minimumCompatibleVersion;
         private List<ExtensionDependency> dependencies = Collections.emptyList();
+        private ExtensionAdditionalSettings additionalSettings;
 
         public Extension(
             String name,
@@ -53,7 +54,8 @@ public Extension(
             String version,
             String opensearchVersion,
             String minimumCompatibleVersion,
-            List<ExtensionDependency> dependencies
+            List<ExtensionDependency> dependencies,
+            ExtensionAdditionalSettings additionalSettings
         ) {
             this.name = name;
             this.uniqueId = uniqueId;
@@ -63,6 +65,7 @@ public Extension(
             this.opensearchVersion = opensearchVersion;
             this.minimumCompatibleVersion = minimumCompatibleVersion;
             this.dependencies = dependencies;
+            this.additionalSettings = additionalSettings;
         }
 
         public Extension() {
@@ -127,6 +130,10 @@ public List<ExtensionDependency> getDependencies() {
             return dependencies;
         }
 
+        public ExtensionAdditionalSettings getAdditionalSettings() {
+            return additionalSettings;
+        }
+
         public String getMinimumCompatibleVersion() {
             return minimumCompatibleVersion;
         }

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

@@ -12,6 +12,7 @@
 import java.net.UnknownHostException;
 import java.nio.file.Path;
 import java.util.Optional;
+import java.util.Set;
 
 import org.opensearch.action.ActionModule;
 import org.opensearch.client.node.NodeClient;
@@ -33,7 +34,7 @@
 public class NoopExtensionsManager extends ExtensionsManager {
 
     public NoopExtensionsManager() throws IOException {
-        super(Path.of(""));
+        super(Path.of(""), Set.of());
     }
 
     @Override

server/src/main/java/org/opensearch/node/Node.java

@@ -54,6 +54,7 @@
 import org.opensearch.extensions.NoopExtensionsManager;
 import org.opensearch.monitor.fs.FsInfo;
 import org.opensearch.monitor.fs.FsProbe;
+import org.opensearch.plugins.ExtensionAwarePlugin;
 import org.opensearch.plugins.SearchPipelinePlugin;
 import org.opensearch.search.backpressure.SearchBackpressureService;
 import org.opensearch.search.backpressure.settings.SearchBackpressureSettings;
@@ -234,6 +235,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
@@ -465,8 +467,14 @@
 
             final IdentityService identityService = new IdentityService(settings, identityPlugins);
 
+            final List<ExtensionAwarePlugin> extensionAwarePlugins = new ArrayList<>();
             if (FeatureFlags.isEnabled(FeatureFlags.EXTENSIONS)) {
-                this.extensionsManager = new ExtensionsManager(initialEnvironment.extensionDir());
+                extensionAwarePlugins.addAll(pluginsService.filterPlugins(ExtensionAwarePlugin.class));
+                Set<Setting<?>> additionalSettings = new HashSet<>();
+                for (ExtensionAwarePlugin extAwarePlugin : extensionAwarePlugins) {
+                    additionalSettings.addAll(extAwarePlugin.getExtensionSettings());
+                }
+                this.extensionsManager = new ExtensionsManager(initialEnvironment.extensionDir(), additionalSettings);
             } else {
                 this.extensionsManager = new NoopExtensionsManager();
             }

server/src/main/java/org/opensearch/plugins/ExtensionAwarePlugin.java

@@ -0,0 +1,28 @@
+/*
+ * 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.plugins;
+
+import org.opensearch.common.settings.Setting;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Plugin that provides extra settings for extensions
+ *
+ * @opensearch.experimental
+ */
+public interface ExtensionAwarePlugin {
+    /**
+     * Returns a list of additional {@link Setting} definitions that this plugin adds for extensions
+     */
+    default List<Setting<?>> getExtensionSettings() {
+        return Collections.emptyList();
+    }
+}

server/src/main/java/org/opensearch/plugins/IdentityPlugin.java

@@ -22,5 +22,5 @@ public interface IdentityPlugin {
      *
      * Should never return null
      * */
-    public Subject getSubject();
+    Subject getSubject();
 }