Dynamically enable / disable plugins in correspondence to stateless mode.

build-tools/src/integTest/groovy/org/elasticsearch/gradle/plugin/PluginBuildPluginFuncTest.groovy

@@ -126,7 +126,7 @@ class PluginBuildPluginFuncTest extends AbstractGradleFuncTest {
         props.get("has.native.controller") == null
         props.get("extended.plugins") == null
         props.get("modulename") == null
-        props.size() == 6
+        props.size() == 7
     }
 
     def "module name is inferred by plugin properties"() {

build-tools/src/integTest/groovy/org/elasticsearch/gradle/plugin/StablePluginBuildPluginFuncTest.groovy

@@ -73,7 +73,7 @@ class StablePluginBuildPluginFuncTest extends AbstractGradleFuncTest {
         props.get("modulename") == null
         props.get("extended.plugins") == null
         props.get("has.native.controller") == null
-        props.size() == 5
+        props.size() == 6
 
     }
 

build-tools/src/main/java/org/elasticsearch/gradle/plugin/BasePluginBuildPlugin.java

@@ -119,6 +119,7 @@ private TaskProvider<Zip> createBundleTasks(final Project project, PluginPropert
             task.getHasNativeController().set(providerFactory.provider(extension::isHasNativeController));
             task.getRequiresKeystore().set(providerFactory.provider(extension::isRequiresKeystore));
             task.getIsLicensed().set(providerFactory.provider(extension::isLicensed));
+            task.getDeploymentTarget().set(providerFactory.provider(extension::getDeploymentTarget));
 
             var mainSourceSet = project.getExtensions().getByType(SourceSetContainer.class).getByName(SourceSet.MAIN_SOURCE_SET_NAME);
             FileCollection moduleInfoFile = mainSourceSet.getOutput()

build-tools/src/main/java/org/elasticsearch/gradle/plugin/GeneratePluginPropertiesTask.java

@@ -39,6 +39,7 @@
 import java.nio.file.Path;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Set;
 
 import javax.inject.Inject;
 
@@ -49,6 +50,8 @@ public abstract class GeneratePluginPropertiesTask extends DefaultTask {
     public static final String STABLE_PROPERTIES_FILENAME = "stable-plugin-descriptor.properties";
     private static final String DESCRIPTION = "Generates Elasticsearch Plugin descriptor file";
 
+    private static final Set<String> DEPLOYMENT_TARGETS = Set.of("ALL", "STATELESS_ONLY", "STATEFUL_ONLY");
+
     @Inject
     public GeneratePluginPropertiesTask(ProjectLayout projectLayout) {
         setDescription(DESCRIPTION);
@@ -95,6 +98,10 @@ public GeneratePluginPropertiesTask(ProjectLayout projectLayout) {
     @Input
     public abstract Property<Boolean> getIsStable();
 
+    @Input
+    @Optional
+    public abstract Property<String> getDeploymentTarget();
+
     @TaskAction
     public void generatePropertiesFile() throws IOException {
         String classname = getClassname().getOrElse("");
@@ -119,6 +126,14 @@ public void generatePropertiesFile() throws IOException {
         props.put("licensed", getIsLicensed().get());
         props.put("modulename", findModuleName());
 
+        String deploymentTarget = getDeploymentTarget().getOrElse("ALL");
+        if (DEPLOYMENT_TARGETS.contains(deploymentTarget) == false) {
+            throw new InvalidUserDataException(
+                "invalid deploymentTarget '" + deploymentTarget + "', expected one of " + DEPLOYMENT_TARGETS
+            );
+        }
+        props.put("deploymentTarget", deploymentTarget);
+
         SimpleTemplateEngine engine = new SimpleTemplateEngine();
         Path outputFile = getOutputFile().get().getAsFile().toPath();
         Files.createDirectories(outputFile.getParent());

build-tools/src/main/java/org/elasticsearch/gradle/plugin/PluginPropertiesExtension.java

@@ -43,6 +43,9 @@ public class PluginPropertiesExtension {
     /** True if the plugin requires the elasticsearch keystore to exist, false otherwise. */
     private boolean requiresKeystore;
 
+    /** The optional deployment target of this plugin. */
+    private String deploymentTarget;
+
     /** A license file that should be included in the built plugin zip. */
     private File licenseFile;
 
@@ -117,6 +120,14 @@ public boolean isRequiresKeystore() {
         return requiresKeystore;
     }
 
+    public String getDeploymentTarget() {
+        return deploymentTarget;
+    }
+
+    public void setDeploymentTarget(String deploymentTarget) {
+        this.deploymentTarget = deploymentTarget;
+    }
+
     public void setRequiresKeystore(boolean requiresKeystore) {
         this.requiresKeystore = requiresKeystore;
     }

build-tools/src/main/resources/plugin-descriptor.properties

@@ -63,3 +63,6 @@ has.native.controller=${hasNativeController}
 # This plugin requires that a license agreement be accepted before installation
 licensed=${licensed}
 <% } %>
+
+# The deployment target describing when to include this plugin
+deployment.target=${deploymentTarget}

distribution/tools/plugin-cli/src/test/java/org/elasticsearch/plugins/cli/ListPluginsCommandTests.java

@@ -123,7 +123,8 @@ public void testPluginWithVerbose() throws Exception {
                 "Native Controller: false",
                 "Licensed: false",
                 "Extended Plugins: []",
-                " * Classname: org.fake"
+                " * Classname: org.fake",
+                "Deployment Target: ALL"
             ),
             terminal.getOutput()
         );
@@ -145,7 +146,8 @@ public void testPluginWithNativeController() throws Exception {
                 "Native Controller: true",
                 "Licensed: false",
                 "Extended Plugins: []",
-                " * Classname: org.fake"
+                " * Classname: org.fake",
+                "Deployment Target: ALL"
             ),
             terminal.getOutput()
         );
@@ -169,6 +171,7 @@ public void testPluginWithVerboseMultiplePlugins() throws Exception {
                 "Licensed: false",
                 "Extended Plugins: []",
                 " * Classname: org.fake",
+                "Deployment Target: ALL",
                 "fake_plugin2",
                 "- Plugin information:",
                 "Name: fake_plugin2",
@@ -179,7 +182,8 @@ public void testPluginWithVerboseMultiplePlugins() throws Exception {
                 "Native Controller: false",
                 "Licensed: false",
                 "Extended Plugins: []",
-                " * Classname: org.fake2"
+                " * Classname: org.fake2",
+                "Deployment Target: ALL"
             ),
             terminal.getOutput()
         );

modules/health-shards-availability/build.gradle

@@ -13,6 +13,7 @@ apply plugin: 'elasticsearch.internal-cluster-test'
 esplugin {
   description = 'Health report API extension providing the shards_availability output'
   classname = 'org.elasticsearch.health.plugin.ShardsAvailabilityPlugin'
+  deploymentTarget = 'STATEFUL_ONLY'
 }
 
 restResources {

server/src/main/java/org/elasticsearch/bootstrap/Elasticsearch.java

@@ -22,6 +22,7 @@
 import org.elasticsearch.ReleaseVersions;
 import org.elasticsearch.action.support.SubscribableListener;
 import org.elasticsearch.cluster.ClusterName;
+import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.common.ReferenceDocs;
 import org.elasticsearch.common.io.stream.InputStreamStreamInput;
 import org.elasticsearch.common.logging.LogConfigurator;
@@ -223,8 +224,9 @@ private static void initPhase2(Bootstrap bootstrap) throws IOException {
         );
 
         // load the plugin Java modules and layers now for use in entitlements
-        var modulesBundles = PluginsLoader.loadModulesBundles(nodeEnv.modulesDir());
-        var pluginsBundles = PluginsLoader.loadPluginsBundles(nodeEnv.pluginsDir());
+        boolean isStatelessMode = DiscoveryNode.isStateless(nodeEnv.settings());
+        var modulesBundles = PluginsLoader.loadModulesBundles(nodeEnv.modulesDir(), isStatelessMode);
+        var pluginsBundles = PluginsLoader.loadPluginsBundles(nodeEnv.pluginsDir(), isStatelessMode);
 
         final PluginsLoader pluginsLoader;
 

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

@@ -23,6 +23,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
@@ -43,6 +44,18 @@ public class PluginDescriptor implements Writeable, ToXContentObject {
     public static final String STABLE_DESCRIPTOR_FILENAME = "stable-plugin-descriptor.properties";
     public static final String NAMED_COMPONENTS_FILENAME = "named_components.json";
 
+    /**
+     * Deployment target describing when to load a plugin (stateful, stateless, or both).
+     */
+    public enum DeploymentTarget {
+        /** Only load plugin on stateful deployments (stateless mode disabled) */
+        STATEFUL_ONLY,
+        /** Only load plugin on stateless deployments (stateless mode enabled) */
+        STATELESS_ONLY,
+        /** All deployment targets (default) */
+        ALL
+    }
+
     private final String name;
     private final String description;
     private final String version;
@@ -55,6 +68,7 @@ public class PluginDescriptor implements Writeable, ToXContentObject {
     private final boolean isLicensed;
     private final boolean isModular;
     private final boolean isStable;
+    private final DeploymentTarget deploymentTarget;
 
     /**
      * Construct plugin info.
@@ -71,6 +85,7 @@ public class PluginDescriptor implements Writeable, ToXContentObject {
      * @param isLicensed           whether is this a licensed plugin
      * @param isModular            whether this plugin should be loaded in a module layer
      * @param isStable             whether this plugin is implemented using the stable plugin API
+     * @param deploymentTarget     when to load this plugin
      */
     public PluginDescriptor(
         String name,
@@ -84,7 +99,8 @@ public PluginDescriptor(
         boolean hasNativeController,
         boolean isLicensed,
         boolean isModular,
-        boolean isStable
+        boolean isStable,
+        DeploymentTarget deploymentTarget
     ) {
         this.name = name;
         this.description = description;
@@ -98,6 +114,7 @@ public PluginDescriptor(
         this.isLicensed = isLicensed;
         this.isModular = isModular;
         this.isStable = isStable;
+        this.deploymentTarget = deploymentTarget;
 
         ensureCorrectArgumentsForPluginType();
     }
@@ -123,6 +140,7 @@ public PluginDescriptor(final StreamInput in) throws IOException {
 
         isModular = in.readBoolean();
         isStable = in.readBoolean();
+        deploymentTarget = DeploymentTarget.ALL; // only read from descriptor property files, not serialized
 
         ensureCorrectArgumentsForPluginType();
     }
@@ -253,8 +271,42 @@ private static PluginDescriptor readerInternalDescriptor(Map<String, String> pro
 
         boolean isLicensed = readBoolean(propsMap, name, "licensed");
         boolean modular = module != null;
-
-        return new PluginDescriptor(name, desc, ver, esVer, javaVer, classname, module, extended, nativeCont, isLicensed, modular, false);
+        DeploymentTarget deploymentTarget = readDeploymentTarget(propsMap, name);
+
+        return new PluginDescriptor(
+            name,
+            desc,
+            ver,
+            esVer,
+            javaVer,
+            classname,
+            module,
+            extended,
+            nativeCont,
+            isLicensed,
+            modular,
+            false,
+            deploymentTarget
+        );
+    }
+
+    private static DeploymentTarget readDeploymentTarget(Map<String, String> propsMap, String pluginId) {
+        String rawValue = propsMap.remove("deployment.target");
+        if (rawValue == null) {
+            return DeploymentTarget.ALL;
+        }
+        try {
+            return DeploymentTarget.valueOf(rawValue.trim());
+        } catch (IllegalArgumentException e) {
+            throw new IllegalArgumentException(
+                Strings.format(
+                    "Descriptor of plugin [%s] contains invalid deployment.target [%s], expected one of %s",
+                    pluginId,
+                    rawValue,
+                    Arrays.toString(DeploymentTarget.values())
+                )
+            );
+        }
     }
 
     private static PluginDescriptor readerStableDescriptor(Map<String, String> propsMap, String filename) {
@@ -264,8 +316,23 @@ private static PluginDescriptor readerStableDescriptor(Map<String, String> props
         String esVer = readElasticsearchVersion(propsMap, name);
         String javaVer = readJavaVersion(propsMap, name);
         boolean isModular = readBoolean(propsMap, name, "modular");
-
-        return new PluginDescriptor(name, desc, ver, esVer, javaVer, null, null, List.of(), false, false, isModular, true);
+        DeploymentTarget deploymentTarget = readDeploymentTarget(propsMap, name);
+
+        return new PluginDescriptor(
+            name,
+            desc,
+            ver,
+            esVer,
+            javaVer,
+            null,
+            null,
+            List.of(),
+            false,
+            false,
+            isModular,
+            true,
+            deploymentTarget
+        );
     }
 
     private static String readNonEmptyString(Map<String, String> propsMap, String pluginId, String name) {
@@ -415,6 +482,13 @@ public boolean isStable() {
         return isStable;
     }
 
+    /**
+     * The deployment target of this plugin, specifically if to include the plugin in stateful and/or stateless mode.
+     */
+    public DeploymentTarget getDeploymentTarget() {
+        return deploymentTarget;
+    }
+
     @Override
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         builder.startObject();
@@ -433,7 +507,6 @@ public XContentBuilder toXContentFragment(XContentBuilder builder, Params params
         builder.field("extended_plugins", extendedPlugins);
         builder.field("has_native_controller", hasNativeController);
         builder.field("licensed", isLicensed);
-
         return builder;
     }
 
@@ -470,6 +543,7 @@ public String toString(String prefix) {
         appendLine(lines, prefix, "Licensed: ", isLicensed);
         appendLine(lines, prefix, "Extended Plugins: ", extendedPlugins.toString());
         appendLine(lines, prefix, " * Classname: ", classname);
+        appendLine(lines, prefix, "Deployment Target: ", deploymentTarget);
 
         return String.join(System.lineSeparator(), lines);
     }