Faster GET _cluster/settings API

docs/changelog/86405.yaml

@@ -0,0 +1,6 @@
+pr: 86405
+summary: Faster GET _cluster/settings API
+area: Infra/Core
+type: enhancement
+issues:
+ - 82342

server/src/main/java/org/elasticsearch/action/ActionModule.java

@@ -59,7 +59,9 @@
 import org.elasticsearch.action.admin.cluster.repositories.verify.VerifyRepositoryAction;
 import org.elasticsearch.action.admin.cluster.reroute.ClusterRerouteAction;
 import org.elasticsearch.action.admin.cluster.reroute.TransportClusterRerouteAction;
+import org.elasticsearch.action.admin.cluster.settings.ClusterGetSettingsAction;
 import org.elasticsearch.action.admin.cluster.settings.ClusterUpdateSettingsAction;
+import org.elasticsearch.action.admin.cluster.settings.TransportClusterGetSettingsAction;
 import org.elasticsearch.action.admin.cluster.settings.TransportClusterUpdateSettingsAction;
 import org.elasticsearch.action.admin.cluster.shards.ClusterSearchShardsAction;
 import org.elasticsearch.action.admin.cluster.shards.TransportClusterSearchShardsAction;
@@ -547,6 +549,7 @@ public <Request extends ActionRequest, Response extends ActionResponse> void reg
         actions.register(ClusterStateAction.INSTANCE, TransportClusterStateAction.class);
         actions.register(ClusterHealthAction.INSTANCE, TransportClusterHealthAction.class);
         actions.register(ClusterUpdateSettingsAction.INSTANCE, TransportClusterUpdateSettingsAction.class);
+        actions.register(ClusterGetSettingsAction.INSTANCE, TransportClusterGetSettingsAction.class);
         actions.register(ClusterRerouteAction.INSTANCE, TransportClusterRerouteAction.class);
         actions.register(ClusterSearchShardsAction.INSTANCE, TransportClusterSearchShardsAction.class);
         actions.register(PendingClusterTasksAction.INSTANCE, TransportPendingClusterTasksAction.class);
@@ -709,7 +712,7 @@ public void initRestHandlers(Supplier<DiscoveryNodes> nodesInCluster) {
         registerHandler.accept(new RestClusterStateAction(settingsFilter, threadPool));
         registerHandler.accept(new RestClusterHealthAction());
         registerHandler.accept(new RestClusterUpdateSettingsAction());
-        registerHandler.accept(new RestClusterGetSettingsAction(settings, clusterSettings, settingsFilter));
+        registerHandler.accept(new RestClusterGetSettingsAction(settings, clusterSettings, settingsFilter, nodesInCluster));
         registerHandler.accept(new RestClusterRerouteAction(settingsFilter));
         registerHandler.accept(new RestClusterSearchShardsAction());
         registerHandler.accept(new RestPendingClusterTasksAction());

server/src/main/java/org/elasticsearch/action/admin/cluster/settings/ClusterGetSettingsAction.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.action.admin.cluster.settings;
+
+import org.elasticsearch.Version;
+import org.elasticsearch.action.ActionRequestValidationException;
+import org.elasticsearch.action.ActionResponse;
+import org.elasticsearch.action.ActionType;
+import org.elasticsearch.action.support.master.MasterNodeReadRequest;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.settings.Settings;
+
+import java.io.IOException;
+import java.util.Objects;
+
+public class ClusterGetSettingsAction extends ActionType<ClusterGetSettingsAction.Response> {
+
+    public static final ClusterGetSettingsAction INSTANCE = new ClusterGetSettingsAction();
+    public static final String NAME = "cluster:monitor/settings";
+
+    public ClusterGetSettingsAction() {
+        super(NAME, Response::new);
+    }
+
+    /**
+     * Request to retrieve the cluster settings
+     */
+    public static class Request extends MasterNodeReadRequest<Request> {
+        public Request() {}
+
+        public Request(StreamInput in) throws IOException {
+            super(in);
+            assert in.getVersion().onOrAfter(Version.V_8_3_0);
+        }
+
+        @Override
+        public void writeTo(StreamOutput out) throws IOException {
+            assert out.getVersion().onOrAfter(Version.V_8_3_0);
+            super.writeTo(out);
+        }
+
+        @Override
+        public ActionRequestValidationException validate() {
+            return null;
+        }
+    }
+
+    /**
+     * Response for cluster settings
+     */
+    public static class Response extends ActionResponse {
+        private final Settings persistentSettings;
+        private final Settings transientSettings;
+        private final Settings settings;
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+            Response response = (Response) o;
+            return Objects.equals(persistentSettings, response.persistentSettings)
+                && Objects.equals(transientSettings, response.transientSettings)
+                && Objects.equals(settings, response.settings);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(persistentSettings, transientSettings, settings);
+        }
+
+        public Response(StreamInput in) throws IOException {
+            super(in);
+            assert in.getVersion().onOrAfter(Version.V_8_3_0);
+            persistentSettings = Settings.readSettingsFromStream(in);
+            transientSettings = Settings.readSettingsFromStream(in);
+            settings = Settings.readSettingsFromStream(in);
+        }
+
+        public Response(Settings persistentSettings, Settings transientSettings, Settings settings) {
+            this.persistentSettings = Objects.requireNonNullElse(persistentSettings, Settings.EMPTY);
+            this.transientSettings = Objects.requireNonNullElse(transientSettings, Settings.EMPTY);
+            this.settings = Objects.requireNonNullElse(settings, Settings.EMPTY);
+        }
+
+        @Override
+        public void writeTo(StreamOutput out) throws IOException {
+            assert out.getVersion().onOrAfter(Version.V_8_3_0);
+            Settings.writeSettingsToStream(persistentSettings, out);
+            Settings.writeSettingsToStream(transientSettings, out);
+            Settings.writeSettingsToStream(settings, out);
+        }
+
+        public Settings persistentSettings() {
+            return persistentSettings;
+        }
+
+        public Settings transientSettings() {
+            return transientSettings;
+        }
+
+        public Settings settings() {
+            return settings;
+        }
+    }
+}

server/src/main/java/org/elasticsearch/action/admin/cluster/settings/TransportClusterGetSettingsAction.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.action.admin.cluster.settings;
+
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.support.ActionFilters;
+import org.elasticsearch.action.support.master.TransportMasterNodeReadAction;
+import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.block.ClusterBlockException;
+import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
+import org.elasticsearch.cluster.metadata.Metadata;
+import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.settings.SettingsFilter;
+import org.elasticsearch.tasks.Task;
+import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.transport.TransportService;
+
+public class TransportClusterGetSettingsAction extends TransportMasterNodeReadAction<
+    ClusterGetSettingsAction.Request,
+    ClusterGetSettingsAction.Response> {
+
+    private final SettingsFilter settingsFilter;
+
+    @Inject
+    public TransportClusterGetSettingsAction(
+        TransportService transportService,
+        ClusterService clusterService,
+        ThreadPool threadPool,
+        SettingsFilter settingsFilter,
+        ActionFilters actionFilters,
+        IndexNameExpressionResolver indexNameExpressionResolver
+    ) {
+        super(
+            ClusterGetSettingsAction.NAME,
+            false,
+            transportService,
+            clusterService,
+            threadPool,
+            actionFilters,
+            ClusterGetSettingsAction.Request::new,
+            indexNameExpressionResolver,
+            ClusterGetSettingsAction.Response::new,
+            ThreadPool.Names.SAME
+        );
+
+        this.settingsFilter = settingsFilter;
+    }
+
+    @Override
+    protected void masterOperation(
+        Task task,
+        ClusterGetSettingsAction.Request request,
+        ClusterState state,
+        ActionListener<ClusterGetSettingsAction.Response> listener
+    ) throws Exception {
+        Metadata metadata = state.metadata();
+        listener.onResponse(
+            new ClusterGetSettingsAction.Response(
+                settingsFilter.filter(metadata.persistentSettings()),
+                settingsFilter.filter(metadata.transientSettings()),
+                settingsFilter.filter(metadata.settings())
+            )
+        );
+    }
+
+    @Override
+    protected ClusterBlockException checkBlock(ClusterGetSettingsAction.Request request, ClusterState state) {
+        return null;
+    }
+}

server/src/main/java/org/elasticsearch/rest/action/admin/cluster/RestClusterGetSettingsAction.java

@@ -8,11 +8,14 @@
 
 package org.elasticsearch.rest.action.admin.cluster;
 
+import org.elasticsearch.Version;
+import org.elasticsearch.action.admin.cluster.settings.ClusterGetSettingsAction;
 import org.elasticsearch.action.admin.cluster.settings.RestClusterGetSettingsResponse;
 import org.elasticsearch.action.admin.cluster.state.ClusterStateRequest;
+import org.elasticsearch.action.support.master.MasterNodeReadRequest;
 import org.elasticsearch.client.internal.Requests;
 import org.elasticsearch.client.internal.node.NodeClient;
-import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.common.settings.ClusterSettings;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.settings.SettingsFilter;
@@ -23,6 +26,7 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Set;
+import java.util.function.Supplier;
 
 import static org.elasticsearch.rest.RestRequest.Method.GET;
 
@@ -31,11 +35,18 @@ public class RestClusterGetSettingsAction extends BaseRestHandler {
     private final Settings settings;
     private final ClusterSettings clusterSettings;
     private final SettingsFilter settingsFilter;
+    private final Supplier<DiscoveryNodes> nodesInCluster;
 
-    public RestClusterGetSettingsAction(Settings settings, ClusterSettings clusterSettings, SettingsFilter settingsFilter) {
+    public RestClusterGetSettingsAction(
+        Settings settings,
+        ClusterSettings clusterSettings,
+        SettingsFilter settingsFilter,
+        Supplier<DiscoveryNodes> nodesInCluster
+    ) {
         this.settings = settings;
         this.clusterSettings = clusterSettings;
         this.settingsFilter = settingsFilter;
+        this.nodesInCluster = nodesInCluster;
     }
 
     @Override
@@ -48,18 +59,51 @@ public String getName() {
         return "cluster_get_settings_action";
     }
 
+    private void setUpRequestParams(MasterNodeReadRequest<?> clusterRequest, RestRequest request) {
+        clusterRequest.local(request.paramAsBoolean("local", clusterRequest.local()));
+        clusterRequest.masterNodeTimeout(request.paramAsTime("master_timeout", clusterRequest.masterNodeTimeout()));
+    }
+
     @Override
     public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
-        ClusterStateRequest clusterStateRequest = Requests.clusterStateRequest().routingTable(false).nodes(false);
         final boolean renderDefaults = request.paramAsBoolean("include_defaults", false);
-        clusterStateRequest.local(request.paramAsBoolean("local", clusterStateRequest.local()));
-        clusterStateRequest.masterNodeTimeout(request.paramAsTime("master_timeout", clusterStateRequest.masterNodeTimeout()));
+
+        if (nodesInCluster.get().getMinNodeVersion().before(Version.V_8_3_0)) {
+            return prepareLegacyRequest(request, client, renderDefaults);
+        }
+
+        ClusterGetSettingsAction.Request clusterSettingsRequest = new ClusterGetSettingsAction.Request();
+
+        setUpRequestParams(clusterSettingsRequest, request);
+
+        return channel -> client.execute(
+            ClusterGetSettingsAction.INSTANCE,
+            clusterSettingsRequest,
+            new RestToXContentListener<RestClusterGetSettingsResponse>(channel).map(
+                r -> response(r, renderDefaults, settingsFilter, clusterSettings, settings)
+            )
+        );
+    }
+
+    private RestChannelConsumer prepareLegacyRequest(final RestRequest request, final NodeClient client, final boolean renderDefaults) {
+        ClusterStateRequest clusterStateRequest = Requests.clusterStateRequest().routingTable(false).nodes(false);
+        setUpRequestParams(clusterStateRequest, request);
         return channel -> client.admin()
             .cluster()
             .state(
                 clusterStateRequest,
                 new RestToXContentListener<RestClusterGetSettingsResponse>(channel).map(
-                    response -> response(response.getState(), renderDefaults, settingsFilter, clusterSettings, settings)
+                    r -> response(
+                        new ClusterGetSettingsAction.Response(
+                            r.getState().metadata().persistentSettings(),
+                            r.getState().metadata().transientSettings(),
+                            r.getState().metadata().settings()
+                        ),
+                        renderDefaults,
+                        settingsFilter,
+                        clusterSettings,
+                        settings
+                    )
                 )
             );
     }
@@ -75,16 +119,16 @@ public boolean canTripCircuitBreaker() {
     }
 
     static RestClusterGetSettingsResponse response(
-        final ClusterState state,
+        final ClusterGetSettingsAction.Response response,
         final boolean renderDefaults,
         final SettingsFilter settingsFilter,
         final ClusterSettings clusterSettings,
         final Settings settings
     ) {
         return new RestClusterGetSettingsResponse(
-            settingsFilter.filter(state.metadata().persistentSettings()),
-            settingsFilter.filter(state.metadata().transientSettings()),
-            renderDefaults ? settingsFilter.filter(clusterSettings.diff(state.metadata().settings(), settings)) : Settings.EMPTY
+            settingsFilter.filter(response.persistentSettings()),
+            settingsFilter.filter(response.transientSettings()),
+            renderDefaults ? settingsFilter.filter(clusterSettings.diff(response.settings(), settings)) : Settings.EMPTY
         );
     }
 

server/src/test/java/org/elasticsearch/action/admin/cluster/settings/ClusterGetSettingsSerializationTests.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.action.admin.cluster.settings;
+
+import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.test.AbstractWireSerializingTestCase;
+
+public class ClusterGetSettingsSerializationTests extends AbstractWireSerializingTestCase<ClusterGetSettingsAction.Response> {
+    @Override
+    protected Writeable.Reader<ClusterGetSettingsAction.Response> instanceReader() {
+        return ClusterGetSettingsAction.Response::new;
+    }
+
+    @Override
+    protected ClusterGetSettingsAction.Response createTestInstance() {
+        final Settings persistentSettings = Settings.builder()
+            .put("persistent.foo.filtered", "bar")
+            .put("persistent.foo.non_filtered", "baz")
+            .build();
+
+        final Settings transientSettings = Settings.builder()
+            .put("transient.foo.filtered", "bar")
+            .put("transient.foo.non_filtered", "baz")
+            .build();
+
+        final Settings allSettings = Settings.builder().put(persistentSettings).put(transientSettings).build();
+
+        return new ClusterGetSettingsAction.Response(persistentSettings, transientSettings, allSettings);
+    }
+
+    @Override
+    protected ClusterGetSettingsAction.Response mutateInstance(ClusterGetSettingsAction.Response instance) {
+        final Settings otherSettings = Settings.builder().put("random.setting", randomAlphaOfLength(randomIntBetween(1, 12))).build();
+        return switch (between(0, 2)) {
+            case 0 -> new ClusterGetSettingsAction.Response(otherSettings, instance.transientSettings(), instance.settings());
+            case 1 -> new ClusterGetSettingsAction.Response(instance.persistentSettings(), otherSettings, instance.settings());
+            case 2 -> new ClusterGetSettingsAction.Response(instance.persistentSettings(), instance.transientSettings(), otherSettings);
+            default -> throw new IllegalStateException("Unexpected switch value");
+        };
+    }
+}