Add autoscaling API skelton (#51564)

The main purpose of this commit is to add a single autoscaling REST
endpoint skeleton, for the purpose of starting to build out the build
and testing infrastructure that will surround it. For example, rather
than commiting a fully-functioning autoscaling API, we introduce here
the skeleton so that we can start wiring up the build and testing
infrastructure, establish security roles/permissions, an so on. This
way, in a forthcoming PR that introduces actual functionality, that PR
will be smaller and have less distractions around that sort of
infrastructure.

client/rest-high-level/src/main/java/org/elasticsearch/client/security/user/privileges/Role.java

@@ -318,6 +318,7 @@ public final class Role {
         public static final String MANAGE_OIDC = "manage_oidc";
         public static final String MANAGE_TOKEN = "manage_token";
         public static final String MANAGE_PIPELINE = "manage_pipeline";
+        public static final String MANAGE_AUTOSCALING = "manage_autoscaling";
         public static final String MANAGE_CCR = "manage_ccr";
         public static final String READ_CCR = "read_ccr";
         public static final String MANAGE_ILM = "manage_ilm";
@@ -326,8 +327,8 @@ public final class Role {
         public static final String[] ALL_ARRAY = new String[] { NONE, ALL, MONITOR, MONITOR_TRANSFORM_DEPRECATED, MONITOR_TRANSFORM,
             MONITOR_ML, MONITOR_WATCHER, MONITOR_ROLLUP, MANAGE, MANAGE_TRANSFORM_DEPRECATED, MANAGE_TRANSFORM,
             MANAGE_ML, MANAGE_WATCHER, MANAGE_ROLLUP, MANAGE_INDEX_TEMPLATES, MANAGE_INGEST_PIPELINES, TRANSPORT_CLIENT,
-                MANAGE_SECURITY, MANAGE_SAML, MANAGE_OIDC, MANAGE_TOKEN, MANAGE_PIPELINE, MANAGE_CCR, READ_CCR, MANAGE_ILM, READ_ILM,
-                MANAGE_ENRICH };
+            MANAGE_SECURITY, MANAGE_SAML, MANAGE_OIDC, MANAGE_TOKEN, MANAGE_PIPELINE, MANAGE_AUTOSCALING, MANAGE_CCR, READ_CCR,
+            MANAGE_ILM, READ_ILM, MANAGE_ENRICH };
     }
 
     /**

docs/reference/autoscaling/apis/autoscaling-apis.asciidoc

@@ -0,0 +1,15 @@
+[role="xpack"]
+[testenv="platinum"]
+[[autoscaling-apis]]
+== Autoscaling APIs
+
+You can use the following APIs to perform autoscaling operations.
+
+[float]
+[[autoscaling-api-top-level]]
+=== Top-Level
+
+* <<autoscaling-get-autoscaling-decision,Get autoscaling decision>>
+
+// top-level
+include::get-autoscaling-decision.asciidoc[]

docs/reference/autoscaling/apis/get-autoscaling-decision.asciidoc

@@ -0,0 +1,52 @@
+[role="xpack"]
+[testenv="platinum"]
+[[autoscaling-get-autoscaling-decision]]
+=== Get autoscaling decision API
+++++
+<titleabbrev>Get autoscaling decision</titleabbrev>
+++++
+
+Get autoscaling decision.
+
+[[autoscaling-get-autoscaling-decision-request]]
+==== {api-request-title}
+
+[source,console]
+--------------------------------------------------
+GET /_autoscaling/decision/
+--------------------------------------------------
+// TEST
+
+[[autoscaling-get-autoscaling-decision-prereqs]]
+==== {api-prereq-title}
+
+* If the {es} {security-features} are enabled, you must have
+`manage_autoscaling` cluster privileges. For more information, see
+<<security-privileges>>.
+
+[[autoscaling-get-autoscaling-decision-desc]]
+==== {api-description-title}
+
+This API gets the current autoscaling decision based on the configured
+autoscaling policy. This API will return whether or not autoscaling is
+needed.
+
+[[autoscaling-get-autoscaling-decision-examples]]
+==== {api-examples-title}
+
+This example retrieves the current autoscaling decision.
+
+[source,console]
+--------------------------------------------------
+GET /_autoscaling/decision
+--------------------------------------------------
+// TEST
+
+The API returns the following result:
+
+[source,console-result]
+--------------------------------------------------
+{
+
+}
+--------------------------------------------------

docs/reference/rest-api/index.asciidoc

@@ -35,6 +35,7 @@ not be included yet.
 --
 
 include::{es-repo-dir}/api-conventions.asciidoc[]
+include::{es-repo-dir}/autoscaling/apis/autoscaling-apis.asciidoc[]
 include::{es-repo-dir}/cat.asciidoc[]
 include::{es-repo-dir}/cluster.asciidoc[]
 include::{es-repo-dir}/ccr/apis/ccr-apis.asciidoc[]

x-pack/docs/en/rest-api/security/get-builtin-privileges.asciidoc

@@ -66,6 +66,7 @@ A successful call returns an object with "cluster" and "index" fields.
     "delegate_pki",
     "manage",
     "manage_api_key",
+    "manage_autoscaling",
     "manage_ccr",
     "manage_data_frame_transforms",
     "manage_enrich",

x-pack/plugin/autoscaling/build.gradle

@@ -18,3 +18,12 @@ dependencies {
   compileOnly project(path: xpackModule('core'), configuration: 'default')
   testCompile project(path: xpackModule('core'), configuration: 'testArtifacts')
 }
+
+// add all sub-projects of the qa sub-project
+gradle.projectsEvaluated {
+  project.subprojects
+    .find { it.path == project.path + ":qa" }
+    .subprojects
+    .findAll { it.path.startsWith(project.path + ":qa") }
+    .each { check.dependsOn it.check }
+}

x-pack/plugin/autoscaling/qa/build.gradle

@@ -0,0 +1,18 @@
+import org.elasticsearch.gradle.test.RestIntegTestTask
+
+apply plugin: 'elasticsearch.build'
+test.enabled = false
+
+dependencies {
+  compile project(':test:framework')
+}
+
+subprojects {
+  project.tasks.withType(RestIntegTestTask) {
+    final File xPackResources = new File(xpackProject('plugin').projectDir, 'src/test/resources')
+    project.copyRestSpec.from(xPackResources) {
+      include 'rest-api-spec/api/**'
+    }
+  }
+
+}

x-pack/plugin/autoscaling/qa/rest/autoscaling-roles.yml

@@ -0,0 +1,3 @@
+autoscaling:
+  cluster:
+    - manage_autoscaling

x-pack/plugin/autoscaling/qa/rest/build.gradle

@@ -0,0 +1,25 @@
+import org.elasticsearch.gradle.test.RestIntegTestTask
+
+apply plugin: 'elasticsearch.testclusters'
+apply plugin: 'elasticsearch.standalone-test'
+
+dependencies {
+  testCompile project(path: xpackModule('core'), configuration: 'testArtifacts')
+  testCompile project(path: xpackModule('autoscaling'), configuration: 'runtime')
+}
+
+task restTest(type: RestIntegTestTask) {
+  mustRunAfter(precommit)
+}
+
+testClusters.restTest {
+  testDistribution = 'DEFAULT'
+  setting 'xpack.autoscaling.enabled', 'true'
+  setting 'xpack.security.enabled', 'true'
+  extraConfigFile 'roles.yml', file('autoscaling-roles.yml')
+  user username: 'autoscaling-admin', password: 'autoscaling-admin-password', role: 'superuser'
+  user username: 'autoscaling-user', password: 'autoscaling-user-password', role: 'autoscaling'
+}
+
+check.dependsOn restTest
+test.enabled = false

x-pack/plugin/autoscaling/qa/rest/src/test/java/org/elasticsearch/xpack/autoscaling/AutoscalingRestIT.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.autoscaling;
+
+import com.carrotsearch.randomizedtesting.annotations.ParametersFactory;
+import org.elasticsearch.common.settings.SecureString;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.util.concurrent.ThreadContext;
+import org.elasticsearch.test.rest.yaml.ClientYamlTestCandidate;
+import org.elasticsearch.test.rest.yaml.ESClientYamlSuiteTestCase;
+
+import static org.elasticsearch.xpack.core.security.authc.support.UsernamePasswordToken.basicAuthHeaderValue;
+
+public class AutoscalingRestIT extends ESClientYamlSuiteTestCase {
+
+    public AutoscalingRestIT(final ClientYamlTestCandidate testCandidate) {
+        super(testCandidate);
+    }
+
+    @ParametersFactory
+    public static Iterable<Object[]> parameters() throws Exception {
+        return ESClientYamlSuiteTestCase.createParameters();
+    }
+
+    @Override
+    protected Settings restAdminSettings() {
+        final String value = basicAuthHeaderValue("autoscaling-admin", new SecureString("autoscaling-admin-password".toCharArray()));
+        return Settings.builder().put(ThreadContext.PREFIX + ".Authorization", value).build();
+    }
+
+    @Override
+    protected Settings restClientSettings() {
+        final String value = basicAuthHeaderValue("autoscaling-user", new SecureString("autoscaling-user-password".toCharArray()));
+        return Settings.builder().put(ThreadContext.PREFIX + ".Authorization", value).build();
+    }
+
+}

x-pack/plugin/autoscaling/qa/rest/src/test/resources/rest-api-spec/test/autoscaling/get_autoscaling_decision.yml

@@ -0,0 +1,4 @@
+---
+"Test get autoscaling decision":
+  - do:
+      autoscaling.get_autoscaling_decision: {}

x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/Autoscaling.java

@@ -7,16 +7,31 @@
 package org.elasticsearch.xpack.autoscaling;
 
 import org.elasticsearch.Build;
+import org.elasticsearch.action.ActionRequest;
+import org.elasticsearch.action.ActionResponse;
+import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
+import org.elasticsearch.cluster.node.DiscoveryNodes;
+import org.elasticsearch.common.settings.ClusterSettings;
+import org.elasticsearch.common.settings.IndexScopedSettings;
 import org.elasticsearch.common.settings.Setting;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.settings.SettingsFilter;
+import org.elasticsearch.plugins.ActionPlugin;
 import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.rest.RestController;
+import org.elasticsearch.rest.RestHandler;
+import org.elasticsearch.xpack.autoscaling.action.GetAutoscalingDecisionAction;
+import org.elasticsearch.xpack.autoscaling.action.TransportGetAutoscalingDecisionAction;
+import org.elasticsearch.xpack.autoscaling.rest.RestGetAutoscalingDecisionHandler;
 
 import java.util.Collections;
 import java.util.List;
+import java.util.function.Supplier;
 
 /**
  * Container class for autoscaling functionality.
  */
-public class Autoscaling extends Plugin {
+public class Autoscaling extends Plugin implements ActionPlugin {
 
     public static final Setting<Boolean> AUTOSCALING_ENABLED_SETTING = Setting.boolSetting(
         "xpack.autoscaling.enabled",
@@ -24,6 +39,12 @@ public class Autoscaling extends Plugin {
         Setting.Property.NodeScope
     );
 
+    private final boolean enabled;
+
+    public Autoscaling(final Settings settings) {
+        this.enabled = AUTOSCALING_ENABLED_SETTING.get(settings);
+    }
+
     /**
      * The settings defined by autoscaling.
      *
@@ -38,6 +59,34 @@ public class Autoscaling extends Plugin {
         }
     }
 
+    @Override
+    public List<ActionHandler<? extends ActionRequest, ? extends ActionResponse>> getActions() {
+        if (enabled) {
+            return Collections.singletonList(
+                new ActionHandler<>(GetAutoscalingDecisionAction.INSTANCE, TransportGetAutoscalingDecisionAction.class)
+            );
+        } else {
+            return Collections.emptyList();
+        }
+    }
+
+    @Override
+    public List<RestHandler> getRestHandlers(
+        final Settings settings,
+        final RestController controller,
+        final ClusterSettings clusterSettings,
+        final IndexScopedSettings indexScopedSettings,
+        final SettingsFilter settingsFilter,
+        final IndexNameExpressionResolver indexNameExpressionResolver,
+        final Supplier<DiscoveryNodes> nodesInCluster
+    ) {
+        if (enabled) {
+            return Collections.singletonList(new RestGetAutoscalingDecisionHandler(controller));
+        } else {
+            return Collections.emptyList();
+        }
+    }
+
     boolean isSnapshot() {
         return Build.CURRENT.isSnapshot();
     }

x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/action/GetAutoscalingDecisionAction.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.autoscaling.action;
+
+import org.elasticsearch.action.ActionRequestValidationException;
+import org.elasticsearch.action.ActionResponse;
+import org.elasticsearch.action.ActionType;
+import org.elasticsearch.action.support.master.AcknowledgedRequest;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.xcontent.ToXContentObject;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+
+import java.io.IOException;
+
+public class GetAutoscalingDecisionAction extends ActionType<GetAutoscalingDecisionAction.Response> {
+
+    public static final GetAutoscalingDecisionAction INSTANCE = new GetAutoscalingDecisionAction();
+    public static final String NAME = "cluster:admin/autoscaling/get_autoscaling_decision";
+
+    private GetAutoscalingDecisionAction() {
+        super(NAME, Response::new);
+    }
+
+    public static class Request extends AcknowledgedRequest<GetAutoscalingDecisionAction.Request> implements ToXContentObject {
+
+        public Request() {
+
+        }
+
+        public Request(final StreamInput in) throws IOException {
+            super(in);
+        }
+
+        @Override
+        public void writeTo(final StreamOutput out) throws IOException {
+            super.writeTo(out);
+        }
+
+        @Override
+        public ActionRequestValidationException validate() {
+            return null;
+        }
+
+        @Override
+        public XContentBuilder toXContent(final XContentBuilder builder, final Params params) throws IOException {
+            builder.startObject();
+            {
+
+            }
+            builder.endObject();
+            return builder;
+        }
+
+    }
+
+    public static class Response extends ActionResponse implements ToXContentObject {
+
+        public Response() {
+
+        }
+
+        public Response(final StreamInput in) throws IOException {
+            super(in);
+        }
+
+        @Override
+        public void writeTo(final StreamOutput out) {
+
+        }
+
+        @Override
+        public XContentBuilder toXContent(final XContentBuilder builder, final Params params) throws IOException {
+            builder.startObject();
+            {
+
+            }
+            builder.endObject();
+            return builder;
+        }
+
+    }
+
+}

x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/action/TransportGetAutoscalingDecisionAction.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.autoscaling.action;
+
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.support.ActionFilters;
+import org.elasticsearch.action.support.master.TransportMasterNodeAction;
+import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.block.ClusterBlockException;
+import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
+import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.transport.TransportService;
+
+import java.io.IOException;
+
+public class TransportGetAutoscalingDecisionAction extends TransportMasterNodeAction<
+    GetAutoscalingDecisionAction.Request,
+    GetAutoscalingDecisionAction.Response> {
+
+    @Inject
+    public TransportGetAutoscalingDecisionAction(
+        final TransportService transportService,
+        final ClusterService clusterService,
+        final ThreadPool threadPool,
+        final ActionFilters actionFilters,
+        final IndexNameExpressionResolver indexNameExpressionResolver
+    ) {
+        super(
+            GetAutoscalingDecisionAction.NAME,
+            transportService,
+            clusterService,
+            threadPool,
+            actionFilters,
+            GetAutoscalingDecisionAction.Request::new,
+            indexNameExpressionResolver
+        );
+    }
+
+    @Override
+    protected String executor() {
+        return ThreadPool.Names.SAME;
+    }
+
+    @Override
+    protected GetAutoscalingDecisionAction.Response read(final StreamInput in) throws IOException {
+        return new GetAutoscalingDecisionAction.Response(in);
+    }
+
+    @Override
+    protected void masterOperation(
+        final GetAutoscalingDecisionAction.Request request,
+        final ClusterState state,
+        final ActionListener<GetAutoscalingDecisionAction.Response> listener
+    ) {
+        listener.onResponse(new GetAutoscalingDecisionAction.Response());
+    }
+
+    @Override
+    protected ClusterBlockException checkBlock(final GetAutoscalingDecisionAction.Request request, final ClusterState state) {
+        return null;
+    }
+
+}

x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/rest/RestGetAutoscalingDecisionHandler.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.autoscaling.rest;
+
+import org.elasticsearch.client.node.NodeClient;
+import org.elasticsearch.rest.BaseRestHandler;
+import org.elasticsearch.rest.RestController;
+import org.elasticsearch.rest.RestRequest;
+import org.elasticsearch.rest.action.RestToXContentListener;
+import org.elasticsearch.xpack.autoscaling.action.GetAutoscalingDecisionAction;
+
+public class RestGetAutoscalingDecisionHandler extends BaseRestHandler {
+
+    public RestGetAutoscalingDecisionHandler(final RestController controller) {
+        controller.registerHandler(RestRequest.Method.GET, "/_autoscaling/decision", this);
+    }
+
+    @Override
+    public String getName() {
+        return "get_autoscaling_decision";
+    }
+
+    @Override
+    protected RestChannelConsumer prepareRequest(final RestRequest restRequest, final NodeClient client) {
+        final GetAutoscalingDecisionAction.Request request = new GetAutoscalingDecisionAction.Request();
+        return channel -> client.execute(GetAutoscalingDecisionAction.INSTANCE, request, new RestToXContentListener<>(channel));
+    }
+
+}

x-pack/plugin/autoscaling/src/test/java/org/elasticsearch/xpack/autoscaling/AutoscalingTests.java

@@ -6,6 +6,7 @@
 
 package org.elasticsearch.xpack.autoscaling;
 
+import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.test.ESTestCase;
 
 import static org.hamcrest.Matchers.hasItem;
@@ -14,7 +15,7 @@ import static org.hamcrest.Matchers.not;
 public class AutoscalingTests extends ESTestCase {
 
     public void testEnabledSettingRegisteredInSnapshotBuilds() {
-        final Autoscaling plugin = new Autoscaling() {
+        final Autoscaling plugin = new Autoscaling(Settings.EMPTY) {
 
             @Override
             protected boolean isSnapshot() {
@@ -26,7 +27,7 @@ public class AutoscalingTests extends ESTestCase {
     }
 
     public void testEnabledSettingNotRegisteredInNonSnapshotBuilds() {
-        final Autoscaling plugin = new Autoscaling() {
+        final Autoscaling plugin = new Autoscaling(Settings.EMPTY) {
 
             @Override
             protected boolean isSnapshot() {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authz/privilege/ClusterPrivilegeResolver.java

@@ -120,6 +120,9 @@ public class ClusterPrivilegeResolver {
     public static final NamedClusterPrivilege MANAGE_API_KEY = new ActionClusterPrivilege("manage_api_key", MANAGE_API_KEY_PATTERN);
     public static final NamedClusterPrivilege MANAGE_PIPELINE = new ActionClusterPrivilege("manage_pipeline",
         Collections.singleton("cluster:admin/ingest/pipeline/*"));
+    public static final NamedClusterPrivilege MANAGE_AUTOSCALING = new ActionClusterPrivilege(
+        "manage_autoscaling",
+        Collections.singleton("cluster:admin/autoscaling/*"));
     public static final NamedClusterPrivilege MANAGE_CCR = new ActionClusterPrivilege("manage_ccr", MANAGE_CCR_PATTERN);
     public static final NamedClusterPrivilege READ_CCR = new ActionClusterPrivilege("read_ccr", READ_CCR_PATTERN);
     public static final NamedClusterPrivilege CREATE_SNAPSHOT = new ActionClusterPrivilege("create_snapshot", CREATE_SNAPSHOT_PATTERN);
@@ -159,6 +162,7 @@ public class ClusterPrivilegeResolver {
         MANAGE_API_KEY,
         MANAGE_PIPELINE,
         MANAGE_ROLLUP,
+        MANAGE_AUTOSCALING,
         MANAGE_CCR,
         READ_CCR,
         CREATE_SNAPSHOT,

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/security/authz/privilege/PrivilegeTests.java

@@ -174,6 +174,10 @@ public class PrivilegeTests extends ESTestCase {
         assertThat(predicate.test("indices:admin/settings/foo"), is(false));
     }
 
+    public void testManageAutoscalingPrivilege() {
+        verifyClusterActionAllowed(ClusterPrivilegeResolver.MANAGE_AUTOSCALING, "cluster:admin/autoscaling/get_decision");
+    }
+
     public void testManageCcrPrivilege() {
         verifyClusterActionAllowed(ClusterPrivilegeResolver.MANAGE_CCR, "cluster:admin/xpack/ccr/follow_index",
             "cluster:admin/xpack/ccr/unfollow_index", "cluster:admin/xpack/ccr/brand_new_api");

x-pack/plugin/src/test/resources/rest-api-spec/api/autoscaling.get_autoscaling_decision.json

@@ -0,0 +1,18 @@
+{
+  "autoscaling.get_autoscaling_decision":{
+    "documentation":{
+      "url":"https://www.elastic.co/guide/en/elasticsearch/reference/current/autoscaling-get-autoscaling-decision.html"
+    },
+    "stability":"experimental",
+    "url":{
+      "paths":[
+        {
+          "path":"/_autoscaling/decision",
+          "methods":[
+            "GET"
+          ]
+        }
+      ]
+    }
+  }
+}

x-pack/plugin/src/test/resources/rest-api-spec/test/privileges/11_builtin.yml

@@ -15,5 +15,5 @@ setup:
   # This is fragile - it needs to be updated every time we add a new cluster/index privilege
   # I would much prefer we could just check that specific entries are in the array, but we don't have
   # an assertion for that
-  - length: { "cluster" : 34 }
+  - length: { "cluster" : 35 }
   - length: { "index" : 18 }