Autoscaling decider and decision service (elastic#59005)

Split the autoscaling decider into a service and configuration
in order to enable having additional context information available
in the service. Added AutoscalingDeciderContext holding generic
information all deciders are expected to need. Implemented GET
_autoscaling/decision

Author: henningandersen

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

@@ -25,6 +25,17 @@ PUT /_autoscaling/policy/my_autoscaling_policy
 --------------------------------------------------
 // TESTSETUP
 
+//////////////////////////
+
+[source,console]
+--------------------------------------------------
+DELETE /_autoscaling/policy/my_autoscaling_policy
+--------------------------------------------------
+// TEST
+// TEARDOWN
+
+//////////////////////////
+
 [source,console]
 --------------------------------------------------
 GET /_autoscaling/policy/<name>

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

@@ -25,6 +25,16 @@ PUT /_autoscaling/policy/<name>
 --------------------------------------------------
 // TEST[s/<name>/name/]
 
+//////////////////////////
+
+[source,console]
+--------------------------------------------------
+DELETE /_autoscaling/policy/name
+--------------------------------------------------
+// TEST[continued]
+
+//////////////////////////
+
 [[autoscaling-put-autoscaling-policy-prereqs]]
 ==== {api-prereq-title}
 
@@ -65,3 +75,13 @@ The API returns the following result:
   "acknowledged": true
 }
 --------------------------------------------------
+
+//////////////////////////
+
+[source,console]
+--------------------------------------------------
+DELETE /_autoscaling/policy/my_autoscaling_policy
+--------------------------------------------------
+// TEST[continued]
+
+//////////////////////////

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

@@ -1,6 +1,31 @@
 ---
-"Test get autoscaling decision":
+"Test get empty autoscaling decision":
   - do:
       autoscaling.get_autoscaling_decision: {}
 
   - match: { "decisions": [] }
+
+---
+"Test get always autoscaling decision":
+  - do:
+      autoscaling.put_autoscaling_policy:
+        name: my_autoscaling_policy
+        body:
+          policy:
+            deciders:
+              always: {}
+
+  - match: { "acknowledged": true }
+
+  - do:
+      autoscaling.get_autoscaling_decision: {}
+
+  - match: { decisions.0.my_autoscaling_policy.decision: scale_up }
+  - match: { decisions.0.my_autoscaling_policy.decisions.0.name: always }
+  - match: { decisions.0.my_autoscaling_policy.decisions.0.type: scale_up }
+  - match: { decisions.0.my_autoscaling_policy.decisions.0.reason: always }
+
+  # test cleanup
+  - do:
+      autoscaling.delete_autoscaling_policy:
+        name: my_autoscaling_policy

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

@@ -6,13 +6,17 @@
 
 package org.elasticsearch.xpack.autoscaling;
 
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.elasticsearch.Build;
 import org.elasticsearch.action.ActionRequest;
 import org.elasticsearch.action.ActionResponse;
+import org.elasticsearch.client.Client;
 import org.elasticsearch.cluster.NamedDiff;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.metadata.Metadata;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
+import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.settings.ClusterSettings;
@@ -21,11 +25,18 @@
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.settings.SettingsFilter;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.env.Environment;
+import org.elasticsearch.env.NodeEnvironment;
 import org.elasticsearch.license.XPackLicenseState;
 import org.elasticsearch.plugins.ActionPlugin;
+import org.elasticsearch.plugins.ExtensiblePlugin;
 import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.repositories.RepositoriesService;
 import org.elasticsearch.rest.RestController;
 import org.elasticsearch.rest.RestHandler;
+import org.elasticsearch.script.ScriptService;
+import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.watcher.ResourceWatcherService;
 import org.elasticsearch.xpack.autoscaling.action.DeleteAutoscalingPolicyAction;
 import org.elasticsearch.xpack.autoscaling.action.GetAutoscalingDecisionAction;
 import org.elasticsearch.xpack.autoscaling.action.GetAutoscalingPolicyAction;
@@ -34,22 +45,29 @@
 import org.elasticsearch.xpack.autoscaling.action.TransportGetAutoscalingDecisionAction;
 import org.elasticsearch.xpack.autoscaling.action.TransportGetAutoscalingPolicyAction;
 import org.elasticsearch.xpack.autoscaling.action.TransportPutAutoscalingPolicyAction;
-import org.elasticsearch.xpack.autoscaling.decision.AlwaysAutoscalingDecider;
-import org.elasticsearch.xpack.autoscaling.decision.AutoscalingDecider;
+import org.elasticsearch.xpack.autoscaling.decision.AlwaysAutoscalingDeciderConfiguration;
+import org.elasticsearch.xpack.autoscaling.decision.AlwaysAutoscalingDeciderService;
+import org.elasticsearch.xpack.autoscaling.decision.AutoscalingDeciderConfiguration;
+import org.elasticsearch.xpack.autoscaling.decision.AutoscalingDeciderService;
+import org.elasticsearch.xpack.autoscaling.decision.AutoscalingDecisionService;
 import org.elasticsearch.xpack.autoscaling.rest.RestDeleteAutoscalingPolicyHandler;
 import org.elasticsearch.xpack.autoscaling.rest.RestGetAutoscalingDecisionHandler;
 import org.elasticsearch.xpack.autoscaling.rest.RestGetAutoscalingPolicyHandler;
 import org.elasticsearch.xpack.autoscaling.rest.RestPutAutoscalingPolicyHandler;
 import org.elasticsearch.xpack.core.XPackPlugin;
 
+import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
+import java.util.Set;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 /**
  * Container class for autoscaling functionality.
  */
-public class Autoscaling extends Plugin implements ActionPlugin {
-
+public class Autoscaling extends Plugin implements ActionPlugin, ExtensiblePlugin, AutoscalingExtension {
+    private static final Logger logger = LogManager.getLogger(AutoscalingExtension.class);
     private static final Boolean AUTOSCALING_FEATURE_FLAG_REGISTERED;
 
     static {
@@ -78,8 +96,11 @@ public class Autoscaling extends Plugin implements ActionPlugin {
 
     private final boolean enabled;
 
+    private final List<AutoscalingExtension> autoscalingExtensions;
+
     public Autoscaling(final Settings settings) {
         this.enabled = AUTOSCALING_ENABLED_SETTING.get(settings);
+        this.autoscalingExtensions = new ArrayList<>(org.elasticsearch.common.collect.List.of(this));
     }
 
     /**
@@ -100,6 +121,23 @@ boolean isSnapshot() {
         return Build.CURRENT.isSnapshot();
     }
 
+    @Override
+    public Collection<Object> createComponents(
+        Client client,
+        ClusterService clusterService,
+        ThreadPool threadPool,
+        ResourceWatcherService resourceWatcherService,
+        ScriptService scriptService,
+        NamedXContentRegistry xContentRegistry,
+        Environment environment,
+        NodeEnvironment nodeEnvironment,
+        NamedWriteableRegistry namedWriteableRegistry,
+        IndexNameExpressionResolver indexNameExpressionResolver,
+        Supplier<RepositoriesService> repositoriesServiceSupplier
+    ) {
+        return org.elasticsearch.common.collect.List.of(new AutoscalingDecisionService.Holder(this));
+    }
+
     @Override
     public List<ActionHandler<? extends ActionRequest, ? extends ActionResponse>> getActions() {
         if (enabled) {
@@ -141,7 +179,11 @@ public List<NamedWriteableRegistry.Entry> getNamedWriteables() {
         return org.elasticsearch.common.collect.List.of(
             new NamedWriteableRegistry.Entry(Metadata.Custom.class, AutoscalingMetadata.NAME, AutoscalingMetadata::new),
             new NamedWriteableRegistry.Entry(NamedDiff.class, AutoscalingMetadata.NAME, AutoscalingMetadata.AutoscalingMetadataDiff::new),
-            new NamedWriteableRegistry.Entry(AutoscalingDecider.class, AlwaysAutoscalingDecider.NAME, AlwaysAutoscalingDecider::new)
+            new NamedWriteableRegistry.Entry(
+                AutoscalingDeciderConfiguration.class,
+                AlwaysAutoscalingDeciderConfiguration.NAME,
+                AlwaysAutoscalingDeciderConfiguration::new
+            )
         );
     }
 
@@ -150,9 +192,9 @@ public List<NamedXContentRegistry.Entry> getNamedXContent() {
         return org.elasticsearch.common.collect.List.of(
             new NamedXContentRegistry.Entry(Metadata.Custom.class, new ParseField(AutoscalingMetadata.NAME), AutoscalingMetadata::parse),
             new NamedXContentRegistry.Entry(
-                AutoscalingDecider.class,
-                new ParseField(AlwaysAutoscalingDecider.NAME),
-                AlwaysAutoscalingDecider::parse
+                AutoscalingDeciderConfiguration.class,
+                new ParseField(AlwaysAutoscalingDeciderConfiguration.NAME),
+                AlwaysAutoscalingDeciderConfiguration::parse
             )
         );
     }
@@ -161,4 +203,17 @@ protected XPackLicenseState getLicenseState() {
         return XPackPlugin.getSharedLicenseState();
     }
 
+    @Override
+    public void loadExtensions(ExtensionLoader loader) {
+        loader.loadExtensions(AutoscalingExtension.class).forEach(autoscalingExtensions::add);
+    }
+
+    @Override
+    public Collection<AutoscalingDeciderService<? extends AutoscalingDeciderConfiguration>> deciders() {
+        return org.elasticsearch.common.collect.List.of(new AlwaysAutoscalingDeciderService());
+    }
+
+    public Set<AutoscalingDeciderService<? extends AutoscalingDeciderConfiguration>> createDeciderServices() {
+        return autoscalingExtensions.stream().flatMap(p -> p.deciders().stream()).collect(Collectors.toSet());
+    }
 }

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

@@ -0,0 +1,20 @@
+/*
+ * 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 org.elasticsearch.xpack.autoscaling.decision.AutoscalingDeciderConfiguration;
+import org.elasticsearch.xpack.autoscaling.decision.AutoscalingDeciderService;
+
+import java.util.Collection;
+
+public interface AutoscalingExtension {
+    /**
+     * Get the list of decider services for this plugin. This is called after createComponents has been called.
+     * @return list of decider services
+     */
+    Collection<AutoscalingDeciderService<? extends AutoscalingDeciderConfiguration>> deciders();
+}

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

@@ -17,22 +17,24 @@
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
+import org.elasticsearch.xpack.autoscaling.decision.AutoscalingDecisionService;
 
 import java.io.IOException;
-import java.util.Collections;
-import java.util.TreeMap;
 
 public class TransportGetAutoscalingDecisionAction extends TransportMasterNodeAction<
     GetAutoscalingDecisionAction.Request,
     GetAutoscalingDecisionAction.Response> {
 
+    private final AutoscalingDecisionService decisionService;
+
     @Inject
     public TransportGetAutoscalingDecisionAction(
         final TransportService transportService,
         final ClusterService clusterService,
         final ThreadPool threadPool,
         final ActionFilters actionFilters,
-        final IndexNameExpressionResolver indexNameExpressionResolver
+        final IndexNameExpressionResolver indexNameExpressionResolver,
+        final AutoscalingDecisionService.Holder decisionServiceHolder
     ) {
         super(
             GetAutoscalingDecisionAction.NAME,
@@ -43,6 +45,8 @@ public TransportGetAutoscalingDecisionAction(
             GetAutoscalingDecisionAction.Request::new,
             indexNameExpressionResolver
         );
+        this.decisionService = decisionServiceHolder.get();
+        assert this.decisionService != null;
     }
 
     @Override
@@ -61,7 +65,7 @@ protected void masterOperation(
         final ClusterState state,
         final ActionListener<GetAutoscalingDecisionAction.Response> listener
     ) {
-        listener.onResponse(new GetAutoscalingDecisionAction.Response(Collections.unmodifiableSortedMap(new TreeMap<>())));
+        listener.onResponse(new GetAutoscalingDecisionAction.Response(decisionService.decide(state)));
     }
 
     @Override

x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/decision/AlwaysAutoscalingDecider.java renamed to x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/decision/AlwaysAutoscalingDeciderConfiguration.java

@@ -14,20 +14,23 @@
 
 import java.io.IOException;
 
-public class AlwaysAutoscalingDecider implements AutoscalingDecider {
+public class AlwaysAutoscalingDeciderConfiguration implements AutoscalingDeciderConfiguration {
 
     public static final String NAME = "always";
 
-    private static final ObjectParser<AlwaysAutoscalingDecider, Void> PARSER = new ObjectParser<>(NAME, AlwaysAutoscalingDecider::new);
+    private static final ObjectParser<AlwaysAutoscalingDeciderConfiguration, Void> PARSER = new ObjectParser<>(
+        NAME,
+        AlwaysAutoscalingDeciderConfiguration::new
+    );
 
-    public static AlwaysAutoscalingDecider parse(final XContentParser parser) {
+    public static AlwaysAutoscalingDeciderConfiguration parse(final XContentParser parser) {
         return PARSER.apply(parser, null);
     }
 
-    public AlwaysAutoscalingDecider() {}
+    public AlwaysAutoscalingDeciderConfiguration() {}
 
     @SuppressWarnings("unused")
-    public AlwaysAutoscalingDecider(final StreamInput in) {
+    public AlwaysAutoscalingDeciderConfiguration(final StreamInput in) {
 
     }
 
@@ -36,11 +39,6 @@ public String name() {
         return NAME;
     }
 
-    @Override
-    public AutoscalingDecision scale() {
-        return new AutoscalingDecision(NAME, AutoscalingDecisionType.SCALE_UP, "always");
-    }
-
     @Override
     public String getWriteableName() {
         return NAME;

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

@@ -0,0 +1,25 @@
+/*
+ * 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.decision;
+
+import org.elasticsearch.common.inject.Inject;
+
+public class AlwaysAutoscalingDeciderService implements AutoscalingDeciderService<AlwaysAutoscalingDeciderConfiguration> {
+
+    @Inject
+    public AlwaysAutoscalingDeciderService() {}
+
+    @Override
+    public String name() {
+        return AlwaysAutoscalingDeciderConfiguration.NAME;
+    }
+
+    @Override
+    public AutoscalingDecision scale(AlwaysAutoscalingDeciderConfiguration decider, AutoscalingDeciderContext context) {
+        return new AutoscalingDecision(AlwaysAutoscalingDeciderConfiguration.NAME, AutoscalingDecisionType.SCALE_UP, "always");
+    }
+}

x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/decision/AutoscalingDecider.java renamed to x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/decision/AutoscalingDeciderConfiguration.java

@@ -12,20 +12,12 @@
 /**
  * Represents an autoscaling decider, a component that determines whether or not to scale.
  */
-public interface AutoscalingDecider extends ToXContentObject, NamedWriteable {
+public interface AutoscalingDeciderConfiguration extends ToXContentObject, NamedWriteable {
 
     /**
      * The name of the autoscaling decider.
      *
      * @return the name
      */
     String name();
-
-    /**
-     * Whether or not to scale based on the current state.
-     *
-     * @return the autoscaling decision
-     */
-    AutoscalingDecision scale();
-
 }