Adds a new Rollup Action

server/src/main/java/org/elasticsearch/cluster/ClusterModule.java

@@ -143,7 +143,7 @@ public static List<Entry> getNamedWriteables() {
             ComposableIndexTemplateMetadata::readDiffFrom);
         registerMetadataCustom(entries, DataStreamMetadata.TYPE, DataStreamMetadata::new, DataStreamMetadata::readDiffFrom);
 
-        if (RollupV2.ROLLUPV2_FEATURE_FLAG_REGISTERED != null && RollupV2.ROLLUPV2_FEATURE_FLAG_REGISTERED) {
+        if (RollupV2.isEnabled()) {
             registerMetadataCustom(entries, RollupMetadata.TYPE, RollupMetadata::new, RollupMetadata::readDiffFrom);
         }
         // Task Status (not Diffable)
@@ -170,7 +170,7 @@ public static List<NamedXContentRegistry.Entry> getNamedXWriteables() {
             ComposableIndexTemplateMetadata::fromXContent));
         entries.add(new NamedXContentRegistry.Entry(Metadata.Custom.class, new ParseField(DataStreamMetadata.TYPE),
             DataStreamMetadata::fromXContent));
-        if (RollupV2.ROLLUPV2_FEATURE_FLAG_REGISTERED != null && RollupV2.ROLLUPV2_FEATURE_FLAG_REGISTERED) {
+        if (RollupV2.isEnabled()) {
             entries.add(new NamedXContentRegistry.Entry(Metadata.Custom.class, new ParseField(RollupMetadata.TYPE),
                 RollupMetadata::fromXContent));
         }

server/src/main/java/org/elasticsearch/cluster/metadata/RollupGroup.java

@@ -33,6 +33,7 @@
 import org.elasticsearch.search.aggregations.bucket.histogram.DateHistogramInterval;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -96,6 +97,12 @@ public RollupGroup(List<String> group, Map<String, DateHistogramInterval> dateIn
         this.dateTimezone = dateTimezone;
     }
 
+    public RollupGroup() {
+        this.group = new ArrayList<>();
+        this.dateInterval = new HashMap<>();
+        this.dateTimezone = new HashMap<>();
+    }
+
     public RollupGroup(StreamInput in) throws IOException {
         this.group = in.readStringList();
         this.dateInterval = in.readMap(StreamInput::readString, DateHistogramInterval::new);

server/src/main/java/org/elasticsearch/rollup/RollupV2.java

@@ -19,26 +19,10 @@
 
 package org.elasticsearch.rollup;
 
-import org.elasticsearch.Build;
-
 public class RollupV2 {
-    public static final Boolean ROLLUPV2_FEATURE_FLAG_REGISTERED;
+    public static final boolean ROLLUP_V2_FEATURE_FLAG_ENABLED = "true".equals(System.getProperty("es.rollup_v2_feature_flag_enabled"));
 
-    static {
-        final String property = System.getProperty("es.rollupv2_feature_flag_registered");
-        if (Build.CURRENT.isSnapshot() && property != null) {
-            throw new IllegalArgumentException("es.rollupv2_feature_flag_registered is only supported in non-snapshot builds");
-        }
-        if ("true".equals(property)) {
-            ROLLUPV2_FEATURE_FLAG_REGISTERED = true;
-        } else if ("false".equals(property)) {
-            ROLLUPV2_FEATURE_FLAG_REGISTERED = false;
-        } else if (property == null) {
-            ROLLUPV2_FEATURE_FLAG_REGISTERED = null;
-        } else {
-            throw new IllegalArgumentException(
-                "expected es.rollupv2_feature_flag_registered to be unset or [true|false] but was [" + property + "]"
-            );
-        }
+    public static boolean isEnabled() {
+        return ROLLUP_V2_FEATURE_FLAG_ENABLED;
     }
 }

server/src/main/java/org/elasticsearch/tasks/Task.java

@@ -185,6 +185,10 @@ public String getHeader(String header) {
         return headers.get(header);
     }
 
+    public Map<String, String> headers() {
+        return headers;
+    }
+
     public TaskResult result(DiscoveryNode node, Exception error) throws IOException {
         return new TaskResult(taskInfo(node.getId(), true), error);
     }