make QueryGroups durable

CHANGELOG.md

@@ -85,6 +85,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Streaming Indexing] Fix intermittent 'The bulk request must be terminated by a newline [\n]' failures [#16337](https://github.com/opensearch-project/OpenSearch/pull/16337))
 - Fix wrong default value when setting `index.number_of_routing_shards` to null on index creation ([#16331](https://github.com/opensearch-project/OpenSearch/pull/16331))
 - Fix disk usage exceeds threshold cluster can't spin up issue ([#15258](https://github.com/opensearch-project/OpenSearch/pull/15258)))
+- [Workload Management] Make query groups persistent across process restarts [#16370](https://github.com/opensearch-project/OpenSearch/pull/16370)
 
 - Fix inefficient Stream API call chains ending with count() ([#15386](https://github.com/opensearch-project/OpenSearch/pull/15386))
 

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

@@ -327,6 +327,13 @@ public static List<NamedXContentRegistry.Entry> getNamedXWriteables() {
                 DecommissionAttributeMetadata::fromXContent
             )
         );
+        entries.add(
+            new NamedXContentRegistry.Entry(
+                Metadata.Custom.class,
+                new ParseField(QueryGroupMetadata.TYPE),
+                QueryGroupMetadata::fromXContent
+            )
+        );
         return entries;
     }
 

server/src/test/java/org/opensearch/cluster/ClusterModuleTests.java

@@ -71,6 +71,7 @@
 import org.opensearch.common.settings.SettingsModule;
 import org.opensearch.common.util.concurrent.ThreadContext;
 import org.opensearch.core.common.io.stream.NamedWriteableRegistry;
+import org.opensearch.core.xcontent.NamedXContentRegistry;
 import org.opensearch.gateway.GatewayAllocator;
 import org.opensearch.plugins.ClusterPlugin;
 import org.opensearch.telemetry.metrics.noop.NoopMetricsRegistry;
@@ -331,10 +332,18 @@ public void testRejectsDuplicateExistingShardsAllocatorName() {
 
     public void testQueryGroupMetadataRegister() {
         List<NamedWriteableRegistry.Entry> customEntries = ClusterModule.getNamedWriteables();
+        List<NamedXContentRegistry.Entry> customXEntries = ClusterModule.getNamedXWriteables();
         assertTrue(
             customEntries.stream()
                 .anyMatch(entry -> entry.categoryClass == Metadata.Custom.class && entry.name.equals(QueryGroupMetadata.TYPE))
         );
+
+        assertTrue(
+            customXEntries.stream()
+                .anyMatch(
+                    entry -> entry.categoryClass == Metadata.Custom.class && entry.name.getPreferredName().equals(QueryGroupMetadata.TYPE)
+                )
+        );
     }
 
     public void testRerouteServiceSetForBalancedShardsAllocator() {