Using a temp IndexService for template validation (elastic#129507)

Author: masseyke

docs/changelog/129507.yaml

@@ -0,0 +1,6 @@
+pr: 129507
+summary: Using a temp `IndexService` for template validation
+area: Indices APIs
+type: bug
+issues:
+ - 129473

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

@@ -37,8 +37,6 @@
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.core.Tuple;
-import org.elasticsearch.index.CloseUtils;
-import org.elasticsearch.index.Index;
 import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.IndexSettingProvider;
 import org.elasticsearch.index.IndexSettingProviders;
@@ -82,7 +80,6 @@
 
 import static java.util.Collections.emptyMap;
 import static org.elasticsearch.cluster.metadata.MetadataCreateDataStreamService.validateTimestampFieldMapping;
-import static org.elasticsearch.indices.cluster.IndexRemovalReason.NO_LONGER_ASSIGNED;
 
 /**
  * Service responsible for submitting index templates updates
@@ -1862,45 +1859,28 @@ private static void validateTemplate(Settings validateSettings, CompressedXConte
             settings = Settings.EMPTY;
         }
 
-        Index createdIndex = null;
         final String temporaryIndexName = UUIDs.randomBase64UUID();
-        try {
-            // use the provided values, otherwise just pick valid dummy values
-            int dummyPartitionSize = IndexMetadata.INDEX_ROUTING_PARTITION_SIZE_SETTING.get(settings);
-            int dummyShards = settings.getAsInt(
-                IndexMetadata.SETTING_NUMBER_OF_SHARDS,
-                dummyPartitionSize == 1 ? 1 : dummyPartitionSize + 1
-            );
-            int shardReplicas = settings.getAsInt(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0);
-
-            // create index service for parsing and validating "mappings"
-            Settings dummySettings = Settings.builder()
-                .put(IndexMetadata.SETTING_VERSION_CREATED, IndexVersion.current())
-                .put(settings)
-                .put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, dummyShards)
-                .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, shardReplicas)
-                .put(IndexMetadata.SETTING_INDEX_UUID, UUIDs.randomBase64UUID())
-                .build();
+        int dummyPartitionSize = IndexMetadata.INDEX_ROUTING_PARTITION_SIZE_SETTING.get(settings);
+        int dummyShards = settings.getAsInt(IndexMetadata.SETTING_NUMBER_OF_SHARDS, dummyPartitionSize == 1 ? 1 : dummyPartitionSize + 1);
+        int shardReplicas = settings.getAsInt(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0);
 
-            final IndexMetadata tmpIndexMetadata = IndexMetadata.builder(temporaryIndexName).settings(dummySettings).build();
-            IndexService dummyIndexService = indicesService.createIndex(tmpIndexMetadata, Collections.emptyList(), false);
-            createdIndex = dummyIndexService.index();
+        // create index service for parsing and validating "mappings"
+        Settings dummySettings = Settings.builder()
+            .put(IndexMetadata.SETTING_VERSION_CREATED, IndexVersion.current())
+            .put(settings)
+            .put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, dummyShards)
+            .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, shardReplicas)
+            .put(IndexMetadata.SETTING_INDEX_UUID, UUIDs.randomBase64UUID())
+            .build();
 
+        final IndexMetadata tmpIndexMetadata = IndexMetadata.builder(temporaryIndexName).settings(dummySettings).build();
+
+        indicesService.withTempIndexService(tmpIndexMetadata, dummyIndexService -> {
             if (mappings != null) {
                 dummyIndexService.mapperService().merge(MapperService.SINGLE_MAPPING_NAME, mappings, MergeReason.INDEX_TEMPLATE);
             }
-
-        } finally {
-            if (createdIndex != null) {
-                indicesService.removeIndex(
-                    createdIndex,
-                    NO_LONGER_ASSIGNED,
-                    " created for parsing template mapping",
-                    CloseUtils.NO_SHARDS_CREATED_EXECUTOR,
-                    ActionListener.noop()
-                );
-            }
-        }
+            return null;
+        });
     }
 
     private void validate(String name, ComponentTemplate template) {