Fix template setting override for replication type

Signed-off-by: Kunal Kotwani <[email protected]>

CHANGELOG.md

@@ -180,6 +180,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Remove shadowJar from `lang-painless` module publication ([#11369](https://github.com/opensearch-project/OpenSearch/issues/11369))
 - Fix remote shards balancer and remove unused variables ([#11167](https://github.com/opensearch-project/OpenSearch/pull/11167))
 - Fix bug where replication lag grows post primary relocation ([#11238](https://github.com/opensearch-project/OpenSearch/pull/11238))
+- Fix template setting override for replication type ([#11417](https://github.com/opensearch-project/OpenSearch/pull/11417))
 
 ### Security
 

server/src/internalClusterTest/java/org/opensearch/snapshots/RestoreSnapshotIT.java

@@ -49,6 +49,7 @@
 import org.opensearch.core.common.unit.ByteSizeUnit;
 import org.opensearch.core.rest.RestStatus;
 import org.opensearch.indices.InvalidIndexNameException;
+import org.opensearch.indices.replication.common.ReplicationType;
 import org.opensearch.repositories.RepositoriesService;
 
 import java.nio.file.Path;
@@ -60,8 +61,10 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+import static org.opensearch.cluster.metadata.IndexMetadata.INDEX_REPLICATION_TYPE_SETTING;
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_REPLICAS;
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_SHARDS;
+import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_REPLICATION_TYPE;
 import static org.opensearch.index.IndexSettings.INDEX_REFRESH_INTERVAL_SETTING;
 import static org.opensearch.index.IndexSettings.INDEX_SOFT_DELETES_SETTING;
 import static org.opensearch.index.query.QueryBuilders.matchQuery;
@@ -1055,4 +1058,48 @@ public void testRestoreBalancedReplica() {
         }
     }
 
+    public void testRestoreWithReplicationTypeSettings() throws Exception {
+        createRepository("test-repo", "fs");
+
+        logger.info("--> create index with baz field");
+        assertAcked(
+            prepareCreate(
+                "test-idx",
+                2,
+                Settings.builder()
+                    .put(indexSettings())
+                    .put(INDEX_REPLICATION_TYPE_SETTING.getKey(), ReplicationType.SEGMENT)
+                    .put(SETTING_NUMBER_OF_REPLICAS, between(0, 1))
+                    .put("refresh_interval", 10, TimeUnit.SECONDS)
+            )
+        );
+        ensureGreen();
+
+        logger.info("--> snapshot it");
+        CreateSnapshotResponse createSnapshotResponse = clusterAdmin().prepareCreateSnapshot("test-repo", "test-snap")
+            .setWaitForCompletion(true)
+            .setIndices("test-idx")
+            .get();
+        assertThat(createSnapshotResponse.getSnapshotInfo().successfulShards(), greaterThan(0));
+        assertThat(
+            createSnapshotResponse.getSnapshotInfo().successfulShards(),
+            equalTo(createSnapshotResponse.getSnapshotInfo().totalShards())
+        );
+
+        logger.info("--> delete the index");
+        cluster().wipeIndices("test-idx");
+
+        logger.info("--> restore all indices from the snapshot");
+        RestoreSnapshotResponse restoreSnapshotResponse = clusterAdmin().prepareRestoreSnapshot("test-repo", "test-snap")
+            .setWaitForCompletion(true)
+            .execute()
+            .actionGet();
+        assertThat(restoreSnapshotResponse.getRestoreInfo().totalShards(), greaterThan(0));
+
+        logger.info("--> assert that old settings are restored");
+        GetSettingsResponse getSettingsResponse = client().admin().indices().prepareGetSettings("test-idx").execute().actionGet();
+        assertThat(getSettingsResponse.getSetting("test-idx", "index.refresh_interval"), equalTo("10s"));
+        assertThat(getSettingsResponse.getSetting("test-idx", SETTING_REPLICATION_TYPE), equalTo(ReplicationType.SEGMENT.name()));
+    }
+
 }

server/src/main/java/org/opensearch/cluster/metadata/MetadataCreateIndexService.java

@@ -891,7 +891,7 @@ static Settings aggregateIndexSettings(
         indexSettingsBuilder.put(IndexMetadata.SETTING_INDEX_PROVIDED_NAME, request.getProvidedName());
         indexSettingsBuilder.put(SETTING_INDEX_UUID, UUIDs.randomBase64UUID());
 
-        updateReplicationStrategy(indexSettingsBuilder, request.settings(), settings);
+        updateReplicationStrategy(indexSettingsBuilder, request.settings(), settings, combinedTemplateSettings);
         updateRemoteStoreSettings(indexSettingsBuilder, settings);
 
         if (sourceMetadata != null) {
@@ -934,17 +934,33 @@ static Settings aggregateIndexSettings(
      * @param settingsBuilder index settings builder to be updated with relevant settings
      * @param requestSettings settings passed in during index create request
      * @param clusterSettings cluster level settings
+     * @param combinedTemplateSettings combined template settings which satisfy the index
      */
-    private static void updateReplicationStrategy(Settings.Builder settingsBuilder, Settings requestSettings, Settings clusterSettings) {
+    private static void updateReplicationStrategy(
+        Settings.Builder settingsBuilder,
+        Settings requestSettings,
+        Settings clusterSettings,
+        Settings combinedTemplateSettings
+    ) {
+        // The replication setting is applied in the following order:
+        // i. Explicit index creation request parameter
+        // ii. Defaults to segment if remote store attributes on the cluster
+        // iii. Template property for replication type
+        // iv. Default cluster level setting
+
+        final ReplicationType indexReplicationType;
         if (INDEX_REPLICATION_TYPE_SETTING.exists(requestSettings)) {
-            settingsBuilder.put(SETTING_REPLICATION_TYPE, INDEX_REPLICATION_TYPE_SETTING.get(requestSettings));
+            indexReplicationType = INDEX_REPLICATION_TYPE_SETTING.get(requestSettings);
+        } else if (INDEX_REPLICATION_TYPE_SETTING.exists(combinedTemplateSettings)) {
+            indexReplicationType = INDEX_REPLICATION_TYPE_SETTING.get(combinedTemplateSettings);
         } else if (CLUSTER_REPLICATION_TYPE_SETTING.exists(clusterSettings)) {
-            settingsBuilder.put(SETTING_REPLICATION_TYPE, CLUSTER_REPLICATION_TYPE_SETTING.get(clusterSettings));
+            indexReplicationType = CLUSTER_REPLICATION_TYPE_SETTING.get(clusterSettings);
         } else if (isRemoteStoreAttributePresent(clusterSettings)) {
-            settingsBuilder.put(SETTING_REPLICATION_TYPE, ReplicationType.SEGMENT);
+            indexReplicationType = ReplicationType.SEGMENT;
         } else {
-            settingsBuilder.put(SETTING_REPLICATION_TYPE, CLUSTER_REPLICATION_TYPE_SETTING.getDefault(clusterSettings));
+            indexReplicationType = CLUSTER_REPLICATION_TYPE_SETTING.getDefault(clusterSettings);
         }
+        settingsBuilder.put(SETTING_REPLICATION_TYPE, indexReplicationType);
     }
 
     /**

server/src/test/java/org/opensearch/cluster/metadata/MetadataCreateIndexServiceTests.java

@@ -117,6 +117,7 @@
 import static org.opensearch.cluster.metadata.IndexMetadata.INDEX_NUMBER_OF_ROUTING_SHARDS_SETTING;
 import static org.opensearch.cluster.metadata.IndexMetadata.INDEX_NUMBER_OF_SHARDS_SETTING;
 import static org.opensearch.cluster.metadata.IndexMetadata.INDEX_READ_ONLY_BLOCK;
+import static org.opensearch.cluster.metadata.IndexMetadata.INDEX_REPLICATION_TYPE_SETTING;
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_REPLICAS;
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_SHARDS;
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_READ_ONLY;
@@ -1217,6 +1218,27 @@ public void testvalidateIndexSettings() {
         threadPool.shutdown();
     }
 
+    public void testIndexTemplateReplicationType() {
+        Settings templateSettings = Settings.builder().put(INDEX_REPLICATION_TYPE_SETTING.getKey(), ReplicationType.SEGMENT).build();
+
+        request = new CreateIndexClusterStateUpdateRequest("create index", "test", "test");
+        final Settings.Builder requestSettings = Settings.builder();
+        request.settings(requestSettings.build());
+        Settings indexSettings = aggregateIndexSettings(
+            ClusterState.EMPTY_STATE,
+            request,
+            templateSettings,
+            null,
+            Settings.EMPTY,
+            IndexScopedSettings.DEFAULT_SCOPED_SETTINGS,
+            randomShardLimitService(),
+            Collections.emptySet(),
+            clusterSettings
+        );
+        assertNotEquals(ReplicationType.SEGMENT, clusterSettings.get(CLUSTER_REPLICATION_TYPE_SETTING));
+        assertEquals(ReplicationType.SEGMENT.toString(), indexSettings.get(INDEX_REPLICATION_TYPE_SETTING.getKey()));
+    }
+
     public void testRemoteStoreNoUserOverrideExceptReplicationTypeSegmentIndexSettings() {
         Settings settings = Settings.builder()
             .put(CLUSTER_REPLICATION_TYPE_SETTING.getKey(), ReplicationType.DOCUMENT)