[Backport 2.x] [Searchable Snapshot] Add Relevant Error handling for Index Creation with remote_snapshot.

CHANGELOG.md

@@ -150,6 +150,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix parsing of single line comments in `lang-painless` ([#11815](https://github.com/opensearch-project/OpenSearch/issues/11815))
 - Fix typo in API annotation check message ([11836](https://github.com/opensearch-project/OpenSearch/pull/11836))
 - Fix memory leak issue in ReorganizingLongHash ([#11953](https://github.com/opensearch-project/OpenSearch/issues/11953))
+- Prevent setting remote_snapshot store type on index creation ([#11867](https://github.com/opensearch-project/OpenSearch/pull/11867))
 
 ### Security
 

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

@@ -40,6 +40,7 @@
 import org.opensearch.OpenSearchException;
 import org.opensearch.ResourceAlreadyExistsException;
 import org.opensearch.Version;
+import org.opensearch.action.admin.cluster.snapshots.restore.RestoreSnapshotRequest;
 import org.opensearch.action.admin.indices.alias.Alias;
 import org.opensearch.action.admin.indices.create.CreateIndexClusterStateUpdateRequest;
 import org.opensearch.action.admin.indices.shrink.ResizeType;
@@ -136,6 +137,7 @@
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_REMOTE_TRANSLOG_STORE_REPOSITORY;
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_REPLICATION_TYPE;
 import static org.opensearch.cluster.metadata.Metadata.DEFAULT_REPLICA_COUNT_SETTING;
+import static org.opensearch.index.IndexModule.INDEX_STORE_TYPE_SETTING;
 import static org.opensearch.indices.IndicesService.CLUSTER_REPLICATION_TYPE_SETTING;
 import static org.opensearch.node.remotestore.RemoteStoreNodeAttribute.isRemoteStoreAttributePresent;
 
@@ -817,6 +819,16 @@ static Settings aggregateIndexSettings(
         final Settings.Builder requestSettings = Settings.builder().put(request.settings());
 
         final Settings.Builder indexSettingsBuilder = Settings.builder();
+
+        // Store type of `remote_snapshot` is intended to be system-managed for searchable snapshot indexes so a special case is needed here
+        // to prevent a user specifying this value when creating an index
+        String storeTypeSetting = request.settings().get(INDEX_STORE_TYPE_SETTING.getKey());
+        if (storeTypeSetting != null && storeTypeSetting.equals(RestoreSnapshotRequest.StorageType.REMOTE_SNAPSHOT.toString())) {
+            throw new IllegalArgumentException(
+                "cannot create index with index setting \"index.store.type\" set to \"remote_snapshot\". Store type can be set to \"remote_snapshot\" only when restoring a remote snapshot by using \"storage_type\": \"remote_snapshot\""
+            );
+        }
+
         if (sourceMetadata == null) {
             final Settings.Builder additionalIndexSettings = Settings.builder();
             final Settings templateAndRequestSettings = Settings.builder().put(combinedTemplateSettings).put(request.settings()).build();

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

@@ -36,6 +36,7 @@
 import org.opensearch.LegacyESVersion;
 import org.opensearch.ResourceAlreadyExistsException;
 import org.opensearch.Version;
+import org.opensearch.action.admin.cluster.snapshots.restore.RestoreSnapshotRequest;
 import org.opensearch.action.admin.indices.alias.Alias;
 import org.opensearch.action.admin.indices.create.CreateIndexClusterStateUpdateRequest;
 import org.opensearch.action.admin.indices.shrink.ResizeType;
@@ -134,6 +135,7 @@
 import static org.opensearch.cluster.metadata.MetadataCreateIndexService.getIndexNumberOfRoutingShards;
 import static org.opensearch.cluster.metadata.MetadataCreateIndexService.parseV1Mappings;
 import static org.opensearch.cluster.metadata.MetadataCreateIndexService.resolveAndValidateAliases;
+import static org.opensearch.index.IndexModule.INDEX_STORE_TYPE_SETTING;
 import static org.opensearch.index.IndexSettings.INDEX_REFRESH_INTERVAL_SETTING;
 import static org.opensearch.index.IndexSettings.INDEX_REMOTE_TRANSLOG_BUFFER_INTERVAL_SETTING;
 import static org.opensearch.index.IndexSettings.INDEX_SOFT_DELETES_SETTING;
@@ -147,6 +149,7 @@
 import static org.opensearch.node.Node.NODE_ATTRIBUTES;
 import static org.opensearch.node.remotestore.RemoteStoreNodeAttribute.REMOTE_STORE_SEGMENT_REPOSITORY_NAME_ATTRIBUTE_KEY;
 import static org.opensearch.node.remotestore.RemoteStoreNodeAttribute.REMOTE_STORE_TRANSLOG_REPOSITORY_NAME_ATTRIBUTE_KEY;
+import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.endsWith;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasKey;
@@ -1945,6 +1948,35 @@ public void testRequestDurabilityWhenRestrictSettingTrue() {
         assertEquals(Translog.Durability.REQUEST, INDEX_TRANSLOG_DURABILITY_SETTING.get(indexSettings));
     }
 
+    public void testIndexCreationWithIndexStoreTypeRemoteStoreThrowsException() {
+        // This checks that aggregateIndexSettings throws exception for the case when the index setting
+        // index.store.type is set to remote_snapshot
+        request = new CreateIndexClusterStateUpdateRequest("create index", "test", "test");
+        final Settings.Builder requestSettings = Settings.builder();
+        requestSettings.put(INDEX_STORE_TYPE_SETTING.getKey(), RestoreSnapshotRequest.StorageType.REMOTE_SNAPSHOT);
+        request.settings(requestSettings.build());
+        final IllegalArgumentException error = expectThrows(
+            IllegalArgumentException.class,
+            () -> aggregateIndexSettings(
+                ClusterState.EMPTY_STATE,
+                request,
+                Settings.EMPTY,
+                null,
+                Settings.EMPTY,
+                IndexScopedSettings.DEFAULT_SCOPED_SETTINGS,
+                randomShardLimitService(),
+                Collections.emptySet(),
+                clusterSettings
+            )
+        );
+        assertThat(
+            error.getMessage(),
+            containsString(
+                "cannot create index with index setting \"index.store.type\" set to \"remote_snapshot\". Store type can be set to \"remote_snapshot\" only when restoring a remote snapshot by using \"storage_type\": \"remote_snapshot\""
+            )
+        );
+    }
+
     private IndexTemplateMetadata addMatchingTemplate(Consumer<IndexTemplateMetadata.Builder> configurator) {
         IndexTemplateMetadata.Builder builder = templateMetadataBuilder("template1", "te*");
         configurator.accept(builder);