Adding number of routing shards to index settings before passing into…

… GetSettingsResponse

Signed-off-by: Sophia <tjdud6024@gmail.com>

CHANGELOG.md

@@ -39,6 +39,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix the computed max shards of cluster to avoid int overflow ([#14155](https://github.com/opensearch-project/OpenSearch/pull/14155))
 - Fixed rest-high-level client searchTemplate & mtermVectors endpoints to have a leading slash ([#14465](https://github.com/opensearch-project/OpenSearch/pull/14465))
 - Write shard level metadata blob when snapshotting searchable snapshot indexes ([#13190](https://github.com/opensearch-project/OpenSearch/pull/13190))
+- Updated GET {index}/_settings to return `number_of_routing_shards` ([#14446](https://github.com/opensearch-project/OpenSearch/pull/14446))
 
 ### Security
 

server/src/main/java/org/opensearch/action/admin/indices/settings/get/TransportGetSettingsAction.java

@@ -130,6 +130,11 @@ protected void clusterManagerOperation(GetSettingsRequest request, ClusterState
                 indexSettings = indexSettings.filter(k -> Regex.simpleMatch(request.names(), k));
             }
 
+            indexSettings = Settings.builder()
+                .put(indexSettings)
+                .put(IndexMetadata.INDEX_NUMBER_OF_ROUTING_SHARDS_SETTING.getKey(), indexMetadata.getRoutingNumShards())
+                .build();
+
             indexToSettingsBuilder.put(concreteIndex.getName(), indexSettings);
             if (request.includeDefaults()) {
                 Settings defaultSettings = settingsFilter.filter(indexScopedSettings.diff(indexSettings, Settings.EMPTY));