Do not api refresh unpromotables for fast refresh

Currently the TransportShardRefreshAction waits for the unpromotables to
be refreshed in all circumstances where they exist. However, when the
indice is marked as fast_refresh, this is not an expectation. This
commit removes this wait.

server/src/main/java/org/elasticsearch/action/admin/indices/refresh/TransportShardRefreshAction.java

@@ -23,6 +23,7 @@
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.logging.LogManager;
@@ -111,21 +112,30 @@ public void onPrimaryOperationComplete(
             ActionListener<Void> listener
         ) {
             assert replicaRequest.primaryRefreshResult.refreshed() : "primary has not refreshed";
-            UnpromotableShardRefreshRequest unpromotableReplicaRequest = new UnpromotableShardRefreshRequest(
-                indexShardRoutingTable,
-                replicaRequest.primaryRefreshResult.generation(),
-                false
-            );
-            transportService.sendRequest(
-                transportService.getLocalNode(),
-                TransportUnpromotableShardRefreshAction.NAME,
-                unpromotableReplicaRequest,
-                new ActionListenerResponseHandler<>(
-                    listener.delegateFailure((l, r) -> l.onResponse(null)),
-                    (in) -> ActionResponse.Empty.INSTANCE,
-                    ThreadPool.Names.REFRESH
-                )
+            boolean fastRefresh = IndexSettings.INDEX_FAST_REFRESH_SETTING.get(
+                clusterService.state().metadata().index(indexShardRoutingTable.shardId().getIndex()).getSettings()
             );
+
+            // Indices marked with fast refresh do not rely on refreshing the unpromotables
+            if (fastRefresh) {
+                listener.onResponse(null);
+            } else {
+                UnpromotableShardRefreshRequest unpromotableReplicaRequest = new UnpromotableShardRefreshRequest(
+                    indexShardRoutingTable,
+                    replicaRequest.primaryRefreshResult.generation(),
+                    false
+                );
+                transportService.sendRequest(
+                    transportService.getLocalNode(),
+                    TransportUnpromotableShardRefreshAction.NAME,
+                    unpromotableReplicaRequest,
+                    new ActionListenerResponseHandler<>(
+                        listener.delegateFailure((l, r) -> l.onResponse(null)),
+                        (in) -> ActionResponse.Empty.INSTANCE,
+                        ThreadPool.Names.REFRESH
+                    )
+                );
+            }
         }
     }
 }