mgets on fast refresh promotable shards (#96879)

Relates ES-6292

Author: kingherc

server/src/main/java/org/elasticsearch/action/get/TransportShardMultiGetAction.java

@@ -21,9 +21,9 @@
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.node.DiscoveryNode;
+import org.elasticsearch.cluster.routing.OperationRouting;
 import org.elasticsearch.cluster.routing.PlainShardIterator;
 import org.elasticsearch.cluster.routing.ShardIterator;
-import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -101,7 +101,10 @@ protected ShardIterator shards(ClusterState state, InternalRequest request) {
         if (iterator == null) {
             return null;
         }
-        return new PlainShardIterator(iterator.shardId(), iterator.getShardRoutings().stream().filter(ShardRouting::isSearchable).toList());
+        return new PlainShardIterator(
+            iterator.shardId(),
+            iterator.getShardRoutings().stream().filter(shardRouting -> OperationRouting.canSearchShard(shardRouting, state)).toList()
+        );
     }
 
     @Override
@@ -110,11 +113,14 @@ protected void asyncShardOperation(MultiGetShardRequest request, ShardId shardId
         IndexService indexService = indicesService.indexServiceSafe(shardId.getIndex());
         IndexShard indexShard = indexService.getShard(shardId.id());
         if (indexShard.routingEntry().isPromotableToPrimary() == false) {
+            assert indexShard.indexSettings().isFastRefresh() == false
+                : "a search shard should not receive a TransportShardMultiGetAction for an index with fast refresh";
             handleMultiGetOnUnpromotableShard(request, indexShard, listener);
             return;
         }
-        assert DiscoveryNode.isStateless(clusterService.getSettings()) == false
-            : "A TransportShardMultiGetAction should always be handled by a search shard in Stateless";
+        assert DiscoveryNode.isStateless(clusterService.getSettings()) == false || indexShard.indexSettings().isFastRefresh()
+            : "in Stateless a promotable to primary shard can receive a TransportShardMultiGetAction only if an index has "
+                + "the fast refresh setting";
         if (request.realtime()) { // we are not tied to a refresh cycle here anyway
             asyncShardMultiGet(request, shardId, listener);
         } else {