// TODO: I only need shardIds, ShardIterator(ShardRouting) is only needed in TransportShardMultiPercolateAction
GroupShardsIterator shards = clusterService.operationRouting().searchShards(
clusterState, percolateRequest.indices(), concreteIndices, routing, percolateRequest.preference()
);
if (shards.size() == 0) {
reducedResponses.set(slot, new UnavailableShardsException(null, "No shards available"));
responsesByItemAndShard.set(slot, new AtomicReferenceArray(0));
expectedOperationsPerItem.set(slot, new AtomicInteger(0));
continue;
}