code: @Override
    protected ShardsIterator shards(ClusterState clusterState, GetIndicesVersionRequest request, String[] concreteIndices) {
      return clusterState.routingTable().allShards(concreteIndices);
    }
docs: Goes across *all* shards, i.e., primaries and replicas.
  
  When elasticsearch will have resolved issue #10708, we will be able to compute an index version based on the
  primary shards only.