docs: function(batchSize, opts) {
          var ctx = u.context(SMALL);
          logger.debugf('Invoke iterator(msgId=%d,batchSize=%d,opts=%s)', ctx.id, batchSize, u.str(opts));
          var remote = future(ctx, 0x31, p.encodeIterStart(batchSize, opts), p.decodeIterId);
          return remote.then(function(result) {
            return iterator(result.iterId, result.conn);
          });
        }