code: function postAddXSetMember (req, res, next) {
    let key = req.body.key;
    let timestamp = req.body.timestamp;
    let field = req.body.field;
    let value = req.body.value;
    let connectionId = req.body.connectionId;
    getConnection(req, res, function () {
        addXSetMember(key, timestamp, field, value, res, next);
    }, connectionId);
  }
docs: stream