How to use the primus.Spark function in primus

app.get(config.brokerHealthcheckPath || '/healthcheck', (req, res) => {
    // healthcheck state depends on websocket connection status
    // value of primus.Spark.OPEN means the websocket connection is open
    const isConnOpen = (io.readyState === primus.Spark.OPEN);
    const status = isConnOpen ? 200 : 500;
    const data = {
      ok: isConnOpen,
      websocketConnectionOpen: isConnOpen,
      brokerServerUrl: io.url.href,
      version,
    };

    return res.status(status).json(data);
  });