全局连接已经存在。 首先调用sql.close()

我试图build立一个node.js后端,我有一个用例,我应该每次连接到服务器,而不是数据库,请参阅一个Web服务:

router.get('/CriticalityGraph/:server/:user/:password/:database/', function(req, res, next) { user = req.params.user; password = req.params.password; server = req.params.server; database = req.params.database; criticalityState=req.params.criticalityState // config for your database var config = { user: user, password: password, server: server, database:database }; sql.connect(config, function (err) { var request = new sql.Request(); request.query("SELECT MachineName, alarmState, criticality FROM MachineTable  ORDER BY criticality DESC" , function (err, recordset) { if (err) console.log(err); else { for(i=0;i<recordset.recordsets.length;i++) { res.send(recordset.recordsets[i]) } sql.close(); } }); }); }); 

现在我想从2个浏览器同时访问这个web服务,我正在抛出node.js Global connection already exists. Call sql.close() first node.js Global connection already exists. Call sql.close() first

任何build议来解决这个问题?