Node.JS中的MySQL请求始终返回旧数据集

Question

I am new to Node.JS, so probably, it's a trivial question, but I spent hours on it and haven't found any solution. The problem. MySQL query in Node.JS always returns the same data set since the startup of the server, no matter how I change the database. After I restart the server, it starts returning the correct data, untl I update them again. IE, data set never changes since the start up.

POST updates the table, GET gets the data set, but always the old data. Tried to update via POST and via MySQL workbench, it's always the same.

I thought, it's because I didn't end the connection. After some research, I added con.end() line after each query, but still of no help

This is my db_connector.js module:

var mysql = require('mysql');

module.exports = {
resSet: function(callback) {
    var con = mysql.createConnection({
    host: "localhost",
    user: "root",
    password: "pass",
    database: "applocator"
    });  
    con.query("SELECT * FROM locations",
    function (err, rows) {
    //here we return the results of the query
    callback(err, rows); 
      }
      );
    con.end();
    },
    resUpd: function(id, lat, long){
    var con = mysql.createConnection({
        host: "localhost",
        user: "root",
        password: "pass",
        database: "applocator"
      });  

      con.connect(function(err) {
        if (err) throw err;
        var sql = "UPDATE locations SET latitude = "+lat+", longitude = 
    "+long+" WHERE id = "+id;
        console.log(sql);
        con.query(sql, function (err, result) {
          if (err) throw err;
          console.log(result.affectedRows + " record(s) updated");
        });
      });    
      con.end();      
    }
}

It exports two functions, one to get the data set, one to update it.

I use it in the server.js this way:

var app = express();

app.use(allowCrossDomain); 
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

app.post('/',function(req,res){
query.resUpd(req.body.id,req.body.lat,req.body.long)
console.log(req.body);
res.send("Success");
});

query.resSet(function (err, myRes){

app.get('*', (req, res) => 
res.status(200).send(JSON.stringify(myRes)));
})


app.listen(3000);

I must get the updated data set after I make an update, but am always getting the old data set, like I have not made any updates to the table. What is my problem? I'll be very grateful for your responses.

Answer 1

The server returns the stale data because you register app.get('*' ...) handler inside the callback that is triggered by mysql select query. It should be vice versa, so in server.js try to change:

query.resSet(function (err, myRes){
  app.get('*', (req, res) =>
    res.status(200).send(JSON.stringify(myRes)));
})

into

app.get('*', (req, res) => {
  query.resSet(function (err, myRes) {
    res.status(200).send(JSON.stringify(myRes));
  })
})