could not get any response - mysql

Question

I am building a rest api with node.js and mysql. But in my GET I am getting a error of "could not get any response" with router.get that uses the mysql.
Here is my code, mt it helps.
server.js
const http = require('http');
const app = require('./app');
const port = process.env.PORT || 3000;
const server = http.createServer(app);
server.listen(port);
app.js
const express = require('express');
const app = express();
const userRoutes = require('./api/routes/user');
var mysql = require("mysql");
//Database connection
app.use(function(req, res, next){
res.locals.connection = mysql.createConnection({
host : 'localhost',
user : 'root',
password : ' ',
database : 'achai_db'
});
res.locals.connection.connect();
next();
});
user.js
const express = require('express');
const router = express.Router();
router.get('/', function(req, res, next) {
res.locals.connection.query('SELECT * from users', function (error, results, fields) {
if (error) throw error;
res.send(JSON.stringify({"status": 200, "error": null, "response": results}));
});
});
module.exports = router;
In that user.js if i use a get without using the mysql the connection works.

Answer 1

You need to understand JavaScript nature(Asynchronous programming) and you must not open mysql connection in each request, you can use connection pooling and keep connection open, just acquire connection and release it after query.
updated app.js
const express = require('express');
const app = express();
const userRoutes = require('./api/routes/user');
const mysql = require('mysql');
//Database connection
const pool = mysql.createPool({
host : 'localhost',
user : 'root',
password : ' ',
database : 'achai_db'
});
app.use(function(req, res, next){
pool.getConnection(function(err, connection) {
res.locals.connection = connection;
next(err);
});
});
updated user.js
const express = require('express');
const router = express.Router();
router.get('/', function(req, res, next) {
res.locals.connection.query('SELECT * from users', function (error, results, fields) {
res.locals.connection.release();
if (error) throw error;
//res.json({"status": 200, "error": null, "response": results});
res.send(JSON.stringify({"status": 200, "error": null, "response": results}));
});
});
module.exports = router;