How to properly pass mysql connection to routes with express.js

Question

I am trying to figure out the best way to pass a mysql connection (using node-mysql) between my routes for express.js. I am dynamically adding each route (using a for each file loop in routes), meaning I can't just pass in the connection to routes that need it. I either need to pass it to every route or none at all. I didn't like the idea of passing it to ones that dont need it so I created a dbConnection.js that the routes can individually import if they need. The problem is that I dont think I am doing it correctly. As of now, my dbConnection.js contains:

var mysql = require('mysql');
var db = null;
module.exports = function () {
    if(!db) {
            db = mysql.createConnection({
                socketPath: '/tmp/mysql.sock',
            user: '*********',
            password: '*********',
            database: '**********'
        });
    }
    return db;
};

And I am importing it into each route using:

var db = require('../dbConnection.js');
var connection = new db();

But I would like to do it like this:

var connection = require('../dbConnection.js');

When I try it like this, however, I get an error saying connection has no method 'query' when I try to make a query.

Answer 1

I find it more reliable to use node-mysql's pool object. Here's how I set mine up. I use environment variable for database information. Keeps it out of the repo.

database.js

var mysql = require('mysql');

var pool = mysql.createPool({
  host: process.env.MYSQL_HOST,
  user: process.env.MYSQL_USER,
  password: process.env.MYSQL_PASS,
  database: process.env.MYSQL_DB,
  connectionLimit: 10,
  supportBigNumbers: true
});

// Get records from a city
exports.getRecords = function(city, callback) {
  var sql = "SELECT name FROM users WHERE city=?";
  // get a connection from the pool
  pool.getConnection(function(err, connection) {
    if(err) { console.log(err); callback(true); return; }
    // make the query
    connection.query(sql, [city], function(err, results) {
      connection.release();
      if(err) { console.log(err); callback(true); return; }
      callback(false, results);
    });
  });
};

Route

var db = require('../database');

exports.GET = function(req, res) {
  db.getRecords("San Francisco", function(err, results) {
    if(err) { res.send(500,"Server Error"); return;
    // Respond with results as JSON
    res.send(results);
  });
};

Answer 2

your solution will work if use db() instead of new db(), which returns an object and not the db connection

var db = require('../dbConnection.js');
//var connection = new db();
var connection = db();