Node.js - Sequelize.js | Create Dynamic Database Connection

Question

I am writing a simple CMS with Node.js and Sequelize.js. I want to get database information from user like Wordpress and create database connection. I wrote the codes below for this but my problem is application don't start before database connection.

Controllers

// Get Database Setup Page
exports.getSetup = (req, res) => {
  return res.render("pages/account/setup");
};

// Post Database Information
exports.postSetup = (req, res) => {

  // Set posted values as ENV Variable
  setEnvValue("DB_NAME", req.body.name);
  setEnvValue("DB_USERNAME", req.body.username);
  setEnvValue("DB_PASSWORD", req.body.password);
  setEnvValue("DB_HOST", req.body.host);

  return res.redirect("/login");
};

// Error occurs here. Application don't start before database connection.
exports.getLogin = async (req, res) => {
  const general = await Models.General.findByPk(1);

  // Check Authenticate
  if (req.session.isAuth) return res.redirect("/admin");

  // Render Page
  return res.render("pages/account/login", {
    title: "Login",
    general: general,
  });
};

.env File After Post

DB_NAME="db-name"
DB_USERNAME="root"
DB_PASSWORD="password"
DB_HOST="localhost"

Database Connection file

I use this in several places like defining models.

const Sequelize = require("sequelize");

const sequelize = new Sequelize(
  process.env.DB_NAME,
  process.env.DB_USERNAME,
  process.env.DB_PASSWORD,
  {
    dialect: "mysql",
    host: process.env.DB_HOST,
  }
);

module.exports = sequelize;

Anatoly · Accepted Answer · 2022-01-20 21:28:50Z

1

You can just wrap creating Sequelize instance into a function and export it to use in login route like this:

const Sequelize = require("sequelize");

let sequelize = null;

function initializeConnection() {
  sequelize = new Sequelize(
    process.env.DB_NAME,
    process.env.DB_USERNAME,
    process.env.DB_PASSWORD,
    {
      dialect: "MySQL",
      host: process.env.DB_HOST,
    }
  );
  // here should be model and their associations' registration
  ...
}

function getConnection() {
  return sequelize;
}

module.exports = { 
  initializeConnection,
  getConnection
}

// Error Occurs here. Application don't start before database connection.
exports.getLogin = async (req, res) => {
  if (req.session.isAuth) {
    return res.redirect("/admin");
  }

  try {
    await intializeConnection();
  catch (err) {
      res.status(500).send('Internal server error')
      return;
  }

  const general = await Models.General.findByPk(1)
  res.render("pages/account/login", {
      title: "Login",
      general: general,
    });
};

Don't forget to disconnect from DB on logout

answered Jan 20, 2022 at 21:28

Anatoly

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3 Comments

Enes Kılıç Over a year ago

Thank's a lot your suggestion. I defined Models at external file like const General = sequelize.define... module.exports = {Admin, General etc.} . I don't know how to register their associations in the function and how to access them. Can you explain it for me.

Anatoly Over a year ago

See mu other answer stackoverflow.com/a/61710568/1376618

Enes Kılıç Over a year ago

I accessed it with the getConnection().models method. Thank's for your interest!

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