Deploying to Heroku

From Localhost to the Internet

Running your API on localhost:5000 only works on your own machine. Deployment means copying your code to a remote server so that anyone on the internet can reach it. Heroku is a cloud platform that removes the complexity of managing servers — you push your code and it handles the rest.

What Is Heroku?

Heroku is a PaaS (Platform as a Service) provider. You do not rent a raw server and configure it yourself. Instead, Heroku provides a managed environment called a dyno — a container that runs your application. You push your code, Heroku builds and runs it.

Heroku is popular for learning and small projects because:

• Free tier available for testing (with sleep-on-inactivity)
• Git-based deployment is simple
• Supports Node.js, Python, Ruby, Go, and more
• Add-ons for databases, logging, and monitoring

Setting Up

1. Install the Heroku CLI

Download from https://devcenter.heroku.com/articles/heroku-cli and log in:

heroku login

2. Create a Heroku App

In your project directory (which must be a git repository):

heroku create my-api-name

Heroku adds a remote named heroku to your git config. You can confirm with:

git remote -v

The Procfile

Heroku needs to know how to start your application. Create a file named Procfile (no extension) in your project root:

web: node server.js

The web process type tells Heroku this is an HTTP-serving dyno. If your entry file is index.js or app.js, adjust accordingly.

The PORT Variable — Critical

Heroku assigns a dynamic port to your dyno via the PORT environment variable. Your app must listen on that port, not a hard-coded one:

// WRONG -- will not work on Heroku
app.listen(5000, () => console.log('Server running'));

// CORRECT
const PORT = process.env.PORT || 5000;
app.listen(PORT, () => console.log(`Server running on port ${PORT}`));

This is one of the most common deployment errors for beginners.

Deploying

# Make sure all changes are committed
git add .
git commit -m "Prepare for Heroku deployment"

# Push to Heroku
git push heroku main

Heroku will:

1. Detect Node.js (via package.json)
2. Run npm install
3. Run the command in your Procfile

Once done, open your app:

heroku open

Setting Config Variables (Environment Variables)

Never hard-code secrets in your code. Set them as Heroku config vars:

heroku config:set MONGODB_URI=mongodb+srv://user:pass@cluster.mongodb.net/mydb
heroku config:set JWT_SECRET=mysecretkey123
heroku config:set NODE_ENV=production

View all config vars:

heroku config

These are available in your app as process.env.MONGODB_URI, etc.

Viewing Logs

heroku logs --tail

This streams live logs from your running dyno. Indispensable for debugging deployment issues.

Common Deployment Issues

Set the Node.js version in package.json to match your local version:

{
  "engines": {
    "node": "18.x"
  }
}

Practice Exercise

1. Create a minimal Express API with a GET / route that returns { message: "Deployed to Heroku!" }.
2. Add a Procfile and ensure your app listens on process.env.PORT.
3. Run heroku create and deploy with git push heroku main.
4. Set a SECRET_KEY config var and log it (masked) on startup.
5. Trigger an error and use heroku logs --tail to identify and fix it.