Module 4 - Deployment and Best Practices

Overview

When you develop and run code on your machine, you run code in its development environment.

Most companies will have a testing environment similar to production; it has the same versions of software and runs on similar, albeit weaker, hardware. They do this to mitigate the risks when moving to production servers that clients use.

Ideally, all environments run on the same stack, platforms, and versions. Still, it is common to have developers on the Windows platform with the latest version of Node.js and the production server running on Linux with the last stable version of Node.js.

Environment Variables

Environment variables are a way to store configuration values that might change between environments. Common examples include:

• Port numbers
• Database connection strings
• API keys
• Feature flags

Using dotenv

The dotenv package is commonly used to load environment variables from a .env file:

// it's recommended to load configuration for .env as early as possible
require('dotenv').config(); // add this line as the first thing to run

// server code...

// we'll read the port from the server environment if it is there
// Heroku for example will have the PORT environment variable set already
const port = process.env.PORT || 9000;

// we can now use that port, use 9000 as a default if not set
server.listen(port, () => {
  console.log(`\n*** Server Running on http://localhost:${port} ***\n`);
});

Best Practices

• Add .env to .gitignore to prevent secrets from being committed
• Provide a .env.example file with dummy values for documentation
• Use sensible defaults for development
• Validate required environment variables at startup
• Never hardcode configuration values directly in your code

Steps to Implement

1. Install the dotenv package: npm install dotenv
2. Add the require statement at the top of your entry file
3. Create a .env file in your project root
4. Add your environment variables in KEY=VALUE format
5. Access variables in your code using process.env.VARIABLE_NAME

Challenge

Extract all secrets and values that need to change between development and production environments.

Overview

In this lesson, we'll deploy an Express API to Heroku. Heroku is a popular platform for deploying web applications. While it no longer provides a free tier, understanding how to deploy to Heroku helps you understand deployment concepts that apply to other platforms.

Note: As of November 2022, Heroku no longer provides a totally free tier like they used to. For learning purposes, we only need you to understand how to make an API deployable to Heroku or similar providers.

Key Requirements for Deployment

• A "start" script in package.json that uses Node (not Nodemon)
• Dynamic port configuration using environment variables
• All dependencies listed in package.json
• No hardcoded configuration values

Continuous Deployment from GitHub

1. Login to Heroku and create an app
2. In the "Deploy" tab, select GitHub in the "Deployment Method" section
3. Authorize Heroku to access your GitHub account if prompted
4. Search for and connect the repository you wish to deploy
5. In the "Automatic deploys" section, enable automatic deploys from your main branch
6. Use "Manual deploy" to trigger your first deployment

Environment Variables on Heroku

Environment variables can be set in the Heroku dashboard:

1. Go to the "Settings" tab
2. Click "Reveal Config Vars"
3. Add your environment variables as key-value pairs

These environment variables override any default values in your code and are not visible in your GitHub repository, making them ideal for storing sensitive information.

Deployment Verification

• Once deployed, test your API endpoints using Postman or a browser
• Check application logs if you encounter any issues
• Make sure your application correctly uses environment variables provided by Heroku

Challenge

Using the information you've obtained from the guided project, create an application on Heroku to set up continuous deployment from one of your GitHub repositories.