Using Docker with NestJS: A Containerization Guide

NestJS is a powerful and versatile framework for building server-side applications in Node.js, offering a robust architecture with TypeScript at its core. One of the main challenges, however, is ensuring that your NestJS application can be deployed consistently across different environments. This is where Docker can make a significant impact.

Docker allows you to package your application along with all its dependencies into a single container, ensuring it runs seamlessly on any system that supports Docker. In this guide, we’ll walk through the steps necessary to containerize a NestJS application using Docker. By the end of this article, you’ll have a running Docker container of your NestJS application that you can deploy anywhere.

Step 1: Setting Up a Basic NestJS Application

First, ensure you have the NestJS CLI installed. If not, you can install it using npm:

npm install -g @nestjs/cli

Now, create a new NestJS application:

nest new my-nest-app

Navigate to the newly created project folder:

cd my-nest-app

You should see a basic NestJS application structure.

Step 2: Writing Your Dockerfile

A Dockerfile is a script that contains a sequence of instructions to create a Docker image. Create a new file named Dockerfile in the root of your NestJS project and add the following content:

# Use the official Node.js 16 image as a base
FROM node:16

# Create a directory for the application
WORKDIR /usr/src/app

# Copy package.json and package-lock.json
COPY package*.json ./

# Install application dependencies
RUN npm install

# Copy the rest of the application code
COPY . .

# Build the NestJS application
RUN npm run build

# Expose the application port
EXPOSE 3000

# Start the application
CMD ["npm", "run", "start:prod"]

This Dockerfile does the following:

• It starts by using the Node.js 16 image.
• It sets the working directory.
• It copies the package.json and package-lock.json files and installs dependencies.
• It copies the rest of the NestJS application code into the Docker container.
• It builds the NestJS application.
• It exposes port 3000, which is the default HTTP port used by NestJS.
• It starts the application in production mode.

Step 3: Creating a .dockerignore File

To prevent unnecessary files from being included in the Docker image, create a .dockerignore file in your project's root:

node_modules
dist
.git
.gitignore
Dockerfile
docker-compose.yml
npm-debug.log

This file ensures that Docker ignores specific files and directories when building the image, making the build faster and smaller.

Step 4: Building and Running the Docker Image

With the Dockerfile and .dockerignore file in place, you can now build and run your Docker image.

Build the Docker Image

Run the following command to build your Docker image:

docker build -t my-nest-app .

Here, my-nest-app is the name of the image. You can name it anything you like.

Run the Docker Container

Now that the image is built, you can run the Docker container:

docker run -p 3000:3000 my-nest-app

The -p 3000:3000 flag maps port 3000 on your host machine to port 3000 on the Docker container. Your application should now be accessible at http://localhost:3000.

Step 5: Using Docker Compose (Optional)

Docker Compose can further simplify the management of your Docker containers, especially if you have multiple services. Create a docker-compose.yml file in your project root:

version: '3.8'
services:
  nest-app:
    build: .
    ports:
      - "3000:3000"
    environment:
      NODE_ENV: production
    command: npm run start:prod

With this setup, you can start your NestJS application with a single command:

docker-compose up

Conclusion

Containerizing your NestJS applications with Docker provides a consistent and reliable deployment process that can be easily shared across different environments. By following the steps outlined in this guide, you can ensure your application runs smoothly, from development to production, with the power and flexibility of Docker. Happy coding!