Next.js, FastAPI, and Docker: A Complete Guide

Hey guys! Ever wondered how to bring together the blazing-fast frontend of Next.js with the robust backend capabilities of FastAPI, all neatly packaged in a Docker container? Well, you’re in the right place! This guide will walk you through setting up a full-stack application using these technologies. Let’s dive in!

Setting Up the Next.js Frontend

First, let’s talk about Next.js . Next.js is a React framework that enables features like server-side rendering and static site generation. It’s fantastic for building performant and SEO-friendly frontends. To get started, you’ll need Node.js and npm or yarn installed. Open your terminal and run the following command to create a new Next.js project:

npx create-next-app frontend
cd frontend

This command sets up a basic Next.js application in a directory named frontend . You can choose a different name if you prefer. Once the project is created, navigate into the project directory. Now, let’s customize the frontend a bit. Open the pages/index.js file and modify it to display a simple message. For example, replace the existing content with:

function HomePage() {
  return (
    <div>
      <h1>Welcome to Next.js!</h1>
      <p>This is the frontend of our application.</p>
    </div>
  );
}

export default HomePage;

This code defines a functional component called HomePage that returns a simple HTML structure. You can start the Next.js development server by running:

npm run dev
# or
yarn dev

This will start the server, usually on http://localhost:3000 . Open your browser and navigate to this address to see your Next.js application running. Next.js also supports features like routing, API routes, and more. You can create new pages by adding .js files to the pages directory. For example, creating pages/about.js will automatically create a route at /about . To fetch data from the backend, you can use the fetch API or a library like axios . You can call your FastAPI backend endpoints from within your Next.js components.

Building the FastAPI Backend

Now, let’s move on to the backend with FastAPI . FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints. It’s incredibly easy to use and comes with automatic data validation and API documentation. To get started, you’ll need Python installed. Create a new directory for your backend, navigate into it, and create a main.py file:

mkdir backend
cd backend
touch main.py

Next, install FastAPI and uvicorn, an ASGI server:

pip install fastapi uvicorn

Now, open main.py and add the following code:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def read_root():
    return {"message": "Hello from FastAPI!"}

This code creates a basic FastAPI application with a single endpoint / that returns a JSON response. To run the FastAPI application, use uvicorn:

uvicorn main:app --reload

The --reload flag tells uvicorn to automatically reload the server whenever you make changes to the code. This is very useful during development. Open your browser and navigate to http://localhost:8000 to see the JSON response from your FastAPI application. FastAPI also automatically generates API documentation using OpenAPI and Swagger UI. You can access the documentation at http://localhost:8000/docs . This documentation is interactive and allows you to test your API endpoints directly from the browser. You can define more complex data models using Pydantic, which is integrated with FastAPI. Pydantic provides data validation and serialization, ensuring that your API receives and returns data in the expected format. FastAPI’s dependency injection system makes it easy to manage dependencies and write testable code. You can define dependencies as function parameters and FastAPI will automatically resolve them. This helps to keep your code clean and maintainable.

Dockerizing the Application

Alright, let’s containerize everything using Docker ! Docker allows you to package your application and its dependencies into a container, ensuring that it runs consistently across different environments. First, create a Dockerfile in both the frontend and backend directories. In the frontend directory, create a Dockerfile with the following content:

# Use an official Node.js runtime as a parent image
FROM node:16-alpine

# Set the working directory in the container
WORKDIR /app

# Copy package.json and package-lock.json to the working directory
COPY package*.json ./

# Install dependencies
RUN npm install

# Copy the rest of the application code
COPY . .

# Build the Next.js application
RUN npm run build

# Expose port 3000 for the Next.js application
EXPOSE 3000

# Command to start the Next.js server
CMD ["npm", "start"]

This Dockerfile uses the node:16-alpine image as the base image, sets the working directory, copies the package.json and package-lock.json files, installs the dependencies, copies the rest of the application code, builds the Next.js application, exposes port 3000, and defines the command to start the Next.js server. Next, create a Dockerfile in the backend directory with the following content:

FROM python:3.9-slim-buster

WORKDIR /app

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY . .

CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Before building the Docker image for the backend, you need to create a requirements.txt file listing the dependencies. In the backend directory, run:

pip freeze > requirements.txt

This command generates a requirements.txt file containing the list of installed packages. The Dockerfile uses the python:3.9-slim-buster image as the base image, sets the working directory, copies the requirements.txt file, installs the dependencies using pip, copies the rest of the application code, and defines the command to start the FastAPI server using uvicorn. Now, let’s create a docker-compose.yml file in the root directory of your project to orchestrate the frontend and backend containers:

version: "3.8"
services:
  frontend:
    build: ./frontend
    ports:
      - "3000:3000"
    depends_on:
      - backend
    environment:
      - NEXT_PUBLIC_BACKEND_URL=http://backend:8000
  backend:
    build: ./backend
    ports:
      - "8000:8000"

This docker-compose.yml file defines two services: frontend and backend . The frontend service builds the Docker image using the Dockerfile in the frontend directory, maps port 3000 to the host, and depends on the backend service. The backend service builds the Docker image using the Dockerfile in the backend directory and maps port 8000 to the host. The NEXT_PUBLIC_BACKEND_URL environment variable is set to http://backend:8000 , which is the address of the backend service within the Docker network. Finally, to build and run the application, navigate to the root directory of your project (the directory containing the docker-compose.yml file) and run:

docker-compose up --build

This command builds the Docker images and starts the containers. Open your browser and navigate to http://localhost:3000 to see your Next.js application running and communicating with the FastAPI backend.

Making it All Work Together

To make the frontend and backend work together, you’ll need to configure the Next.js application to fetch data from the FastAPI backend. In your Next.js component, use the fetch API or a library like axios to make requests to the backend endpoints. For example, you can modify the pages/index.js file to fetch a message from the backend:

import { useEffect, useState } from 'react';

function HomePage() {
  const [message, setMessage] = useState('');

  useEffect(() => {
    async function fetchMessage() {
      const res = await fetch(process.env.NEXT_PUBLIC_BACKEND_URL);
      const data = await res.json();
      setMessage(data.message);
    }

    fetchMessage();
  }, []);

  return (
    <div>
      <h1>Welcome to Next.js!</h1>
      <p>Message from backend: {message}</p>
    </div>
  );
}

export default HomePage;

This code uses the useEffect hook to fetch the message from the backend when the component mounts. The NEXT_PUBLIC_BACKEND_URL environment variable is used to construct the URL of the backend endpoint. Remember to set the NEXT_PUBLIC_BACKEND_URL environment variable in your docker-compose.yml file as shown in the previous section. This variable tells the Next.js application where to find the backend service within the Docker network. By following these steps, you can successfully integrate your Next.js frontend with your FastAPI backend and deploy the entire application using Docker. This setup provides a scalable, maintainable, and efficient solution for building full-stack web applications.

Conclusion

So there you have it! You’ve successfully integrated Next.js, FastAPI, and Docker. This powerful combination allows you to build modern, scalable, and maintainable web applications. You can now create more complex APIs, add databases, and implement user authentication. The possibilities are endless! Keep experimenting and building awesome stuff!