Building a Simple Cloud-Native App with Docker

In this demo, we'll create a basic cloud-native application using Docker. This app will run in a container, and we’ll explore how Docker enables cloud-native principles such as portability and isolation.

Step 1: Create a Simple Node.js Microservice

• First, create a server.js file:

  const express = require('express');
  const app = express();
  const port = process.env.PORT || 3000;

  app.get('/', (req, res) => {
    res.send('Hello from Docker Cloud-Native App!');
  });

  app.listen(port, () => {
    console.log(`Server running on port ${port}`);
  });

• Install dependencies:

  npm init -y
  npm install express

Step 2: Dockerize the Application

• Create a Dockerfile to define the container:

  # Use official Node.js image from Docker Hub
  FROM node:20

  # Set working directory inside the container
  WORKDIR /app

  # Copy package.json and install dependencies
  COPY package*.json ./
  RUN npm install

  # Copy the rest of the app's source code
  COPY . .

  # Expose the port the app will run on
  EXPOSE 3000

  # Command to run the app
  CMD ["node", "server.js"]

Step 3: Build and Run the Docker Container

• Build the Docker image:

  docker build -t cloud-native-app .

• Run the container:

  docker run -p 3000:3000 cloud-native-app

Step 4: Access the Application

• Open your browser and visit http://localhost:3000. You should see:

  Hello from Docker Cloud-Native App!

Conclusion

You've successfully built and run a simple cloud-native application using Docker. This app is now isolated in a container, and you can easily move or scale it across different environments without worrying about dependencies.