**Course Title:** Build and Package Management in Modern Development **Section Title:** Containerization with Docker **Topic:** Containerize a Node.js application using Docker.(Lab topic) **Table of Contents** ======================== 1. [Introduction to Containerizing a Node.js application](#introduction) 2. [Prerequisites and Setup](#prerequisites) 3. [Creating a Dockerfile for a Node.js application](#dockerfile) 4. [Building a Docker image](#building-image) 5. [Running a Docker container](#running-container) 6. [Managing dependencies and environment variables](#dependencies) 7. [Best practices and troubleshooting](#best-practices) 8. [Conclusion and Next Steps](#conclusion) Introduction to Containerizing a Node.js application ---------------------------------------------------------- Containerization is a powerful tool for ensuring consistency and reliability in software development. By containerizing a Node.js application, you can package your code, dependencies, and environment into a single, portable unit that can be easily deployed to any environment. In this lab, you will learn how to containerize a Node.js application using Docker. We'll cover the process of creating a Dockerfile, building a Docker image, and running a Docker container. Prerequisites and Setup --------------------------- Before you begin, make sure you have the following installed on your system: * Docker (https://www.docker.com/get-started) * Node.js (https://nodejs.org/en/download/) * npm or yarn (https://www.npmjs.com/ or https://yarnpkg.com/en/) Creating a Dockerfile for a Node.js application ------------------------------------------------- A Dockerfile is a text file that contains instructions for building a Docker image. Here's an example Dockerfile for a Node.js application: ```dockerfile # Use an official Node.js image as the base FROM node:14 # Set the working directory in the container to /app WORKDIR /app # Copy the package*.json files into the container COPY package*.json . # Install the dependencies RUN npm install # Copy the application code into the container COPY . . # Expose the port that the application will use EXPOSE 3000 # Run the command to start the application CMD ["npm", "start"] ``` Let's break down what each line of this Dockerfile does: * `FROM node:14`: This line tells Docker to use the official Node.js 14 image as the base for our own image. * `WORKDIR /app`: This line sets the working directory in the container to `/app`. * `COPY package*.json .`: This line copies the `package.json` file into the container. * `RUN npm install`: This line installs the dependencies listed in the `package.json` file. * `COPY . .`: This line copies the application code into the container. * `EXPOSE 3000`: This line tells Docker to expose port 3000 from the container to the host machine. * `CMD ["npm", "start"]`: This line sets the default command to run when the container starts. Building a Docker image ------------------------- To build a Docker image from the Dockerfile, navigate to the directory containing the Dockerfile and run the following command: ```bash docker build -t my-node-app . ``` This command tells Docker to build an image with the tag `my-node-app` using the instructions in the Dockerfile. Running a Docker container --------------------------- To run a Docker container from the image we just built, use the following command: ```bash docker run -p 3000:3000 my-node-app ``` This command tells Docker to start a new container from the `my-node-app` image and map port 3000 on the host machine to port 3000 in the container. Managing dependencies and environment variables ---------------------------------------------- To manage dependencies and environment variables in your Docker container, you can use the following techniques: * Use the `npm install` command to install dependencies during the build process. * Use environment variables to pass configuration settings to the container. * Use a `.env` file to store sensitive configuration settings. Best practices and troubleshooting ------------------------------------ Here are some best practices to keep in mind when containerizing a Node.js application: * Use official images as the base for your own images. * Keep your Dockerfile short and sweet. * Use environment variables to pass configuration settings to the container. * Use a `.env` file to store sensitive configuration settings. If you encounter issues during the build or run process, here are some troubleshooting tips: * Check the Dockerfile for syntax errors. * Verify that the dependencies are installed correctly. * Check the environment variables for correct values. Conclusion and Next Steps --------------------------- In this lab, you learned how to containerize a Node.js application using Docker. You created a Dockerfile, built a Docker image, and ran a Docker container. You also learned some best practices and troubleshooting tips to keep in mind. In the next topic, we'll cover "Understanding Build and Dependency Management Best Practices". This topic will provide you with more insights into managing dependencies and building your application in a structured and efficient manner. **What's next?** Read the next topic: "Understanding Build and Dependency Management Best Practices" to learn more about managing dependencies and building your application. **Leave a comment/ask for help?** If you have any questions or need help with any of the concepts covered in this topic, feel free to ask in the comments section below.