Docker Tutorial for CMSC389T Project

This is a tutorial for using Docker to containerize your web application. It is intended for students in CMSC389T at the University of Maryland.

Understanding the Dockerfile

A Dockerfile is a text document containing all the commands a user could call to assemble an image. Here's a breakdown of each part:

FROM

FROM node:10-alpine

• Specifies the base image for your Docker image. In this case, node:10-alpine is a lightweight version of the Node.js 10 image.

RUN

RUN mkdir -p /home/node/app && chown -R node:node /home/node/app

• Executes shell commands in the container. Here, it creates a directory /home/node/app and sets its owner to the node user.

WORKDIR

WORKDIR /home/node/app

• Sets the working directory for the subsequent Dockerfile commands.

COPY

COPY package*.json ./

• Copies package.json and package-lock.json (if available) from your project directory into the container.

USER

USER node

• Switches to the node user for security purposes.

RUN (npm install)

RUN npm install

• Installs the dependencies defined in package.json.

EXPOSE

EXPOSE 8080

• Informs Docker that the container listens on port 8080 at runtime.

COPY (App Code)

COPY --chown=node:node . .

• Copies your app's source code into the container, setting the node user as the owner.

CMD

CMD node app.js

• Specifies the command to run the app. In this case, it's starting a Node.js app.

Understanding docker-compose.yml

The docker-compose.yml file defines the services, networks, and volumes for your Docker application.

Services

nodejs

• Builds and configures the Node.js service. The build section specifies the Dockerfile and context for building the image. The image and container_name provide names for the image and the container, respectively.

webserver

• Configures the Nginx web server. It uses the nginx:mainline-alpine image, sets container parameters, and defines volume mappings and dependencies.

Volumes

• Persistent data storage configurations. The web-root volume is configured with local driver options, including the absolute path to your web template folder.

Networks

• Defines the network configuration. In this case, a bridge network is used for inter-container communication.

Visualizing the Architecture

You can use a diagramming tool like Mermaid to illustrate the architecture. For example:

graph LR
    A[Browser] -- HTTP Requests --> B{Nginx Container}
    B --> C[Node.js Container]
    C --> D{Node App}

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This shows the flow from the user's browser through Nginx to the Node.js app.

If you have gotten to the bottom of this README, thank you for reading, and as a reward, note that the docker-compose.yml and Dockerfile files that are within this repo are the ones that I used when I created this project (so they are tested and work). Meaning that you could just copy and paste them into your own project and they should work with the exception of the absolute path to the web template folder in the docker-compose.yml file. You will need to change that to the absolute path to your web template folder.