benhall / express-demo

This documentation covers the use of Docker within the development environment for the benhall/express-demo project, detailing the necessary configurations and commands needed to successfully run the application using Docker.

Prerequisites

Ensure that Docker and Docker Compose are installed on your system. This setup assumes familiarity with JavaScript, Docker, and Node.js.

Directory Structure

Before diving into the Docker configuration, it’s essential to understand the structure of the project. The key files relevant for Docker usage include:

  • Dockerfile
  • docker-compose.yml
  • Application source files (JavaScript, Handlebars templates, CSS)

Dockerfile

The Dockerfile is a critical component that defines how to build the Docker image for the application. Below is an in-depth look at the Dockerfile used in the benhall/express-demo project.

# Ability to override to ensure it matches .nvmrc
ARG NODE=20.11.0
FROM node:${NODE}

WORKDIR /usr/src/app

# Install Webpack + dependencies for compiling
ENV ADBLOCK=1
COPY package*.json ./
RUN npm ci

COPY . .

# Rebuild Webpack
RUN npm run build 

FROM node:${NODE}

# Create app directory and define defaults
WORKDIR /usr/src/app
EXPOSE 3000
CMD [ "./bin/www" ]
ENV ADBLOCK=1

# Install app dependencies
COPY package*.json ./
RUN npm ci --production

# Bundle app source
COPY --from=0 /usr/src/app/public public
COPY --from=0 /usr/src/app/webpack.version.json .
COPY . .

Explanation

  1. Base Image and Node Version: The image starts from a specified Node.js version defined by the ARG NODE. The default is set to 20.11.0.

  2. Working Directory: The WORKDIR is set to /usr/src/app where the application code resides.

  3. Dependency Installation: Initially, it copies the package.json and package-lock.json files. The command RUN npm ci installs dependencies specified in these files while ensuring a clean installation.

  4. Code Copy: The command COPY . . copies the entire application source code to the container.

  5. Webpack Build: The RUN npm run build command compiles the application, building necessary assets.

  6. Second Stage Build: A second stage of the build process follows the initial setup to further streamline the image. It starts with another FROM node:${NODE}, setting up a new layer ensuring that only relevant production dependencies are incorporated afterward.

  7. Expose Port: The application exposes Port 3000, allowing external access to the web services provided by the application.

  8. Command to Start Application: The command CMD [ "./bin/www" ] specifies the entry point for the application, activating the server.

Development Customization

For development purposes, you might customize the build by removing the production flag from the npm ci command to ensure all development dependencies are included. This would modify the respective line in the Dockerfile:

RUN npm ci

Docker Compose Configuration

The docker-compose.yml file manages multi-container Docker applications. In the case of benhall/express-demo, it specifies how to build and run the web service.

version: "3.9"
services:
  web:
    build: .
    ports:
      - "3000:3000"

Explanation

  1. Version: This specifies the version of the Docker Compose file format being used.

  2. Services:

    • Under the services section, a service named web is defined.
    • The build: . line indicates that Docker should build the Dockerfile in the current directory.
    • The ports section maps the host’s port 3000 to the container’s port 3000.

Getting Started

To run the application using Docker, execute the following command in the project root directory:

docker-compose up --build

This command will build the Docker image as defined in the Dockerfile, start the service as configured in the docker-compose.yml, and expose it on port 3000.

Conclusion

The Docker configuration for the benhall/express-demo project facilitates a robust and flexible development environment. By following the steps outlined above, developers can efficiently set up and run the application within a Docker container, ensuring consistency across various development environments.

The provided configurations and commands are essential for expert developers looking to work with containerized applications within this specific project context.