Dockerizing a Node.js and MongoDB app with CI/CD Pipelines on Gitlab for staging and production environments.

Dockerfile

# Use an official Node runtime as a parent image
FROM node:latest

# Set the working directory to /app
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install any needed packages specified in package.json as well as PM2 to ensure the app integrity.
RUN npm install
RUN npm install pm2 -g

# Make port 80 available to the world outside this container
EXPOSE 80

# Run app.js under PM2 when the container launches
CMD ["pm2-runtime", "app.js"]