docker-compose.builder.yml

# This Docker Compose file is designed to set up a build environment for the "mothership" Node.js app.
# It creates "base", "install", and "build" services using the same Node.js image and shared volumes.
# The "install" service runs "npm install" to install the project dependencies,
# and the "build" service executes "npm run build" to compile the application.
# By doing so, it ensures the build process happens within a container, guaranteeing consistency across different environments.
#

version: '3'  # Specifies the version of Docker Compose file format. As of 2021, version '3' is the most current.

services:  # Defines the set of services (i.e., containers) that comprise your application.

  base: &base  # An anchor (&) creates a named chunk of YAML that will be inserted where you use a pointer (*).
    image: node:19  # Specifies the Docker image to use for this service. We're using the Node.js image, version 19.
    volumes:  # Specifies the directories that should be shared between the host and the container.
      - nodemodules:/usr/src/app/node_modules  # Mounts the nodemodules volume at the specified path in the container.
      - .:/usr/src/app  # Mounts the current directory on the host to the specified path in the container.
    working_dir: /usr/src/app  # Defines the working directory for commands to run in.

  install:  # A service named "install".
    <<: *base  # Inserts the chunk of YAML defined under "base" above.
    command: npm install  # Runs "npm install" when the container starts.

  build:  # A service named "build".
    <<: *base  # Inserts the chunk of YAML defined under "base" above.
    command: npm run build  # Runs "npm run build" when the container starts.

volumes:  # Defines named volumes that can be used by any service.
  nodemodules:  # A named volume for node modules.
    external: true  # Indicates that this volume is managed outside of Docker Compose.