Compose

Running multiple containers

Why

• Configure relationships between containers

• Save docker container run settings in easy-to-read file

• create one-liner development environment startups

Comprised of 2 separate but related things:

• YAML formatted file that describes solution options for:

  • containers

  • volumes

  • networks

• A CLI tool docker-compose used for local dev/test automation

Installed automatically on Mac and Windows with Docker Desktop, for Linux must be downloaded separately.

Links

• Compose on GitHub

• Compose documentation

Example

version: '3'

services:
  drupal:
    image: drupal:8-apache
    ports:
    - '8080:80'
    volumes:
    - drupal-modules:/var/www/html/modules
    - drupal-profiles:/var/www/html/profiles
    - drupal-sites:/var/www/html/sites
    - drupal-themes:/var/www/html/themes
    restart: always
  postgres:
    image: postgres:10
    environment:
      POSTGRES_PASSWORD: pgPass@1
    restart: always

volumes:
  drupal-modules:
  drupal-profiles:
  drupal-sites:
  drupal-themes:

Commands

To start

docker-compose up [--build] [...options]

To tear down

docker-compose down [-v] [...other options]

Using compose with build

• compose can also build your images

• will build them with docker-compose up if not found in cache

• also rebuild with docker-compose build

• great for complex builds that have lots of vars or build args

Example

version: '3'

services:
  proxy:
    build:
      context: .
      dockerfile: nginx.Dockerfile
    image: nginx-custom
    ports:
    - '80:80'
  web:
    image: httpd
    volumes:
    - ./html:/usr/local/apache2/htdocs/

Restart policies

• "no" - never attempt to restart this container if it stops or crashes (must be in "")

• always - if this container stops, for any reason, always attempt to restart it

• on-failure - only restart if the container stops with an error code

• unless-stopped - always restart unless we forcibly stop it