Docker Compose

• Define and run multi-containers applications
• Define using YAML files
• Run using the docker CLI with the compose plugin
• Docker compose
• Compose Specs
• https://compose-spec.io

Compose V2

• GA at DockerCon Live 2022
• Incorporates the docker compose command into the Docker CLI
• You type docker compose instead of docker compose
• Drop-in replacement for docker compose
• docker compose commands maps directly to the docker compose ones
• Installed with Docker Desktop
• Linux: apt-get install docker compose-plugin
• Written in Go
• docker compose is written in Python
• In summary, it's simply a faster version of the good old docker compose tool that is shipped as a plugin instead of a Python app

Use Cases

• Workloads that don't require a full orchestrator
• Development and tests
• Use of a service that can run Docker Compose files
• Azure App Service
• AWS ECS
• Virtual machines

Docker Compose Cheat Sheet

docker compose build                  # Build the images
docker compose start                  # Start the containers
docker compose stop                   # Stop the containers
docker compose up -d                  # Build and start
docker compose ps                     # List what's running
docker compose rm                     # Remove from memory
docker compose down                   # Stop and remove
docker compose logs                   # Get the logs
docker compose exec [container] bash  # Run a command in a container

Compose V2 - New Commands

docker compose --project-name test1 up -d               # Run an instance as a project
docker compose -p test2 up -d                           # Shortcut
docker compose ls                                       # List running projects
docker compose cp [containerID]:[SRC_PATH] [DEST_PATH]  # Copy files from the container
docker compose cp [SRC_PATH] [containerID]:[DEST_PATH]  # Copy files to the container

Example

# build the service
docker compose build

# builds, (re)creates, starts, attaches to containers for a service
docker compose up

# list the services
docker compose ps

# bring down what was created by UP
docker compose down

See L09-04 Docker Compose if you want to see a full example.

Compose Features

Resource Limits

services:
  redis:
    image: redis:alpine
    deploy:
      resources:
        limits:
          cpus: '0.50'
          memory: 150M
        reservations:
          cpus: '0.25'
          memory: 20M

Environment Variables

services:
  web:
    image: nginx:alpine
    environment:
      - DEBUG=1
      - FOO=BAR

Networking

services:
  web:
    image: nginx:alpine
    ports:
      - "8080:80"
  db:
    image: postgres
    ports:
      - "5432"

services:
  web:
    image: nginx:alpine
    networks:
      - frontend
  app:
    image: myapp
    networks:
      - frontend
      - backend
  db:
    image: postgres
    networks:
      - backend
      - frontend

networks:
  frontend:
  backend:

Dependence

services:
  web:
    build: .
    depends_on:
      - db
  db:
    image: postgres

Volumes - Named

services:
  app:
    image: myapp
    depends_on:
      - db
  db:
    image: postgres
    volumes:
      - db-data:/etc/data
    networks:
      - back-tier
volumes:
  db-data:

Volumes - Anonymous

services:
  app:
    image: myapp
    depends_on:
      - db
  db:
    image: postgres
    volumes:
      - ./db:/etc/data
    networks:
      - back-tier

Restart Policy

services:
  app:
    image: myapp
    restart: always
    depends_on:
      - db
  db:
    image: postgres
    restart: always

• по
• The default restart policy.
• Does not restart a container under any circumstances.
• always
• Always restarts the container until its removal.
• on-failure
• Restarts a container if the exit code indicates an error.
• unless-stopped
• Restarts a container irrespective of the exit code but will stop restarting when the service is stopped or removed.