Creating compose.yaml files

Intermediate Docker

Mike Metzger

Data Engineering Consultant

YAML

Yet Another Markup Language
- YAML Ain't Markup Language
Text file, but spacing matters (like Python)
Used in many development scenarios for configuration
Rules can be tricky, mainly keep entries lined up as in examples

services:
  postgres:
    container_name: postgres
    image: postgres:latest
    ports:
      - "5432:5432"
    restart: always
  pgadmin:
    container_name: pgadmin
    image: dpage/pgadmin4:latest
    ports:
      - "5050:80"
    restart: always

Main sections

Different sections handle different components
services: list the containers to load
networks: handles networking definitions
volumes: controls any volume mounting
configs: handles configuration options without custom images
secrets: Provides options to handle passwords, tokens, API keys, etc
Refer to the Docker Compose Documentation for more information

services:
  ... # Define containers

networks:
  ... # Define any networking details

volumes:
  ... # Define storage requirements

configs:
  ... # Define special config details

secrets:
  ... # Define passwords / etc

¹ https://docs.docker.com/compose/compose-file/

Services section

Defines all required resources for the application
Primarily specifies the containers and images to be used
Extensive options available, but only apply to the individual container(s)
Indention is applied as needed
First subsection is the name of each component, followed by the settings

Services example

services:

  # Resource name
  postgres:

    # Container name, otherwise random
    container_name: postgres

    # Container image to use
    image: postgres:latest

    # Any port mapping required
    ports:
      # Network details
      - "5432:5432"

  # Next resource
  pgadmin:
      ...

Resource name
container_name:, the assigned name of the container otherwise it's random
image:, which container image to use
ports:, contains a list of any port mapping required
Followed by next resources required

Additional comments

config.yaml syntax is extensive
- Covering very small portion of compose.yaml options
- Review the documentation!
It's typically not required to build a compose.yaml file from scratch

¹ https://docs.docker.com/compose/compose-file/

Let's practice!

Intermediate Docker