service-dependencies-alphabetical-order-rule.md

Service Dependencies Alphabetical Order Rule

Ensures that the list of services within depends_on is sorted alphabetically. This rule promotes consistency and readability by maintaining a predictable order for service dependencies.

This rule is fixable. The linter can automatically reorder the list of services in depends_on without altering their internal content.

• Rule Name: service-dependencies-alphabetical-order
• Type: warning
• Category: style
• Severity: info
• Fixable: true

Problematic code example

services:
  web:
    image: image
    depends_on:
      - redis
      - db

services:
  web:
    image: nginx
    depends_on:
      redis:
        condition: service_started
      db:
        condition: service_healthy
        restart: true

Correct code example

services:
  web:
    image: nginx
    depends_on:
      - db
      - redis

services:
  web:
    image: nginx
    depends_on:
      db:
        condition: service_healthy
        restart: true
      redis:
        condition: service_started

Rule Details and Rationale

Sorting the list of services within depends_on alphabetically enhances readability and predictability, making it easier to manage service dependencies. By maintaining a consistent order, developers can avoid confusion when working on large configurations.

Version

This rule was introduced in Docker-Compose-Linter 1.0.0.

References

• Forum Discussion: Docker-compose.yml Best Practices
• Docker Compose Reference