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Component Inheritance

Atmos Design Pattern

The Component Inheritance pattern allows an Atmos component to inherit configuration from a base component, then override specific values. This creates DRY configurations where common settings are defined once and reused.

Use-cases​

Use the Component Inheritance pattern when:

  • Multiple components share common configuration

  • You want to define defaults once and override only what differs

How It Works​

A component inherits from a base component using metadata.inherits:

stacks/catalog/vpc/defaults.yaml

components:
  terraform:
    vpc/defaults:
      vars:
        enabled: true
        nat_gateway_enabled: true
        max_subnet_count: 3

stacks/deploy/dev.yaml

import:
  - catalog/vpc/defaults

components:
  terraform:
    vpc:
      metadata:
        component: vpc
        inherits:
          - vpc/defaults
      vars:
        # Override only what's different
        max_subnet_count: 2

The vpc component inherits all vars from vpc/defaults, then overrides max_subnet_count.

Inheritance Order​

When multiple sources define the same value, later sources win:

base component → inherited components (in order) → inline vars

This allows progressive specialization from general defaults to specific overrides.

References​