Variables

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Reuse specs across environments and services with minimal templating.

Overview

Variables can be declared in your specs and overridden at runtime. They resolve into Terraform variables so you can keep a single spec and tune it per environment.

Declare variables

Define inputs in your spec and reference them with ${var.<name>}: 

variables:
  min_nodes: "2"
  max_nodes: "5"
modules:
  - id: eks
    type: aws_eks
    inputs:
      min_nodes: "${var.min_nodes}"
      max_nodes: "${var.max_nodes}"

Override at runtime

Use repeatable --var flags or environment variables: 

pltf terraform apply -f env.yaml -e prod --var min_nodes=3 --var max_nodes=6
# or
PLTF_VAR_min_nodes=3 PLTF_VAR_max_nodes=6 pltf generate -f env.yaml -e prod

Scope rules

  • Stack variables provide shared defaults and are auto‑applied.
  • Environment/Service variables are defined at the top level and must not reuse stack variable names.

Parent outputs

Services can use environment outputs via ${parent.<output>}: 

public_uri: "${parent.domain}/hello"

Placeholder catalog

  • ${env_name}, ${layer_name} (intrinsics)
  • ${module.<module_name>.<output_name>}
  • ${parent.<output_name>} (service only)
  • ${var.<name>} (declared variables or CLI/env overrides)

Notes

  • Required variables without defaults must be provided via --var or env.
  • Precedence: stack variables → spec variables → CLI --var.
  • Secrets remain Terraform variables; non-secret values may also be mirrored into locals for wiring.
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