Variables

Architect helps automate a huge chunk of application configuration by injecting the addresses and details of other components and services, but there are still many cases where you'd need to provide critical values manually like credentials for external services.

Architect makes it easy for component authors to declare the variables their application needs by using variables:

variables:
  my_key:
    default: default-value
    description: My description
    required: false

Merging values

By default, values for variables are intended to be provided manually by the developer who deploy's the component. However, there are some cases where we want to collect variable values from upstream components (e.g. components that cite this ones as a dependency) instead. To enable this, variables can be annotated with the merge flag indicating that values provided from each source should be merged together in an array.

A good example of this is collecting a list of allowed return URLs to prevent XSS attacks. Upstream applications can provide one or more values for the variable when they declare the component:

# architect/backend component
variables:
  allowed_return_urls:
    description: URLs that the service can safely redirect to after auth flows
    merge: true

ingresses:
  auth:
    service: auth
    headers:
      Access-Control-Allow-Origin: ${{ variables.allowed_return_urls }}
      Access-Control-Allow-Methods: '["GET", "OPTIONS", "POST", "PUT", "DELETE"]'
      Access-Control-Allow-Headers: '*'
      Access-Control-Allow-Credentials: 'true'

---
# architect/frontend component
ingresses:
  app:
    service: app

dependencies:
  backend:
    component: architect/backend
    variables:
      allowed_return_urls:
        - ${{ ingresses.app.url }}