Creating Resources

Using [[create_resource]] to Build the Graph

Creating Derived Resources: [[create_resource]]

This is the primary directive for creating new resources. It transforms a single origin_resource into one or more new, derived resources, forming the backbone of your architectural model. [[create_resource]] is versatile and supports several distinct patterns for generating your graph:

1. Direct Derivation: Creating a new resource based on the existence of an origin_resource (e.g., a server for every application). This can be unconditional or made conditional with match_on.
2. Data-Driven Derivation: Creating new resources based on the data inside a property of an origin_resource (using create_from). This is a powerful convention-over-configuration pattern for creating multiple resources from a list or string.
3. Generation from a Data Source: Creating new resources by iterating over an abstract list of data from the header (using create_from). This is ideal for bootstrapping parts of a graph from configuration.

The following sections explain each pattern in detail.

Unconditional Creation

This rule creates one new resource for every origin_resource.

Goal: For every application, create a corresponding server resource.

# The model reads resources of type "application".
origin_resource = "application"

server_specs = { standard_cpu = 4, large_cpu = 8 }

[[create_resource]]
resource_type = "server"
relation_type = "HOSTED_ON"
name = "{{origin_resource.name}}_server"
[create_resource.properties]
os = "Linux"
cpu_cores = "{{ server_specs.standard_cpu }}" # Access data from header
managed_by = "{{origin_resource.owner}}"   # Inherit property from application

The [[create_resource]] block has several powerful options:

relation_properties: You can also add properties to the newly created relationship using a [create_resource.relation_properties] block.

[[create_resource]]
resource_type = "server"
relation_type = "HOSTED_ON"
name = "{{origin_resource.name}}_server"
[create_resource.properties]
# ... server properties
[create_resource.relation_properties]
source_app_env = "{{ origin_resource.environment }}"
managed = true

• Result: An application named billing-api results in a new server named billing-api_server. (application:billing-api) -[HOSTED_ON]-> (server:billing-api_server)

This process can be visualized as follows:

graph TD
    subgraph "Input & Rules"
        A["Origin Resource: <code>application</code>"]
        B["<code>[[create_resource]]</code> rule<br/>to create a <code>server</code>"]
    end
    subgraph "rescile Process"
        C{"For each <code>application</code>..."}
        D["1. Render <code>name</code>, <code>properties</code>, and <code>relation_properties</code> from templates"]
        E["2. Create new <code>server</code> resource"]
        F["3. Create <code>HOSTED_ON</code> relationship with its properties"]
    end
    subgraph "Output Graph"
        G(application: billing-api)
        H(server: billing-api_server)
        G -- "HOSTED_ON<br/>{ source_app_env: 'prod', ... }" --> H
    end
    A & B --> C --> D --> E --> F
    F --> G & H

Conditional Creation with match_on

Goal: For every application running in the prod environment, create a corresponding classification resource to label it as restricted.

# In data/models/classification.toml
origin_resource = "application"

[[create_resource]]
match_on = [
  { property = "environment", value = "prod" }
]
resource_type = "classification"
relation_type = "IS_CLASSIFIED_AS"
name = "{{origin_resource.name}}_prod"
[create_resource.properties]
level = "Restricted"

• Result: An application with environment: "prod" will be linked to a new classification resource named <app_name>_prod with level: "Restricted". Applications in other environments will be ignored by this rule.

The match_on block supports several operators:

To express OR logic, use a nested or block:

origin_resource = "server"

match_on = [
  { property = "status", value = "active" }, # Must be active AND...
  { or = [ [ { property = "cores", greater = 8 } ], [ { property = "legacy_system", value = "false" } ] ] } # (...have >8 cores OR not be a legacy system)
]