Configuration scripts#

Configuration scripts execute in Config Engine, and are deterministic, run-to-completion logic that is responsible for deriving the set of configurations to push to targets. Scripts can do this by either creating any other resource (like the script in the Fabric app creates VNET resource and so on), or by directly emitting NodeConfig resources - being the lowest level resource that is pushed to a target.

Due to executing in Config Engine, configuration scripts are limited to the following libraries available in its runtime:

• eda_common
• eda_config, for interacting with allocation pools (resources)

Triggering scripts#

A configuration script is attached to a particular resource via the applications manifest.yaml:

apiVersion: core.eda.nokia.com/v1
kind: Manifest
metadata:
  name: banners
spec:
  components:
    - crd:
        api:
          expose: readWrite
        path: banners/crds/banners.eda.local_banners.yaml
        schema: banners/openapiv3/eda_oas_banners.eda.local_banners.json
        ui:
          category: Banner
          name: Banner
    - script:
        path: banners/intents/banner/config_intent.py
        trigger:
          kind: Banner
        type: config

The manifest presented above results in the logic contained in banners/intents/banner/config_intent.py script being run whenever a Banner resource is created or updated. The Banner resource is added to the EDA API via the crd component defined in the same manifest file.

Entrypoint#

The entrypoint to a configuration script is the process_cr function, which is called by Config Engine with the resource object passed as a dictionary to the function.

def process_cr(cr):
    """Process Banner CR."""
    ...

The main task of a configuration script is to take this input dict which represents the declarative abstracted intent and either directly transform it to the node-specific configuration blob, or to emit sub-resources which will be processed by other scripts.

The configuration script also emits the input for the state script and triggers its execution.