Depends_on attribute#

The depends_on attribute allows to handle hidden resource or module/package dependencies that KForm cannot automatically infer. You only need to explicitly specify a dependency when a resource or module/package relies on another resource's behavior but does not access any of that resource's data in its arguments.

Processing impact#

The depends_on attributes instructs Kform to complete all actions on the dependency resource before performing any actions on the resource declaring the dependency. When the dependency resource is a module/package, depends_on affects the order in which Kform processes all of the resources associated with that module.

Instead of depends_on, we recommend using expression references to imply dependencies when possible. Expression references let KForm understand which value the reference derives from and avoid planning changes if that particular value hasn’t changed, even if other parts of the upstream object have planned changes.

Usage#

You can use the depends_on attribute in all block-types except the input block-type. It requires a list of references to other resources or child modules/packages in the same calling module/package expressed as a comma, seperated string. This list cannot include arbitrary expressions because the depends_on value must be known before Kform knows resource relationships and thus before it can safely evaluate expressions.

It is good practice to document why a depend_on attribute is needed. The following example uses depends_on to handle a "hidden" dependency on the kubernetes_manifest.my-namespace.

apiVersion: v1
kind: Namespace
metadata:
  name: my-namespace
  annotations:
    kform.dev/block-type: resource
    kform.dev/resource-type: kubernetes_manifest 

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
  namespace: my-namespace
  labels:
    app: my-app
  annotations:
    kform.dev/block-type: resource
    kform.dev/resource-type: kubernetes_manifest 
    kform.dev/resource-id: deployment
    #depend_on hidden dependency to the kubernetes_manifest.my-namespace resource
    kform.dev/depends_on: kubernetes_manifest.my-namespace 
spec:
  replicas: 1
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      serviceAccountName: my-app
      containers:
      - name: my-app
        image: my-image
        imagePullPolicy: Always