kubevela.github.io/docs/kube/component.md

title
How-to

In this section, it will introduce how to use raw K8s Object to declare app components via ComponentDefinition.

Before reading this part, please make sure you've learned the definition and template concepts.

Declare ComponentDefinition

Here is a raw template based ComponentDefinition example which provides a abstraction for worker workload type:

apiVersion: core.oam.dev/v1beta1
kind: ComponentDefinition
metadata:
  name: kube-worker
  namespace: default
spec:
  workload: 
    definition: 
      apiVersion: apps/v1
      kind: Deployment
  schematic:
    kube: 
      template:
        apiVersion: apps/v1
        kind: Deployment
        spec:
          selector:
            matchLabels:
              app: nginx
          template:
            metadata:
              labels:
                app: nginx
            spec:
              containers:
              - name: nginx
                ports:
                - containerPort: 80 
      parameters: 
      - name: image
        required: true
        type: string
        fieldPaths: 
        - "spec.template.spec.containers[0].image"

In detail, the .spec.schematic.kube contains template of a workload resource and configurable parameters.

• .spec.schematic.kube.template is the raw template in YAML format.
• .spec.schematic.kube.parameters contains a set of configurable parameters. The name, type, and fieldPaths are required fields, description and required are optional fields.
  • The parameter name must be unique in a ComponentDefinition.
  • type indicates the data type of value set to the field. This is a required field which will help KubeVela to generate a OpenAPI JSON schema for the parameters automatically. In raw template, only basic data types are allowed, including string, number, and boolean, while array and object are not.
  • fieldPaths in the parameter specifies an array of fields within the template that will be overwritten by the value of this parameter. Fields are specified as JSON field paths without a leading dot, for example spec.replicas, spec.containers[0].image.

Declare an Application

Here is an example Application.

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: myapp
  namespace: default
spec:
  components:
    - name: mycomp
      type: kube-worker
      properties: 
        image: nginx:1.14.0

Since parameters only support basic data type, values in properties should be simple key-value, <parameterName>: <parameterValue>.

Deploy the Application and verify the running workload instance.

$ kubectl get deploy
NAME                     READY   UP-TO-DATE   AVAILABLE   AGE
mycomp                   1/1     1            1           66m

And check the parameter works.

$ kubectl get deployment mycomp -o json | jq '.spec.template.spec.containers[0].image'
"nginx:1.14.0"