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Version: v1.0

How-to

In this section, it will introduce how to use simple template to declare Kubernetes API resource into a component.

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

Declare ComponentDefinition#

Here is a simple 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 simple 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 simple 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"
Last updated on by kubevela-bot