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. Thename
,type
, andfieldPaths
are required fields,description
andrequired
are optional fields.- The parameter
name
must be unique in aComponentDefinition
. 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, includingstring
,number
, andboolean
, whilearray
andobject
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 examplespec.replicas
,spec.containers[0].image
.
- The parameter
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"