Attach Traits

Traits in KubeVela can be attached to Helm based component seamlessly.

In this sample application below, we add two traits, scaler and virtualgroup to a Helm based component.

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: myapp
  namespace: default
spec:
  components:
    - name: demo-podinfo 
      type: webapp-chart
      properties: 
        image:
          tag: "5.1.2"
      traits:
        - type: scaler
          properties:
            replicas: 4
        - type: virtualgroup
          properties:
            group: "my-group1"
            type: "cluster"

Note: when use traits with Helm based component, please make sure the target workload in your Helm chart strictly follows the qualified-full-name convention in Helm. For example in this chart, the workload name is composed of release name and chart name.

This is because KubeVela relies on the name to discovery the workload, otherwise it cannot apply traits to the workload. KubeVela will generate a release name based on your Application name and component name automatically, so you need to make sure never override the full name template in your Helm chart.

Verify traits work correctly

You may need to wait a few seconds to check the trait attached because of reconciliation interval.

Check the scaler trait takes effect.

$ kubectl get manualscalertrait
NAME                            AGE
demo-podinfo-scaler-d8f78c6fc   13m

$ kubectl get deployment myapp-demo-podinfo -o json | jq .spec.replicas
4

Check the virtualgroup trait.

$ kubectl get deployment myapp-demo-podinfo -o json | jq .spec.template.metadata.labels
{
  "app.cluster.virtual.group": "my-group1",
  "app.kubernetes.io/name": "myapp-demo-podinfo"
}

Update Application

After the application is deployed and workloads/traits are created successfully, you can update the application, and corresponding changes will be applied to the workload instances.

Let’s make several changes on the configuration of the sample application.

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: myapp
  namespace: default
spec:
  components:
    - name: demo-podinfo 
      type: webapp-chart
      properties: 
        image:
          tag: "5.1.3" # 5.1.2 => 5.1.3 
      traits:
        - type: scaler
          properties:
            replicas: 2 # 4 => 2
        - type: virtualgroup
          properties:
            group: "my-group2" # my-group1 => my-group2
            type: "cluster"

Apply the new configuration and check the results after several minutes.

Check the new values (image.tag = 5.1.3) from application’s properties are assigned to the chart.

$ kubectl get deployment myapp-demo-podinfo -o json | jq '.spec.template.spec.containers[0].image'
"ghcr.io/stefanprodan/podinfo:5.1.3"

Under the hood, Helm makes an upgrade to the release (revision 1 => 2).

$ helm ls -A
NAME                NAMESPACE   REVISION    UPDATED                                 STATUS      CHART           APP VERSION
myapp-demo-podinfo  default     2           2021-03-15 08:52:00.037690148 +0000 UTC deployed    podinfo-5.1.4   5.1.4

Check the scaler trait.

$ kubectl get deployment myapp-demo-podinfo -o json | jq .spec.replicas
2

Check the virtualgroup trait.

$ kubectl get deployment myapp-demo-podinfo -o json | jq .spec.template.metadata.labels
{
  "app.cluster.virtual.group": "my-group2",
  "app.kubernetes.io/name": "myapp-demo-podinfo"
}

Detach Trait

Let’s have a try detach a trait from the application.

apiVersion: core.oam.dev/v1alpha2
kind: Application
metadata:
  name: myapp
  namespace: default
spec:
  components:
    - name: demo-podinfo 
      type: webapp-chart 
      settings: 
        image:
          tag: "5.1.3"
      traits:
        # - name: scaler
        #   properties:
        #    replicas: 2 
        - name: virtualgroup
          properties:
            group: "my-group2"
            type: "cluster"

Apply the application and check manualscalertrait has been deleted.

$ kubectl get manualscalertrait
No resources found