Garbage Collect

By default, KubeVela Application will recycle outdated resources when new version is deployed and confirmed to be healthy. In some cases, you may want to have more customized control to the recycle of outdated resources, where you can leverage the garbage-collect policy.

In garbage-collect policy, there are two major capabilities you can use.

Keep legacy resources

Suppose you want to keep the resources created by the old version of the application. Use the garbage-collect policy and enable the option keepLegacyResource.

1. create app

cat <<EOF | vela up -f -
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: first-vela-app
spec:
  components:
    - name: express-server
      type: webservice
      properties:
        image: oamdev/hello-world
        port: 8000
      traits:
        - type: gateway
          properties:
            class: traefik
            domain: 47.251.8.82.nip.io
            http:
              "/": 8000
  policies:
    - name: keep-legacy-resource
      type: garbage-collect
      properties:
        keepLegacyResource: true
EOF

Check the status:

vela status first-vela-app --tree

expected output

CLUSTER       NAMESPACE     RESOURCE                  STATUS
local     ─── default   ─┬─ Service/express-server    updated
                         ├─ Deployment/express-server updated
                         └─ Ingress/express-server    updated

1. update the app

cat <<EOF | vela up -f -
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: first-vela-app
spec:
  components:
    - name: express-server-1
      type: webservice
      properties:
        image: oamdev/hello-world
        port: 8000
      traits:
        - type: gateway
          properties:
            class: traefik
            domain: 47.251.8.82.nip.io
            http:
              "/": 8000
  policies:
    - name: keep-legacy-resource
      type: garbage-collect
      properties:
        keepLegacyResource: true
EOF

Check the status again:

vela status first-vela-app --tree

expected output

CLUSTER       NAMESPACE     RESOURCE                    STATUS
local     ─── default   ─┬─ Service/express-server      outdated
                         ├─ Service/express-server-1    updated
                         ├─ Deployment/express-server   outdated
                         ├─ Deployment/express-server-1 updated
                         ├─ Ingress/express-server      outdated
                         └─ Ingress/express-server-1    updated

You can see the legacy resources are reserved but the status is outdated, it will not be synced by periodically reconciliation.

1. delete the app

$ vela delete first-vela-app

If you hope to delete resources in one specified version, you can run kubectl delete resourcetracker first-vela-app-v1-default.

Persist partial resources

You can also persist part of the resources, which skips the normal garbage-collect process when the application is updated.

Take the following app as an example, in the garbage-collect policy, a rule is added which marks all the resources created by the expose trait to use the onAppDelete strategy. This will keep those services until application is deleted.

cat <<EOF | vela up -f -
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: garbage-collect-app
spec:
  components:
    - name: demo-gc
      type: webservice
      properties:
        image: oamdev/hello-world
      traits:
        - type: expose
          properties:
            port: [8000]
  policies:
    - name: garbage-collect
      type: garbage-collect
      properties:
        rules:
          - selector:
              traitTypes:
                - expose
            strategy: onAppDelete
EOF

You can find deployment and service created.

$ kubectl get deployment
NAME          READY   UP-TO-DATE   AVAILABLE   AGE
hello-world   1/1     1            1           74s
$ kubectl get service   
NAME          TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
hello-world   ClusterIP   10.96.160.208   <none>        8000/TCP   78s

If you upgrade the application and use a different component, you will find the old versioned deployment is deleted but the service is kept.

cat <<EOF | vela up -f -
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: garbage-collect-app
spec:
  components:
    - name: hello-world-new
      type: webservice
      properties:
        image: oamdev/hello-world
      traits:
        - type: expose
          properties:
            port: [8000]
  policies:
    - name: garbage-collect
      type: garbage-collect
      properties:
        rules:
          - selector:
              traitTypes:
                - expose
            strategy: onAppDelete
EOF
$ kubectl get deployment
NAME              READY   UP-TO-DATE   AVAILABLE   AGE
hello-world-new   1/1     1            1           10s
$ kubectl get service   
NAME              TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
hello-world       ClusterIP   10.96.160.208   <none>        8000/TCP   5m56s
hello-world-new   ClusterIP   10.96.20.4      <none>        8000/TCP   13s

If you want to deploy job-like components, in which cases the resources in the component are not expected to be recycled even after the application is deleted, you can use the component type selector and set strategy to never as follows.

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: garbage-collect-app
spec:
  components:
    - name: hello-world-new
      type: job-like-component
  policies:
    - name: garbage-collect
      type: garbage-collect
      properties:
        rules:
          - selector:
              componentTypes:
                - webservice
            strategy: never

An alternative selector for the component resources is the component name selector.

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: create-ns-app
spec:
  components:
    - name: example-addon-namespace
      type: k8s-objects
      properties:
        objects:
          - apiVersion: v1
            kind: Namespace
  policies:
    - name: garbage-collect
      type: garbage-collect
      properties:
        rules:
          - selector:
              componentNames:
                - example-addon-namespace
            strategy: never

Delete resource in the dependency order

If you want to garbage collect resources in the order of reverse dependency, you can add order: dependency in the garbage-collect policy.

note

This delete in order feature is only available for the resources that created in the components. Custom Resources deployed in WorkflowStep will not be included.

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: gc-dependency
  namespace: default
spec:
  components:
  - name: test1
    type: webservice
    properties:
      image: crccheck/hello-world
      port: 8000
    dependsOn:
      - "test2"
  - name: test2
    type: webservice
    properties:
      image: crccheck/hello-world
      port: 8000
    inputs:
      - from: test3-output
        parameterKey: test
  - name: test3
    type: webservice
    properties:
      image: crccheck/hello-world
      port: 8000
    outputs:
      - name: test3-output
        valueFrom: output.metadata.name
  policies:
    - name: gc-dependency
      type: garbage-collect
      properties:
        order: dependency

In the example above, component test1 depends on test2, and test2 need the output from test3.

So the creation order of deployment is: test3 -> test2 -> test1.

When we add order: dependency in garbage-collect policy and delete the application, the order of garbage collection is: test1 -> test2 -> test3.