Dependency

This section will introduce how to specify dependencies for workflow steps.

Note: In the current version (1.4), the steps in the workflow are executed sequentially, which means that there is an implicit dependency between steps, ie: the next step depends on the successful execution of the previous step. At this point, specifying dependencies in the workflow may not make much sense.

In future versions (1.5+), you will be able to display the execution method of the specified workflow steps (eg: change to DAG parallel execution). At this time, you can control the execution of the workflow by specifying the dependencies of the steps.

How to use

In KubeVela, the dependencies between steps can be specified by dependsOn in the steps.

For example: we want to send a message notification after deploying the component:

...
workflow:
  steps:
    - name: comp
      type: apply-component
    - name: notify
      type: notification
      dependsOn:
        - comp

In this case, KubeVela waits for the completion of the step comp before executing the notify step to send a message notification.

Apply the following YAML:

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: dependsOn-app
  namespace: default
spec:
  components:
  - name: express-server
    type: webservice
    properties:
      image: oamdev/hello-world
      ports:
        - port: 8000
  workflow:
    steps:
      - name: comp
        type: apply-component
        properties:
          component: express-server
      - name: slack-message
        type: notification
        dependsOn:
          - comp
        properties:
          slack:
            url:
              value: <your slack url>
            message:
              text: depends on comp

Expected outcome

Use vela status to check the status of the Application:

$ vela status depends
About:

  Name:         depends
  Namespace:    default
  Created at:   2022-06-24 17:20:50 +0800 CST
  Status:       running

Workflow:

  mode: StepByStep
  finished: true
  Suspend: false
  Terminated: false
  Steps
  - id:e6votsntq3
    name:comp
    type:apply-component
    phase:succeeded
    message:
  - id:esvzxehgwc
    name:slack-message
    type:notification
    phase:succeeded
    message:

Services:

  - Name: express-server
    Cluster: local  Namespace: default
    Type: webservice
    Healthy Ready:1/1
    No trait applied

As you can see, all step statuses are succeeded. And when the component is successfully deployed, a message is also sent in slack.