[Feature] Support user defined context in vela core about kubevela

[FogDong]

So for an application with context, it will be like:

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: test
  namespace: default
spec:
  components:
  - name: express-server
    type: webservice
    properties:
      image: oamdev/hello-world
      ports:
        - port: 8000
  workflow:
    context:
       myName: "my-comp"
    steps:
      - name: apply-comp
        type: apply-component
        properties:
          component: express-server

And if in the definition we have cue template like:

name: context.myName

Then when the application is deployed, the name will be my-comp.

I'd like to discuss more about where we should put this context field. If we put the context in parallel with the component it will make more sense. However, this will also change the model of OAM so we'll probably need more discussion.

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: test
  namespace: default
spec:
  components:
  - name: express-server
    type: webservice
    properties:
      image: oamdev/hello-world
      ports:
        - port: 8000
  context:
    myName: "my-comp"
  workflow:
    steps:
      - name: apply-comp
        type: apply-component
        properties:
          component: express-server

[testinfected]

We need something similar to pass additional runtime information to the workflow steps. It is possible in standalone workflow runs but not in Applications, which is a shame, and thus we cannot refer to existing workflow templates which expect context parameters.

It would be a great addition if we could define runtime context information for the workflow steps, the same way we do it for workflow runs.

Thanks

[FogDong]

Hi @testinfected
According to your description, the capability you want is to use the context in workflow steps but not trait and component, right?
If so, we can add the context field inside the workflow but not the whole application like:

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: test
  namespace: default
spec:
  components:
  - name: express-server
    type: webservice
    properties:
      image: oamdev/hello-world
      ports:
        - port: 8000
  workflow:
    context:
       myName: "my-comp"
    steps:
      - name: apply-comp
        type: apply-component
        properties:
          component: express-server

[testinfected]

Hi @FogDong yes this is correct.

One use case is using an external workflow template. It's possible to add context parameters in workflow runs, but not applications.

Thanks

[FogDong]

I think it's a valuable feature for Application and I'm good with supporting it.
If other maintainers also like this idea then I'll start working on this.
cc @wonderflow @StevenLeiZhang

[oanasc]

For us would be beneficial to be able to use the user context in the applications and traits like in your first example
If you add it just to workflow steps will is still be available to use in the application cue templates?

[FogDong]

For us would be beneficial to be able to use the user context in the applications and traits like in your first example If you add it just to workflow steps will is still be available to use in the application cue templates?

If we want this context to be used in the whole Application, then we may need to re-struct the Application template to add context field, which might affect the OAM model and need more discussion.

[oanasc]

Having it at a application OAM level and usable in all templating at components, traits, workflow, policy on the application would work for us

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: test
  namespace: default
spec:
  components:
  - name: express-server
    type: webservice
    properties:
      image: oamdev/hello-world
      ports:
        - port: 8000
  context:
    myName: "my-comp"
  workflow:
    steps:
      - name: apply-comp
        type: apply-component
        properties:
          component: express-server