Provide CloudEvents when scaling workload(s) from/to 0

[tomkerkhove]

Proposal

Event Types

• keda.workload.scaletozero.v1
• keda.workload.scalefromzero.v1

Payload:

{
    "specversion" : "1.0",
    "type" : "keda.workload.scaletozero.v1",
    "subject" : "/{kubernetes-cluster-name}/{namespace}/workload/{resource-name}/",
    "time" : "2018-04-05T17:31:00Z",
    "datacontenttype" : "application/json",
    "data" : {
      "scaleTarget": {
         "name": "sample-workload",
         "apiVersion": "Deployment",
         "kind": "apps/v1",
      }
   }
}

Use-Case

Allow end-users to get notified when workloads are scaling to/from 0.

Anything else?

Relates to #479

[tomkerkhove]

@neelanjan00 will look in to this

[neelanjan00]

A question, do we want to emit an event for a ScaledJob scaling from/to 0? If yes, can you suggest at which point during the reconciliation we can check if the runningJobCount has become zero?

Sorry if it's a dumb question. As far as I understood KEDA doesn't actively scale the ScaledJob workloads to zero since Kubernetes Jobs are not meant to keep executing, and after they complete executing the number of pods becomes zero.

CC: @tomkerkhove

[neelanjan00]

Hi @tomkerkhove can you PTAL at the above comment? Thanks!

[tomkerkhove]

There are no stupid questions so no worries =) Let's leave out ScaledJobs indeed given we do not scale to 0 but only activate new instances when need be

[tomkerkhove]

Re-assigned to @SpiritZhou after @neelanjan00's comment on PR - Thanks for effort anyway!