A way to programmatically disable scalers/triggers temporarily

[aliaqel-stripe]

Proposal

Recently, a use case as arisen with us where we would like to disable a scaler or trigger without changing the scaled object definiton of a service. The idea here is that we can temporarily disable the scaler without a redeployment or a code change.

I would imagine this being a ScaledObject level annotation.

Use-Case

A service that is providing data for a scaler is misbehaving, however, we have decided this is not worth having the HPA block scale down via other scalers due to this scaler's errors. We set this annotation on our ScaledObjects via a controller or manual action and when the outage subsides, we can remove the annotation and things return to normal

Is this a feature you are interested in implementing yourself?

Yes

Anything else?

No response

[rickbrouwer]

I think it is now the case that if you do not configure a fallback, and a trigger fails, it will continue to scale on the existing triggers. But if you explicitly want a fallback, what about a new behavior "ignoreAndContinue"?

And you also mentioned in the KEDA Community Call that if a certain trigger fails, you want to go to a certain number of replicas. But maybe I misunderstood that. But if so, perhaps it's an idea to configure it that way.

spec:
  fallback:
    failureThreshold: 3
    behavior: static
    replicas: 2
    perTrigger:
      prometheus: 5
      rabbitmq: 1

In this example it could be that if a prometheus trigger fails it has to go to 5 replicas, and if a rabbitmq trigger fails it has to go to 1 replica.

[aliaqel-stripe]

@rickbrouwer We don't actually want to fall back to some replica count in this case. We want the scaler disabled for that ScaledObject. I see something like:

spec:
  fallback:
    failureThreshold: 3
    behavior: static
    replicas: 2
    perTrigger:
      prometheus: 5
      rabbitmq: DisableScaler