Integrate KEDA scale logic with coming HPA scale to zero features

[jeffhollan]

kubernetes/kubernetes#74526

[mikhailshilkov]

If I read it correctly, the scale to/from zero feature of HPA has been released in 1.16. Does it mean that it will replace the KEDA way of enabling/disabling the deployment any time soon? Does it make the whole controller obsolete?

[jeffhollan]

A few things to note

• While HPA can scale custom metrics to zero, it still needs metrics to scale. So KEDA still relevant in being a single spot for a bunch of metric publishers and authentication with them

• Will also be some time before 1.16 is widely adopted so in interim good to have.

We should do it but just means one of the things KEDA does today it can offload to HPA, but would still need to do others

[mikhailshilkov]

Yes, I'm not questioning KEDA, I guess the whole controller was an exaggeration but handleScaleLoop can probably go.
Thanks for the quick response!

[jeffhollan]

Makes sense. The other thing I want to check out (let me know if others know in meantime) is the polling interval and latency of HPA scaling from 0. In KEDA it’s configurable. Not sure if we’d leave KEDA as an option to still drive if it’s providing some additional features

[tomkerkhove]

We should check how this impacts 2.0 /cc @zroubalik

[zroubalik]

It's still alpha in kubernetes: https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/#feature-gates-for-alpha-or-beta-features (search for HPAScaleToZero). It has to be enabled in the cluster by admin and it is not stable enough to be used by KEDA. We could include this later.

[tomkerkhove]

Sound like a plan!

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.

[tomkerkhove]

/keep-alive

[JorTurFer]

Does having this issue open make sense?

[tomkerkhove]

It depends - Do we align or still have our own approach? If the latter, why?

[JorTurFer]

HPA still doesn't support scale to 0, we deactivate the HPA according to official docs, but the scale to zero features aren't available yet in the HPA itself. We do that part with the operator (activation phase)

[zroubalik]

This KEP is still active, kubernetes/enhancements#2022

Let's keep this issue opened to track this effort.

[tomkerkhove]

Ok; I thought this was shipped already.