autoscaler: enforce bounds when scaling hint is NONE

[adrobisch]

One-line summary

Follow up to c53f570 which moved the responsibility to enforce bounds to the autoscaler.

Description

This fixes the scenario when ScalingHint is NONE and no other scaling decision is triggered either. In that case we still want to enforce the replica bounds.

Types of Changes

• Bug fix (non-breaking change which fixes an issue)

[hooseins]

The change look good.

For context, we observed that the EDS is not immediately scaling out after patching it with min replica > current replicas. But with any next scaling hint of either "UP" or "DOWN", it correctly scales to the new min replicas. This indicates that somewhere we were not executing the scaling operation when the "replica" field is missing (which is after the patch) and the scaling hint is "NONE".

Code owners to review further.

[otrosien]

@adrobisch this should finally fix the scaling-to-zero issue, and generally LGTM. But, the more I think about it, the more I believe that there's a general design flaw in making edsReplicas return int32 and not a pointer. As such, it hides all these edge cases that we uncovered (and maybe re-introduce similar issues in the future because of that).

Can you prepare a changeset with going for *int32 for comparison?

[adrobisch]

@adrobisch this should finally fix the scaling-to-zero issue, and generally LGTM. But, the more I think about it, the more I believe that there's a general design flaw in making edsReplicas return int32 and not a pointer. As such, it hides all these edge cases that we uncovered (and maybe re-introduce similar issues in the future because of that).

Can you prepare a changeset with going for *int32 for comparison?

@otrosien I drafted https://github.com/zalando-incubator/es-operator/compare/master...adrobisch:es-operator:eds-replicas-pointer?expand=1 where I made it a pointer, but did not push it down to scaleUpOrDown since we are applying the bounds at that point.
Still a more conservative change, not sure if this is what you had in mind?

[otrosien]

We decided to merge this first, and follow-up on an improvement.

[otrosien]

👍

[adrobisch]

👍