cluster-autoscaler: terminating an instance does not mean there will be less desired instances

[grosser]

What type of PR is this?

/kind bug

What this PR does / why we need it:

while working on #5411 to fix #4095 I realized that the core bug is that we decrement the currentSize (aka asg desired size) when terminating an instance
... but that's now how aws works, terminating an instance does not decreases the desired size, it only makes a new instance come up

(#5411 is still useful since it reduces api call overhead and log spam)

partially reverts #1378

/cc @alam0rt @johanneswuerbach @aleksandra-malinowska

Which issue(s) this PR fixes:

Fixes #4095

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

[k8s-ci-robot]

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Note that only kubernetes members and repo collaborators can review this PR, and authors cannot review their own PRs.

In response to this:

…

What type of PR is this?

/kind bug

What this PR does / why we need it:

while working on #5411 to fix #4095 I realized that the core bug is that we decrement the currentSize (aka asg desired size) when terminating an instance
... but that's now how aws works, terminating an instance does not decreates the desired size, it only makes a new instance come up

(#5411 is still useful since it reduces api call overhead and log spam)

partially reverts #1378

/cc @alam0rt @johanneswuerbach @aleksandra-malinowska

Which issue(s) this PR fixes:

Fixes #4095

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-ci-robot]

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[johanneswuerbach]

terminating an instance does not decreases the desired size, it only makes a new instance come up

The terminate call above is made with ShouldDecrementDesiredCapacity: aws.Bool(true), so I think it actually does both, terminate the instance and decreases the desired size.

[grosser]

ah missed that, thx!