fix(cpumanager): Do not release CPUs of init containers while they are being reused in app containers

[eggiter]

What type of PR is this?

/kind bug

What this PR does / why we need it:

• Currently, app containers in pod inherit CPUs from the pod's init containers when using static policy.
• When init container is somehow removed(manually removed, GCed by docker, etc.), the inherited CPUs are released without checking if they are being used by app containers.
• This PR fixes this by not releasing CPUs used by other containers in the pod.

Special notes for your reviewer:

• It was introduced in PR Update strategy used to reuse CPUs from init containers in CPUManager #90419.

Does this PR introduce a user-facing change?

Fixes regression in CPUManager that it will release exclusive CPUs in app containers inherited from init containers when the init containers were removed. 

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Hi @eggiter. Thanks for your PR.

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[eggiter]

reply here with a new comment

I signed it.

[matthyx]

/ok-to-test

[eggiter]

/assign @klueska @matthyx

[matthyx]

nit: cpusInUse ?

[eggiter]

updated, thanks.

[matthyx]

/lgtm

[pacoxu]

/triage accepted

[pacoxu]

/priority important-soon
since it is regression

BTW, should it be cherry-picked to 1.19-1.22 once merged?

[ffromani]

Thanks for this PR! does it fix a problem actually observed on some cluster or is it a robustness fix?
If this fixes a problem happened on a cluster, could you please file an issue describing the scenario and link it to this PR?
EDIT
that said, I see the merit in the fix here. I want to review a bit more the case but it seems a good fix.

[eggiter]

does it fix a problem actually observed on some cluster or is it a robustness fix?
If this fixes a problem happened on a cluster, could you please file an issue describing the scenario and link it to this PR?

• The former. it was indeed observed.
• sure thing.
  EDIT
• it was indeed observed but with my intervention, which i was testing some bug fixes of our internal Kubelet version. In order to do so, i manually removed the completed init container then the bug occurred.
• Is this robustness fix? i'm not sure. Anyway, the issued is filed: CPUManager releases CPUs of init containers while they are being reused in app containers #105114.

[ffromani]

does it fix a problem actually observed on some cluster or is it a robustness fix?
If this fixes a problem happened on a cluster, could you please file an issue describing the scenario and link it to this PR?

* The former. it was indeed observed.

* sure thing.
  EDIT

* it was indeed observed but with **my intervention**, which i was testing some bug fixes of our internal Kubelet version. In order to do so, i manually removed the completed init container then the bug occurred.

* Is this robustness fix? i'm not sure. Anyway, the issued is filed: [CPUManager releases CPUs of init containers while they are being reused in app containers #105114](https://github.com/kubernetes/kubernetes/issues/105114).

Thanks. The only missing piece is if there is a kubernetes flow (GC is a good example) that triggers this bug without explicit manual action. The problem with manual action is that it's easy to void some key assumptions of the code, and in that case a fix is not warranted: in normal circumstances, the issue won't trigger.
Let's evaluate the scenarios on the issue discussion.

[eggiter]

Let's evaluate the scenarios on the issue discussion.

Sure.

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/lifecycle stale

[eggiter]

/remove-lifecycle stale

[dims]

/assign @mrunalp

@klueska @mrunalp this looks ready with at least one LGTM already.

[klueska]

This is a very weird edge case and can only be triggered if someone manually terminates a container using some mechanism external to kubernetes. I'm fine to include this change since it is fairly small and well contained, but as @fromanirh mentions in #104837 (comment) one should always be wary of what could happen when triggering container lifecycle events outside of the standard kubernetes mechanisms.

[klueska]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: eggiter, klueska, matthyx

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