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handle kubelet skew with and without dockershim support #2626

Closed neolit123 closed 1 week ago

neolit123 commented 2 years ago

dockershim was removed from the kubelet in early 1.24 development. related flags are also being removed.

history here: https://github.com/kubernetes/kubeadm/issues/1412

a few tasks need to be performed to adapt kubeadm for 1.24 and later.

1.24:

1.25: in kubeadm 1.25 kubelet 1.23 will go out of support, because kubeadm 1.25 would only support kubelet 1.25 and 1.24:

1.26

1.27

neolit123 commented 2 years ago

first 1.24 PR is here: https://github.com/kubernetes/kubernetes/pull/106973

pacoxu commented 2 years ago

I may take change autodetection to not mix containerd and docker sockets for docker 18.xx+ task. /assign

neolit123 commented 2 years ago

I will send PRs for all the 1.24 changes as these are a bit tricky. But reviews will be appreciated. On Dec 14, 2021 10:08, "Paco Xu" @.***> wrote:

I may take change autodetection to not mix containerd and docker sockets for docker 18.xx+ task. /assign

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neolit123 commented 2 years ago

second PR that changes the kubeadm defaults / auto detection is here: https://github.com/kubernetes/kubernetes/pull/107317

neolit123 commented 2 years ago

tasks are completed for 1.24, moving to 1.25 milestone.

neolit123 commented 2 years ago

1.25 cleanup PR is here: https://github.com/kubernetes/kubernetes/pull/110022

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/lifecycle stale

neolit123 commented 2 years ago

/remove-lifecycle stale

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/lifecycle stale

SataQiu commented 1 year ago

/remove-lifecycle stale

pacoxu commented 1 year ago

https://github.com/kubernetes/kubernetes/issues/106893#issuecomment-1465875895 pod-infra-container-image removal will be postponed to v1.28 or later.

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/lifecycle stale

neolit123 commented 11 months ago

so, one issue is that since we now support kubelet skew of N-3, we can't remove the flag --pod-infra-container-image in kubeadm deployments until 1.29 kubelet goes out of support (if my math is correct). EDIT: or 1.30 if the kubelet removes the flag in 1.30...

up until now we waited 2 releases before removing a flag, because the skew was N-1. but N-3 changes this. so we either need to modify kubeadm upgrade to wait for kubelet upgrade, check the version and then perform the flag cleanup (behavior change) or ask the kubelet maintainers to delay the removal of --pod-infra-container-image, until 1.29 goes out of support (if my math is correct).

@liggitt this is an example of the complexity at hand for N-3. cc @SataQiu @pacoxu @afbjorklund

x-posting a note here: https://github.com/kubernetes/kubernetes/issues/106893#issuecomment-1761481690

liggitt commented 11 months ago

having some way to indicate the version kubeadm should make a config for seems like it could help simplify this

neolit123 commented 11 months ago

having some way to indicate the version kubeadm should make a config for seems like it could help simplify this

agreed, and seems like an oversight that kubeadm upgrade is not wrapping this kubelet upgrade and checking what version if kubelet the user installs, and then perform some action.

one quick fix might be to call "kubeadm upgrade ..." another time after the user upgrades a kubelet on a node. for control plane nodes this will be a bit slow.

what i don't like is the deprecation progression of the --pod-infra-container-image flag in the kubelet and i think it is messy.

that doesn't seem right, and will force all tools on top of kubelet to have version branching around the k8s support skew. if they care about the GC problem, that is..

https://github.com/kubernetes/kubernetes/pull/118544/files#r1359721938

liggitt commented 11 months ago

what i don't like is the deprecation progression of the --pod-infra-container-image flag in the kubelet and i think it is messy.

  • the flag was needed to pin the pause image and prevent GC
  • in 1.29 the flag is no-op-ed
  • in 1.30 it is planned for removal

Making it easy for tools to keep setting the no-op flag until the release where it was needed hits EOL would be nice, especially if it is ~zero cost for sig-node. I'd ask them about that.

carlory commented 10 months ago

Hi @liggitt any update about it?

kubeadm and scripts are still using this flag in 1.29. Can we remove this flag from kubelet in 1.30?

if cleanFlagSet.Changed("pod-infra-container-image") {
klog.InfoS("--pod-infra-container-image will not be pruned by the image garbage collector in kubelet and should also be set in the remote runtime")
_ = cmd.Flags().MarkDeprecated("pod-infra-container-image", "--pod-infra-container-image will be removed in 1.30. Image garbage collector will get sandbox image information from CRI.")
}

Or update the deprecated message with a different release?

liggitt commented 9 months ago

In what release can we count on CRI having the info required so --pod-infra-container-image no longer needs to be passed?

liggitt commented 9 months ago

in 1.29 the flag is no-op-ed

If the flag is no-op and cheap for node to keep around, I'd ask if they can keep it until 1.29 is the oldest release.

Separately, kubeadm knowing what kubelet version it is generating a config for seem like a really important gap to close, and would let kubeadm stop setting this flag for >=1.29 kubelets.

neolit123 commented 9 months ago

In what release can we count on CRI having the info required so --pod-infra-container-image no longer needs to be passed?

@adisky do you know? the problem here is the variance in CRI implementor schedules - e.g. if cri-o implements the latest CRI that has the feature, that would mean that users need to update cri-o, updating kubelet will not suffice.

in 1.29 the flag is no-op-ed

If the flag is no-op and cheap for node to keep around, I'd ask if they can keep it until 1.29 is the oldest release.

+1, but it seems if the flag is no-op-ed this would mean that users need to upgrade their container runtime as well. otherwise there will be nothing to handle the GC problem (CR is old, kubelet is no-op).

Separately, kubeadm knowing what kubelet version it is generating a config for seem like a really important gap to close, and would let kubeadm stop setting this flag for >=1.29 kubelets.

yes, that is the upgrade problem discussed earlier. https://github.com/kubernetes/kubeadm/issues/2626#issuecomment-1763244783 currently the kubelet binary upgrade is done after kubeadm upgrade and is manually done by the user. it needs discussion - we need to figure out what to do with this.

pacoxu commented 9 months ago

https://github.com/kubernetes/kubernetes/issues/106893#issuecomment-1867197876 some updates about the pinned image feature in containerd side:

From containerd side, containerd v1.7.3 and containerd 1.6.22 includes the support of pinned image:

However, there are still two bugfix pull requests in progress:

EDITED Add below context The two WIP PR are not blockers. https://github.com/containerd/containerd/pull/9381 is not a blocker as well.(It will pin some more than expected.)

To use that feature, we at least should use containerd v1.7.3+ and containerd 1.6.22+.

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/lifecycle stale

carlory commented 5 months ago

/remove-lifecycle stale

k8s-triage-robot commented 2 months ago

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/lifecycle stale

neolit123 commented 1 week ago

cleanup remaining flags pod-infra-container-image .. ? https://github.com/kubernetes/kubernetes/issues/106893

scoped this item in a dedicated ticket:

all other AIs are done here.