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Move control plane certs renewal "spread out" into the systemd timer #10596

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VannTen
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@VannTen VannTen commented Nov 6, 2023

What type of PR is this?
/kind bug

What this PR does / why we need it:
Instead of relying on the index for spacing out the auto renewal of certifcates, we instead use 'RandomizedDelaySec' and 'FixedRandomDelay' in the timer unit file.
This prevents having an invalid OnCalendar spec when there is more than 6 control plane nodes.

We also make the timer "Persistent" to avoid missing renewal if the node was offline during the scheduled time for the renewal.

Special notes for your reviewer:

Alternative to #10594

Two potential downsides with the random approach:

  • renewal order is not predictable (at least the first time)
  • Less customizable. We could add a var to opt-in/opt-out of that behavior if really necessary

Does this PR introduce a user-facing change?:

The auto renewal of control plane nodes certificates delay (different for each node to avoid concurrent renewal) is now randomized in a fixed way by node. This means it will happend each time with the same delay for the same node.
action required: if you were using a non-default value for auto_renew_certificates_systemd_calendar, you should review the new unit file.

If the number of control plane node is superior to 6, using (index * 10
minutes) will fail (03:60:00 is not a valid timestamp).

Compared to just fixing the jinja expression (to use a modulo for
example), this should avoid having two control planes certificates
update node being triggered at the same time.
If the control plane happens to be offline during the scheduled
certificates renewal (node failure or anything like that), we still want
the renewal to happen.
@k8s-ci-robot k8s-ci-robot added kind/bug Categorizes issue or PR as related to a bug. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. labels Nov 6, 2023
@k8s-ci-robot k8s-ci-robot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Nov 6, 2023
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Hi @VannTen. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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@k8s-ci-robot k8s-ci-robot added the size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. label Nov 6, 2023
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@floryut floryut left a comment

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@VannTen Looks cleaner to me 👍

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floryut commented Nov 7, 2023

/ok-to-test

@k8s-ci-robot k8s-ci-robot added approved Indicates a PR has been approved by an approver from all required OWNERS files. ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Nov 7, 2023
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Thanks! :D
/lgtm

@k8s-ci-robot k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Nov 8, 2023
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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: floryut, MrFreezeex, VannTen

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@k8s-ci-robot k8s-ci-robot merged commit b3f6d05 into kubernetes-sigs:master Nov 8, 2023
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@yankay yankay mentioned this pull request Dec 15, 2023
pedro-peter pushed a commit to pedro-peter/kubespray that referenced this pull request May 8, 2024
…ubernetes-sigs#10596)

* Use RandomizedDelaySec to spread out control certificates renewal plane

If the number of control plane node is superior to 6, using (index * 10
minutes) will fail (03:60:00 is not a valid timestamp).

Compared to just fixing the jinja expression (to use a modulo for
example), this should avoid having two control planes certificates
update node being triggered at the same time.

* Make k8s-certs-renew.timer Persistent

If the control plane happens to be offline during the scheduled
certificates renewal (node failure or anything like that), we still want
the renewal to happen.
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4 participants