CronJob will be run twice, when switching to wintertime

[muffl0n]

What happened?

We have a CronJob configured to run each day at 02:00. The timezone is set to "Europe/Berlin" corresponding to CEST in summer (+02:00) and CET in winter (+01:00).

Which works fine most of the year, "exploded" this early morning, when Europe switched from CEST to CET going back from 03:00 to 02:00. Cause 02:00 happened again, the CronJob ran again causing conflicts with a restore job still running (started at around 02:45 CEST).

Comparing this behaviour to Debian's cron, where this is handled differently:

Conversely, if the time has moved backwards by less than 3 hours, those jobs that fall into the repeated time will not be re-run.

What did you expect to happen?

CronJob should only be run once, even when switching DST

How can we reproduce it (as minimally and precisely as possible)?

• create cluster
• change time on cluster to "before switch to wintertime", e.g. 2023-10-28 23:30 UTC
• schedule CronJob to be run at a time like mentioned above, e.g. 0 2 * * *
• set timezone in CronJob to Europe/Berlin
• wait for switch to wintertime: scheduled CronJob will run twice: 00:00 UTC (02:00 CEST) and 01:00 UTC (02:00 CEST)

Anything else we need to know?

Also posted to Reddit: https://www.reddit.com/r/kubernetes/comments/17jbw5s/cronjob_will_be_run_twice_when_switching_to/

Kubernetes version

1.26.6-gke.1700

Cloud provider

GCP

OS version

# On Linux:
$ cat /etc/os-release
# paste output here
$ uname -a
# paste output here

# On Windows:
C:\> wmic os get Caption, Version, BuildNumber, OSArchitecture
# paste output here

Install tools

Container runtime (CRI) and version (if applicable)

Related plugins (CNI, CSI, ...) and versions (if applicable)

[k8s-ci-robot]

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[muffl0n]

/wg batch

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/lifecycle stale

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/close not-planned

[k8s-ci-robot]

@k8s-triage-robot: Closing this issue, marking it as "Not Planned".

In response to this:

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Reopen this issue with /reopen
• Mark this issue as fresh with /remove-lifecycle rotten
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/close not-planned

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