kubectl debug: ability to disable health check probes on pod copies

Debugging pods by creating a copy (specifically changing the container image or the running command) can lead to the pod being restarted via liveness & startup health check failures.

eg: if I have a http service with a httpGet liveness probe configured, starting a debug container via kubectl debug myapp -it --copy-to=myapp-debug --container=myapp -- sh won't be listening on a port, and will fail the liveness checks and be restarted, killing my debug shell.

What would you like to be added:

An easy way of disabling liveness & startup probes for debug pod copies, and doing it by default. Longer discussion on readiness probes follows below.

Why is this needed:

Debug shells dying every few seconds is a bit a hindrance to debugging. 😄

Readiness Probes:

These prevent pods from receiving traffic, so they're IMO conceptually useful to keep: if I start a http service in my debug pod with verbose logging enabled, having it receive traffic could be a good idea. Ctrl-C it and it'd go back to being unready and stop receiving traffic. Not copying readiness probes marks the pod as always ready.

Labels aren't copied by default to debug pods, so to get any service traffic routed I need to add labels to my running debug pod.

Alternative viewpoint: if I was making & stepping through test requests with a daemon running in a debugger, kubernetes doing GET /healthz every 3 seconds could be extremely annoying.

Ideas:

Don't copy liveness & startup probes when using --copy-to=, only readiness probes
Don't copy any probes when using --copy-to=.
Adding a --copy-probes=all|none|(liveness|readiness|startup,...) flag, with default as readiness
(3), with default as none

(2) is probably the simplest approach that covers the most use cases.

Jun 08 '21 09:06 rcoup

/cc @verb

Jun 10 '21 19:06 eddiezane

Thanks for the feedback @rcoup. I agree, and I think this is part of a bigger issue where we need a bit more configurability in kubectl debug. I'll add this to the list of issues we're tracking in kubernetes/enhancements#1441.

I think I also agree that your second idea seems like a better default, regardless of the above, but I need to think about it a bit more.

/triage accepted

Jun 14 '21 14:06 verb

/assign verb

Aug 20 '21 10:08 lauchokyip

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Jan 17 '22 12:01 k8s-triage-robot

@k8s-triage-robot: Closing this issue.

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Jan 17 '22 12:01 k8s-ci-robot

/reopen /remove-lifecycle rotten

Should be fixed by https://github.com/kubernetes/kubernetes/pull/110526

Jul 04 '22 14:07 gautierdelorme

@gautierdelorme: Reopened this issue.

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/reopen /remove-lifecycle rotten

Should be fixed by https://github.com/kubernetes/kubernetes/pull/110526

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Nov 01 '22 15:11 k8s-triage-robot

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/close not-planned

Dec 01 '22 16:12 k8s-triage-robot

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

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