Document Kubernetes preStop handler when using a Docker image without a shell

[andrej-urvantsev]

Or, maybe, not exactly inconsistency but now it's a bit misleading...

In the Kubernetes Container Lifecycle there is a suggestion to use preStop handler like this: command: ["sh", "-c", "sleep 10"]

Problem is that by default Spring Boot paketo images from now on use paketobuildpacks/builder-jammy-java-tiny image, which does not have any shell.

So, either a new recipe should be suggested or a word of warning should say that for default spring boot images that won't work anymore.

As a suggestion - maybe include "sleep" command into the image, so something like this would work?

lifecycle:
  preStop:
    exec:
      command:
        - sleep
        - 60

[philwebb]

We also have #20995 open

[andrej-urvantsev]

Then this ticket can be considered mostly as a documentation update and maybe worth to review #20995 in the light that situation has changed now - by default(using paketo buildpacks) there is no option to execute shell commands in container anymore.

[andrej-urvantsev]

@philwebb maybe #20995 is not needed anymore - #20995 (comment)

Since 1.32 is GA and sleep option is enabled there, then right thing to do would be just to update the documentation.

[mhalbritter]

The sleep option in the Kubernetes preStop hook is behind a feature gate: https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#hook-handler-implementations

Sleep - Pauses the container for a specified duration. This is a beta-level feature default enabled by the PodLifecycleSleepAction feature gate.

[andrej-urvantsev]

@mhalbritter from the release notes 1.32: PodLifecycleSleepAction is graduated to GA

Unfortunately, don't have 1.32 yet to verify, but looks like it's GA now.

[mhalbritter]

Huh, yeah, looks like it. Then the doc is outdated.

[mhalbritter]

Just tested it with Kubernetes 1.32.0 and

lifecycle:
  preStop:
    sleep:
      seconds: 10

works.

We'll update the documentation.