Revert "Suppress error message in cmdDel, in thick plugin"

[pliurh]

This reverts commit 5d64ec3.

Multus shall return an error to the caller if a DEL fails.

[coveralls]

coverage: 49.824% (-3.1%) from 52.959%
when pulling 8462978 on pliurh:return_error
into 18630fd on k8snetworkplumbingwg:master.

[s1061123]

Multus shall return an error to the caller if a DEL fails.

In CNI Specification, here is the sentence.

Plugins should generally complete a DEL action without error even if some resources are missing. 

So CNI specification point of view, CNI plugin should execute DEL command without error. Multus CNI is CNI Plugin and it should be alined with specification. So I suppose we should keep it.

If you have something stale resources (e.g. something cannot be cleaned up by DEL command), CNI Spec provides GC command.
https://github.com/containernetworking/cni.dev/blob/main/content/docs/spec.md#gc-clean-up-any-stale-resources

Multus CNI already supports GC command, so I strongly recommend to use GC command to cleanup stale resources, something cannot be cleaned up by failed DEL command.

[s1061123]

@dougbtv PTAL?

[danwinship]

Multus shall return an error to the caller if a DEL fails.

In CNI Specification, here is the sentence.

Plugins should generally complete a DEL action without error even if some resources are missing. 

So CNI specification point of view, CNI plugin should execute DEL command without error.

That's not what it says. (Or at least, not what it meant.) It just means that a CNI plugin should not return a "not found" error if it is asked to delete something that already doesn't exist. If it is aware that there is something that it needs to delete, and it is unable to delete it, then it's supposed to return an error.

If CNI plugins were never supposed to return errors from DEL, then why would DEL even allow returning an error?

We discussed this in the CNI meeting on 2025-06-16 and @squeed agreed that Multus's interpretation of the spec is wrong.

[SchSeba]

LGTM

[github-actions]

This pull request is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[JensErat]

still relevant

[github-actions]

This pull request is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[JensErat]

still relevant