Panic when using watcher with a resource that does not expose a resourceVersion

[umanwizard]

Current and expected behavior

See title. The offending line is here.

Possible solution

No response

Additional context

metrics-server apparently creates PodMetrics resources without this field, and my code panics when trying to watch them.

Environment

Client Version: v1.22.10
Server Version: v1.23.4

FROM ubuntu:jammy-20221101

Configuration and features

No response

Affected crates

kube-runtime

Would you like to work on fixing this bug?

No response

[nightkr]

I believe metrics-server is using an extension API, so I'm not sure they support watches at all. That said, we should definitely at least have clearer error messages for this, and avoid panicking...

[goenning]

I've hit this wall too, watch is not supported: /~https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/1013-metrics-watch-api

Polling is the only alternative AFAIK

[clux]

In that case should probably extend watcher::Error here with a NoResourceVersion error variant and bubble that up from the offending line above.

[clux]

Quick PR in #1101 to turn the unwrap into an error. This will cause a repeating error when watch is not supported though, but hopefully it's more informative and a developer can catch/notice this earlier and be less confused about it than if it was an unwrap.

[nightkr]

We may also want to add a poll_watcher at some point to cope with these cases...