add k8s.container.status.state metric

[povilasv]

Fixes #1672

Changes

Adds k8s.container.status.state metric, it would allow us to alert and monitor containers in not ready state.

I'm still not sure if this should be multiple different metrics or a single one 🤔

The current problems, with single metric:

• Running state doesn't have a reason, so we would set reason to empty.
• Waiting state and Terminated state have different sets of reasons:

Waiting state - "ContainerCreating", "CrashLoopBackOff", "CreateContainerConfigError", "ErrImagePull", "ImagePullBackOff"

Terminated state - "OOMKilled", "Completed", "Error", "ContainerCannotRun"

Alternative approach would be to do what KSM does:

• k8s.container.status.state metric without reason attribute.
• k8s.container.status.waiting_reason metric for waiting reason enum.
• k8s.container.status.terminated_reason metric for terminated reason enum.

This is not intended to merge, I would appreciate any feedback to see what we want to do here.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• schema-next.yaml updated with changes to existing conventions.

[ChrsMark]

I think we need to name these as k8s.container.status.state and k8s.container.status.reason so as to have meaningful names in case we want to re-use them in other signals like Entities (k8s.container.reason does not make a lot of sense).

[povilasv]

Renamed the attributes, thanks!

[ChrsMark]

If we have it as required, the problem is that states which do not have a reason won't have it provided. Maybe that could be left "unknown" or just empty?

@open-telemetry/semconv-k8s-approvers @open-telemetry/specs-semconv-approvers thoughts?

[povilasv]

Removed the "required" for now, but would appreciate suggestions what we want to do here