Comparable Resource Version

[michaelasp]

Enhancement Description

• One-line enhancement description (can be used as a release note): Allow clients to compare resource versions between each other for objects of the same type.
• Kubernetes Enhancement Proposal: KEP-5504: Comparable Resource Version #5505
• Discussion Links:
  • sig-apimachinery
  • sig-arch
• PRs by stage and milestone:
  • Stable - v1.35
    • KEP (k/enhancements) update PR(s): KEP-5504: Comparable Resource Version #5505
    • Code (k/k) update PR(s): Add resource version comparison function in client-go along with conformance kubernetes#134330
    • Docs (k/website) update PR(s): Clarify comparison rules for resource versions website#52848

Please keep this description up to date. This will help the Enhancement Team to track the evolution of the enhancement efficiently.

[michaelasp]

/sig api-machinery

[michaelasp]

/assign @michaelasp

[lmktfy]

For the one-line description, maybe we can emphasize that it's between different versions of the same thing (aiming to imply that, even after this change, you can't compare the resourceVersion of a Pod and a ConfigMap and make meaningful assumptions).

[michaelasp]

For the one-line description, maybe we can emphasize that it's between different versions of the same thing (aiming to imply that, even after this change, you can't compare the resourceVersion of a Pod and a ConfigMap and make meaningful assumptions).

Good point, this was discussed and it only makes sense to do between objects of the same type since otherwise things like sharding can cause RV to not be comparable, updated!

[csviri]

For the one-line description, maybe we can emphasize that it's between different versions of the same thing (aiming to imply that, even after this change, you can't compare the resourceVersion of a Pod and a ConfigMap and make meaningful assumptions).

Can you actionally compare resources version between two resources with same kind but different name+namespace?
I guess this will work just between the same resource (GVK + name + namespace) ?
btw doesn't that work already?

thank you!

[michaelasp]

For the one-line description, maybe we can emphasize that it's between different versions of the same thing (aiming to imply that, even after this change, you can't compare the resourceVersion of a Pod and a ConfigMap and make meaningful assumptions).

Can you actionally compare resources version between two resources with same kind but different name+namespace? I guess this will work just between the same resource (GVK + name + namespace) ? btw doesn't that work already?

thank you!

1. Yeah as long as they are the same kind and resource endpoint that should work.

2. Currently the resource version can only be used as an opaque string where equality is the only comparison that can be made. The apiserver and internal machinery does use these guarantees however. See https://kubernetes.io/docs/reference/using-api/api-concepts/#resource-versions for the current semantics. Technically it works right now in most cases since backends almost always use etcd but there are no guarantees, that's why we are adding conformance tests along with a helper function.