replace logic and optimistic locking in general

[shawkins]

We had a discussion about how optimistic locking is performed in general and the expectations for client methods.

Some possible topics that is spawned are:

• kubectl replace --force was the rationale for the deleteExisting support we had, but that has been removed - do we want to add some support back now that we can support a better blocking delete routine?

• digging through the rest of the kubectl replace implementation:

  • it does not do logic like modifyItemForReplaceOrPatch, for example the ClusterIP is not updated. Moving forward things like that should not be needed Service: Fix semantics for Update wrt allocations kubernetes/kubernetes#103532
  • there's no locking flag. If the resource has a resourceVerion, then that is used. If none is supplied, then it will fetch latest.
  • it does not perform a retry, just a single attempt at getting the latest resourceVersion

Should we simplify/modify the replace routine?

• Deprecate modifyItemForReplaceOrPatch so that its usage does not proliferate. If a user hits a similar problem on a legacy version it's better to push them towards a merge, apply, or strategic merge patch.
• Remove retry
• Ideally match the kubectl resourceVersion behavior, but that is a breaking change. It would make lockResourceVerion().replace() necessary. It also make things more consistent with patch behavior.

On patch behavior:

• a patchStatus() call was added. But there is no patch(), nor patch(context) calls - those should probably be added. Additional patch methods #4142
• the javadoc for patch(item) is currently wrong wrt to the implementation - it does not matter if you have used a load or a resource call, the patch base is always the latest state from the server. Additional patch methods #4142
• kubectl edit will use either strategic merge or merge, not json. We should have support for generating merge and strategic merge patches - however the implementation support for strategic merge is quite involved https://github.com/kubernetes/apimachinery/blob/master/pkg/util/strategicpatch/patch.go

[manusa]

WIP

Relates to: #4142