CreateOrReplace not fully equivalent with `apply`

Describe the bug

Client Version: 5.12.1 K8s version: 1.19

Function createOrReplace is not equivalent to kubectl apply is instead behaves more like kubectl create (as expressed in the code comments )

Despite being an old comment this is what we’re experiencing (https://github.com/kubernetes/kubernetes/issues/25238#issuecomment-306549174)

what is currently happening is that we have

• Deployment with no replica set
• HPA with min replicas 1

when using manually kubectl apply it behaves as expected, doing the proper rolling update (25%, max unavailable 0)

when using the client it behaves like a create(or replace) operation forcing the deployment object to update to replicas 1 (default by k8s) and updating the replica set back to 1 this immediately terminates all remaining pods breaking what would else be a smooth deployment.

This completely invalidates the use of fabric8 client for applying manifests in a safe way.

Other refs: https://github.com/kubernetes/kubernetes/issues/25238#issuecomment-406415297 https://www.linkedin.com/pulse/kubectl-createreplace-vs-apply-which-one-use-samrat-sen/

Fabric8 Kubernetes Client version

5.12.1@latest

Steps to reproduce

1. Use client apply twice a manifest with 1.1 HPA 10 min replicas (10 just allows to easily observe the behaviour) 1.2 Deployment with no replicas specified, rolling update (max surge 25%, max unavailable 0)

Expected behavior

Second apply should show a smooth transition of the pods to the new ones.

Runtime

Kubernetes (vanilla)

Kubernetes API Server version

other (please specify in additional context)

Environment

Amazon

[shawkins]

@sunix @rohanKanojia it would probably be good to still have an issue for a higher-level apply or serverSideApply method. That will be easier for users to find.

[manusa]

is this fixed with #3937 ?

No, see https://github.com/fabric8io/kubernetes-client/issues/3896#issuecomment-1066739461.

It would be nice to have a DSL method to perform the Server Side Apply logic, instead of manually configuring the patch.