Bug 2028601

Summary: Cluster-version operator does not default Deployment replicas to one
Product: OpenShift Container Platform Reporter: OpenShift BugZilla Robot <openshift-bugzilla-robot>
Component: Cluster Version OperatorAssignee: W. Trevor King <wking>
Status: CLOSED DEFERRED QA Contact: Yang Yang <yanyang>
Severity: low Docs Contact:
Priority: medium    
Version: 4.1.zCC: aos-bugs, yanyang
Target Milestone: ---   
Target Release: 4.8.z   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: No Doc Update
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2023-01-25 18:35:52 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2028602    
Bug Blocks:    

Description OpenShift BugZilla Robot 2021-12-02 18:06:57 UTC 
+++ This bug was initially created as a clone of Bug #2028217 +++

Tomas and Vadim noticed that, when a Deployment manifest leaves 'replicas' unset, the CVO ignores the property.  This means that cluster admins can scale those Deployments up or, worse, down to 0, and the CVO will happily continue on without stomping them.  Auditing 4.9.10:

  $ oc adm release extract --to manifests quay.io/openshift-release-dev/ocp-release:4.9.10-x86_64
  Extracted release payload from digest sha256:e1853d68d8ff093ec353ca7078b6b6df1533729688bb016b8208263ee7423f66 created at 2021-12-01T09:19:24Z
  $ for F in $(grep -rl 'kind: Deployment' manifests); do yaml2json < "${F}" | jq -r '.[] | select(.kind == "Deployment" and .spec.replicas == null).metadata | .namespace + " " + .name'; done | sort | uniq
  openshift-cluster-machine-approver machine-approver
  openshift-insights insights-operator
  openshift-network-operator network-operator

Those are all important operators, and I'm fairly confident that none of their maintainers expect "cluster admin scales them down to 0" to be a supported UX.  We should have the CVO default Deployment replicas to 1 (the type's default [1]), so admins who decide they don't want a network operator pod, etc., have to use some more explicit, alarming API to remove those pods (e.g. setting spec.overrides in the ClusterVersion object to assume control of the resource themselves).

[1]: https://kubernetes.io/docs/reference/kubernetes-api/workload-resources/deployment-v1/#DeploymentSpec
Comment 3 W. Trevor King 2023-01-25 18:35:52 UTC 
We'd fixed this in 4.9.12 [1], and nobody seems to be bothered by the lack of 4.8 fix.  4.8 goes end-of-life on 2023-01-27 [2], so closing this DEFERRED.

[1]: https://bugzilla.redhat.com/show_bug.cgi?id=2028602#c8
[2]: https://access.redhat.com/support/policy/updates/openshift#dates