Karmada propagates resources to all clusters when pp clusterAffinity is empty

[NickYadance]

PP will propagate resource to all clusters when with empty clusterAffinity, i wonder is this intended ? This seems wried since the resources shows 0/0 in control panel, but actually propagates to all clusters. And empty pp behaves differently from no pp, which will not propagate resource. @XiShanYongYe-Chang

  ~/.live  kkarmada get deploy nginx                                                                                                                                 ok  3s  base py  kind-kruise kube  17:59:43
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   0/0     0            0           3d23h

 ~/.live  kkarmada get pp nginx-propagation -oyaml                                                                                                                      ok  base py  kind-kruise kube  17:59:47
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"policy.karmada.io/v1alpha1","kind":"PropagationPolicy","metadata":{"annotations":{},"name":"nginx-propagation","namespace":"default"},"spec":{"placement":{"clusterAffinity":{"clusterNames":["lyra-backup-controll-sg10"]}},"resourceSelectors":[{"apiVersion":"apps/v1","kind":"Deployment","name":"nginx"}]}}
  creationTimestamp: "2023-05-29T08:21:11Z"
  generation: 3
  name: nginx-propagation
  namespace: default
  resourceVersion: "130809292"
  uid: 920c7b31-455a-4b8c-9720-7f2bd6560b6e
spec:
  placement:
    clusterAffinity: {}
  priority: 0
  resourceSelectors:
  - apiVersion: apps/v1
    kind: Deployment
    name: nginx
    namespace: default
  schedulerName: default-scheduler

 ~/.live  kkarmadactl get deploy                                                                                                                                                          ok  base py  17:59:59
NAME                            CLUSTER                           READY   UP-TO-DATE   AVAILABLE   AGE      ADOPTION
nginx                           member1             0/0     0            0           28m      Y
nginx                           member2              0/0     0            0           28m      Y
nginx                           member3   0/0     0            0           28m      Y

[XiShanYongYe-Chang]

PP will propagate resource to all clusters when with empty clusterAffinity,

@NickYadance This behavior is expected, ref the API:

karmada/pkg/apis/policy/v1alpha1/propagation_types.go

Lines 471 to 477 in 6a17ea8

	// ClusterAffinity represents scheduling restrictions to a certain set of clusters.
	// Note:
	// 1. ClusterAffinity can not co-exist with ClusterAffinities.
	// 2. If both ClusterAffinity and ClusterAffinities are not set, any cluster
	// can be scheduling candidates.
	// +optional
	ClusterAffinity *ClusterAffinity `json:"clusterAffinity,omitempty"`

The system replicates and distributes it as a regular resource.