Merge pull request #3788 from RainbowMango/pr_pp_add_Preemption

Proposing PropagationPolicy Preemption API

api/openapi-spec/swagger.json

@@ -15875,8 +15875,16 @@
           "default": {},
           "$ref": "#/definitions/com.github.karmada-io.karmada.pkg.apis.policy.v1alpha1.Placement"
         },
+        "preemption": {
+          "description": "Preemption declares the behaviors for preempting. Valid options are \"Always\" and \"Never\".\n\n\nPossible enum values:\n - `\"Always\"` means that preemption is allowed. If it is applied to a PropagationPolicy, it can preempt any resource as per Priority, regardless of whether it has been claimed by a PropagationPolicy or a ClusterPropagationPolicy, as long as it can match the rules defined in ResourceSelector. In addition, if a resource has already been claimed by a ClusterPropagationPolicy, the PropagationPolicy can still preempt it without considering Priority. If it is applied to a ClusterPropagationPolicy, it can only preempt from ClusterPropagationPolicy, and from PropagationPolicy is not allowed.\n - `\"Never\"` means that a PropagationPolicy(ClusterPropagationPolicy) never preempts resources.",
+          "type": "string",
+          "enum": [
+            "Always",
+            "Never"
+          ]
+        },
         "priority": {
-          "description": "Priority indicates the importance of a policy(PropagationPolicy or ClusterPropagationPolicy). A policy will be applied for the matched resource templates if there is no other policies with higher priority at the point of the resource template be processed. Once a resource template has been claimed by a policy, by default it will not be preempted by following policies even with a higher priority.\n\nIn case of two policies have the same priority, the one with a more precise matching rules in ResourceSelectors wins: - matching by name(resourceSelector.name) has higher priority than\n  by selector(resourceSelector.labelSelector)\n- matching by selector(resourceSelector.labelSelector) has higher priority\n  than by APIVersion(resourceSelector.apiVersion) and Kind(resourceSelector.kind).\nIf there is still no winner at this point, the one with the lower alphabetic order wins, e.g. policy 'bar' has higher priority than 'foo'.\n\nThe higher the value, the higher the priority. Defaults to zero.",
+          "description": "Priority indicates the importance of a policy(PropagationPolicy or ClusterPropagationPolicy). A policy will be applied for the matched resource templates if there is no other policies with higher priority at the point of the resource template be processed. Once a resource template has been claimed by a policy, by default it will not be preempted by following policies even with a higher priority. See Preemption for more details.\n\nIn case of two policies have the same priority, the one with a more precise matching rules in ResourceSelectors wins: - matching by name(resourceSelector.name) has higher priority than\n  by selector(resourceSelector.labelSelector)\n- matching by selector(resourceSelector.labelSelector) has higher priority\n  than by APIVersion(resourceSelector.apiVersion) and Kind(resourceSelector.kind).\nIf there is still no winner at this point, the one with the lower alphabetic order wins, e.g. policy 'bar' has higher priority than 'foo'.\n\nThe higher the value, the higher the priority. Defaults to zero.",
           "type": "integer",
           "format": "int32"
         },

charts/karmada/_crds/bases/policy/policy.karmada.io_clusterpropagationpolicies.yaml

@@ -620,23 +620,31 @@ spec:
                       type: object
                     type: array
                 type: object
+              preemption:
+                default: Never
+                description: Preemption declares the behaviors for preempting. Valid
+                  options are "Always" and "Never".
+                enum:
+                - Always
+                - Never
+                type: string
               priority:
                 default: 0
                 description: "Priority indicates the importance of a policy(PropagationPolicy
                   or ClusterPropagationPolicy). A policy will be applied for the matched
                   resource templates if there is no other policies with higher priority
                   at the point of the resource template be processed. Once a resource
                   template has been claimed by a policy, by default it will not be
-                  preempted by following policies even with a higher priority. \n
-                  In case of two policies have the same priority, the one with a more
-                  precise matching rules in ResourceSelectors wins: - matching by
-                  name(resourceSelector.name) has higher priority than by selector(resourceSelector.labelSelector)
-                  - matching by selector(resourceSelector.labelSelector) has higher
-                  priority than by APIVersion(resourceSelector.apiVersion) and Kind(resourceSelector.kind).
-                  If there is still no winner at this point, the one with the lower
-                  alphabetic order wins, e.g. policy 'bar' has higher priority than
-                  'foo'. \n The higher the value, the higher the priority. Defaults
-                  to zero."
+                  preempted by following policies even with a higher priority. See
+                  Preemption for more details. \n In case of two policies have the
+                  same priority, the one with a more precise matching rules in ResourceSelectors
+                  wins: - matching by name(resourceSelector.name) has higher priority
+                  than by selector(resourceSelector.labelSelector) - matching by selector(resourceSelector.labelSelector)
+                  has higher priority than by APIVersion(resourceSelector.apiVersion)
+                  and Kind(resourceSelector.kind). If there is still no winner at
+                  this point, the one with the lower alphabetic order wins, e.g. policy
+                  'bar' has higher priority than 'foo'. \n The higher the value, the
+                  higher the priority. Defaults to zero."
                 format: int32
                 type: integer
               propagateDeps:

charts/karmada/_crds/bases/policy/policy.karmada.io_propagationpolicies.yaml

@@ -616,23 +616,31 @@ spec:
                       type: object
                     type: array
                 type: object
+              preemption:
+                default: Never
+                description: Preemption declares the behaviors for preempting. Valid
+                  options are "Always" and "Never".
+                enum:
+                - Always
+                - Never
+                type: string
               priority:
                 default: 0
                 description: "Priority indicates the importance of a policy(PropagationPolicy
                   or ClusterPropagationPolicy). A policy will be applied for the matched
                   resource templates if there is no other policies with higher priority
                   at the point of the resource template be processed. Once a resource
                   template has been claimed by a policy, by default it will not be
-                  preempted by following policies even with a higher priority. \n
-                  In case of two policies have the same priority, the one with a more
-                  precise matching rules in ResourceSelectors wins: - matching by
-                  name(resourceSelector.name) has higher priority than by selector(resourceSelector.labelSelector)
-                  - matching by selector(resourceSelector.labelSelector) has higher
-                  priority than by APIVersion(resourceSelector.apiVersion) and Kind(resourceSelector.kind).
-                  If there is still no winner at this point, the one with the lower
-                  alphabetic order wins, e.g. policy 'bar' has higher priority than
-                  'foo'. \n The higher the value, the higher the priority. Defaults
-                  to zero."
+                  preempted by following policies even with a higher priority. See
+                  Preemption for more details. \n In case of two policies have the
+                  same priority, the one with a more precise matching rules in ResourceSelectors
+                  wins: - matching by name(resourceSelector.name) has higher priority
+                  than by selector(resourceSelector.labelSelector) - matching by selector(resourceSelector.labelSelector)
+                  has higher priority than by APIVersion(resourceSelector.apiVersion)
+                  and Kind(resourceSelector.kind). If there is still no winner at
+                  this point, the one with the lower alphabetic order wins, e.g. policy
+                  'bar' has higher priority than 'foo'. \n The higher the value, the
+                  higher the priority. Defaults to zero."
                 format: int32
                 type: integer
               propagateDeps:

pkg/apis/policy/v1alpha1/propagation_types.go

@@ -76,6 +76,7 @@ type PropagationSpec struct {
 	// template be processed.
 	// Once a resource template has been claimed by a policy, by default it will
 	// not be preempted by following policies even with a higher priority.
+	// See Preemption for more details.
 	//
 	// In case of two policies have the same priority, the one with a more precise
 	// matching rules in ResourceSelectors wins:
@@ -91,6 +92,14 @@ type PropagationSpec struct {
 	// +kubebuilder:default=0
 	Priority *int32 `json:"priority,omitempty"`
 
+	// Preemption declares the behaviors for preempting.
+	// Valid options are "Always" and "Never".
+	//
+	// +kubebuilder:default="Never"
+	// +kubebuilder:validation:Enum=Always;Never
+	// +optional
+	Preemption PreemptionBehavior `json:"preemption,omitempty"`
+
 	// DependentOverrides represents the list of overrides(OverridePolicy)
 	// which must present before the current PropagationPolicy takes effect.
 	//
@@ -443,6 +452,30 @@ const (
 	DynamicWeightByAvailableReplicas DynamicWeightFactor = "AvailableReplicas"
 )
 
+// PreemptionBehavior describes whether and how to preempt resources that are
+// claimed by lower-priority PropagationPolicy(ClusterPropagationPolicy).
+// +enum
+type PreemptionBehavior string
+
+const (
+	// PreemptAlways means that preemption is allowed.
+	//
+	// If it is applied to a PropagationPolicy, it can preempt any resource as
+	// per Priority, regardless of whether it has been claimed by a PropagationPolicy
+	// or a ClusterPropagationPolicy, as long as it can match the rules defined
+	// in ResourceSelector. In addition, if a resource has already been claimed
+	// by a ClusterPropagationPolicy, the PropagationPolicy can still preempt it
+	// without considering Priority.
+	//
+	// If it is applied to a ClusterPropagationPolicy, it can only preempt from
+	// ClusterPropagationPolicy, and from PropagationPolicy is not allowed.
+	PreemptAlways PreemptionBehavior = "Always"
+
+	// PreemptNever means that a PropagationPolicy(ClusterPropagationPolicy) never
+	// preempts resources.
+	PreemptNever PreemptionBehavior = "Never"
+)
+
 // +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
 
 // PropagationPolicyList contains a list of PropagationPolicy.