update inter-pod affinity predicates, check PodAntiAffinity even when pod has no AntiAffinity constraints

plugin/pkg/scheduler/algorithm/predicates/predicates.go

@@ -925,7 +925,7 @@ func (checker *PodAffinityChecker) NodeMatchesHardPodAffinity(pod *api.Pod, allP
 // break any existing pods' anti-affinity rules, then return true.
 func (checker *PodAffinityChecker) NodeMatchesHardPodAntiAffinity(pod *api.Pod, allPods []*api.Pod, node *api.Node, podAntiAffinity *api.PodAntiAffinity) bool {
 	var podAntiAffinityTerms []api.PodAffinityTerm
-	if len(podAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution) != 0 {
+	if podAntiAffinity != nil && len(podAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution) != 0 {
 		podAntiAffinityTerms = podAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution
 	}
 	// TODO: Uncomment this block when implement RequiredDuringSchedulingRequiredDuringExecution.
@@ -999,19 +999,15 @@ func (checker *PodAffinityChecker) NodeMatchPodAffinityAntiAffinity(pod *api.Pod
 	}
 
 	// check if the current node match the inter-pod affinity scheduling rules.
+	// hard inter-pod affinity is not symmetric, check only when affinity.PodAffinity is not nil.
 	if affinity.PodAffinity != nil {
 		if !checker.NodeMatchesHardPodAffinity(pod, allPods, node, affinity.PodAffinity) {
 			return false
 		}
 	}
 
-	// check if the current node match the inter-pod anti-affinity scheduling rules.
+	// hard inter-pod anti-affinity is symmetric, check both when affinity.PodAntiAffinity is nil and not nil.
-	if affinity.PodAntiAffinity != nil {
+	return checker.NodeMatchesHardPodAntiAffinity(pod, allPods, node, affinity.PodAntiAffinity)
-		if !checker.NodeMatchesHardPodAntiAffinity(pod, allPods, node, affinity.PodAntiAffinity) {
-			return false
-		}
-	}
-	return true
 }
 
 func PodToleratesNodeTaints(pod *api.Pod, meta interface{}, nodeInfo *schedulercache.NodeInfo) (bool, error) {

plugin/pkg/scheduler/algorithm/predicates/predicates_test.go

@@ -2254,6 +2254,62 @@ func TestInterPodAffinity(t *testing.T) {
 			fits: false,
 			test: "pod matches its own Label in PodAffinity and that matches the existing pod Labels",
 		},
+		{
+			pod: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Labels: podLabel,
+				},
+			},
+			pods: []*api.Pod{{Spec: api.PodSpec{NodeName: "machine1"},
+				ObjectMeta: api.ObjectMeta{Labels: podLabel,
+					Annotations: map[string]string{
+						api.AffinityAnnotationKey: `
+						{"PodAntiAffinity": {
+							"requiredDuringSchedulingIgnoredDuringExecution": [{
+								"labelSelector": {
+									"matchExpressions": [{
+										"key": "service",
+										"operator": "In",
+										"values": ["securityscan", "value2"]
+									}]
+								},
+								"topologyKey": "zone"
+							}]
+						}}`,
+					}},
+			}},
+			node: &node1,
+			fits: false,
+			test: "verify that PodAntiAffinity from existing pod is respected when pod has no AntiAffinity constraints. doesn't satisfy PodAntiAffinity symmetry with the existing pod",
+		},
+		{
+			pod: &api.Pod{
+				ObjectMeta: api.ObjectMeta{
+					Labels: podLabel,
+				},
+			},
+			pods: []*api.Pod{{Spec: api.PodSpec{NodeName: "machine1"},
+				ObjectMeta: api.ObjectMeta{Labels: podLabel,
+					Annotations: map[string]string{
+						api.AffinityAnnotationKey: `
+                        {"PodAntiAffinity": {
+                            "requiredDuringSchedulingIgnoredDuringExecution": [{
+                                "labelSelector": {
+                                    "matchExpressions": [{
+                                        "key": "service",
+                                        "operator": "NotIn",
+                                        "values": ["securityscan", "value2"]
+                                    }]
+                                },
+                                "topologyKey": "zone"
+                            }]
+                        }}`,
+					}},
+			}},
+			node: &node1,
+			fits: true,
+			test: "verify that PodAntiAffinity from existing pod is respected when pod has no AntiAffinity constraints. satisfy PodAntiAffinity symmetry with the existing pod",
+		},
 	}
 	for _, test := range tests {
 		node := test.node