Merge pull request #31605 from resouer/eclass-1

Automatic merge from submit-queue

[Part 1] Implementation of equivalence pod

Part 1 of #30844

This PR: 

- Refactored `predicate.go`, so that `GetResourceRequest` can be used in other places to `GetEquivalencePod`.
- Implement a `equivalence_cache.go` to deal with all information we need to calculate an equivalent pod.
- Define and register a `RegisterGetEquivalencePodFunction `.

Work in next PR:
- The update of `equivalence_cache.go`
- Unit test
- Integration/e2e test

I think we can begin from the `equivalence_cache.go`? Thanks.  cc @wojtek-t @davidopp 

If I missed any other necessary part, please point it out.

plugin/pkg/scheduler/algorithmprovider/defaults/defaults.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"strconv"
 
+	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/cloudprovider/providers/aws"
 	"k8s.io/kubernetes/pkg/util/sets"
 	"k8s.io/kubernetes/plugin/pkg/scheduler"
@@ -36,6 +37,7 @@ const (
 	// GCE instances can have up to 16 PD volumes attached.
 	DefaultMaxGCEPDVolumes    = 16
 	ClusterAutoscalerProvider = "ClusterAutoscalerProvider"
+	PetSetKind                = "PetSet"
 )
 
 // getMaxVols checks the max PD volumes environment variable, otherwise returning a default value
@@ -105,6 +107,8 @@ func init() {
 	factory.RegisterFitPredicate("MatchNodeSelector", predicates.PodSelectorMatches)
 	// Optional, cluster-autoscaler friendly priority function - give used nodes higher priority.
 	factory.RegisterPriorityFunction2("MostRequestedPriority", priorities.MostRequestedPriorityMap, nil, 1)
+	// Use equivalence class to speed up predicates & priorities
+	factory.RegisterGetEquivalencePodFunction(GetEquivalencePod)
 }
 
 func replace(set sets.String, replaceWhat, replaceWith string) sets.String {
@@ -205,3 +209,39 @@ func defaultPriorities() sets.String {
 		),
 	)
 }
+
+// GetEquivalencePod returns a EquivalencePod which contains a group of pod attributes which can be reused.
+func GetEquivalencePod(pod *api.Pod) interface{} {
+	equivalencePod := EquivalencePod{}
+	// For now we only consider pods:
+	// 1. OwnerReferences is Controller
+	// 2. OwnerReferences kind is in valid controller kinds
+	// 3. with same OwnerReferences
+	// to be equivalent
+	if len(pod.OwnerReferences) != 0 {
+		for _, ref := range pod.OwnerReferences {
+			if *ref.Controller && isValidControllerKind(ref.Kind) {
+				equivalencePod.ControllerRef = ref
+				// a pod can only belongs to one controller
+				break
+			}
+		}
+	}
+	return &equivalencePod
+}
+
+// isValidControllerKind checks if a given controller's kind can be applied to equivalence pod algorithm.
+func isValidControllerKind(kind string) bool {
+	switch kind {
+	// list of kinds that we cannot handle
+	case PetSetKind:
+		return false
+	default:
+		return true
+	}
+}
+
+// EquivalencePod is a group of pod attributes which can be reused as equivalence to schedule other pods.
+type EquivalencePod struct {
+	ControllerRef api.OwnerReference
+}