Merge pull request #41541 from resouer/eclass-algorithm

Automatic merge from submit-queue

Update algorithm of equivalence class cache predicates

NOTE: This is the first two commits of #36238

**What's in this PR:**

1. Definition of equivalence class
2. An update of `equivalence_cache.go` algorithms to implement enable/disable equivalence cache for individual predicate
3. Added equivalence class data structure to `Generic Scheduler` but did not initialize it. This is used to show how we will use equivalence class when scheduling.

**Why I did this:**

Although #36238 has been finished for a period of time, we found it's still very hard to review, because it mixed 1) definition of equivalence class, 2) how to use equivalence cache, and 3) how to keep this cache up-to-date, 4) e2e tests to verify (3) works.  

So reviewers are easily distracted by different technical points like `hash algorithms`, `how to properly use Informer` etc, left the more important equivalence algorithms untouched.

So this PR I only includes 1) and 2), leaves updating this cache in #36238. I can see this part is totally independent from the rest part of it. So we can definitely review this equivalence  strategies first.

cc @kubernetes/sig-scheduling-pr-reviews @davidopp @jayunit100 @wojtek-t

plugin/pkg/scheduler/BUILD

@@ -43,6 +43,7 @@ go_library(
         "//pkg/client/listers/core/v1:go_default_library",
         "//plugin/pkg/scheduler/algorithm:go_default_library",
         "//plugin/pkg/scheduler/api:go_default_library",
+        "//plugin/pkg/scheduler/core:go_default_library",
         "//plugin/pkg/scheduler/metrics:go_default_library",
         "//plugin/pkg/scheduler/schedulercache:go_default_library",
         "//plugin/pkg/scheduler/util:go_default_library",

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

@@ -247,22 +247,21 @@ func copyAndReplace(set sets.String, replaceWhat, replaceWith string) sets.Strin
 
 // GetEquivalencePod returns a EquivalencePod which contains a group of pod attributes which can be reused.
 func GetEquivalencePod(pod *v1.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
+	// 2. with same OwnerReferences
 	// to be equivalent
 	if len(pod.OwnerReferences) != 0 {
 		for _, ref := range pod.OwnerReferences {
 			if *ref.Controller {
-				equivalencePod.ControllerRef = ref
 				// a pod can only belongs to one controller
-				break
+				return &EquivalencePod{
+					ControllerRef: ref,
 				}
 			}
 		}
-	return &equivalencePod
+	}
+	return nil
 }
 
 // EquivalencePod is a group of pod attributes which can be reused as equivalence to schedule other pods.

plugin/pkg/scheduler/core/BUILD

@@ -11,6 +11,7 @@ load(
 go_test(
     name = "go_default_test",
     srcs = [
+        "equivalence_cache_test.go",
         "extender_test.go",
         "generic_scheduler_test.go",
     ],
@@ -53,6 +54,7 @@ go_library(
         "//vendor:github.com/golang/groupcache/lru",
         "//vendor:k8s.io/apimachinery/pkg/util/errors",
         "//vendor:k8s.io/apimachinery/pkg/util/net",
+        "//vendor:k8s.io/apimachinery/pkg/util/sets",
         "//vendor:k8s.io/apiserver/pkg/util/trace",
         "//vendor:k8s.io/client-go/rest",
         "//vendor:k8s.io/client-go/util/workqueue",

plugin/pkg/scheduler/core/equivalence_cache.go

@@ -18,18 +18,19 @@ package core
 
 import (
 	"hash/fnv"
-
-	"github.com/golang/groupcache/lru"
-
 	"sync"
 
+	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/kubernetes/pkg/api/v1"
 	hashutil "k8s.io/kubernetes/pkg/util/hash"
 	"k8s.io/kubernetes/plugin/pkg/scheduler/algorithm"
+
+	"github.com/golang/glog"
+	"github.com/golang/groupcache/lru"
 )
 
-// TODO(harryz) figure out the right number for this, 4096 may be too big
-const maxCacheEntries = 4096
+// we use predicate names as cache's key, its count is limited
+const maxCacheEntries = 100
 
 type HostPredicate struct {
 	Fit         bool
@@ -41,6 +42,9 @@ type AlgorithmCache struct {
 	predicatesCache *lru.Cache
 }
 
+// PredicateMap use equivalence hash as key
+type PredicateMap map[uint64]HostPredicate
+
 func newAlgorithmCache() AlgorithmCache {
 	return AlgorithmCache{
 		predicatesCache: lru.New(maxCacheEntries),
@@ -61,74 +65,151 @@ func NewEquivalenceCache(getEquivalencePodFunc algorithm.GetEquivalencePodFunc)
 	}
 }
 
-// addPodPredicate adds pod predicate for equivalence class
-func (ec *EquivalenceCache) addPodPredicate(podKey uint64, nodeName string, fit bool, failReasons []algorithm.PredicateFailureReason) {
+// UpdateCachedPredicateItem updates pod predicate for equivalence class
+func (ec *EquivalenceCache) UpdateCachedPredicateItem(pod *v1.Pod, nodeName, predicateKey string, fit bool, reasons []algorithm.PredicateFailureReason, equivalenceHash uint64) {
+	ec.Lock()
+	defer ec.Unlock()
 	if _, exist := ec.algorithmCache[nodeName]; !exist {
 		ec.algorithmCache[nodeName] = newAlgorithmCache()
 	}
-	ec.algorithmCache[nodeName].predicatesCache.Add(podKey, HostPredicate{Fit: fit, FailReasons: failReasons})
+	predicateItem := HostPredicate{
+		Fit:         fit,
+		FailReasons: reasons,
 	}
-
-// AddPodPredicatesCache cache pod predicate for equivalence class
-func (ec *EquivalenceCache) AddPodPredicatesCache(pod *v1.Pod, fitNodeList []*v1.Node, failedPredicates *FailedPredicateMap) {
-	equivalenceHash := ec.hashEquivalencePod(pod)
-
-	for _, fitNode := range fitNodeList {
-		ec.addPodPredicate(equivalenceHash, fitNode.Name, true, nil)
-	}
-	for failNodeName, failReasons := range *failedPredicates {
-		ec.addPodPredicate(equivalenceHash, failNodeName, false, failReasons)
-	}
-}
-
-// GetCachedPredicates gets cached predicates for equivalence class
-func (ec *EquivalenceCache) GetCachedPredicates(pod *v1.Pod, nodes []*v1.Node) ([]*v1.Node, FailedPredicateMap, []*v1.Node) {
-	fitNodeList := []*v1.Node{}
-	failedPredicates := FailedPredicateMap{}
-	noCacheNodeList := []*v1.Node{}
-	equivalenceHash := ec.hashEquivalencePod(pod)
-	for _, node := range nodes {
-		findCache := false
-		if algorithmCache, exist := ec.algorithmCache[node.Name]; exist {
-			if cachePredicate, exist := algorithmCache.predicatesCache.Get(equivalenceHash); exist {
-				hostPredicate := cachePredicate.(HostPredicate)
-				if hostPredicate.Fit {
-					fitNodeList = append(fitNodeList, node)
+	// if cached predicate map already exists, just update the predicate by key
+	if v, ok := ec.algorithmCache[nodeName].predicatesCache.Get(predicateKey); ok {
+		predicateMap := v.(PredicateMap)
+		// maps in golang are references, no need to add them back
+		predicateMap[equivalenceHash] = predicateItem
 	} else {
-					failedPredicates[node.Name] = hostPredicate.FailReasons
+		ec.algorithmCache[nodeName].predicatesCache.Add(predicateKey,
+			PredicateMap{
+				equivalenceHash: predicateItem,
+			})
 	}
-				findCache = true
-			}
-		}
-		if !findCache {
-			noCacheNodeList = append(noCacheNodeList, node)
-		}
-	}
-	return fitNodeList, failedPredicates, noCacheNodeList
+	glog.V(5).Infof("Updated cached predicate: %v for pod: %v on node: %s, with item %v", predicateKey, pod.GetName(), nodeName, predicateItem)
 }
 
-// SendInvalidAlgorithmCacheReq marks AlgorithmCache item as invalid
-func (ec *EquivalenceCache) SendInvalidAlgorithmCacheReq(nodeName string) {
+// PredicateWithECache returns:
+// 1. if fit
+// 2. reasons if not fit
+// 3. if this cache is invalid
+// based on cached predicate results
+func (ec *EquivalenceCache) PredicateWithECache(pod *v1.Pod, nodeName, predicateKey string, equivalenceHash uint64) (bool, []algorithm.PredicateFailureReason, bool) {
+	ec.RLock()
+	defer ec.RUnlock()
+	glog.V(5).Infof("Begin to calculate predicate: %v for pod: %s on node: %s based on equivalence cache", predicateKey, pod.GetName(), nodeName)
+	if algorithmCache, exist := ec.algorithmCache[nodeName]; exist {
+		if cachePredicate, exist := algorithmCache.predicatesCache.Get(predicateKey); exist {
+			predicateMap := cachePredicate.(PredicateMap)
+			// TODO(resouer) Is it possible a race that cache failed to update immediately?
+			if hostPredicate, ok := predicateMap[equivalenceHash]; ok {
+				if hostPredicate.Fit {
+					return true, []algorithm.PredicateFailureReason{}, false
+				} else {
+					return false, hostPredicate.FailReasons, false
+				}
+			} else {
+				// is invalid
+				return false, []algorithm.PredicateFailureReason{}, true
+			}
+		}
+	}
+	return false, []algorithm.PredicateFailureReason{}, true
+}
+
+// InvalidateCachedPredicateItem marks all items of given predicateKeys, of all pods, on the given node as invalid
+func (ec *EquivalenceCache) InvalidateCachedPredicateItem(nodeName string, predicateKeys sets.String) {
+	if len(predicateKeys) == 0 {
+		return
+	}
 	ec.Lock()
 	defer ec.Unlock()
-	// clear the cache of this node
-	delete(ec.algorithmCache, nodeName)
+	if algorithmCache, exist := ec.algorithmCache[nodeName]; exist {
+		for predicateKey := range predicateKeys {
+			algorithmCache.predicatesCache.Remove(predicateKey)
+		}
+	}
+	glog.V(5).Infof("Done invalidating cached predicates: %v on node: %s", predicateKeys, nodeName)
 }
 
-// SendClearAllCacheReq marks all cached item as invalid
-func (ec *EquivalenceCache) SendClearAllCacheReq() {
+// InvalidateCachedPredicateItemOfAllNodes marks all items of given predicateKeys, of all pods, on all node as invalid
+func (ec *EquivalenceCache) InvalidateCachedPredicateItemOfAllNodes(predicateKeys sets.String) {
+	if len(predicateKeys) == 0 {
+		return
+	}
 	ec.Lock()
 	defer ec.Unlock()
-	// clear cache of all nodes
-	for nodeName := range ec.algorithmCache {
-		delete(ec.algorithmCache, nodeName)
+	// algorithmCache uses nodeName as key, so we just iterate it and invalid given predicates
+	for _, algorithmCache := range ec.algorithmCache {
+		for predicateKey := range predicateKeys {
+			// just use keys is enough
+			algorithmCache.predicatesCache.Remove(predicateKey)
 		}
 	}
+	glog.V(5).Infof("Done invalidating cached predicates: %v on all node", predicateKeys)
+}
 
-// hashEquivalencePod returns the hash of equivalence pod.
-func (ec *EquivalenceCache) hashEquivalencePod(pod *v1.Pod) uint64 {
+// InvalidateAllCachedPredicateItemOfNode marks all cached items on given node as invalid
+func (ec *EquivalenceCache) InvalidateAllCachedPredicateItemOfNode(nodeName string) {
+	ec.Lock()
+	defer ec.Unlock()
+	delete(ec.algorithmCache, nodeName)
+	glog.V(5).Infof("Done invalidating all cached predicates on node: %s", nodeName)
+}
+
+// InvalidateCachedPredicateItemForPod marks item of given predicateKeys, of given pod, on the given node as invalid
+func (ec *EquivalenceCache) InvalidateCachedPredicateItemForPod(nodeName string, predicateKeys sets.String, pod *v1.Pod) {
+	if len(predicateKeys) == 0 {
+		return
+	}
+	equivalenceHash := ec.getHashEquivalencePod(pod)
+	if equivalenceHash == 0 {
+		// no equivalence pod found, just return
+		return
+	}
+	ec.Lock()
+	defer ec.Unlock()
+	if algorithmCache, exist := ec.algorithmCache[nodeName]; exist {
+		for predicateKey := range predicateKeys {
+			if cachePredicate, exist := algorithmCache.predicatesCache.Get(predicateKey); exist {
+				// got the cached item of by predicateKey & pod
+				predicateMap := cachePredicate.(PredicateMap)
+				delete(predicateMap, equivalenceHash)
+			}
+		}
+	}
+	glog.V(5).Infof("Done invalidating cached predicates %v on node %s, for pod %v", predicateKeys, nodeName, pod.GetName())
+}
+
+// InvalidateCachedPredicateItemForPodAdd is a wrapper of InvalidateCachedPredicateItem for pod add case
+func (ec *EquivalenceCache) InvalidateCachedPredicateItemForPodAdd(pod *v1.Pod, nodeName string) {
+	// MatchInterPodAffinity: we assume scheduler can make sure newly binded pod
+	// will not break the existing inter pod affinity. So we does not need to invalidate
+	// MatchInterPodAffinity when pod added.
+	//
+	// But when a pod is deleted, existing inter pod affinity may become invalid.
+	// (e.g. this pod was preferred by some else, or vice versa)
+	//
+	// NOTE: assumptions above will not stand when we implemented features like
+	// RequiredDuringSchedulingRequiredDuringExecution.
+
+	// NoDiskConflict: the newly scheduled pod fits to existing pods on this node,
+	// it will also fits to equivalence class of existing pods
+
+	// GeneralPredicates: will always be affected by adding a new pod
+	invalidPredicates := sets.NewString("GeneralPredicates")
+	ec.InvalidateCachedPredicateItem(nodeName, invalidPredicates)
+}
+
+// getHashEquivalencePod returns the hash of equivalence pod.
+// if no equivalence pod found, return 0
+func (ec *EquivalenceCache) getHashEquivalencePod(pod *v1.Pod) uint64 {
 	equivalencePod := ec.getEquivalencePod(pod)
+	if equivalencePod != nil {
 		hash := fnv.New32a()
 		hashutil.DeepHashObject(hash, equivalencePod)
 		return uint64(hash.Sum32())
 	}
+	return 0
+}

plugin/pkg/scheduler/core/equivalence_cache_test.go

@@ -0,0 +1,131 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package core
+
+import (
+	"reflect"
+	"testing"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/kubernetes/pkg/api/v1"
+	"k8s.io/kubernetes/plugin/pkg/scheduler/algorithm"
+	"k8s.io/kubernetes/plugin/pkg/scheduler/algorithm/predicates"
+)
+
+func TestUpdateCachedPredicateItem(t *testing.T) {
+	tests := []struct {
+		name            string
+		pod             *v1.Pod
+		predicateKey    string
+		nodeName        string
+		fit             bool
+		reasons         []algorithm.PredicateFailureReason
+		equivalenceHash uint64
+		expectCacheItem HostPredicate
+	}{
+		{
+			name:            "test 1",
+			pod:             &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "testPod"}},
+			predicateKey:    "GeneralPredicates",
+			nodeName:        "node1",
+			fit:             true,
+			equivalenceHash: 123,
+			expectCacheItem: HostPredicate{
+				Fit: true,
+			},
+		},
+	}
+	for _, test := range tests {
+		// this case does not need to calculate equivalence hash, just pass an empty function
+		fakeGetEquivalencePodFunc := func(pod *v1.Pod) interface{} { return nil }
+		ecache := NewEquivalenceCache(fakeGetEquivalencePodFunc)
+		ecache.UpdateCachedPredicateItem(test.pod, test.nodeName, test.predicateKey, test.fit, test.reasons, test.equivalenceHash)
+
+		value, ok := ecache.algorithmCache[test.nodeName].predicatesCache.Get(test.predicateKey)
+		if !ok {
+			t.Errorf("Failed : %s, can't find expected cache item: %v", test.name, test.expectCacheItem)
+		} else {
+			cachedMapItem := value.(PredicateMap)
+			if !reflect.DeepEqual(cachedMapItem[test.equivalenceHash], test.expectCacheItem) {
+				t.Errorf("Failed : %s, expected cached item: %v, but got: %v", test.name, test.expectCacheItem, cachedMapItem[test.equivalenceHash])
+			}
+		}
+	}
+}
+
+type predicateItemType struct {
+	fit     bool
+	reasons []algorithm.PredicateFailureReason
+}
+
+func TestInvalidateCachedPredicateItem(t *testing.T) {
+	tests := []struct {
+		name                  string
+		pod                   *v1.Pod
+		nodeName              string
+		predicateKey          string
+		equivalenceHash       uint64
+		cachedItem            predicateItemType
+		expectedInvalid       bool
+		expectedPredicateItem predicateItemType
+	}{
+		{
+			name:            "test 1",
+			pod:             &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "testPod"}},
+			nodeName:        "node1",
+			equivalenceHash: 123,
+			predicateKey:    "GeneralPredicates",
+			cachedItem: predicateItemType{
+				fit:     false,
+				reasons: []algorithm.PredicateFailureReason{predicates.ErrPodNotFitsHostPorts},
+			},
+			expectedInvalid: true,
+			expectedPredicateItem: predicateItemType{
+				fit:     false,
+				reasons: []algorithm.PredicateFailureReason{},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		// this case does not need to calculate equivalence hash, just pass an empty function
+		fakeGetEquivalencePodFunc := func(pod *v1.Pod) interface{} { return nil }
+		ecache := NewEquivalenceCache(fakeGetEquivalencePodFunc)
+		// set cached item to equivalence cache
+		ecache.UpdateCachedPredicateItem(test.pod, test.nodeName, test.predicateKey, test.cachedItem.fit, test.cachedItem.reasons, test.equivalenceHash)
+		// if we want to do invalid, invalid the cached item
+		if test.expectedInvalid {
+			predicateKeys := sets.NewString()
+			predicateKeys.Insert(test.predicateKey)
+			ecache.InvalidateCachedPredicateItem(test.nodeName, predicateKeys)
+		}
+		// calculate predicate with equivalence cache
+		fit, reasons, invalid := ecache.PredicateWithECache(test.pod, test.nodeName, test.predicateKey, test.equivalenceHash)
+		// returned invalid should match expectedInvalid
+		if invalid != test.expectedInvalid {
+			t.Errorf("Failed : %s, expected invalid: %v, but got: %v", test.name, test.expectedInvalid, invalid)
+		}
+		// returned predicate result should match expected predicate item
+		if fit != test.expectedPredicateItem.fit {
+			t.Errorf("Failed : %s, expected fit: %v, but got: %v", test.name, test.cachedItem.fit, fit)
+		}
+		if !reflect.DeepEqual(reasons, test.expectedPredicateItem.reasons) {
+			t.Errorf("Failed : %s, expected reasons: %v, but got: %v", test.name, test.cachedItem.reasons, reasons)
+		}
+	}
+}

plugin/pkg/scheduler/core/extender_test.go

@@ -293,7 +293,7 @@ func TestGenericSchedulerWithExtenders(t *testing.T) {
 			cache.AddNode(&v1.Node{ObjectMeta: metav1.ObjectMeta{Name: name}})
 		}
 		scheduler := NewGenericScheduler(
-			cache, test.predicates, algorithm.EmptyMetadataProducer, test.prioritizers, algorithm.EmptyMetadataProducer, extenders)
+			cache, nil, test.predicates, algorithm.EmptyMetadataProducer, test.prioritizers, algorithm.EmptyMetadataProducer, extenders)
 		podIgnored := &v1.Pod{}
 		machine, err := scheduler.Schedule(podIgnored, schedulertesting.FakeNodeLister(makeNodeList(test.nodes)))
 		if test.expectsErr {

plugin/pkg/scheduler/core/generic_scheduler.go

@@ -69,6 +69,7 @@ func (f *FitError) Error() string {
 
 type genericScheduler struct {
 	cache                 schedulercache.Cache
+	equivalenceCache      *EquivalenceCache
 	predicates            map[string]algorithm.FitPredicate
 	priorityMetaProducer  algorithm.MetadataProducer
 	predicateMetaProducer algorithm.MetadataProducer
@@ -79,8 +80,6 @@ type genericScheduler struct {
 	lastNodeIndex         uint64
 
 	cachedNodeInfoMap map[string]*schedulercache.NodeInfo
-
-	equivalenceCache *EquivalenceCache
 }
 
 // Schedule tries to schedule the given pod to one of node in the node list.
@@ -104,10 +103,8 @@ func (g *genericScheduler) Schedule(pod *v1.Pod, nodeLister algorithm.NodeLister
 		return "", err
 	}
 
-	// TODO(harryz) Check if equivalenceCache is enabled and call scheduleWithEquivalenceClass here
-
 	trace.Step("Computing predicates")
-	filteredNodes, failedPredicateMap, err := findNodesThatFit(pod, g.cachedNodeInfoMap, nodes, g.predicates, g.extenders, g.predicateMetaProducer)
+	filteredNodes, failedPredicateMap, err := findNodesThatFit(pod, g.cachedNodeInfoMap, nodes, g.predicates, g.extenders, g.predicateMetaProducer, g.equivalenceCache)
 	if err != nil {
 		return "", err
 	}
@@ -158,6 +155,7 @@ func findNodesThatFit(
 	predicateFuncs map[string]algorithm.FitPredicate,
 	extenders []algorithm.SchedulerExtender,
 	metadataProducer algorithm.MetadataProducer,
+	ecache *EquivalenceCache,
 ) ([]*v1.Node, FailedPredicateMap, error) {
 	var filtered []*v1.Node
 	failedPredicateMap := FailedPredicateMap{}
@@ -176,7 +174,7 @@ func findNodesThatFit(
 		meta := metadataProducer(pod, nodeNameToInfo)
 		checkNode := func(i int) {
 			nodeName := nodes[i].Name
-			fits, failedPredicates, err := podFitsOnNode(pod, meta, nodeNameToInfo[nodeName], predicateFuncs)
+			fits, failedPredicates, err := podFitsOnNode(pod, meta, nodeNameToInfo[nodeName], predicateFuncs, ecache)
 			if err != nil {
 				predicateResultLock.Lock()
 				errs = append(errs, err)
@@ -221,15 +219,45 @@ func findNodesThatFit(
 }
 
 // Checks whether node with a given name and NodeInfo satisfies all predicateFuncs.
-func podFitsOnNode(pod *v1.Pod, meta interface{}, info *schedulercache.NodeInfo, predicateFuncs map[string]algorithm.FitPredicate) (bool, []algorithm.PredicateFailureReason, error) {
-	var failedPredicates []algorithm.PredicateFailureReason
-	for _, predicate := range predicateFuncs {
-		fit, reasons, err := predicate(pod, meta, info)
+func podFitsOnNode(pod *v1.Pod, meta interface{}, info *schedulercache.NodeInfo, predicateFuncs map[string]algorithm.FitPredicate,
+	ecache *EquivalenceCache) (bool, []algorithm.PredicateFailureReason, error) {
+	var (
+		equivalenceHash  uint64
+		failedPredicates []algorithm.PredicateFailureReason
+		eCacheAvailable  bool
+		invalid          bool
+		fit              bool
+		reasons          []algorithm.PredicateFailureReason
+		err              error
+	)
+	if ecache != nil {
+		// getHashEquivalencePod will return immediately if no equivalence pod found
+		equivalenceHash = ecache.getHashEquivalencePod(pod)
+		eCacheAvailable = (equivalenceHash != 0)
+	}
+	for predicateKey, predicate := range predicateFuncs {
+		// If equivalenceCache is available
+		if eCacheAvailable {
+			// PredicateWithECache will returns it's cached predicate results
+			fit, reasons, invalid = ecache.PredicateWithECache(pod, info.Node().GetName(), predicateKey, equivalenceHash)
+		}
+
+		if !eCacheAvailable || invalid {
+			// we need to execute predicate functions since equivalence cache does not work
+			fit, reasons, err = predicate(pod, meta, info)
 			if err != nil {
-			err := fmt.Errorf("SchedulerPredicates failed due to %v, which is unexpected.", err)
 				return false, []algorithm.PredicateFailureReason{}, err
 			}
+
+			if eCacheAvailable {
+				// update equivalence cache with newly computed fit & reasons
+				// TODO(resouer) should we do this in another thread? any race?
+				ecache.UpdateCachedPredicateItem(pod, info.Node().GetName(), predicateKey, fit, reasons, equivalenceHash)
+			}
+		}
+
 		if !fit {
+			// eCache is available and valid, and predicates result is unfit, record the fail reasons
 			failedPredicates = append(failedPredicates, reasons...)
 		}
 	}
@@ -386,6 +414,7 @@ func EqualPriorityMap(_ *v1.Pod, _ interface{}, nodeInfo *schedulercache.NodeInf
 
 func NewGenericScheduler(
 	cache schedulercache.Cache,
+	eCache *EquivalenceCache,
 	predicates map[string]algorithm.FitPredicate,
 	predicateMetaProducer algorithm.MetadataProducer,
 	prioritizers []algorithm.PriorityConfig,
@@ -393,6 +422,7 @@ func NewGenericScheduler(
 	extenders []algorithm.SchedulerExtender) algorithm.ScheduleAlgorithm {
 	return &genericScheduler{
 		cache:                 cache,
+		equivalenceCache:      eCache,
 		predicates:            predicates,
 		predicateMetaProducer: predicateMetaProducer,
 		prioritizers:          prioritizers,

plugin/pkg/scheduler/core/generic_scheduler_test.go

@@ -307,7 +307,7 @@ func TestGenericScheduler(t *testing.T) {
 		}
 
 		scheduler := NewGenericScheduler(
-			cache, test.predicates, algorithm.EmptyMetadataProducer, test.prioritizers, algorithm.EmptyMetadataProducer,
+			cache, nil, test.predicates, algorithm.EmptyMetadataProducer, test.prioritizers, algorithm.EmptyMetadataProducer,
 			[]algorithm.SchedulerExtender{})
 		machine, err := scheduler.Schedule(test.pod, schedulertesting.FakeNodeLister(makeNodeList(test.nodes)))
 
@@ -328,7 +328,7 @@ func TestFindFitAllError(t *testing.T) {
 		"2": schedulercache.NewNodeInfo(),
 		"1": schedulercache.NewNodeInfo(),
 	}
-	_, predicateMap, err := findNodesThatFit(&v1.Pod{}, nodeNameToInfo, makeNodeList(nodes), predicates, nil, algorithm.EmptyMetadataProducer)
+	_, predicateMap, err := findNodesThatFit(&v1.Pod{}, nodeNameToInfo, makeNodeList(nodes), predicates, nil, algorithm.EmptyMetadataProducer, nil)
 
 	if err != nil {
 		t.Errorf("unexpected error: %v", err)
@@ -362,7 +362,7 @@ func TestFindFitSomeError(t *testing.T) {
 		nodeNameToInfo[name].SetNode(&v1.Node{ObjectMeta: metav1.ObjectMeta{Name: name}})
 	}
 
-	_, predicateMap, err := findNodesThatFit(pod, nodeNameToInfo, makeNodeList(nodes), predicates, nil, algorithm.EmptyMetadataProducer)
+	_, predicateMap, err := findNodesThatFit(pod, nodeNameToInfo, makeNodeList(nodes), predicates, nil, algorithm.EmptyMetadataProducer, nil)
 	if err != nil {
 		t.Errorf("unexpected error: %v", err)
 	}

plugin/pkg/scheduler/factory/factory.go

@@ -189,7 +189,7 @@ func (c *ConfigFactory) GetScheduledPodLister() corelisters.PodLister {
 	return c.scheduledPodLister
 }
 
-// TODO(harryz) need to update all the handlers here and below for equivalence cache
+// TODO(resouer) need to update all the handlers here and below for equivalence cache
 func (c *ConfigFactory) addPodToCache(obj interface{}) {
 	pod, ok := obj.(*v1.Pod)
 	if !ok {
@@ -370,7 +370,8 @@ func (f *ConfigFactory) CreateFromKeys(predicateKeys, priorityKeys sets.String,
 	}
 
 	f.Run()
-	algo := core.NewGenericScheduler(f.schedulerCache, predicateFuncs, predicateMetaProducer, priorityConfigs, priorityMetaProducer, extenders)
+	// TODO(resouer) use equivalence cache instead of nil here when #36238 get merged
+	algo := core.NewGenericScheduler(f.schedulerCache, nil, predicateFuncs, predicateMetaProducer, priorityConfigs, priorityMetaProducer, extenders)
 	podBackoff := util.CreateDefaultPodBackoff()
 	return &scheduler.Config{
 		SchedulerCache: f.schedulerCache,

plugin/pkg/scheduler/scheduler.go

@@ -27,6 +27,7 @@ import (
 	corelisters "k8s.io/kubernetes/pkg/client/listers/core/v1"
 	"k8s.io/kubernetes/plugin/pkg/scheduler/algorithm"
 	schedulerapi "k8s.io/kubernetes/plugin/pkg/scheduler/api"
+	"k8s.io/kubernetes/plugin/pkg/scheduler/core"
 	"k8s.io/kubernetes/plugin/pkg/scheduler/metrics"
 	"k8s.io/kubernetes/plugin/pkg/scheduler/schedulercache"
 	"k8s.io/kubernetes/plugin/pkg/scheduler/util"
@@ -92,6 +93,9 @@ type Config struct {
 	// It is expected that changes made via SchedulerCache will be observed
 	// by NodeLister and Algorithm.
 	SchedulerCache schedulercache.Cache
+	// Ecache is used for optimistically invalid affected cache items after
+	// successfully binding a pod
+	Ecache     *core.EquivalenceCache
 	NodeLister algorithm.NodeLister
 	Algorithm  algorithm.ScheduleAlgorithm
 	Binder     Binder
@@ -193,6 +197,13 @@ func (sched *Scheduler) scheduleOne() {
 		return
 	}
 
+	// Optimistically assume that the binding will succeed, so we need to invalidate affected
+	// predicates in equivalence cache.
+	// If the binding fails, these invalidated item will not break anything.
+	if sched.config.Ecache != nil {
+		sched.config.Ecache.InvalidateCachedPredicateItemForPodAdd(pod, dest)
+	}
+
 	go func() {
 		defer metrics.E2eSchedulingLatency.Observe(metrics.SinceInMicroseconds(start))
 

plugin/pkg/scheduler/scheduler_test.go

@@ -480,6 +480,7 @@ func TestSchedulerFailedSchedulingReasons(t *testing.T) {
 func setupTestScheduler(queuedPodStore *clientcache.FIFO, scache schedulercache.Cache, nodeLister schedulertesting.FakeNodeLister, predicateMap map[string]algorithm.FitPredicate) (*Scheduler, chan *v1.Binding, chan error) {
 	algo := core.NewGenericScheduler(
 		scache,
+		nil,
 		predicateMap,
 		algorithm.EmptyMetadataProducer,
 		[]algorithm.PriorityConfig{},
@@ -510,6 +511,7 @@ func setupTestScheduler(queuedPodStore *clientcache.FIFO, scache schedulercache.
 func setupTestSchedulerLongBindingWithRetry(queuedPodStore *clientcache.FIFO, scache schedulercache.Cache, nodeLister schedulertesting.FakeNodeLister, predicateMap map[string]algorithm.FitPredicate, stop chan struct{}, bindingTime time.Duration) (*Scheduler, chan *v1.Binding) {
 	algo := core.NewGenericScheduler(
 		scache,
+		nil,
 		predicateMap,
 		algorithm.EmptyMetadataProducer,
 		[]algorithm.PriorityConfig{},