Merge pull request #78097 from draveness/feature/post-filter-extension-point

feat: implement "post-filter" extension point for scheduling framework

pkg/scheduler/core/BUILD

@@ -59,6 +59,7 @@ go_test(
         "//staging/src/k8s.io/api/core/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/api/resource:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/types:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/errors:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/sets:go_default_library",

pkg/scheduler/core/generic_scheduler.go

@@ -29,7 +29,7 @@ import (
 
 	"k8s.io/klog"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	policy "k8s.io/api/policy/v1beta1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/labels"
@@ -89,9 +89,10 @@ type FailedPredicateMap map[string][]predicates.PredicateFailureReason
 
 // FitError describes a fit error of a pod.
 type FitError struct {
-	Pod              *v1.Pod
-	NumAllNodes      int
-	FailedPredicates FailedPredicateMap
+	Pod                   *v1.Pod
+	NumAllNodes           int
+	FailedPredicates      FailedPredicateMap
+	FilteredNodesStatuses framework.NodeToStatusMap
 }
 
 // ErrNoNodesAvailable is used to describe the error that no nodes available to schedule pods.
@@ -111,6 +112,10 @@ func (f *FitError) Error() string {
 		}
 	}
 
+	for _, status := range f.FilteredNodesStatuses {
+		reasons[status.Message()]++
+	}
+
 	sortReasonsHistogram := func() []string {
 		reasonStrings := []string{}
 		for k, v := range reasons {
@@ -206,16 +211,23 @@ func (g *genericScheduler) Schedule(pod *v1.Pod, nodeLister algorithm.NodeLister
 
 	trace.Step("Basic checks done")
 	startPredicateEvalTime := time.Now()
-	filteredNodes, failedPredicateMap, err := g.findNodesThatFit(pluginContext, pod, nodeLister)
+	filteredNodes, failedPredicateMap, filteredNodesStatuses, err := g.findNodesThatFit(pluginContext, pod, nodeLister)
 	if err != nil {
 		return result, err
 	}
 
+	// Run "postfilter" plugins.
+	postfilterStatus := g.framework.RunPostFilterPlugins(pluginContext, pod, filteredNodes, filteredNodesStatuses)
+	if !postfilterStatus.IsSuccess() {
+		return result, postfilterStatus.AsError()
+	}
+
 	if len(filteredNodes) == 0 {
 		return result, &FitError{
-			Pod:              pod,
-			NumAllNodes:      numNodes,
-			FailedPredicates: failedPredicateMap,
+			Pod:                   pod,
+			NumAllNodes:           numNodes,
+			FailedPredicates:      failedPredicateMap,
+			FilteredNodesStatuses: filteredNodesStatuses,
 		}
 	}
 	trace.Step("Computing predicates done")
@@ -449,9 +461,10 @@ func (g *genericScheduler) numFeasibleNodesToFind(numAllNodes int32) (numNodes i
 
 // Filters the nodes to find the ones that fit based on the given predicate functions
 // Each node is passed through the predicate functions to determine if it is a fit
-func (g *genericScheduler) findNodesThatFit(pluginContext *framework.PluginContext, pod *v1.Pod, nodeLister algorithm.NodeLister) ([]*v1.Node, FailedPredicateMap, error) {
+func (g *genericScheduler) findNodesThatFit(pluginContext *framework.PluginContext, pod *v1.Pod, nodeLister algorithm.NodeLister) ([]*v1.Node, FailedPredicateMap, framework.NodeToStatusMap, error) {
 	var filtered []*v1.Node
 	failedPredicateMap := FailedPredicateMap{}
+	filteredNodesStatuses := framework.NodeToStatusMap{}
 
 	if len(g.predicates) == 0 {
 		filtered = nodeLister.ListNodes()
@@ -495,8 +508,7 @@ func (g *genericScheduler) findNodesThatFit(pluginContext *framework.PluginConte
 				status := g.framework.RunFilterPlugins(pluginContext, pod, nodeName)
 				if !status.IsSuccess() {
 					predicateResultLock.Lock()
-					failedPredicateMap[nodeName] = append(failedPredicateMap[nodeName],
-						predicates.NewFailureReason(status.Message()))
+					filteredNodesStatuses[nodeName] = status
 					if status.Code() != framework.Unschedulable {
 						errs[status.Message()]++
 					}
@@ -524,7 +536,7 @@ func (g *genericScheduler) findNodesThatFit(pluginContext *framework.PluginConte
 
 		filtered = filtered[:filteredLen]
 		if len(errs) > 0 {
-			return []*v1.Node{}, FailedPredicateMap{}, errors.CreateAggregateFromMessageCountMap(errs)
+			return []*v1.Node{}, FailedPredicateMap{}, framework.NodeToStatusMap{}, errors.CreateAggregateFromMessageCountMap(errs)
 		}
 	}
 
@@ -539,9 +551,9 @@ func (g *genericScheduler) findNodesThatFit(pluginContext *framework.PluginConte
 					klog.Warningf("Skipping extender %v as it returned error %v and has ignorable flag set",
 						extender, err)
 					continue
-				} else {
-					return []*v1.Node{}, FailedPredicateMap{}, err
 				}
+
+				return []*v1.Node{}, FailedPredicateMap{}, framework.NodeToStatusMap{}, err
 			}
 
 			for failedNodeName, failedMsg := range failedMap {
@@ -556,7 +568,7 @@ func (g *genericScheduler) findNodesThatFit(pluginContext *framework.PluginConte
 			}
 		}
 	}
-	return filtered, failedPredicateMap, nil
+	return filtered, failedPredicateMap, filteredNodesStatuses, nil
 }
 
 // addNominatedPods adds pods with equal or greater priority which are nominated

pkg/scheduler/core/generic_scheduler_test.go

@@ -26,9 +26,10 @@ import (
 	"time"
 
 	apps "k8s.io/api/apps/v1"
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/errors"
 	"k8s.io/apimachinery/pkg/util/sets"
@@ -139,6 +140,42 @@ func getNodeReducePriority(pod *v1.Pod, meta interface{}, nodeNameToInfo map[str
 var EmptyPluginRegistry = framework.Registry{}
 var emptyFramework, _ = framework.NewFramework(EmptyPluginRegistry, nil, []schedulerconfig.PluginConfig{})
 
+// FakeFilterPlugin is a test filter plugin used by default scheduler.
+type FakeFilterPlugin struct {
+	numFilterCalled int
+	failFilter      bool
+}
+
+var filterPlugin = &FakeFilterPlugin{}
+
+// Name returns name of the plugin.
+func (fp *FakeFilterPlugin) Name() string {
+	return "fake-filter-plugin"
+}
+
+// reset is used to reset filter plugin.
+func (fp *FakeFilterPlugin) reset() {
+	fp.numFilterCalled = 0
+	fp.failFilter = false
+}
+
+// Filter is a test function that returns an error or nil, depending on the
+// value of "failFilter".
+func (fp *FakeFilterPlugin) Filter(pc *framework.PluginContext, pod *v1.Pod, nodeName string) *framework.Status {
+	fp.numFilterCalled++
+
+	if fp.failFilter {
+		return framework.NewStatus(framework.Unschedulable, fmt.Sprintf("injecting failure for pod %v", pod.Name))
+	}
+
+	return nil
+}
+
+// NewFilterPlugin is the factory for filtler plugin.
+func NewFilterPlugin(_ *runtime.Unknown, _ framework.FrameworkHandle) (framework.Plugin, error) {
+	return filterPlugin, nil
+}
+
 func makeNodeList(nodeNames []string) []*v1.Node {
 	result := make([]*v1.Node, 0, len(nodeNames))
 	for _, nodeName := range nodeNames {
@@ -219,6 +256,21 @@ func TestSelectHost(t *testing.T) {
 
 func TestGenericScheduler(t *testing.T) {
 	defer algorithmpredicates.SetPredicatesOrderingDuringTest(order)()
+
+	filterPluginRegistry := framework.Registry{filterPlugin.Name(): NewFilterPlugin}
+	filterFramework, err := framework.NewFramework(filterPluginRegistry, &schedulerconfig.Plugins{
+		Filter: &schedulerconfig.PluginSet{
+			Enabled: []schedulerconfig.Plugin{
+				{
+					Name: filterPlugin.Name(),
+				},
+			},
+		},
+	}, []schedulerconfig.PluginConfig{})
+	if err != nil {
+		t.Errorf("Unexpected error when initialize scheduling framework, err :%v", err.Error())
+	}
+
 	tests := []struct {
 		name                     string
 		predicates               map[string]algorithmpredicates.FitPredicate
@@ -229,6 +281,7 @@ func TestGenericScheduler(t *testing.T) {
 		pod                      *v1.Pod
 		pods                     []*v1.Pod
 		buildPredMeta            bool // build predicates metadata or not
+		failFilter               bool
 		expectedHosts            sets.String
 		expectsErr               bool
 		wErr                     error
@@ -246,7 +299,9 @@ func TestGenericScheduler(t *testing.T) {
 				FailedPredicates: FailedPredicateMap{
 					"machine1": []algorithmpredicates.PredicateFailureReason{algorithmpredicates.ErrFakePredicate},
 					"machine2": []algorithmpredicates.PredicateFailureReason{algorithmpredicates.ErrFakePredicate},
-				}},
+				},
+				FilteredNodesStatuses: framework.NodeToStatusMap{},
+			},
 		},
 		{
 			predicates:    map[string]algorithmpredicates.FitPredicate{"true": truePredicate},
@@ -309,6 +364,7 @@ func TestGenericScheduler(t *testing.T) {
 					"2": []algorithmpredicates.PredicateFailureReason{algorithmpredicates.ErrFakePredicate},
 					"1": []algorithmpredicates.PredicateFailureReason{algorithmpredicates.ErrFakePredicate},
 				},
+				FilteredNodesStatuses: framework.NodeToStatusMap{},
 			},
 		},
 		{
@@ -339,6 +395,7 @@ func TestGenericScheduler(t *testing.T) {
 					"1": []algorithmpredicates.PredicateFailureReason{algorithmpredicates.ErrFakePredicate},
 					"2": []algorithmpredicates.PredicateFailureReason{algorithmpredicates.ErrFakePredicate},
 				},
+				FilteredNodesStatuses: framework.NodeToStatusMap{},
 			},
 		},
 		{
@@ -426,6 +483,7 @@ func TestGenericScheduler(t *testing.T) {
 				FailedPredicates: FailedPredicateMap{
 					"1": []algorithmpredicates.PredicateFailureReason{algorithmpredicates.ErrFakePredicate, algorithmpredicates.ErrFakePredicate},
 				},
+				FilteredNodesStatuses: framework.NodeToStatusMap{},
 			},
 		},
 		{
@@ -538,9 +596,29 @@ func TestGenericScheduler(t *testing.T) {
 			expectedHosts: sets.NewString("machine2", "machine3"),
 			wErr:          nil,
 		},
+		{
+			name:          "test with failed filter plugin",
+			predicates:    map[string]algorithmpredicates.FitPredicate{"true": truePredicate},
+			prioritizers:  []priorities.PriorityConfig{{Function: numericPriority, Weight: 1}},
+			nodes:         []string{"3"},
+			pod:           &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "test-filter", UID: types.UID("test-filter")}},
+			expectedHosts: nil,
+			failFilter:    true,
+			expectsErr:    true,
+			wErr: &FitError{
+				Pod:              &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "test-filter", UID: types.UID("test-filter")}},
+				NumAllNodes:      1,
+				FailedPredicates: FailedPredicateMap{},
+				FilteredNodesStatuses: framework.NodeToStatusMap{
+					"3": framework.NewStatus(framework.Unschedulable, "injecting failure for pod test-filter"),
+				},
+			},
+		},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
+			filterPlugin.failFilter = test.failFilter
+
 			cache := internalcache.New(time.Duration(0), wait.NeverStop)
 			for _, pod := range test.pods {
 				cache.AddPod(pod)
@@ -564,7 +642,7 @@ func TestGenericScheduler(t *testing.T) {
 				predMetaProducer,
 				test.prioritizers,
 				priorities.EmptyPriorityMetadataProducer,
-				emptyFramework,
+				filterFramework,
 				[]algorithm.SchedulerExtender{},
 				nil,
 				pvcLister,
@@ -575,11 +653,13 @@ func TestGenericScheduler(t *testing.T) {
 				false)
 			result, err := scheduler.Schedule(test.pod, schedulertesting.FakeNodeLister(makeNodeList(test.nodes)), framework.NewPluginContext())
 			if !reflect.DeepEqual(err, test.wErr) {
-				t.Errorf("Unexpected error: %v, expected: %v", err, test.wErr)
+				t.Errorf("Unexpected error: %v, expected: %v", err.Error(), test.wErr)
 			}
 			if test.expectedHosts != nil && !test.expectedHosts.Has(result.SuggestedHost) {
 				t.Errorf("Expected: %s, got: %s", test.expectedHosts, result.SuggestedHost)
 			}
+
+			filterPlugin.reset()
 		})
 	}
 }
@@ -613,7 +693,7 @@ func TestFindFitAllError(t *testing.T) {
 	nodes := makeNodeList([]string{"3", "2", "1"})
 	scheduler := makeScheduler(predicates, nodes)
 
-	_, predicateMap, err := scheduler.findNodesThatFit(nil, &v1.Pod{}, schedulertesting.FakeNodeLister(nodes))
+	_, predicateMap, _, err := scheduler.findNodesThatFit(nil, &v1.Pod{}, schedulertesting.FakeNodeLister(nodes))
 
 	if err != nil {
 		t.Errorf("unexpected error: %v", err)
@@ -643,7 +723,7 @@ func TestFindFitSomeError(t *testing.T) {
 	scheduler := makeScheduler(predicates, nodes)
 
 	pod := &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "1", UID: types.UID("1")}}
-	_, predicateMap, err := scheduler.findNodesThatFit(nil, pod, schedulertesting.FakeNodeLister(nodes))
+	_, predicateMap, _, err := scheduler.findNodesThatFit(nil, pod, schedulertesting.FakeNodeLister(nodes))
 
 	if err != nil {
 		t.Errorf("unexpected error: %v", err)

pkg/scheduler/framework/v1alpha1/framework.go

@@ -21,7 +21,7 @@ import (
 	"fmt"
 	"time"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/util/workqueue"
@@ -41,6 +41,7 @@ type framework struct {
 	queueSortPlugins          []QueueSortPlugin
 	prefilterPlugins          []PrefilterPlugin
 	filterPlugins             []FilterPlugin
+	postFilterPlugins         []PostFilterPlugin
 	scorePlugins              []ScorePlugin
 	scoreWithNormalizePlugins []ScoreWithNormalizePlugin
 	reservePlugins            []ReservePlugin
@@ -168,6 +169,20 @@ func NewFramework(r Registry, plugins *config.Plugins, args []config.PluginConfi
 		}
 	}
 
+	if plugins.PostFilter != nil {
+		for _, r := range plugins.PostFilter.Enabled {
+			if pg, ok := pluginsMap[r.Name]; ok {
+				p, ok := pg.(PostFilterPlugin)
+				if !ok {
+					return nil, fmt.Errorf("plugin %v does not extend post-filter plugin", r.Name)
+				}
+				f.postFilterPlugins = append(f.postFilterPlugins, p)
+			} else {
+				return nil, fmt.Errorf("post-filter plugin %v does not exist", r.Name)
+			}
+		}
+	}
+
 	if plugins.PreBind != nil {
 		for _, pb := range plugins.PreBind.Enabled {
 			if pg, ok := pluginsMap[pb.Name]; ok {
@@ -287,6 +302,7 @@ func (f *framework) RunPrefilterPlugins(
 			return NewStatus(Error, msg)
 		}
 	}
+
 	return nil
 }
 
@@ -296,13 +312,12 @@ func (f *framework) RunPrefilterPlugins(
 // Meanwhile, the failure message and status are set for the given node.
 func (f *framework) RunFilterPlugins(pc *PluginContext,
 	pod *v1.Pod, nodeName string) *Status {
-
-	for _, p := range f.filterPlugins {
-		status := p.Filter(pc, pod, nodeName)
+	for _, pl := range f.filterPlugins {
+		status := pl.Filter(pc, pod, nodeName)
 		if !status.IsSuccess() {
 			if status.Code() != Unschedulable {
-				errMsg := fmt.Sprintf("RunFilterPlugins: error while running %s filter plugin for pod %s: %s",
-					p.Name(), pod.Name, status.Message())
+				errMsg := fmt.Sprintf("RunFilterPlugins: error while running %v filter plugin for pod %v: %v",
+					pl.Name(), pod.Name, status.Message())
 				klog.Error(errMsg)
 				return NewStatus(Error, errMsg)
 			}
@@ -313,6 +328,27 @@ func (f *framework) RunFilterPlugins(pc *PluginContext,
 	return nil
 }
 
+// RunPostFilterPlugins runs the set of configured post-filter plugins. If any
+// of these plugins returns any status other than "Success", the given node is
+// rejected. The filteredNodeStatuses is the set of filtered nodes and their statuses.
+func (f *framework) RunPostFilterPlugins(
+	pc *PluginContext,
+	pod *v1.Pod,
+	nodes []*v1.Node,
+	filteredNodesStatuses NodeToStatusMap,
+) *Status {
+	for _, pl := range f.postFilterPlugins {
+		status := pl.PostFilter(pc, pod, nodes, filteredNodesStatuses)
+		if !status.IsSuccess() {
+			msg := fmt.Sprintf("error while running %v postfilter plugin for pod %v: %v", pl.Name(), pod.Name, status.Message())
+			klog.Error(msg)
+			return NewStatus(Error, msg)
+		}
+	}
+
+	return nil
+}
+
 // RunScorePlugins runs the set of configured scoring plugins. It returns a map that
 // stores for each scoring plugin name the corresponding NodeScoreList(s).
 // It also returns *Status, which is set to non-success if any of the plugins returns

pkg/scheduler/framework/v1alpha1/interface.go

@@ -22,7 +22,7 @@ import (
 	"errors"
 	"time"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/types"
 	internalcache "k8s.io/kubernetes/pkg/scheduler/internal/cache"
 )
@@ -36,6 +36,9 @@ type NodeScoreList []int
 // PluginToNodeScoreMap declares a map from plugin name to its NodeScoreList.
 type PluginToNodeScoreMap map[string]NodeScoreList
 
+// NodeToStatusMap declares map from node name to its status.
+type NodeToStatusMap map[string]*Status
+
 // These are predefined codes used in a Status.
 const (
 	// Success means that plugin ran correctly and found pod schedulable.
@@ -160,6 +163,19 @@ type FilterPlugin interface {
 	Filter(pc *PluginContext, pod *v1.Pod, nodeName string) *Status
 }
 
+// PostFilterPlugin is an interface for Post-filter plugin. Post-filter is an
+// informational extension point. Plugins will be called with a list of nodes
+// that passed the filtering phase. A plugin may use this data to update internal
+// state or to generate logs/metrics.
+type PostFilterPlugin interface {
+	Plugin
+	// PostFilter is called by the scheduling framework after a list of nodes
+	// passed the filtering phase. All postfilter plugins must return success or
+	// the pod will be rejected. The filteredNodesStatuses is the set of filtered nodes
+	// and their filter status.
+	PostFilter(pc *PluginContext, pod *v1.Pod, nodes []*v1.Node, filteredNodesStatuses NodeToStatusMap) *Status
+}
+
 // ScorePlugin is an interface that must be implemented by "score" plugins to rank
 // nodes that passed the filtering phase.
 type ScorePlugin interface {
@@ -269,6 +285,11 @@ type Framework interface {
 	// the given node is not suitable for running the pod.
 	RunFilterPlugins(pc *PluginContext, pod *v1.Pod, nodeName string) *Status
 
+	// RunPostFilterPlugins runs the set of configured post-filter plugins. If any
+	// of these plugins returns any status other than "Success", the given node is
+	// rejected. The filteredNodeStatuses is the set of filtered nodes and their statuses.
+	RunPostFilterPlugins(pc *PluginContext, pod *v1.Pod, nodes []*v1.Node, filteredNodesStatuses NodeToStatusMap) *Status
+
 	// RunScorePlugins runs the set of configured scoring plugins. It returns a map that
 	// stores for each scoring plugin name the corresponding NodeScoreList(s).
 	// It also returns *Status, which is set to non-success if any of the plugins returns

pkg/scheduler/internal/queue/scheduling_queue_test.go

@@ -24,7 +24,7 @@ import (
 	"time"
 
 	dto "github.com/prometheus/client_model/go"
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/clock"
@@ -197,6 +197,10 @@ func (*fakeFramework) RunBindPlugins(pc *framework.PluginContext, pod *v1.Pod, n
 
 func (*fakeFramework) RunPostbindPlugins(pc *framework.PluginContext, pod *v1.Pod, nodeName string) {}
 
+func (*fakeFramework) RunPostFilterPlugins(pc *framework.PluginContext, pod *v1.Pod, nodes []*v1.Node, filteredNodesStatuses framework.NodeToStatusMap) *framework.Status {
+	return nil
+}
+
 func (*fakeFramework) RunReservePlugins(pc *framework.PluginContext, pod *v1.Pod, nodeName string) *framework.Status {
 	return nil
 }

pkg/scheduler/scheduler_test.go

@@ -26,7 +26,7 @@ import (
 	"testing"
 	"time"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/api/events/v1beta1"
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -415,9 +415,12 @@ func TestSchedulerNoPhantomPodAfterDelete(t *testing.T) {
 	select {
 	case err := <-errChan:
 		expectErr := &core.FitError{
-			Pod:              secondPod,
-			NumAllNodes:      1,
-			FailedPredicates: core.FailedPredicateMap{node.Name: []predicates.PredicateFailureReason{predicates.ErrPodNotFitsHostPorts}},
+			Pod:         secondPod,
+			NumAllNodes: 1,
+			FailedPredicates: core.FailedPredicateMap{
+				node.Name: []predicates.PredicateFailureReason{predicates.ErrPodNotFitsHostPorts},
+			},
+			FilteredNodesStatuses: framework.NodeToStatusMap{},
 		}
 		if !reflect.DeepEqual(expectErr, err) {
 			t.Errorf("err want=%v, get=%v", expectErr, err)
@@ -620,9 +623,10 @@ func TestSchedulerFailedSchedulingReasons(t *testing.T) {
 	select {
 	case err := <-errChan:
 		expectErr := &core.FitError{
-			Pod:              podWithTooBigResourceRequests,
-			NumAllNodes:      len(nodes),
-			FailedPredicates: failedPredicatesMap,
+			Pod:                   podWithTooBigResourceRequests,
+			NumAllNodes:           len(nodes),
+			FailedPredicates:      failedPredicatesMap,
+			FilteredNodesStatuses: framework.NodeToStatusMap{},
 		}
 		if len(fmt.Sprint(expectErr)) > 150 {
 			t.Errorf("message is too spammy ! %v ", len(fmt.Sprint(expectErr)))

test/integration/scheduler/framework_test.go

@@ -21,7 +21,7 @@ import (
 	"testing"
 	"time"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -58,6 +58,11 @@ type ReservePlugin struct {
 	failReserve      bool
 }
 
+type PostFilterPlugin struct {
+	numPostFilterCalled int
+	failPostFilter      bool
+}
+
 type PrebindPlugin struct {
 	numPrebindCalled int
 	failPrebind      bool
@@ -100,6 +105,7 @@ const (
 	scorePluginName              = "score-plugin"
 	scoreWithNormalizePluginName = "score-with-normalize-plugin"
 	filterPluginName             = "filter-plugin"
+	postFilterPluginName         = "postfilter-plugin"
 	reservePluginName            = "reserve-plugin"
 	prebindPluginName            = "prebind-plugin"
 	unreservePluginName          = "unreserve-plugin"
@@ -113,6 +119,7 @@ var _ = framework.FilterPlugin(&FilterPlugin{})
 var _ = framework.ScorePlugin(&ScorePlugin{})
 var _ = framework.ScoreWithNormalizePlugin(&ScoreWithNormalizePlugin{})
 var _ = framework.ReservePlugin(&ReservePlugin{})
+var _ = framework.PostFilterPlugin(&PostFilterPlugin{})
 var _ = framework.PrebindPlugin(&PrebindPlugin{})
 var _ = framework.BindPlugin(&BindPlugin{})
 var _ = framework.PostbindPlugin(&PostbindPlugin{})
@@ -241,6 +248,34 @@ func NewReservePlugin(_ *runtime.Unknown, _ framework.FrameworkHandle) (framewor
 	return resPlugin, nil
 }
 
+// Name returns name of the plugin.
+func (*PostFilterPlugin) Name() string {
+	return postFilterPluginName
+}
+
+var postFilterPlugin = &PostFilterPlugin{}
+
+// PostFilter is a test function.
+func (pfp *PostFilterPlugin) PostFilter(_ *framework.PluginContext, pod *v1.Pod, _ []*v1.Node, _ framework.NodeToStatusMap) *framework.Status {
+	pfp.numPostFilterCalled++
+	if pfp.failPostFilter {
+		return framework.NewStatus(framework.Error, fmt.Sprintf("injecting failure for pod %v", pod.Name))
+	}
+
+	return nil
+}
+
+// reset used to reset postfilter plugin.
+func (pfp *PostFilterPlugin) reset() {
+	pfp.numPostFilterCalled = 0
+	pfp.failPostFilter = false
+}
+
+// NewPostFilterPlugin is the factory for post-filter plugin.
+func NewPostFilterPlugin(_ *runtime.Unknown, _ framework.FrameworkHandle) (framework.Plugin, error) {
+	return postFilterPlugin, nil
+}
+
 var pbdPlugin = &PrebindPlugin{}
 
 // Name returns name of the plugin.
@@ -1447,6 +1482,65 @@ func TestFilterPlugin(t *testing.T) {
 	}
 }
 
+// TestPostFilterPlugin tests invocation of post-filter plugins.
+func TestPostFilterPlugin(t *testing.T) {
+	// Create a plugin registry for testing. Register only a post-filter plugin.
+	registry := framework.Registry{postFilterPluginName: NewPostFilterPlugin}
+
+	// Setup initial post-filter plugin for testing.
+	pluginsConfig := &schedulerconfig.Plugins{
+		PostFilter: &schedulerconfig.PluginSet{
+			Enabled: []schedulerconfig.Plugin{
+				{
+					Name: postFilterPluginName,
+				},
+			},
+		},
+	}
+	// Set empty plugin config for testing
+	emptyPluginConfig := []schedulerconfig.PluginConfig{}
+
+	// Create the master and the scheduler with the test plugin set.
+	context := initTestSchedulerWithOptions(t,
+		initTestMaster(t, "post-filter-plugin", nil),
+		false, nil, registry, pluginsConfig, emptyPluginConfig, false, time.Second)
+	defer cleanupTest(t, context)
+
+	cs := context.clientSet
+	// Add a few nodes.
+	_, err := createNodes(cs, "test-node", nil, 2)
+	if err != nil {
+		t.Fatalf("Cannot create nodes: %v", err)
+	}
+
+	for _, fail := range []bool{false, true} {
+		postFilterPlugin.failPostFilter = fail
+		// Create a best effort pod.
+		pod, err := createPausePod(cs,
+			initPausePod(cs, &pausePodConfig{Name: "test-pod", Namespace: context.ns.Name}))
+		if err != nil {
+			t.Errorf("Error while creating a test pod: %v", err)
+		}
+
+		if fail {
+			if err = waitForPodUnschedulable(cs, pod); err != nil {
+				t.Errorf("Didn't expect the pod to be scheduled. error: %v", err)
+			}
+		} else {
+			if err = waitForPodToSchedule(cs, pod); err != nil {
+				t.Errorf("Expected the pod to be scheduled. error: %v", err)
+			}
+		}
+
+		if postFilterPlugin.numPostFilterCalled == 0 {
+			t.Errorf("Expected the post-filter plugin to be called.")
+		}
+
+		postFilterPlugin.reset()
+		cleanupPods(cs, t, []*v1.Pod{pod})
+	}
+}
+
 // TestPreemptWithPermitPlugin tests preempt with permit plugins.
 func TestPreemptWithPermitPlugin(t *testing.T) {
 	// Create a plugin registry for testing. Register only a permit plugin.