Merge pull request #41119 from sarat-k/master

Automatic merge from submit-queue (batch tested with PRs 41701, 41818, 41897, 41119, 41562)

Optimization of on-wire information sent to scheduler extender interfaces that are stateful

The changes are to address the issue described in https://github.com/kubernetes/kubernetes/issues/40991

```release-note
Added support to minimize sending verbose node information to scheduler extender by sending only node names and expecting extenders to cache the rest of the node information
```

cc @ravigadde

examples/scheduler-policy-config-with-extender.json

@@ -21,7 +21,8 @@
         "filterVerb": "filter",
         "prioritizeVerb": "prioritize",
         "weight": 5,
-        "enableHttps": false
+        "enableHttps": false,
+        "nodeCacheCapable": false
 	}
     ]
 }

plugin/pkg/scheduler/algorithm/scheduler_interface.go

@@ -19,6 +19,7 @@ package algorithm
 import (
 	"k8s.io/kubernetes/pkg/api/v1"
 	schedulerapi "k8s.io/kubernetes/plugin/pkg/scheduler/api"
+	"k8s.io/kubernetes/plugin/pkg/scheduler/schedulercache"
 )
 
 // SchedulerExtender is an interface for external processes to influence scheduling
@@ -28,7 +29,7 @@ type SchedulerExtender interface {
 	// Filter based on extender-implemented predicate functions. The filtered list is
 	// expected to be a subset of the supplied list. failedNodesMap optionally contains
 	// the list of failed nodes and failure reasons.
-	Filter(pod *v1.Pod, nodes []*v1.Node) (filteredNodes []*v1.Node, failedNodesMap schedulerapi.FailedNodesMap, err error)
+	Filter(pod *v1.Pod, nodes []*v1.Node, nodeNameToInfo map[string]*schedulercache.NodeInfo) (filteredNodes []*v1.Node, failedNodesMap schedulerapi.FailedNodesMap, err error)
 
 	// Prioritize based on extender-implemented priority functions. The returned scores & weight
 	// are used to compute the weighted score for an extender. The weighted scores are added to

plugin/pkg/scheduler/api/types.go

@@ -128,6 +128,10 @@ type ExtenderConfig struct {
 	// HTTPTimeout specifies the timeout duration for a call to the extender. Filter timeout fails the scheduling of the pod. Prioritize
 	// timeout is ignored, k8s/other extenders priorities are used to select the node.
 	HTTPTimeout time.Duration
+	// NodeCacheCapable specifies that the extender is capable of caching node information,
+	// so the scheduler should only send minimal information about the eligible nodes
+	// assuming that the extender already cached full details of all nodes in the cluster
+	NodeCacheCapable bool
 }
 
 // ExtenderArgs represents the arguments needed by the extender to filter/prioritize
@@ -135,8 +139,12 @@ type ExtenderConfig struct {
 type ExtenderArgs struct {
 	// Pod being scheduled
 	Pod v1.Pod
-	// List of candidate nodes where the pod can be scheduled
-	Nodes v1.NodeList
+	// List of candidate nodes where the pod can be scheduled; to be populated
+	// only if ExtenderConfig.NodeCacheCapable == false
+	Nodes *v1.NodeList
+	// List of candidate node names where the pod can be scheduled; to be
+	// populated only if ExtenderConfig.NodeCacheCapable == true
+	NodeNames *[]string
 }
 
 // FailedNodesMap represents the filtered out nodes, with node names and failure messages
@@ -144,8 +152,12 @@ type FailedNodesMap map[string]string
 
 // ExtenderFilterResult represents the results of a filter call to an extender
 type ExtenderFilterResult struct {
-	// Filtered set of nodes where the pod can be scheduled
-	Nodes v1.NodeList
+	// Filtered set of nodes where the pod can be scheduled; to be populated
+	// only if ExtenderConfig.NodeCacheCapable == false
+	Nodes *v1.NodeList
+	// Filtered set of nodes where the pod can be scheduled; to be populated
+	// only if ExtenderConfig.NodeCacheCapable == true
+	NodeNames *[]string
 	// Filtered out nodes where the pod can't be scheduled and the failure messages
 	FailedNodes FailedNodesMap
 	// Error message indicating failure

plugin/pkg/scheduler/api/v1/types.go

@@ -128,6 +128,10 @@ type ExtenderConfig struct {
 	// HTTPTimeout specifies the timeout duration for a call to the extender. Filter timeout fails the scheduling of the pod. Prioritize
 	// timeout is ignored, k8s/other extenders priorities are used to select the node.
 	HTTPTimeout time.Duration `json:"httpTimeout,omitempty"`
+	// NodeCacheCapable specifies that the extender is capable of caching node information,
+	// so the scheduler should only send minimal information about the eligible nodes
+	// assuming that the extender already cached full details of all nodes in the cluster
+	NodeCacheCapable bool `json:"nodeCacheCapable,omitempty"`
 }
 
 // ExtenderArgs represents the arguments needed by the extender to filter/prioritize
@@ -135,8 +139,12 @@ type ExtenderConfig struct {
 type ExtenderArgs struct {
 	// Pod being scheduled
 	Pod apiv1.Pod `json:"pod"`
-	// List of candidate nodes where the pod can be scheduled
-	Nodes apiv1.NodeList `json:"nodes"`
+	// List of candidate nodes where the pod can be scheduled; to be populated
+	// only if ExtenderConfig.NodeCacheCapable == false
+	Nodes *apiv1.NodeList `json:"nodes,omitempty"`
+	// List of candidate node names where the pod can be scheduled; to be
+	// populated only if ExtenderConfig.NodeCacheCapable == true
+	NodeNames *[]string `json:"nodenames,omitempty"`
 }
 
 // FailedNodesMap represents the filtered out nodes, with node names and failure messages
@@ -144,8 +152,12 @@ type FailedNodesMap map[string]string
 
 // ExtenderFilterResult represents the results of a filter call to an extender
 type ExtenderFilterResult struct {
-	// Filtered set of nodes where the pod can be scheduled
-	Nodes apiv1.NodeList `json:"nodes,omitempty"`
+	// Filtered set of nodes where the pod can be scheduled; to be populated
+	// only if ExtenderConfig.NodeCacheCapable == false
+	Nodes *apiv1.NodeList `json:"nodes,omitempty"`
+	// Filtered set of nodes where the pod can be scheduled; to be populated
+	// only if ExtenderConfig.NodeCacheCapable == true
+	NodeNames *[]string `json:"nodenames,omitempty"`
 	// Filtered out nodes where the pod can't be scheduled and the failure messages
 	FailedNodes FailedNodesMap `json:"failedNodes,omitempty"`
 	// Error message indicating failure

plugin/pkg/scheduler/core/extender.go

@@ -29,6 +29,7 @@ import (
 	"k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/plugin/pkg/scheduler/algorithm"
 	schedulerapi "k8s.io/kubernetes/plugin/pkg/scheduler/api"
+	"k8s.io/kubernetes/plugin/pkg/scheduler/schedulercache"
 )
 
 const (
@@ -37,12 +38,12 @@ const (
 
 // HTTPExtender implements the algorithm.SchedulerExtender interface.
 type HTTPExtender struct {
-	extenderURL    string
-	filterVerb     string
-	prioritizeVerb string
-	weight         int
-	apiVersion     string
-	client         *http.Client
+	extenderURL      string
+	filterVerb       string
+	prioritizeVerb   string
+	weight           int
+	client           *http.Client
+	nodeCacheCapable bool
 }
 
 func makeTransport(config *schedulerapi.ExtenderConfig) (http.RoundTripper, error) {
@@ -68,7 +69,7 @@ func makeTransport(config *schedulerapi.ExtenderConfig) (http.RoundTripper, erro
 	return utilnet.SetTransportDefaults(&http.Transport{}), nil
 }
 
-func NewHTTPExtender(config *schedulerapi.ExtenderConfig, apiVersion string) (algorithm.SchedulerExtender, error) {
+func NewHTTPExtender(config *schedulerapi.ExtenderConfig) (algorithm.SchedulerExtender, error) {
 	if config.HTTPTimeout.Nanoseconds() == 0 {
 		config.HTTPTimeout = time.Duration(DefaultExtenderTimeout)
 	}
@@ -82,45 +83,69 @@ func NewHTTPExtender(config *schedulerapi.ExtenderConfig, apiVersion string) (al
 		Timeout:   config.HTTPTimeout,
 	}
 	return &HTTPExtender{
-		extenderURL:    config.URLPrefix,
-		apiVersion:     apiVersion,
-		filterVerb:     config.FilterVerb,
-		prioritizeVerb: config.PrioritizeVerb,
-		weight:         config.Weight,
-		client:         client,
+		extenderURL:      config.URLPrefix,
+		filterVerb:       config.FilterVerb,
+		prioritizeVerb:   config.PrioritizeVerb,
+		weight:           config.Weight,
+		client:           client,
+		nodeCacheCapable: config.NodeCacheCapable,
 	}, nil
 }
 
 // Filter based on extender implemented predicate functions. The filtered list is
 // expected to be a subset of the supplied list. failedNodesMap optionally contains
 // the list of failed nodes and failure reasons.
-func (h *HTTPExtender) Filter(pod *v1.Pod, nodes []*v1.Node) ([]*v1.Node, schedulerapi.FailedNodesMap, error) {
-	var result schedulerapi.ExtenderFilterResult
+func (h *HTTPExtender) Filter(pod *v1.Pod, nodes []*v1.Node, nodeNameToInfo map[string]*schedulercache.NodeInfo) ([]*v1.Node, schedulerapi.FailedNodesMap, error) {
+	var (
+		result     schedulerapi.ExtenderFilterResult
+		nodeList   *v1.NodeList
+		nodeNames  *[]string
+		nodeResult []*v1.Node
+		args       *schedulerapi.ExtenderArgs
+	)
 
 	if h.filterVerb == "" {
 		return nodes, schedulerapi.FailedNodesMap{}, nil
 	}
 
-	nodeItems := make([]v1.Node, 0, len(nodes))
-	for _, node := range nodes {
-		nodeItems = append(nodeItems, *node)
-	}
-	args := schedulerapi.ExtenderArgs{
-		Pod:   *pod,
-		Nodes: v1.NodeList{Items: nodeItems},
+	if h.nodeCacheCapable {
+		nodeNameSlice := make([]string, 0, len(nodes))
+		for _, node := range nodes {
+			nodeNameSlice = append(nodeNameSlice, node.Name)
+		}
+		nodeNames = &nodeNameSlice
+	} else {
+		nodeList = &v1.NodeList{}
+		for _, node := range nodes {
+			nodeList.Items = append(nodeList.Items, *node)
+		}
 	}
 
-	if err := h.send(h.filterVerb, &args, &result); err != nil {
+	args = &schedulerapi.ExtenderArgs{
+		Pod:       *pod,
+		Nodes:     nodeList,
+		NodeNames: nodeNames,
+	}
+
+	if err := h.send(h.filterVerb, args, &result); err != nil {
 		return nil, nil, err
 	}
 	if result.Error != "" {
 		return nil, nil, fmt.Errorf(result.Error)
 	}
 
-	nodeResult := make([]*v1.Node, 0, len(result.Nodes.Items))
-	for i := range result.Nodes.Items {
-		nodeResult = append(nodeResult, &result.Nodes.Items[i])
+	if h.nodeCacheCapable && result.NodeNames != nil {
+		nodeResult = make([]*v1.Node, 0, len(*result.NodeNames))
+		for i := range *result.NodeNames {
+			nodeResult = append(nodeResult, nodeNameToInfo[(*result.NodeNames)[i]].Node())
+		}
+	} else if result.Nodes != nil {
+		nodeResult = make([]*v1.Node, 0, len(result.Nodes.Items))
+		for i := range result.Nodes.Items {
+			nodeResult = append(nodeResult, &result.Nodes.Items[i])
+		}
 	}
+
 	return nodeResult, result.FailedNodes, nil
 }
 
@@ -128,7 +153,12 @@ func (h *HTTPExtender) Filter(pod *v1.Pod, nodes []*v1.Node) ([]*v1.Node, schedu
 // up for each such priority function. The returned score is added to the score computed
 // by Kubernetes scheduler. The total score is used to do the host selection.
 func (h *HTTPExtender) Prioritize(pod *v1.Pod, nodes []*v1.Node) (*schedulerapi.HostPriorityList, int, error) {
-	var result schedulerapi.HostPriorityList
+	var (
+		result    schedulerapi.HostPriorityList
+		nodeList  *v1.NodeList
+		nodeNames *[]string
+		args      *schedulerapi.ExtenderArgs
+	)
 
 	if h.prioritizeVerb == "" {
 		result := schedulerapi.HostPriorityList{}
@@ -138,16 +168,26 @@ func (h *HTTPExtender) Prioritize(pod *v1.Pod, nodes []*v1.Node) (*schedulerapi.
 		return &result, 0, nil
 	}
 
-	nodeItems := make([]v1.Node, 0, len(nodes))
-	for _, node := range nodes {
-		nodeItems = append(nodeItems, *node)
-	}
-	args := schedulerapi.ExtenderArgs{
-		Pod:   *pod,
-		Nodes: v1.NodeList{Items: nodeItems},
+	if h.nodeCacheCapable {
+		nodeNameSlice := make([]string, 0, len(nodes))
+		for _, node := range nodes {
+			nodeNameSlice = append(nodeNameSlice, node.Name)
+		}
+		nodeNames = &nodeNameSlice
+	} else {
+		nodeList = &v1.NodeList{}
+		for _, node := range nodes {
+			nodeList.Items = append(nodeList.Items, *node)
+		}
 	}
 
-	if err := h.send(h.prioritizeVerb, &args, &result); err != nil {
+	args = &schedulerapi.ExtenderArgs{
+		Pod:       *pod,
+		Nodes:     nodeList,
+		NodeNames: nodeNames,
+	}
+
+	if err := h.send(h.prioritizeVerb, args, &result); err != nil {
 		return nil, 0, err
 	}
 	return &result, h.weight, nil
@@ -160,7 +200,7 @@ func (h *HTTPExtender) send(action string, args interface{}, result interface{})
 		return err
 	}
 
-	url := h.extenderURL + "/" + h.apiVersion + "/" + action
+	url := h.extenderURL + "/" + action
 
 	req, err := http.NewRequest("POST", url, bytes.NewReader(out))
 	if err != nil {

plugin/pkg/scheduler/core/extender_test.go

@@ -104,12 +104,13 @@ func machine2Prioritizer(_ *v1.Pod, nodeNameToInfo map[string]*schedulercache.No
 }
 
 type FakeExtender struct {
-	predicates   []fitPredicate
-	prioritizers []priorityConfig
-	weight       int
+	predicates       []fitPredicate
+	prioritizers     []priorityConfig
+	weight           int
+	nodeCacheCapable bool
 }
 
-func (f *FakeExtender) Filter(pod *v1.Pod, nodes []*v1.Node) ([]*v1.Node, schedulerapi.FailedNodesMap, error) {
+func (f *FakeExtender) Filter(pod *v1.Pod, nodes []*v1.Node, nodeNameToInfo map[string]*schedulercache.NodeInfo) ([]*v1.Node, schedulerapi.FailedNodesMap, error) {
 	filtered := []*v1.Node{}
 	failedNodesMap := schedulerapi.FailedNodesMap{}
 	for _, node := range nodes {
@@ -130,6 +131,10 @@ func (f *FakeExtender) Filter(pod *v1.Pod, nodes []*v1.Node) ([]*v1.Node, schedu
 			failedNodesMap[node.Name] = "FakeExtender failed"
 		}
 	}
+
+	if f.nodeCacheCapable {
+		return filtered, failedNodesMap, nil
+	}
 	return filtered, failedNodesMap, nil
 }
 

plugin/pkg/scheduler/core/generic_scheduler.go

@@ -200,7 +200,7 @@ func findNodesThatFit(
 
 	if len(filtered) > 0 && len(extenders) != 0 {
 		for _, extender := range extenders {
-			filteredList, failedMap, err := extender.Filter(pod, filtered)
+			filteredList, failedMap, err := extender.Filter(pod, filtered, nodeNameToInfo)
 			if err != nil {
 				return []*v1.Node{}, FailedPredicateMap{}, err
 			}

plugin/pkg/scheduler/factory/factory.go

@@ -325,7 +325,7 @@ func (f *ConfigFactory) CreateFromConfig(policy schedulerapi.Policy) (*scheduler
 	if len(policy.ExtenderConfigs) != 0 {
 		for ii := range policy.ExtenderConfigs {
 			glog.V(2).Infof("Creating extender with config %+v", policy.ExtenderConfigs[ii])
-			if extender, err := core.NewHTTPExtender(&policy.ExtenderConfigs[ii], policy.APIVersion); err != nil {
+			if extender, err := core.NewHTTPExtender(&policy.ExtenderConfigs[ii]); err != nil {
 				return nil, err
 			} else {
 				extenders = append(extenders, extender)

test/integration/scheduler/extender_test.go

@@ -62,9 +62,10 @@ type priorityConfig struct {
 }
 
 type Extender struct {
-	name         string
-	predicates   []fitPredicate
-	prioritizers []priorityConfig
+	name             string
+	predicates       []fitPredicate
+	prioritizers     []priorityConfig
+	nodeCacheCapable bool
 }
 
 func (e *Extender) serveHTTP(t *testing.T, w http.ResponseWriter, req *http.Request) {
@@ -82,12 +83,9 @@ func (e *Extender) serveHTTP(t *testing.T, w http.ResponseWriter, req *http.Requ
 
 	if strings.Contains(req.URL.Path, filter) {
 		resp := &schedulerapi.ExtenderFilterResult{}
-		nodes, failedNodes, err := e.Filter(&args.Pod, &args.Nodes)
+		resp, err := e.Filter(&args)
 		if err != nil {
 			resp.Error = err.Error()
-		} else {
-			resp.Nodes = *nodes
-			resp.FailedNodes = failedNodes
 		}
 
 		if err := encoder.Encode(resp); err != nil {
@@ -96,7 +94,7 @@ func (e *Extender) serveHTTP(t *testing.T, w http.ResponseWriter, req *http.Requ
 	} else if strings.Contains(req.URL.Path, prioritize) {
 		// Prioritize errors are ignored. Default k8s priorities or another extender's
 		// priorities may be applied.
-		priorities, _ := e.Prioritize(&args.Pod, &args.Nodes)
+		priorities, _ := e.Prioritize(&args)
 
 		if err := encoder.Encode(priorities); err != nil {
 			t.Fatalf("Failed to encode %+v", priorities)
@@ -106,15 +104,21 @@ func (e *Extender) serveHTTP(t *testing.T, w http.ResponseWriter, req *http.Requ
 	}
 }
 
-func (e *Extender) Filter(pod *v1.Pod, nodes *v1.NodeList) (*v1.NodeList, schedulerapi.FailedNodesMap, error) {
-	filtered := []v1.Node{}
+func (e *Extender) filterUsingNodeCache(args *schedulerapi.ExtenderArgs) (*schedulerapi.ExtenderFilterResult, error) {
+	nodeSlice := make([]string, 0)
 	failedNodesMap := schedulerapi.FailedNodesMap{}
-	for _, node := range nodes.Items {
+	for _, nodeName := range *args.NodeNames {
 		fits := true
 		for _, predicate := range e.predicates {
-			fit, err := predicate(pod, &node)
+			fit, err := predicate(&args.Pod,
+				&v1.Node{ObjectMeta: metav1.ObjectMeta{Name: nodeName}})
 			if err != nil {
-				return &v1.NodeList{}, schedulerapi.FailedNodesMap{}, err
+				return &schedulerapi.ExtenderFilterResult{
+					Nodes:       nil,
+					NodeNames:   nil,
+					FailedNodes: schedulerapi.FailedNodesMap{},
+					Error:       err.Error(),
+				}, err
 			}
 			if !fit {
 				fits = false
@@ -122,24 +126,78 @@ func (e *Extender) Filter(pod *v1.Pod, nodes *v1.NodeList) (*v1.NodeList, schedu
 			}
 		}
 		if fits {
-			filtered = append(filtered, node)
+			nodeSlice = append(nodeSlice, nodeName)
 		} else {
-			failedNodesMap[node.Name] = fmt.Sprintf("extender failed: %s", e.name)
+			failedNodesMap[nodeName] = fmt.Sprintf("extender failed: %s", e.name)
 		}
 	}
-	return &v1.NodeList{Items: filtered}, failedNodesMap, nil
+
+	return &schedulerapi.ExtenderFilterResult{
+		Nodes:       nil,
+		NodeNames:   &nodeSlice,
+		FailedNodes: failedNodesMap,
+	}, nil
 }
 
-func (e *Extender) Prioritize(pod *v1.Pod, nodes *v1.NodeList) (*schedulerapi.HostPriorityList, error) {
+func (e *Extender) Filter(args *schedulerapi.ExtenderArgs) (*schedulerapi.ExtenderFilterResult, error) {
+	filtered := []v1.Node{}
+	failedNodesMap := schedulerapi.FailedNodesMap{}
+
+	if e.nodeCacheCapable {
+		return e.filterUsingNodeCache(args)
+	} else {
+		for _, node := range args.Nodes.Items {
+			fits := true
+			for _, predicate := range e.predicates {
+				fit, err := predicate(&args.Pod, &node)
+				if err != nil {
+					return &schedulerapi.ExtenderFilterResult{
+						Nodes:       &v1.NodeList{},
+						NodeNames:   nil,
+						FailedNodes: schedulerapi.FailedNodesMap{},
+						Error:       err.Error(),
+					}, err
+				}
+				if !fit {
+					fits = false
+					break
+				}
+			}
+			if fits {
+				filtered = append(filtered, node)
+			} else {
+				failedNodesMap[node.Name] = fmt.Sprintf("extender failed: %s", e.name)
+			}
+		}
+
+		return &schedulerapi.ExtenderFilterResult{
+			Nodes:       &v1.NodeList{Items: filtered},
+			NodeNames:   nil,
+			FailedNodes: failedNodesMap,
+		}, nil
+	}
+}
+
+func (e *Extender) Prioritize(args *schedulerapi.ExtenderArgs) (*schedulerapi.HostPriorityList, error) {
 	result := schedulerapi.HostPriorityList{}
 	combinedScores := map[string]int{}
+	var nodes = &v1.NodeList{Items: []v1.Node{}}
+
+	if e.nodeCacheCapable {
+		for _, nodeName := range *args.NodeNames {
+			nodes.Items = append(nodes.Items, v1.Node{ObjectMeta: metav1.ObjectMeta{Name: nodeName}})
+		}
+	} else {
+		nodes = args.Nodes
+	}
+
 	for _, prioritizer := range e.prioritizers {
 		weight := prioritizer.weight
 		if weight == 0 {
 			continue
 		}
 		priorityFunc := prioritizer.function
-		prioritizedList, err := priorityFunc(pod, nodes)
+		prioritizedList, err := priorityFunc(&args.Pod, nodes)
 		if err != nil {
 			return &schedulerapi.HostPriorityList{}, err
 		}
@@ -220,6 +278,17 @@ func TestSchedulerExtender(t *testing.T) {
 	}))
 	defer es2.Close()
 
+	extender3 := &Extender{
+		name:             "extender3",
+		predicates:       []fitPredicate{machine_1_2_3_Predicate},
+		prioritizers:     []priorityConfig{{machine_2_Prioritizer, 5}},
+		nodeCacheCapable: true,
+	}
+	es3 := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		extender3.serveHTTP(t, w, req)
+	}))
+	defer es3.Close()
+
 	policy := schedulerapi.Policy{
 		ExtenderConfigs: []schedulerapi.ExtenderConfig{
 			{
@@ -236,6 +305,14 @@ func TestSchedulerExtender(t *testing.T) {
 				Weight:         4,
 				EnableHttps:    false,
 			},
+			{
+				URLPrefix:        es3.URL,
+				FilterVerb:       filter,
+				PrioritizeVerb:   prioritize,
+				Weight:           10,
+				EnableHttps:      false,
+				NodeCacheCapable: true,
+			},
 		},
 	}
 	policy.APIVersion = api.Registry.GroupOrDie(v1.GroupName).GroupVersion.String()
@@ -313,10 +390,11 @@ func DoTestPodScheduling(ns *v1.Namespace, t *testing.T, cs clientset.Interface)
 		t.Fatalf("Failed to schedule pod: %v", err)
 	}
 
-	if myPod, err := cs.Core().Pods(ns.Name).Get(myPod.Name, metav1.GetOptions{}); err != nil {
+	myPod, err = cs.Core().Pods(ns.Name).Get(myPod.Name, metav1.GetOptions{})
+	if err != nil {
 		t.Fatalf("Failed to get pod: %v", err)
-	} else if myPod.Spec.NodeName != "machine3" {
-		t.Fatalf("Failed to schedule using extender, expected machine3, got %v", myPod.Spec.NodeName)
+	} else if myPod.Spec.NodeName != "machine2" {
+		t.Fatalf("Failed to schedule using extender, expected machine2, got %v", myPod.Spec.NodeName)
 	}
 	t.Logf("Scheduled pod using extenders")
 }