prefilter extension point implementation for the scheduler

pkg/scheduler/core/extender_test.go

@@ -29,6 +29,7 @@ import (
 	"k8s.io/kubernetes/pkg/scheduler/algorithm/predicates"
 	"k8s.io/kubernetes/pkg/scheduler/algorithm/priorities"
 	schedulerapi "k8s.io/kubernetes/pkg/scheduler/api"
+	framework "k8s.io/kubernetes/pkg/scheduler/framework/v1alpha1"
 	internalcache "k8s.io/kubernetes/pkg/scheduler/internal/cache"
 	internalqueue "k8s.io/kubernetes/pkg/scheduler/internal/queue"
 	schedulernodeinfo "k8s.io/kubernetes/pkg/scheduler/nodeinfo"
@@ -552,7 +553,7 @@ func TestGenericSchedulerWithExtenders(t *testing.T) {
 				schedulerapi.DefaultPercentageOfNodesToScore,
 				false)
 			podIgnored := &v1.Pod{}
-			result, err := scheduler.Schedule(podIgnored, schedulertesting.FakeNodeLister(makeNodeList(test.nodes)))
+			result, err := scheduler.Schedule(podIgnored, schedulertesting.FakeNodeLister(makeNodeList(test.nodes)), framework.NewPluginContext())
 			if test.expectsErr {
 				if err == nil {
 					t.Errorf("Unexpected non-error, result %+v", result)

pkg/scheduler/core/generic_scheduler.go

@@ -126,7 +126,7 @@ func (f *FitError) Error() string {
 // onto machines.
 // TODO: Rename this type.
 type ScheduleAlgorithm interface {
-	Schedule(*v1.Pod, algorithm.NodeLister) (scheduleResult ScheduleResult, err error)
+	Schedule(*v1.Pod, algorithm.NodeLister, *framework.PluginContext) (scheduleResult ScheduleResult, err error)
 	// Preempt receives scheduling errors for a pod and tries to create room for
 	// the pod by preempting lower priority pods if possible.
 	// It returns the node where preemption happened, a list of preempted pods, a
@@ -181,14 +181,20 @@ func (g *genericScheduler) snapshot() error {
 // Schedule tries to schedule the given pod to one of the nodes in the node list.
 // If it succeeds, it will return the name of the node.
 // If it fails, it will return a FitError error with reasons.
-func (g *genericScheduler) Schedule(pod *v1.Pod, nodeLister algorithm.NodeLister) (result ScheduleResult, err error) {
+func (g *genericScheduler) Schedule(pod *v1.Pod, nodeLister algorithm.NodeLister, pluginContext *framework.PluginContext) (result ScheduleResult, err error) {
 	trace := utiltrace.New(fmt.Sprintf("Scheduling %s/%s", pod.Namespace, pod.Name))
 	defer trace.LogIfLong(100 * time.Millisecond)
 
 	if err := podPassesBasicChecks(pod, g.pvcLister); err != nil {
 		return result, err
 	}
 
+	// Run "prefilter" plugins.
+	prefilterStatus := g.framework.RunPrefilterPlugins(pluginContext, pod)
+	if !prefilterStatus.IsSuccess() {
+		return result, prefilterStatus.AsError()
+	}
+
 	nodes, err := nodeLister.List()
 	if err != nil {
 		return result, err

pkg/scheduler/core/generic_scheduler_test.go

@@ -466,8 +466,7 @@ func TestGenericScheduler(t *testing.T) {
 				false,
 				schedulerapi.DefaultPercentageOfNodesToScore,
 				false)
-			result, err := scheduler.Schedule(test.pod, schedulertesting.FakeNodeLister(makeNodeList(test.nodes)))
-
+			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)
 			}

pkg/scheduler/framework/v1alpha1/framework.go

@@ -36,6 +36,7 @@ type framework struct {
 	waitingPods      *waitingPodsMap
 	plugins          map[string]Plugin // a map of initialized plugins. Plugin name:plugin instance.
 	queueSortPlugins []QueueSortPlugin
+	prefilterPlugins []PrefilterPlugin
 	reservePlugins   []ReservePlugin
 	prebindPlugins   []PrebindPlugin
 	postbindPlugins  []PostbindPlugin
@@ -85,6 +86,20 @@ func NewFramework(r Registry, plugins *config.Plugins, args []config.PluginConfi
 		f.plugins[name] = p
 	}
 
+	if plugins.PreFilter != nil {
+		for _, pf := range plugins.PreFilter.Enabled {
+			if pg, ok := f.plugins[pf.Name]; ok {
+				p, ok := pg.(PrefilterPlugin)
+				if !ok {
+					return nil, fmt.Errorf("plugin %v does not extend prefilter plugin", pf.Name)
+				}
+				f.prefilterPlugins = append(f.prefilterPlugins, p)
+			} else {
+				return nil, fmt.Errorf("prefilter plugin %v does not exist", pf.Name)
+			}
+		}
+	}
+
 	if plugins.Reserve != nil {
 		for _, r := range plugins.Reserve.Enabled {
 			if pg, ok := f.plugins[r.Name]; ok {
@@ -185,6 +200,28 @@ func (f *framework) QueueSortFunc() LessFunc {
 	return f.queueSortPlugins[0].Less
 }
 
+// RunPrefilterPlugins runs the set of configured prefilter plugins. It returns
+// *Status and its code is set to non-success if any of the plugins returns
+// anything but Success. If a non-success status is returned, then the scheduling
+// cycle is aborted.
+func (f *framework) RunPrefilterPlugins(
+	pc *PluginContext, pod *v1.Pod) *Status {
+	for _, pl := range f.prefilterPlugins {
+		status := pl.Prefilter(pc, pod)
+		if !status.IsSuccess() {
+			if status.Code() == Unschedulable {
+				msg := fmt.Sprintf("rejected by %v at prefilter: %v", pl.Name(), status.Message())
+				klog.V(4).Infof(msg)
+				return NewStatus(status.Code(), msg)
+			}
+			msg := fmt.Sprintf("error while running %v prefilter plugin for pod %v: %v", pl.Name(), pod.Name, status.Message())
+			klog.Error(msg)
+			return NewStatus(Error, msg)
+		}
+	}
+	return nil
+}
+
 // RunPrebindPlugins runs the set of configured prebind plugins. It returns a
 // failure (bool) if any of the plugins returns an error. It also returns an
 // error containing the rejection message or the error occurred in the plugin.

pkg/scheduler/framework/v1alpha1/interface.go

@@ -126,6 +126,15 @@ type QueueSortPlugin interface {
 	Less(*PodInfo, *PodInfo) bool
 }
 
+// PrefilterPlugin is an interface that must be implemented by "prefilter" plugins.
+// These plugins are called at the beginning of the scheduling cycle.
+type PrefilterPlugin interface {
+	Plugin
+	// Prefilter is called at the beginning of the scheduling cycle. All prefilter
+	// plugins must return success or the pod will be rejected.
+	Prefilter(pc *PluginContext, p *v1.Pod) *Status
+}
+
 // ReservePlugin is an interface for Reserve plugins. These plugins are called
 // at the reservation point. These are meant to update the state of the plugin.
 // This concept used to be called 'assume' in the original scheduler.
@@ -190,6 +199,12 @@ type Framework interface {
 	// QueueSortFunc returns the function to sort pods in scheduling queue
 	QueueSortFunc() LessFunc
 
+	// RunPrefilterPlugins runs the set of configured prefilter plugins. It returns
+	// *Status and its code is set to non-success if any of the plugins returns
+	// anything but Success. If a non-success status is returned, then the scheduling
+	// cycle is aborted.
+	RunPrefilterPlugins(pc *PluginContext, pod *v1.Pod) *Status
+
 	// RunPrebindPlugins runs the set of configured prebind plugins. It returns
 	// *Status and its code is set to non-success if any of the plugins returns
 	// anything but Success. If the Status code is "Unschedulable", it is

pkg/scheduler/internal/queue/scheduling_queue_test.go

@@ -167,6 +167,10 @@ func (*fakeFramework) NodeInfoSnapshot() *internalcache.NodeInfoSnapshot {
 	return nil
 }
 
+func (*fakeFramework) RunPrefilterPlugins(pc *framework.PluginContext, pod *v1.Pod) *framework.Status {
+	return nil
+}
+
 func (*fakeFramework) RunPrebindPlugins(pc *framework.PluginContext, pod *v1.Pod, nodeName string) *framework.Status {
 	return nil
 }

pkg/scheduler/scheduler.go

@@ -280,8 +280,8 @@ func (sched *Scheduler) recordSchedulingFailure(pod *v1.Pod, err error, reason s
 
 // schedule implements the scheduling algorithm and returns the suggested result(host,
 // evaluated nodes number,feasible nodes number).
-func (sched *Scheduler) schedule(pod *v1.Pod) (core.ScheduleResult, error) {
-	result, err := sched.config.Algorithm.Schedule(pod, sched.config.NodeLister)
+func (sched *Scheduler) schedule(pod *v1.Pod, pluginContext *framework.PluginContext) (core.ScheduleResult, error) {
+	result, err := sched.config.Algorithm.Schedule(pod, sched.config.NodeLister, pluginContext)
 	if err != nil {
 		pod = pod.DeepCopy()
 		sched.recordSchedulingFailure(pod, err, v1.PodReasonUnschedulable, err.Error())
@@ -458,7 +458,7 @@ func (sched *Scheduler) scheduleOne() {
 	// Synchronously attempt to find a fit for the pod.
 	start := time.Now()
 	pluginContext := framework.NewPluginContext()
-	scheduleResult, err := sched.schedule(pod)
+	scheduleResult, err := sched.schedule(pod, pluginContext)
 	if err != nil {
 		// schedule() may have failed because the pod would not fit on any host, so we try to
 		// preempt, with the expectation that the next time the pod is tried for scheduling it

pkg/scheduler/scheduler_test.go

@@ -58,7 +58,7 @@ import (
 )
 
 // EmptyFramework is an empty framework used in tests.
-// Note: If the test runs in goroutine, please don't using this variable to avoid a race condition.
+// Note: If the test runs in goroutine, please don't use this variable to avoid a race condition.
 var EmptyFramework, _ = framework.NewFramework(EmptyPluginRegistry, nil, EmptyPluginConfig)
 
 // EmptyPluginConfig is an empty plugin config used in tests.
@@ -159,7 +159,7 @@ type mockScheduler struct {
 	err    error
 }
 
-func (es mockScheduler) Schedule(pod *v1.Pod, ml algorithm.NodeLister) (core.ScheduleResult, error) {
+func (es mockScheduler) Schedule(pod *v1.Pod, ml algorithm.NodeLister, pc *framework.PluginContext) (core.ScheduleResult, error) {
 	return es.result, es.err
 }
 

test/integration/scheduler/framework_test.go

@@ -31,10 +31,13 @@ import (
 // TesterPlugin is common ancestor for a test plugin that allows injection of
 // failures and some other test functionalities.
 type TesterPlugin struct {
+	numPrefilterCalled  int
 	numReserveCalled    int
 	numPrebindCalled    int
 	numPostbindCalled   int
 	numUnreserveCalled  int
+	failPrefilter       bool
+	rejectPrefilter     bool
 	failReserve         bool
 	failPrebind         bool
 	rejectPrebind       bool
@@ -46,6 +49,10 @@ type TesterPlugin struct {
 	waitAndAllowPermit  bool
 }
 
+type PrefilterPlugin struct {
+	TesterPlugin
+}
+
 type ReservePlugin struct {
 	TesterPlugin
 }
@@ -68,13 +75,15 @@ type PermitPlugin struct {
 }
 
 const (
+	prefilterPluginName = "prefilter-plugin"
 	reservePluginName   = "reserve-plugin"
 	prebindPluginName   = "prebind-plugin"
 	unreservePluginName = "unreserve-plugin"
 	postbindPluginName  = "postbind-plugin"
 	permitPluginName    = "permit-plugin"
 )
 
+var _ = framework.PrefilterPlugin(&PrefilterPlugin{})
 var _ = framework.ReservePlugin(&ReservePlugin{})
 var _ = framework.PrebindPlugin(&PrebindPlugin{})
 var _ = framework.PostbindPlugin(&PostbindPlugin{})
@@ -154,6 +163,30 @@ func NewPostbindPlugin(_ *runtime.Unknown, _ framework.FrameworkHandle) (framewo
 	return ptbdPlugin, nil
 }
 
+var pfPlugin = &PrefilterPlugin{}
+
+// Name returns name of the plugin.
+func (pp *PrefilterPlugin) Name() string {
+	return prefilterPluginName
+}
+
+// Prefilter is a test function that returns (true, nil) or errors for testing.
+func (pp *PrefilterPlugin) Prefilter(pc *framework.PluginContext, pod *v1.Pod) *framework.Status {
+	pp.numPrefilterCalled++
+	if pp.failPrefilter {
+		return framework.NewStatus(framework.Error, fmt.Sprintf("injecting failure for pod %v", pod.Name))
+	}
+	if pp.rejectPrefilter {
+		return framework.NewStatus(framework.Unschedulable, fmt.Sprintf("reject pod %v", pod.Name))
+	}
+	return nil
+}
+
+// NewPrebindPlugin is the factory for prebind plugin.
+func NewPrefilterPlugin(_ *runtime.Unknown, _ framework.FrameworkHandle) (framework.Plugin, error) {
+	return pfPlugin, nil
+}
+
 var unresPlugin = &UnreservePlugin{}
 
 // Name returns name of the plugin.
@@ -226,6 +259,84 @@ func NewPermitPlugin(_ *runtime.Unknown, fh framework.FrameworkHandle) (framewor
 	return perPlugin, nil
 }
 
+// TestPrefilterPlugin tests invocation of prefilter plugins.
+func TestPrefilterPlugin(t *testing.T) {
+	// Create a plugin registry for testing. Register only a reserve plugin.
+	registry := framework.Registry{prefilterPluginName: NewPrefilterPlugin}
+
+	// Setup initial prefilter plugin for testing.
+	prefilterPlugin := &schedulerconfig.Plugins{
+		PreFilter: &schedulerconfig.PluginSet{
+			Enabled: []schedulerconfig.Plugin{
+				{
+					Name: prefilterPluginName,
+				},
+			},
+		},
+	}
+	// 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, "prefilter-plugin", nil),
+		false, nil, registry, prefilterPlugin, 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)
+	}
+
+	tests := []struct {
+		fail   bool
+		reject bool
+	}{
+		{
+			fail:   false,
+			reject: false,
+		},
+		{
+			fail:   true,
+			reject: false,
+		},
+		{
+			fail:   false,
+			reject: true,
+		},
+	}
+
+	for i, test := range tests {
+		pfPlugin.failPrefilter = test.fail
+		pfPlugin.rejectPrefilter = test.reject
+		// 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 test.reject || test.fail {
+			if err = waitForPodUnschedulable(cs, pod); err != nil {
+				t.Errorf("test #%v: Didn't expect the pod to be scheduled. error: %v", i, err)
+			}
+		} else {
+			if err = waitForPodToSchedule(cs, pod); err != nil {
+				t.Errorf("test #%v: Expected the pod to be scheduled. error: %v", i, err)
+			}
+		}
+
+		if pfPlugin.numPrefilterCalled == 0 {
+			t.Errorf("Expected the prefilter plugin to be called.")
+		}
+
+		cleanupPods(cs, t, []*v1.Pod{pod})
+	}
+}
+
 // TestReservePlugin tests invocation of reserve plugins.
 func TestReservePlugin(t *testing.T) {
 	// Create a plugin registry for testing. Register only a reserve plugin.