Move `ScheduleAlgorithm` to the core package.

This moves the type `ScheduleAlgorithm` from `pkg/scheduler/algorithm`
to `pkg/scheduler/core`. The reason for this move is to fix our import
dependency graph and allow predicate & priority types to be moved into
their appropriate packages.

The new location makes sense because `core` is the only package that
exports an implementation of this type.

pkg/scheduler/algorithm/scheduler_interface.go

@@ -72,20 +72,3 @@ type SchedulerExtender interface {
 	// is unavailable. This gives scheduler ability to fail fast and tolerate non-critical extenders as well.
 	IsIgnorable() bool
 }
-
-// ScheduleAlgorithm is an interface implemented by things that know how to schedule pods
-// onto machines.
-type ScheduleAlgorithm interface {
-	Schedule(*v1.Pod, NodeLister) (selectedMachine string, 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
-	// list of pods whose nominated node name should be removed, and error if any.
-	Preempt(*v1.Pod, NodeLister, error) (selectedNode *v1.Node, preemptedPods []*v1.Pod, cleanupNominatedPods []*v1.Pod, err error)
-	// Predicates() returns a pointer to a map of predicate functions. This is
-	// exposed for testing.
-	Predicates() map[string]FitPredicate
-	// Prioritizers returns a slice of priority config. This is exposed for
-	// testing.
-	Prioritizers() []PriorityConfig
-}

pkg/scheduler/core/generic_scheduler.go

@@ -96,6 +96,24 @@ func (f *FitError) Error() string {
 	return reasonMsg
 }
 
+// ScheduleAlgorithm is an interface implemented by things that know how to schedule pods
+// onto machines.
+// TODO: Rename this type.
+type ScheduleAlgorithm interface {
+	Schedule(*v1.Pod, algorithm.NodeLister) (selectedMachine string, 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
+	// list of pods whose nominated node name should be removed, and error if any.
+	Preempt(*v1.Pod, algorithm.NodeLister, error) (selectedNode *v1.Node, preemptedPods []*v1.Pod, cleanupNominatedPods []*v1.Pod, err error)
+	// Predicates() returns a pointer to a map of predicate functions. This is
+	// exposed for testing.
+	Predicates() map[string]algorithm.FitPredicate
+	// Prioritizers returns a slice of priority config. This is exposed for
+	// testing.
+	Prioritizers() []algorithm.PriorityConfig
+}
+
 type genericScheduler struct {
 	cache                    schedulerinternalcache.Cache
 	equivalenceCache         *equivalence.Cache
@@ -1164,7 +1182,7 @@ func NewGenericScheduler(
 	alwaysCheckAllPredicates bool,
 	disablePreemption bool,
 	percentageOfNodesToScore int32,
-) algorithm.ScheduleAlgorithm {
+) ScheduleAlgorithm {
 	return &genericScheduler{
 		cache:                    cache,
 		equivalenceCache:         eCache,

pkg/scheduler/factory/factory.go

@@ -103,7 +103,7 @@ type Config struct {
 	// successfully binding a pod
 	Ecache     *equivalence.Cache
 	NodeLister algorithm.NodeLister
-	Algorithm  algorithm.ScheduleAlgorithm
+	Algorithm  core.ScheduleAlgorithm
 	GetBinder  func(pod *v1.Pod) Binder
 	// PodConditionUpdater is used only in case of scheduling errors. If we succeed
 	// with scheduling, PodScheduled condition will be updated in apiserver in /bind

pkg/scheduler/scheduler_test.go

@@ -211,7 +211,7 @@ func TestScheduler(t *testing.T) {
 		name             string
 		injectBindError  error
 		sendPod          *v1.Pod
-		algo             algorithm.ScheduleAlgorithm
+		algo             core.ScheduleAlgorithm
 		expectErrorPod   *v1.Pod
 		expectForgetPod  *v1.Pod
 		expectAssumedPod *v1.Pod