remove datastore dependency from the scheduler (kubernetes-sigs#1049)

* remove datastore dependency from the scheduler

Signed-off-by: Nir Rozenbaum <nirro@il.ibm.com>

* added back comments on snapshotting pods from datastore before calling schedule

Signed-off-by: Nir Rozenbaum <nirro@il.ibm.com>

* removed fake datastore from conformance scheduler test

Signed-off-by: Nir Rozenbaum <nirro@il.ibm.com>

---------

Signed-off-by: Nir Rozenbaum <nirro@il.ibm.com>

Author: nirrozenbaum

cmd/epp/runner/runner.go

@@ -241,7 +241,7 @@ func (r *Runner) Run(ctx context.Context) error {
 	}
 
 	// --- Initialize Core EPP Components ---
-	scheduler, err := r.initializeScheduler(datastore)
+	scheduler, err := r.initializeScheduler()
 	if err != nil {
 		setupLog.Error(err, "Failed to create scheduler")
 		return err
@@ -292,13 +292,13 @@ func (r *Runner) Run(ctx context.Context) error {
 	return nil
 }
 
-func (r *Runner) initializeScheduler(datastore datastore.Datastore) (*scheduling.Scheduler, error) {
+func (r *Runner) initializeScheduler() (*scheduling.Scheduler, error) {
 	if r.schedulerConfig != nil {
-		return scheduling.NewSchedulerWithConfig(datastore, r.schedulerConfig), nil
+		return scheduling.NewSchedulerWithConfig(r.schedulerConfig), nil
 	}
 
 	// otherwise, no one configured from outside scheduler config. use existing configuration
-	scheduler := scheduling.NewScheduler(datastore)
+	scheduler := scheduling.NewScheduler()
 	if schedulerV2 {
 		queueScorerWeight := envutil.GetEnvInt("QUEUE_SCORE_WEIGHT", scorer.DefaultQueueScorerWeight, setupLog)
 		kvCacheScorerWeight := envutil.GetEnvInt("KV_CACHE_SCORE_WEIGHT", scorer.DefaultKVCacheScorerWeight, setupLog)
@@ -316,11 +316,11 @@ func (r *Runner) initializeScheduler(datastore datastore.Datastore) (*scheduling
 		}
 
 		schedulerConfig := scheduling.NewSchedulerConfig(profile.NewSingleProfileHandler(), map[string]*framework.SchedulerProfile{"schedulerv2": schedulerProfile})
-		scheduler = scheduling.NewSchedulerWithConfig(datastore, schedulerConfig)
+		scheduler = scheduling.NewSchedulerWithConfig(schedulerConfig)
 	}
 
 	if reqHeaderBasedSchedulerForTesting {
-		scheduler = conformance_epp.NewReqHeaderBasedScheduler(datastore)
+		scheduler = conformance_epp.NewReqHeaderBasedScheduler()
 	}
 
 	return scheduler, nil

conformance/testing-epp/scheduler.go

@@ -27,11 +27,11 @@ import (
 // NewReqHeaderBasedScheduler creates a scheduler for conformance tests that selects
 // an endpoint based on the "test-epp-endpoint-selection" request header. If the
 // header is missing or the specified endpoint doesn't exist, no endpoint is returned.
-func NewReqHeaderBasedScheduler(datastore scheduling.Datastore) *scheduling.Scheduler {
+func NewReqHeaderBasedScheduler() *scheduling.Scheduler {
 	predicatableSchedulerProfile := framework.NewSchedulerProfile().
 		WithFilters(filter.NewHeaderBasedTestingFilter()).
 		WithPicker(picker.NewMaxScorePicker())
 
-	return scheduling.NewSchedulerWithConfig(datastore, scheduling.NewSchedulerConfig(
+	return scheduling.NewSchedulerWithConfig(scheduling.NewSchedulerConfig(
 		profile.NewSingleProfileHandler(), map[string]*framework.SchedulerProfile{"req-header-based-profile": predicatableSchedulerProfile}))
 }

conformance/testing-epp/sheduler_test.go

@@ -31,13 +31,13 @@ import (
 func TestSchedule(t *testing.T) {
 	tests := []struct {
 		name    string
-		input   []*backendmetrics.FakePodMetrics
+		input   []backendmetrics.PodMetrics
 		req     *types.LLMRequest
 		wantRes *types.SchedulingResult
 		err     bool
 	}{
 		{
-			name: "no pods in datastore and req header is set",
+			name: "no candidate pods and req header is set",
 			req: &types.LLMRequest{
 				Headers:   map[string]string{"test-epp-endpoint-selection": "random-endpoint"},
 				RequestId: uuid.NewString(),
@@ -47,8 +47,8 @@ func TestSchedule(t *testing.T) {
 		},
 		{
 			name: "req header not set",
-			input: []*backendmetrics.FakePodMetrics{
-				{Pod: &backend.Pod{Address: "random-endpoint"}},
+			input: []backendmetrics.PodMetrics{
+				&backendmetrics.FakePodMetrics{Pod: &backend.Pod{Address: "random-endpoint"}},
 			},
 			req: &types.LLMRequest{
 				Headers:   map[string]string{}, // Deliberately set an empty header.
@@ -58,9 +58,9 @@ func TestSchedule(t *testing.T) {
 			err:     true,
 		},
 		{
-			name: "no pods address in datastore matches req header address",
-			input: []*backendmetrics.FakePodMetrics{
-				{Pod: &backend.Pod{Address: "nonmatched-endpoint"}},
+			name: "no pods address from the candidate pods matches req header address",
+			input: []backendmetrics.PodMetrics{
+				&backendmetrics.FakePodMetrics{Pod: &backend.Pod{Address: "nonmatched-endpoint"}},
 			},
 			req: &types.LLMRequest{
 				Headers:   map[string]string{"test-epp-endpoint-selection": "matched-endpoint"},
@@ -70,10 +70,10 @@ func TestSchedule(t *testing.T) {
 			err:     true,
 		},
 		{
-			name: "one pod address in datastore matches req header address",
-			input: []*backendmetrics.FakePodMetrics{
-				{Pod: &backend.Pod{Address: "nonmatched-endpoint"}},
-				{Pod: &backend.Pod{Address: "matched-endpoint"}},
+			name: "one pod address from the candidate pods matches req header address",
+			input: []backendmetrics.PodMetrics{
+				&backendmetrics.FakePodMetrics{Pod: &backend.Pod{Address: "nonmatched-endpoint"}},
+				&backendmetrics.FakePodMetrics{Pod: &backend.Pod{Address: "matched-endpoint"}},
 			},
 			req: &types.LLMRequest{
 				Headers:   map[string]string{"test-epp-endpoint-selection": "matched-endpoint"},
@@ -99,8 +99,8 @@ func TestSchedule(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			scheduler := NewReqHeaderBasedScheduler(&fakeDataStore{pods: test.input})
-			got, err := scheduler.Schedule(context.Background(), test.req)
+			scheduler := NewReqHeaderBasedScheduler()
+			got, err := scheduler.Schedule(context.Background(), test.req, types.ToSchedulerPodMetrics(test.input))
 			if test.err != (err != nil) {
 				t.Errorf("Unexpected error, got %v, want %v", err, test.err)
 			}
@@ -111,15 +111,3 @@ func TestSchedule(t *testing.T) {
 		})
 	}
 }
-
-type fakeDataStore struct {
-	pods []*backendmetrics.FakePodMetrics
-}
-
-func (fds *fakeDataStore) PodGetAll() []backendmetrics.PodMetrics {
-	pm := make([]backendmetrics.PodMetrics, 0, len(fds.pods))
-	for _, pod := range fds.pods {
-		pm = append(pm, pod)
-	}
-	return pm
-}

pkg/epp/requestcontrol/director.go

@@ -41,7 +41,7 @@ import (
 
 // Scheduler defines the interface required by the Director for scheduling.
 type Scheduler interface {
-	Schedule(ctx context.Context, b *schedulingtypes.LLMRequest) (result *schedulingtypes.SchedulingResult, err error)
+	Schedule(ctx context.Context, request *schedulingtypes.LLMRequest, candidatePods []schedulingtypes.Pod) (result *schedulingtypes.SchedulingResult, err error)
 }
 
 // SaturationDetector provides a signal indicating whether the backends are considered saturated.
@@ -135,7 +135,11 @@ func (d *Director) HandleRequest(ctx context.Context, reqCtx *handlers.RequestCo
 	}
 
 	// --- 3. Call Scheduler ---
-	results, err := d.scheduler.Schedule(ctx, reqCtx.SchedulingRequest)
+	// Snapshot pod metrics from the datastore to:
+	// 1. Reduce concurrent access to the datastore.
+	// 2. Ensure consistent data during the scheduling operation of a request between all scheduling cycles.
+	candidatePods := schedulingtypes.ToSchedulerPodMetrics(d.datastore.PodGetAll())
+	results, err := d.scheduler.Schedule(ctx, reqCtx.SchedulingRequest, candidatePods)
 	if err != nil {
 		return reqCtx, errutil.Error{Code: errutil.InferencePoolResourceExhausted, Msg: fmt.Errorf("failed to find target pod: %w", err).Error()}
 	}

pkg/epp/requestcontrol/director_test.go

@@ -58,7 +58,7 @@ type mockScheduler struct {
 	scheduleErr     error
 }
 
-func (m *mockScheduler) Schedule(ctx context.Context, req *schedulingtypes.LLMRequest) (*schedulingtypes.SchedulingResult, error) {
+func (m *mockScheduler) Schedule(_ context.Context, _ *schedulingtypes.LLMRequest, _ []schedulingtypes.Pod) (*schedulingtypes.SchedulingResult, error) {
 	return m.scheduleResults, m.scheduleErr
 }
 

pkg/epp/scheduling/framework/scheduler_profile.go

@@ -106,8 +106,8 @@ func (p *SchedulerProfile) AddPlugins(pluginObjects ...plugins.Plugin) error {
 
 // RunCycle runs a SchedulerProfile cycle. In other words, it invokes all the SchedulerProfile plugins in this
 // order - Filters, Scorers, Picker, PostCyclePlugins. After completing all, it returns the result.
-func (p *SchedulerProfile) Run(ctx context.Context, request *types.LLMRequest, cycleState *types.CycleState, podsSnapshot []types.Pod) (*types.ProfileRunResult, error) {
-	pods := p.runFilterPlugins(ctx, request, cycleState, podsSnapshot)
+func (p *SchedulerProfile) Run(ctx context.Context, request *types.LLMRequest, cycleState *types.CycleState, candidatePods []types.Pod) (*types.ProfileRunResult, error) {
+	pods := p.runFilterPlugins(ctx, request, cycleState, candidatePods)
 	if len(pods) == 0 {
 		return nil, errutil.Error{Code: errutil.Internal, Msg: "no pods available for the given request"}
 	}

pkg/epp/scheduling/scheduler.go

@@ -39,7 +39,7 @@ type Datastore interface {
 }
 
 // NewScheduler returns a new scheduler with default scheduler plugins configuration.
-func NewScheduler(datastore Datastore) *Scheduler {
+func NewScheduler() *Scheduler {
 	// When the scheduler is initialized with NewScheduler function, thw below config will be used as default.
 	// it's possible to call NewSchedulerWithConfig to pass a different scheduler config.
 	// For build time plugins changes, it's recommended to call in main.go to NewSchedulerWithConfig.
@@ -75,26 +75,24 @@ func NewScheduler(datastore Datastore) *Scheduler {
 
 	profileHandler := profile.NewSingleProfileHandler()
 
-	return NewSchedulerWithConfig(datastore, NewSchedulerConfig(profileHandler, map[string]*framework.SchedulerProfile{"default": defaultProfile}))
+	return NewSchedulerWithConfig(NewSchedulerConfig(profileHandler, map[string]*framework.SchedulerProfile{"default": defaultProfile}))
 }
 
 // NewSchedulerWithConfig returns a new scheduler with the given scheduler plugins configuration.
-func NewSchedulerWithConfig(datastore Datastore, config *SchedulerConfig) *Scheduler {
+func NewSchedulerWithConfig(config *SchedulerConfig) *Scheduler {
 	return &Scheduler{
-		datastore:      datastore,
 		profileHandler: config.profileHandler,
 		profiles:       config.profiles,
 	}
 }
 
 type Scheduler struct {
-	datastore      Datastore
 	profileHandler framework.ProfileHandler
 	profiles       map[string]*framework.SchedulerProfile
 }
 
 // Schedule finds the target pod based on metrics and the requested lora adapter.
-func (s *Scheduler) Schedule(ctx context.Context, request *types.LLMRequest) (*types.SchedulingResult, error) {
+func (s *Scheduler) Schedule(ctx context.Context, request *types.LLMRequest, candidatePods []types.Pod) (*types.SchedulingResult, error) {
 	logger := log.FromContext(ctx).WithValues("request", request)
 	loggerDebug := logger.V(logutil.DEBUG)
 
@@ -103,12 +101,6 @@ func (s *Scheduler) Schedule(ctx context.Context, request *types.LLMRequest) (*t
 		metrics.RecordSchedulerE2ELatency(time.Since(scheduleStart))
 	}()
 
-	// Snapshot pod metrics from the datastore to:
-	// 1. Reduce concurrent access to the datastore.
-	// 2. Ensure consistent data during the scheduling operation of a request between all scheduling cycles.
-	podsSnapshot := types.ToSchedulerPodMetrics(s.datastore.PodGetAll())
-	loggerDebug.Info(fmt.Sprintf("Scheduling a request, Metrics: %+v", podsSnapshot))
-
 	profileRunResults := map[string]*types.ProfileRunResult{}
 	cycleState := types.NewCycleState()
 
@@ -122,7 +114,7 @@ func (s *Scheduler) Schedule(ctx context.Context, request *types.LLMRequest) (*t
 
 		for name, profile := range profiles {
 			// run the selected profiles and collect results (current code runs all profiles)
-			profileRunResult, err := profile.Run(ctx, request, cycleState, podsSnapshot)
+			profileRunResult, err := profile.Run(ctx, request, cycleState, candidatePods)
 			if err != nil {
 				loggerDebug.Info("failed to run scheduler profile", "profile", name, "error", err.Error())
 			}

pkg/epp/scheduling/scheduler_test.go

@@ -33,17 +33,17 @@ func TestSchedule(t *testing.T) {
 	tests := []struct {
 		name    string
 		req     *types.LLMRequest
-		input   []*backendmetrics.FakePodMetrics
+		input   []backendmetrics.PodMetrics
 		wantRes *types.SchedulingResult
 		err     bool
 	}{
 		{
-			name: "no pods in datastore",
+			name: "no candidate pods",
 			req: &types.LLMRequest{
 				TargetModel: "any-model",
 				RequestId:   uuid.NewString(),
 			},
-			input:   []*backendmetrics.FakePodMetrics{},
+			input:   []backendmetrics.PodMetrics{},
 			wantRes: nil,
 			err:     true,
 		},
@@ -55,8 +55,8 @@ func TestSchedule(t *testing.T) {
 			},
 			// pod2 will be picked because it has relatively low queue size, with the requested
 			// model being active, and has low KV cache.
-			input: []*backendmetrics.FakePodMetrics{
-				{
+			input: []backendmetrics.PodMetrics{
+				&backendmetrics.FakePodMetrics{
 					Pod: &backend.Pod{NamespacedName: k8stypes.NamespacedName{Name: "pod1"}},
 					Metrics: &backendmetrics.MetricsState{
 						WaitingQueueSize:    0,
@@ -68,7 +68,7 @@ func TestSchedule(t *testing.T) {
 						},
 					},
 				},
-				{
+				&backendmetrics.FakePodMetrics{
 					Pod: &backend.Pod{NamespacedName: k8stypes.NamespacedName{Name: "pod2"}},
 					Metrics: &backendmetrics.MetricsState{
 						WaitingQueueSize:    3,
@@ -80,7 +80,7 @@ func TestSchedule(t *testing.T) {
 						},
 					},
 				},
-				{
+				&backendmetrics.FakePodMetrics{
 					Pod: &backend.Pod{NamespacedName: k8stypes.NamespacedName{Name: "pod3"}},
 					Metrics: &backendmetrics.MetricsState{
 						WaitingQueueSize:    10,
@@ -119,8 +119,8 @@ func TestSchedule(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			scheduler := NewScheduler(&fakeDataStore{pods: test.input})
-			got, err := scheduler.Schedule(context.Background(), test.req)
+			scheduler := NewScheduler()
+			got, err := scheduler.Schedule(context.Background(), test.req, types.ToSchedulerPodMetrics(test.input))
 			if test.err != (err != nil) {
 				t.Errorf("Unexpected error, got %v, want %v", err, test.err)
 			}
@@ -131,15 +131,3 @@ func TestSchedule(t *testing.T) {
 		})
 	}
 }
-
-type fakeDataStore struct {
-	pods []*backendmetrics.FakePodMetrics
-}
-
-func (fds *fakeDataStore) PodGetAll() []backendmetrics.PodMetrics {
-	pm := make([]backendmetrics.PodMetrics, 0, len(fds.pods))
-	for _, pod := range fds.pods {
-		pm = append(pm, pod)
-	}
-	return pm
-}

test/integration/epp/hermetic_test.go

@@ -925,7 +925,7 @@ func BeforeSuite() func() {
 	// Adjust from defaults
 	serverRunner.PoolNamespacedName = types.NamespacedName{Name: testPoolName, Namespace: testNamespace}
 	serverRunner.Datastore = datastore.NewDatastore(context.Background(), pmf)
-	scheduler := scheduling.NewScheduler(serverRunner.Datastore)
+	scheduler := scheduling.NewScheduler()
 
 	sdConfig := &saturationdetector.Config{
 		QueueDepthThreshold:       saturationdetector.DefaultQueueDepthThreshold,