Have a default configuration for the EndpointPicker

cmd/epp/runner/runner.go

@@ -439,10 +439,6 @@ func (r *Runner) registerInTreePlugins() {
 }
 
 func (r *Runner) parseConfigurationPhaseOne(ctx context.Context, opts *runserver.Options) (*configapi.EndpointPickerConfig, error) {
-	if opts.ConfigText == "" && opts.ConfigFile == "" {
-		return nil, nil // configuring through code, not through file
-	}
-
 	logger := log.FromContext(ctx)
 
 	var configBytes []byte

pkg/epp/config/loader/configloader.go

@@ -55,11 +55,19 @@ func RegisterFeatureGate(gate string) {
 // LoadRawConfig parses the raw configuration bytes, applies initial defaults, and extracts feature gates.
 // It does not instantiate plugins.
 func LoadRawConfig(configBytes []byte, logger logr.Logger) (*configapi.EndpointPickerConfig, map[string]bool, error) {
-	rawConfig, err := decodeRawConfig(configBytes)
-	if err != nil {
-		return nil, nil, err
+	var rawConfig *configapi.EndpointPickerConfig
+	var err error
+	if len(configBytes) != 0 {
+		rawConfig, err = decodeRawConfig(configBytes)
+		if err != nil {
+			return nil, nil, err
+		}
+		logger.Info("Loaded raw configuration", "config", rawConfig.String())
+	} else {
+		logger.Info("A configuration wasn't specified. A default one is being used.")
+		rawConfig = loadDefaultConfig()
+		logger.Info("Default raw configuration used", "config", rawConfig.String())
 	}
-	logger.Info("Loaded raw configuration", "config", rawConfig)
 
 	applyStaticDefaults(rawConfig)
 

pkg/epp/config/loader/configloader_test.go

@@ -43,6 +43,8 @@ import (
 	framework "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/interface/scheduling"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/plugins/scheduling/picker"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/plugins/scheduling/profile"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/plugins/scheduling/scorer"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/plugins/scheduling/scorer/prefix"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/saturationdetector/framework/plugins/utilizationdetector"
 	"sigs.k8s.io/gateway-api-inference-extension/test/utils"
 )
@@ -67,6 +69,10 @@ func TestLoadRawConfiguration(t *testing.T) {
 	RegisterFeatureGate(datalayer.ExperimentalDatalayerFeatureGate)
 	RegisterFeatureGate(flowcontrol.FeatureGate)
 
+	queueScorerWeight := 2.0
+	kvCacheUtilizationScorerWeight := 2.0
+	prefixCacheScorerWeight := 3.0
+
 	tests := []struct {
 		name       string
 		configText string
@@ -124,6 +130,51 @@ func TestLoadRawConfiguration(t *testing.T) {
 			},
 			wantErr: false,
 		},
+		{
+			name:       "Success - Default configuration",
+			configText: "",
+			want: &configapi.EndpointPickerConfig{
+				TypeMeta: metav1.TypeMeta{
+					APIVersion: "inference.networking.x-k8s.io/v1alpha1",
+					Kind:       "EndpointPickerConfig",
+				},
+				FeatureGates: configapi.FeatureGates{},
+				Plugins: []configapi.PluginSpec{
+					{
+						Name: scorer.QueueScorerType,
+						Type: scorer.QueueScorerType,
+					},
+					{
+						Name: scorer.KvCacheUtilizationScorerType,
+						Type: scorer.KvCacheUtilizationScorerType,
+					},
+					{
+						Name: prefix.PrefixCachePluginType,
+						Type: prefix.PrefixCachePluginType,
+					},
+				},
+				SchedulingProfiles: []configapi.SchedulingProfile{
+					{
+						Name: "default",
+						Plugins: []configapi.SchedulingPlugin{
+							{
+								PluginRef: scorer.QueueScorerType,
+								Weight:    &queueScorerWeight,
+							},
+							{
+								PluginRef: scorer.KvCacheUtilizationScorerType,
+								Weight:    &kvCacheUtilizationScorerWeight,
+							},
+							{
+								PluginRef: prefix.PrefixCachePluginType,
+								Weight:    &prefixCacheScorerWeight,
+							},
+						},
+					},
+				},
+			},
+			wantErr: false,
+		},
 		{
 			name:       "Error - Invalid YAML",
 			configText: errorBadYamlText,

pkg/epp/config/loader/defaults.go

@@ -19,19 +19,65 @@ package loader
 import (
 	"fmt"
 
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
 	configapi "sigs.k8s.io/gateway-api-inference-extension/apix/config/v1alpha1"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/registry"
 	fwkplugin "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/interface/plugin"
 	framework "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/interface/scheduling"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/plugins/scheduling/picker"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/plugins/scheduling/profile"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/plugins/scheduling/scorer"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/framework/plugins/scheduling/scorer/prefix"
 )
 
 // DefaultScorerWeight is the weight used for scorers referenced in the configuration without explicit weights.
 const DefaultScorerWeight = 1.0
 
 var defaultScorerWeight = DefaultScorerWeight
 
+func loadDefaultConfig() *configapi.EndpointPickerConfig {
+	queueScorerWeight := 2.0
+	kvCacheUtilizationScorerWeight := 2.0
+	prefixCacheScorerWeight := 3.0
+	return &configapi.EndpointPickerConfig{
+		TypeMeta: metav1.TypeMeta{
+			APIVersion: "inference.networking.x-k8s.io/v1alpha1",
+			Kind:       "EndpointPickerConfig",
+		},
+		Plugins: []configapi.PluginSpec{
+			{
+				Type: scorer.QueueScorerType,
+			},
+			{
+				Type: scorer.KvCacheUtilizationScorerType,
+			},
+			{
+				Type: prefix.PrefixCachePluginType,
+			},
+		},
+		SchedulingProfiles: []configapi.SchedulingProfile{
+			{
+				Name: "default",
+				Plugins: []configapi.SchedulingPlugin{
+					{
+						PluginRef: scorer.QueueScorerType,
+						Weight:    &queueScorerWeight,
+					},
+					{
+						PluginRef: scorer.KvCacheUtilizationScorerType,
+						Weight:    &kvCacheUtilizationScorerWeight,
+					},
+					{
+						PluginRef: prefix.PrefixCachePluginType,
+						Weight:    &prefixCacheScorerWeight,
+					},
+				},
+			},
+		},
+	}
+}
+
 // applyStaticDefaults sanitizes the configuration object before plugin instantiation.
 // It handles "Static" defaults: simple structural changes to the API object that do not require access to the plugin
 // registry.

pkg/epp/server/options.go

@@ -228,9 +228,6 @@ func (opts *Options) Validate() error {
 		}
 	}
 
-	if opts.ConfigText == "" && opts.ConfigFile == "" {
-		return fmt.Errorf("one of the %q and %q flags must be set", "configText", "configFile")
-	}
 	if opts.ConfigText != "" && opts.ConfigFile != "" {
 		return fmt.Errorf("both the %q and %q flags can not be set at the same time", "configText", "configFile")
 	}