Add a set of configuration defaults (#1223)

* If a picker wasn't specified, add one

Signed-off-by: Shmuel Kallner <kallner@il.ibm.com>

* If there is only one profile and a profile handler wasn't specified, add one

Signed-off-by: Shmuel Kallner <kallner@il.ibm.com>

* If there aren't any ScehdulingProfiles, add one

Signed-off-by: Shmuel Kallner <kallner@il.ibm.com>

* Updated and fixed tests

Signed-off-by: Shmuel Kallner <kallner@il.ibm.com>

* Updated the configuration guide

Signed-off-by: Shmuel Kallner <kallner@il.ibm.com>

* Don't hard code the default scorer weight

Signed-off-by: Shmuel Kallner <kallner@il.ibm.com>

* If a picker is missing, always add a MaxScorePicker

Signed-off-by: Shmuel Kallner <kallner@il.ibm.com>

---------

Signed-off-by: Shmuel Kallner <kallner@il.ibm.com>

Author: shmuelk

apix/config/v1alpha1/defaults.go

@@ -21,9 +21,27 @@ package v1alpha1
 //
 // This naming convension is required by the defalter-gen code.
 func SetDefaults_EndpointPickerConfig(cfg *EndpointPickerConfig) {
+	// If no name was given for the plugin, use it's type as the name
 	for idx, pluginConfig := range cfg.Plugins {
 		if pluginConfig.Name == "" {
 			cfg.Plugins[idx].Name = pluginConfig.Type
 		}
 	}
+
+	// If No SchedulerProfiles were specified in the confguration,
+	// create one named default with references to all of the
+	// plugins mentioned in the Plugins section of the configuration.
+	if len(cfg.SchedulingProfiles) == 0 {
+		cfg.SchedulingProfiles = make([]SchedulingProfile, 1)
+
+		thePlugins := []SchedulingPlugin{}
+		for _, pluginConfig := range cfg.Plugins {
+			thePlugins = append(thePlugins, SchedulingPlugin{PluginRef: pluginConfig.Name})
+		}
+
+		cfg.SchedulingProfiles[0] = SchedulingProfile{
+			Name:    "default",
+			Plugins: thePlugins,
+		}
+	}
 }

pkg/epp/common/config/defaults.go

@@ -25,4 +25,8 @@ const (
 	// DefaultQueueThresholdCritical is the default backend waiting queue size
 	// threshold.
 	DefaultQueueThresholdCritical = 5
+
+	// DefaultScorerWeight is the weight used for scorers referenced in the
+	// configuration without explicit weights.
+	DefaultScorerWeight = 1
 )

pkg/epp/common/config/loader/configloader.go

@@ -26,9 +26,12 @@ import (
 	"k8s.io/apimachinery/pkg/util/sets"
 
 	configapi "sigs.k8s.io/gateway-api-inference-extension/apix/config/v1alpha1"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/common/config"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/plugins"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/scheduling"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/scheduling/framework"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/scheduling/framework/plugins/picker"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/scheduling/framework/plugins/profile"
 )
 
 var scheme = runtime.NewScheme()
@@ -64,18 +67,31 @@ func LoadSchedulerConfig(configProfiles []configapi.SchedulingProfile, handle pl
 	profiles := map[string]*framework.SchedulerProfile{}
 	for _, namedProfile := range configProfiles {
 		profile := framework.NewSchedulerProfile()
+		pickerAdded := false
 		for _, plugin := range namedProfile.Plugins {
 			referencedPlugin := handle.Plugin(plugin.PluginRef)
 			if scorer, ok := referencedPlugin.(framework.Scorer); ok {
-				if plugin.Weight == nil {
-					return nil, fmt.Errorf("scorer '%s' is missing a weight", plugin.PluginRef)
+				// Set default weight if one wasn't set in the configuration
+				weight := config.DefaultScorerWeight
+				if plugin.Weight != nil {
+					weight = *plugin.Weight
 				}
-				referencedPlugin = framework.NewWeightedScorer(scorer, *plugin.Weight)
+				referencedPlugin = framework.NewWeightedScorer(scorer, weight)
+			}
+			if _, ok := referencedPlugin.(framework.Picker); ok {
+				pickerAdded = true
 			}
 			if err := profile.AddPlugins(referencedPlugin); err != nil {
 				return nil, fmt.Errorf("failed to load scheduler config - %w", err)
 			}
 		}
+		if !pickerAdded {
+			// There isn't a picker in this profile, add one
+			thePicker := picker.NewMaxScorePicker(picker.DefaultMaxNumOfEndpoints)
+			if err := profile.AddPlugins(thePicker); err != nil {
+				return nil, fmt.Errorf("failed to load scheduler config - %w", err)
+			}
+		}
 		profiles[namedProfile.Name] = profile
 	}
 
@@ -89,7 +105,10 @@ func LoadSchedulerConfig(configProfiles []configapi.SchedulingProfile, handle pl
 		}
 	}
 	if profileHandler == nil {
-		return nil, errors.New("no profile handler was specified")
+		if len(profiles) != 1 {
+			return nil, errors.New("no profile handler was specified")
+		}
+		profileHandler = profile.NewSingleProfileHandler()
 	}
 
 	return scheduling.NewSchedulerConfig(profileHandler, profiles), nil
@@ -125,10 +144,6 @@ func instantiatePlugins(configuredPlugins []configapi.PluginSpec, handle plugins
 }
 
 func validateSchedulingProfiles(config *configapi.EndpointPickerConfig) error {
-	if len(config.SchedulingProfiles) == 0 {
-		return errors.New("there must be at least one scheduling profile in the configuration")
-	}
-
 	profileNames := sets.New[string]()
 	for _, profile := range config.SchedulingProfiles {
 		if profile.Name == "" {