Refactor director to split into smaller functions

Author: rahulgurnani

pkg/epp/requestcontrol/director.go

@@ -26,6 +26,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/go-logr/logr"
 	"sigs.k8s.io/controller-runtime/pkg/log"
 
 	v1 "sigs.k8s.io/gateway-api-inference-extension/api/v1"
@@ -89,42 +90,59 @@ type Director struct {
 	defaultPriority int
 }
 
-// HandleRequest orchestrates the request lifecycle.
-// It always returns the requestContext even in the error case, as the request context is used in error handling.
-func (d *Director) HandleRequest(ctx context.Context, reqCtx *handlers.RequestContext) (*handlers.RequestContext, error) {
-	logger := log.FromContext(ctx)
+// getInferenceObjective creates inferenceObjective based on reqCtx.
+func (d *Director) getInferenceObjective(logger logr.Logger, reqCtx *handlers.RequestContext) *v1alpha2.InferenceObjective {
+	infObjective := d.datastore.ObjectiveGet(reqCtx.ObjectiveKey)
+	if infObjective == nil {
+		logger.V(logutil.VERBOSE).Info("No associated InferenceObjective found, using default", "objectiveKey", reqCtx.ObjectiveKey)
+		infObjective = &v1alpha2.InferenceObjective{
+			Spec: v1alpha2.InferenceObjectiveSpec{
+				Priority: &d.defaultPriority,
+			},
+		}
+	} else if infObjective.Spec.Priority == nil {
+		// Default to 0 if not specified.
+		infObjective.Spec.Priority = &d.defaultPriority
+	}
+	return infObjective
+}
 
-	// Parse Request, Resolve Target Models, and Determine Parameters
+// resolveTargetModel is a helper that resolves targetModel
+// and updates the reqCtx and ctx.
+func (d *Director) resolveTargetModel(reqCtx *handlers.RequestContext) error {
 	requestBodyMap := reqCtx.Request.Body
 	var ok bool
 	reqCtx.IncomingModelName, ok = requestBodyMap["model"].(string)
-
 	if !ok {
-		return reqCtx, errutil.Error{Code: errutil.BadRequest, Msg: "model not found in request body"}
+		return errutil.Error{Code: errutil.BadRequest, Msg: "model not found in request body"}
 	}
 	if reqCtx.TargetModelName == "" {
 		// Default to incoming model name
 		reqCtx.TargetModelName = reqCtx.IncomingModelName
 	}
 	reqCtx.Request.Body["model"] = reqCtx.TargetModelName
+	return nil
+}
+
+// HandleRequest orchestrates the request lifecycle.
+// It always returns the requestContext even in the error case, as the request context is used in error handling.
+func (d *Director) HandleRequest(ctx context.Context, reqCtx *handlers.RequestContext) (*handlers.RequestContext, error) {
+	logger := log.FromContext(ctx)
+
+	// Resolve target model and update req context.
+	err := d.resolveTargetModel(reqCtx)
+	if err != nil {
+		return reqCtx, err
+	}
 
+	// Parse request body.
 	requestBody, err := requtil.ExtractRequestBody(reqCtx.Request.Body)
 	if err != nil {
 		return reqCtx, errutil.Error{Code: errutil.BadRequest, Msg: fmt.Errorf("failed to extract request data: %w", err).Error()}
 	}
 
-	infObjective := d.datastore.ObjectiveGet(reqCtx.ObjectiveKey)
-	if infObjective == nil {
-		logger.V(logutil.VERBOSE).Info("No associated InferenceObjective found, using default", "objectiveKey", reqCtx.ObjectiveKey)
-		infObjective = &v1alpha2.InferenceObjective{
-			Spec: v1alpha2.InferenceObjectiveSpec{
-				Priority: &d.defaultPriority,
-			},
-		}
-	} else if infObjective.Spec.Priority == nil {
-		// Default to 0 if not specified.
-		infObjective.Spec.Priority = &d.defaultPriority
-	}
+	// Parse inference objective.
+	infObjective := d.getInferenceObjective(logger, reqCtx)
 
 	// Prepare LLMRequest (needed for both saturation detection and Scheduler)
 	reqCtx.SchedulingRequest = &schedulingtypes.LLMRequest{