feat: Light epp

Makefile

@@ -129,6 +129,15 @@ generate-proto: protoc-gen-go protoc-gen-go-grpc ## Generate Golang code from pr
 		--go-grpc_out=module=sigs.k8s.io/gateway-api-inference-extension:. \
 		pkg/epp/framework/plugins/requesthandling/parsers/vllmgrpc/api/proto/*.proto
 
+.PHONY: generate-proto-light
+generate-proto-light: protoc-gen-go protoc-gen-go-grpc ## Generate Golang code from light EPP protobuf files.
+	PATH="$(LOCALBIN):$$PATH" $(PROTOC) \
+		-I pkg/epp-light/proto \
+		-I . \
+		--go_out=module=sigs.k8s.io/gateway-api-inference-extension:. \
+		--go-grpc_out=module=sigs.k8s.io/gateway-api-inference-extension:. \
+		pkg/epp-light/proto/*.proto
+
 # Use same code-generator version as k8s.io/api
 CODEGEN_VERSION := $(shell go list -m -f '{{.Version}}' k8s.io/api)
 CODEGEN = $(shell pwd)/bin/code-generator

cmd/epp-light/main.go

@@ -0,0 +1,33 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// The epp-light binary is a minimal, reference Endpoint Picker (EPP) implementation.
+// To use a custom picker, call runner.NewRunner().WithPicker(myPicker).Run(...).
+package main
+
+import (
+	"os"
+
+	ctrl "sigs.k8s.io/controller-runtime"
+
+	"sigs.k8s.io/gateway-api-inference-extension/cmd/epp-light/runner"
+)
+
+func main() {
+	if err := runner.NewRunner().Run(ctrl.SetupSignalHandler()); err != nil {
+		os.Exit(1)
+	}
+}

cmd/epp-light/runner/runner.go

@@ -0,0 +1,118 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package runner
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/spf13/pflag"
+	"k8s.io/apimachinery/pkg/runtime"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/log/zap"
+
+	v1 "sigs.k8s.io/gateway-api-inference-extension/api/v1"
+	epplight "sigs.k8s.io/gateway-api-inference-extension/pkg/epp-light"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp-light/server"
+)
+
+var scheme = runtime.NewScheme()
+
+func init() {
+	utilruntime.Must(clientgoscheme.AddToScheme(scheme))
+	utilruntime.Must(v1.Install(scheme))
+}
+
+// Runner encapsulates the light EPP server lifecycle.
+// External projects can import this, swap in a custom EndpointPicker via
+// WithPicker(), and call Run().
+type Runner struct {
+	picker epplight.EndpointPicker
+}
+
+// NewRunner creates a Runner with the default RandomPicker.
+func NewRunner() *Runner {
+	return &Runner{
+		picker: epplight.NewRandomPicker(),
+	}
+}
+
+// WithPicker sets a custom EndpointPicker implementation.
+func (r *Runner) WithPicker(picker epplight.EndpointPicker) *Runner {
+	r.picker = picker
+	return r
+}
+
+// Run parses flags, creates the controller manager, wires everything together,
+// and blocks until the context is cancelled.
+func (r *Runner) Run(ctx context.Context) error {
+	opts := server.NewOptions()
+	opts.AddFlags(pflag.CommandLine)
+	pflag.Parse()
+
+	ctrl.SetLogger(zap.New())
+	logger := ctrl.Log.WithName("epp-light")
+
+	if err := opts.Validate(); err != nil {
+		return fmt.Errorf("invalid options: %w", err)
+	}
+
+	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
+		Scheme: scheme,
+	})
+	if err != nil {
+		return fmt.Errorf("unable to create controller manager: %w", err)
+	}
+
+	datastore := epplight.NewDatastore()
+
+	// Use remote gRPC picker if --picker-address is set, otherwise use in-process picker.
+	picker := r.picker
+	if opts.PickerAddress != "" {
+		logger.Info("Using remote gRPC picker", "address", opts.PickerAddress)
+		grpcPicker, err := epplight.NewGRPCPicker(opts.PickerAddress)
+		if err != nil {
+			return fmt.Errorf("failed to create gRPC picker: %w", err)
+		}
+		picker = grpcPicker
+	}
+
+	serverRunner := &server.ExtProcServerRunner{
+		GRPCPort:      opts.GRPCPort,
+		PoolNamespace: opts.PoolNamespace,
+		PoolName:      opts.PoolName,
+		Datastore:     datastore,
+		Picker:        picker,
+		SecureServing: opts.SecureServing,
+		CertPath:      opts.CertPath,
+	}
+
+	if err := serverRunner.SetupWithManager(mgr); err != nil {
+		return fmt.Errorf("failed to setup controllers: %w", err)
+	}
+
+	if err := mgr.Add(serverRunner.AsRunnable(logger)); err != nil {
+		return fmt.Errorf("failed to add ext-proc server runnable: %w", err)
+	}
+
+	logger.Info(fmt.Sprintf("Starting light EPP for pool %s/%s on port %d",
+		opts.PoolNamespace, opts.PoolName, opts.GRPCPort))
+
+	return mgr.Start(ctx)
+}