move interfaces from backend.metrics to datalayer

Signed-off-by: Etai Lev Ran <elevran@gmail.com>

Author: elevran

pkg/epp/backend/metrics/logger.go

@@ -24,7 +24,7 @@ import (
 	"github.com/go-logr/logr"
 	"sigs.k8s.io/controller-runtime/pkg/log"
 
-	v1 "sigs.k8s.io/gateway-api-inference-extension/api/v1"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/datalayer"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/metrics"
 	logutil "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/util/logging"
 )
@@ -33,15 +33,9 @@ const (
 	debugPrintInterval = 5 * time.Second
 )
 
-type Datastore interface {
-	PoolGet() (*v1.InferencePool, error)
-	// PodMetrics operations
-	PodList(func(PodMetrics) bool) []PodMetrics
-}
-
 // StartMetricsLogger starts goroutines to 1) Print metrics debug logs if the DEBUG log level is
 // enabled; 2) flushes Prometheus metrics about the backend servers.
-func StartMetricsLogger(ctx context.Context, datastore Datastore, refreshPrometheusMetricsInterval, metricsStalenessThreshold time.Duration) {
+func StartMetricsLogger(ctx context.Context, datastore datalayer.PoolInfo, refreshPrometheusMetricsInterval, metricsStalenessThreshold time.Duration) {
 	logger := log.FromContext(ctx)
 	ticker := time.NewTicker(refreshPrometheusMetricsInterval)
 	go func() {
@@ -82,7 +76,7 @@ func StartMetricsLogger(ctx context.Context, datastore Datastore, refreshPrometh
 	}
 }
 
-func refreshPrometheusMetrics(logger logr.Logger, datastore Datastore, metricsStalenessThreshold time.Duration) {
+func refreshPrometheusMetrics(logger logr.Logger, datastore datalayer.PoolInfo, metricsStalenessThreshold time.Duration) {
 	pool, err := datastore.PoolGet()
 	if err != nil {
 		// No inference pool or not initialize.

pkg/epp/backend/metrics/pod_metrics.go

@@ -40,7 +40,7 @@ type podMetrics struct {
 	pod      atomic.Pointer[backend.Pod]
 	metrics  atomic.Pointer[MetricsState]
 	pmc      PodMetricsClient
-	ds       Datastore
+	ds       datalayer.PoolInfo
 	interval time.Duration
 
 	startOnce sync.Once // ensures the refresh loop goroutine is started only once

pkg/epp/backend/metrics/types.go

@@ -32,12 +32,6 @@ var (
 	AllPodPredicate = func(PodMetrics) bool { return true }
 )
 
-// EndpointFactory defines an interface for allocating and retiring endpoints.
-type EndpointFactory interface {
-	NewEndpoint(parent context.Context, in *corev1.Pod, ds Datastore) PodMetrics
-	ReleaseEndpoint(ep PodMetrics)
-}
-
 func NewPodMetricsFactory(pmc PodMetricsClient, refreshMetricsInterval, metricsStalenessThreshold time.Duration) *PodMetricsFactory {
 	return &PodMetricsFactory{
 		pmc:                       pmc,
@@ -52,7 +46,7 @@ type PodMetricsFactory struct {
 	metricsStalenessThreshold time.Duration
 }
 
-func (f *PodMetricsFactory) NewEndpoint(parentCtx context.Context, in *corev1.Pod, ds Datastore) PodMetrics {
+func (f *PodMetricsFactory) NewEndpoint(parentCtx context.Context, in *corev1.Pod, ds datalayer.PoolInfo) PodMetrics {
 	pod := toInternalPod(in)
 	pm := &podMetrics{
 		pmc:       f.pmc,

pkg/epp/datalayer/factory.go

@@ -0,0 +1,46 @@
+/*
+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 datalayer
+
+import (
+	"context"
+
+	corev1 "k8s.io/api/core/v1"
+
+	v1 "sigs.k8s.io/gateway-api-inference-extension/api/v1"
+)
+
+// PoolInfo represents the DataStore information needed for endpoints.
+// TODO:
+// Consider if to remove/simplify in follow-ups. This is mostly for backward
+// compatibility with backend.metrics' expectations and allowing a shared
+// implementation during the transition.
+//   - Endpoint metric scraping uses PoolGet to access the pool's Port and Name.
+//   - Global metrics logging uses PoolGet solely for error return and PodList to enumerate
+//     all endpoints for metrics summarization.
+type PoolInfo interface {
+	PoolGet() (*v1.InferencePool, error)
+	PodList(func(Endpoint) bool) []Endpoint
+}
+
+// EndpointFactory defines an interface for managing Endpoint lifecycle. Specifically,
+// providing methods to allocate and retire endpoints. This can potentially be used for
+// pooled memory or other management chores in the implementation.
+type EndpointFactory interface {
+	NewEndpoint(parent context.Context, inpod *corev1.Pod, poolinfo PoolInfo) Endpoint
+	ReleaseEndpoint(ep Endpoint)
+}

pkg/epp/datastore/datastore.go

@@ -32,6 +32,7 @@ import (
 	v1 "sigs.k8s.io/gateway-api-inference-extension/api/v1"
 	"sigs.k8s.io/gateway-api-inference-extension/apix/v1alpha2"
 	backendmetrics "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/backend/metrics"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/datalayer"
 	logutil "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/util/logging"
 	podutil "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/util/pod"
 )
@@ -66,7 +67,7 @@ type Datastore interface {
 	Clear()
 }
 
-func NewDatastore(parentCtx context.Context, epFactory backendmetrics.EndpointFactory) Datastore {
+func NewDatastore(parentCtx context.Context, epFactory datalayer.EndpointFactory) Datastore {
 	store := &datastore{
 		parentCtx:           parentCtx,
 		poolAndObjectivesMu: sync.RWMutex{},
@@ -87,7 +88,7 @@ type datastore struct {
 	objectives map[string]*v1alpha2.InferenceObjective
 	// key: types.NamespacedName, value: backendmetrics.PodMetrics
 	pods *sync.Map
-	epf  backendmetrics.EndpointFactory
+	epf  datalayer.EndpointFactory
 }
 
 func (ds *datastore) Clear() {