Create NEG metrics collector interface

Create NEG metris collector that would periodically emits NEG syncer
metrics.

pkg/neg/metrics/metrics.go

@@ -139,6 +139,8 @@ func RegisterMetrics() {
 		prometheus.MustRegister(SyncerSyncLatency)
 		prometheus.MustRegister(LastSyncTimestamp)
 		prometheus.MustRegister(InitializationLatency)
+
+		RegisterSyncerMetrics()
 	})
 }
 

pkg/neg/metrics/neg_metrics_collector.go

@@ -0,0 +1,87 @@
+/*
+Copyright 2023 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 metrics
+
+import (
+	"sync"
+	"time"
+
+	"k8s.io/apimachinery/pkg/util/wait"
+	negtypes "k8s.io/ingress-gce/pkg/neg/types"
+	"k8s.io/klog/v2"
+)
+
+type SyncerMetricsCollector interface {
+	UpdateSyncer(key negtypes.NegSyncerKey, result *negtypes.NegSyncResult)
+	SetSyncerEPMetrics(key negtypes.NegSyncerKey, epState *negtypes.SyncerEPStat)
+}
+
+type SyncerMetrics struct {
+	// syncerStatusmap tracks the status of each syncer
+	syncerStatusMap map[negtypes.NegSyncerKey]string
+	// syncerEndpointStateMap is a map between syncer and SyncerEPState
+	syncerEndpointStateMap map[negtypes.NegSyncerKey]negtypes.StateCountMap
+	// syncerEPSStateMap is a map between syncer and SyncerEPSState
+	syncerEPSStateMap map[negtypes.NegSyncerKey]negtypes.StateCountMap
+	// mu avoid race conditions and ensure correctness of metrics
+	mu sync.Mutex
+	// duration between metrics exports
+	metricsInterval time.Duration
+	// logger logs message related to NegMetricsCollector
+	logger klog.Logger
+}
+
+// NewNEGMetricsCollector initializes SyncerMetrics and starts a go routine to compute and export metrics periodically.
+func NewNegMetricsCollector(exportInterval time.Duration, logger klog.Logger) *SyncerMetrics {
+	return &SyncerMetrics{
+		syncerStatusMap:        make(map[negtypes.NegSyncerKey]string),
+		syncerEndpointStateMap: make(map[negtypes.NegSyncerKey]negtypes.StateCountMap),
+		syncerEPSStateMap:      make(map[negtypes.NegSyncerKey]negtypes.StateCountMap),
+		metricsInterval:        exportInterval,
+		logger:                 logger.WithName("NegMetricsCollector"),
+	}
+}
+
+// FakeSyncerMetrics creates new NegMetricsCollector with fixed 5 second metricsInterval, to be used in tests
+func FakeSyncerMetrics() *SyncerMetrics {
+	return NewNegMetricsCollector(5*time.Second, klog.TODO())
+}
+
+func RegisterSyncerMetrics() {
+}
+
+func (sm *SyncerMetrics) Run(stopCh <-chan struct{}) {
+	sm.logger.V(3).Info("Syncer Metrics initialized.", "exportInterval", sm.metricsInterval)
+	// Compute and export metrics periodically.
+	go func() {
+		time.Sleep(sm.metricsInterval)
+		wait.Until(sm.export, sm.metricsInterval, stopCh)
+	}()
+	<-stopCh
+}
+
+// export exports syncer metrics.
+func (sm *SyncerMetrics) export() {
+}
+
+// UpdateSyncer updates the count of sync results based on the result/error of sync
+func (sm *SyncerMetrics) UpdateSyncer(key negtypes.NegSyncerKey, syncResult *negtypes.NegSyncResult) {
+}
+
+// SetSyncerEPMetrics update the endpoint count based on the endpointStat
+func (sm *SyncerMetrics) SetSyncerEPMetrics(key negtypes.NegSyncerKey, endpointStat *negtypes.SyncerEPStat) {
+}