proxy: add some useful metrics

This adds some useful metrics around pending changes and last successful
sync time.

The goal is for administrators to be able to alert on proxies that, for
whatever reason, are quite stale.

Signed-off-by: Casey Callendrello <cdc@redhat.com>

pkg/proxy/service.go

@@ -30,6 +30,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/client-go/tools/record"
 	apiservice "k8s.io/kubernetes/pkg/api/v1/service"
+	"k8s.io/kubernetes/pkg/proxy/metrics"
 	utilproxy "k8s.io/kubernetes/pkg/proxy/util"
 	utilnet "k8s.io/utils/net"
 )
@@ -198,6 +199,7 @@ func (sct *ServiceChangeTracker) Update(previous, current *v1.Service) bool {
 	if svc == nil {
 		return false
 	}
+	metrics.ServiceChangesTotal.Inc()
 	namespacedName := types.NamespacedName{Namespace: svc.Namespace, Name: svc.Name}
 
 	sct.lock.Lock()
@@ -214,6 +216,7 @@ func (sct *ServiceChangeTracker) Update(previous, current *v1.Service) bool {
 	if reflect.DeepEqual(change.previous, change.current) {
 		delete(sct.items, namespacedName)
 	}
+	metrics.ServiceChangesPending.Set(float64(len(sct.items)))
 	return len(sct.items) > 0
 }
 
@@ -296,6 +299,7 @@ func (sm *ServiceMap) apply(changes *ServiceChangeTracker, UDPStaleClusterIP set
 	}
 	// clear changes after applying them to ServiceMap.
 	changes.items = make(map[types.NamespacedName]*serviceChange)
+	metrics.ServiceChangesPending.Set(0)
 	return
 }