Merge pull request #42104 from piosz/kube-proxy-metrics

Automatic merge from submit-queue (batch tested with PRs 41116, 41804, 42104, 42111, 42120)

Export Prometheus metrics in kube-proxy

Some metrics are already collected inside of kube-proxy (see https://github.com/kubernetes/kubernetes/blob/master/cmd/kube-proxy/proxy.go#L28). This exposes `/metrics` endpoint on healtz port.

ref #40736 #9125

cc @brancz @fabxc

cmd/kube-proxy/app/BUILD

@@ -35,6 +35,7 @@ go_library(
         "//pkg/util/resourcecontainer:go_default_library",
         "//pkg/util/sysctl:go_default_library",
         "//vendor:github.com/golang/glog",
+        "//vendor:github.com/prometheus/client_golang/prometheus",
         "//vendor:github.com/spf13/cobra",
         "//vendor:github.com/spf13/pflag",
         "//vendor:k8s.io/apimachinery/pkg/apis/meta/v1",

cmd/kube-proxy/app/server.go

@@ -57,6 +57,7 @@ import (
 	utilsysctl "k8s.io/kubernetes/pkg/util/sysctl"
 
 	"github.com/golang/glog"
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/spf13/cobra"
 	"github.com/spf13/pflag"
 )
@@ -342,6 +343,7 @@ func (s *ProxyServer) Run() error {
 		http.HandleFunc("/proxyMode", func(w http.ResponseWriter, r *http.Request) {
 			fmt.Fprintf(w, "%s", s.ProxyMode)
 		})
+		http.Handle("/metrics", prometheus.Handler())
 		configz.InstallHandler(http.DefaultServeMux)
 		go wait.Until(func() {
 			err := http.ListenAndServe(s.Config.HealthzBindAddress+":"+strconv.Itoa(int(s.Config.HealthzPort)), nil)