Move /resetMetrics to DELETE /metrics

Reduces the surface area of the API server slightly and allows
downstream components to have deleteable metrics. After this change
genericapiserver will *not* have metrics unless the caller defines it
(allows different apiserver implementations to make that choice on their
own).

pkg/apiserver/apiserver.go

@@ -46,7 +46,6 @@ import (
 
 	"github.com/emicklei/go-restful"
 	"github.com/golang/glog"
-	"github.com/prometheus/client_golang/prometheus"
 )
 
 func init() {
@@ -171,7 +170,6 @@ func (g *APIGroupVersion) newInstaller() *APIInstaller {
 func InstallSupport(mux Mux, ws *restful.WebService, checks ...healthz.HealthzChecker) {
 	// TODO: convert healthz and metrics to restful and remove container arg
 	healthz.InstallHandler(mux, checks...)
-	mux.Handle("/metrics", prometheus.Handler())
 
 	// Set up a service to return the git code version.
 	ws.Path("/version")

pkg/master/master.go

@@ -175,10 +175,17 @@ func New(c *Config) (*Master, error) {
 	return m, nil
 }
 
-func resetMetrics(w http.ResponseWriter, req *http.Request) {
+var defaultMetricsHandler = prometheus.Handler().ServeHTTP
+
+// MetricsWithReset is a handler that resets metrics when DELETE is passed to the endpoint.
+func MetricsWithReset(w http.ResponseWriter, req *http.Request) {
+	if req.Method == "DELETE" {
 		apiservermetrics.Reset()
 		etcdmetrics.Reset()
 		io.WriteString(w, "metrics reset\n")
+		return
+	}
+	defaultMetricsHandler(w, req)
 }
 
 func (m *Master) InstallAPIs(c *Config) {
@@ -220,8 +227,11 @@ func (m *Master) InstallAPIs(c *Config) {
 
 	// TODO(nikhiljindal): Refactor generic parts of support services (like /versions) to genericapiserver.
 	apiserver.InstallSupport(m.MuxHelper, m.RootWebService, healthzChecks...)
+
 	if c.EnableProfiling {
-		m.MuxHelper.HandleFunc("/resetMetrics", resetMetrics)
+		m.MuxHelper.HandleFunc("/metrics", MetricsWithReset)
+	} else {
+		m.MuxHelper.HandleFunc("/metrics", defaultMetricsHandler)
 	}
 
 	// Install root web services

test/e2e/framework/metrics_util.go

@@ -315,7 +315,7 @@ func VerifyPodStartupLatency(latency PodStartupLatency) error {
 // Resets latency metrics in apiserver.
 func ResetMetrics(c *client.Client) error {
 	Logf("Resetting latency metrics in apiserver...")
-	body, err := c.Get().AbsPath("/resetMetrics").DoRaw()
+	body, err := c.Delete().AbsPath("/metrics").DoRaw()
 	if err != nil {
 		return err
 	}