Merge pull request #13202 from jimmidyson/prometheus-with-no-cadvisor-port

Ensure container metrics are registered with prometheus even without cadvisor http server

pkg/kubelet/cadvisor/cadvisor_linux.go

@@ -64,13 +64,10 @@ func New(port uint) (Interface, error) {
 		Manager: m,
 	}
 
-	// Export the HTTP endpoint if a port was specified.
-	if port > 0 {
 	err = cadvisorClient.exportHTTP(port)
 	if err != nil {
 		return nil, err
 	}
-	}
 	return cadvisorClient, nil
 }
 
@@ -79,12 +76,16 @@ func (cc *cadvisorClient) Start() error {
 }
 
 func (cc *cadvisorClient) exportHTTP(port uint) error {
+	// Register the handlers regardless as this registers the prometheus
+	// collector properly.
 	mux := http.NewServeMux()
 	err := cadvisorHttp.RegisterHandlers(mux, cc, "", "", "", "", "/metrics")
 	if err != nil {
 		return err
 	}
 
+	// Only start the http server if port > 0
+	if port > 0 {
 		serv := &http.Server{
 			Addr:    fmt.Sprintf(":%d", port),
 			Handler: mux,
@@ -103,6 +104,7 @@ func (cc *cadvisorClient) exportHTTP(port uint) error {
 				err = serv.ListenAndServe()
 			}
 		}()
+	}
 
 	return nil
 }