Fix heapster client config to make it work when master moves

Previously the heapster client would always talk to the same IP, even
when the master moved somewhere. Now it reuses apiserver client and
abstracts service proxy. This makes is always work when the apiserver
client is correct.

Author: bryk

src/app/backend/heapsterclient.go

@@ -15,16 +15,40 @@
 package main
 
 import (
-	"bytes"
 	"log"
 
 	client "k8s.io/kubernetes/pkg/client/unversioned"
 )
 
 // Clients for making requests to a Heapster instance.
 type HeapsterClient interface {
-	// Creates a new GET http request to heapster.
-	Get() *client.Request
+	// Creates a new GET HTTP request to heapster, specified by the path param, to the V1 API
+	// endpoint. The path param is without the API prefix, e.g.,
+	// /model/namespaces/default/pod-list/foo/metrics/memory-usage
+
+	Get(path string) *client.Request
+}
+
+// In-cluster implementation of heapster client. Talks with heapster through service proxy.
+type InClusterHeapsterClient struct {
+	client *client.Client
+}
+
+func (c InClusterHeapsterClient) Get(path string) *client.Request {
+	return c.client.Get().Prefix("proxy").
+		Namespace("kube-system").
+		Resource("services").
+		Name("heapster").
+		Suffix("/api/v1" + path)
+}
+
+// Remote heapster client based implementation. Talks with heapster through raw RESTClient.
+type RemoteHeapsterClient struct {
+	client *client.RESTClient
+}
+
+func (c RemoteHeapsterClient) Get(path string) *client.Request {
+	return c.client.Get().Suffix(path)
 }
 
 // Creates new Heapster REST client. When heapsterHost param is empty string the function
@@ -33,21 +57,16 @@ type HeapsterClient interface {
 func CreateHeapsterRESTClient(heapsterHost string, apiclient *client.Client) (
 	HeapsterClient, error) {
 
-	cfg := client.Config{}
-
 	if heapsterHost == "" {
-		bufferProxyHost := bytes.NewBufferString("http://")
-		bufferProxyHost.WriteString(apiclient.RESTClient.Get().URL().Host)
-		cfg.Host = bufferProxyHost.String()
-		cfg.Prefix = "/api/v1/proxy/namespaces/kube-system/services/heapster/api"
+		log.Printf("Creating in-cluster Heapster client")
+		return InClusterHeapsterClient{client: apiclient}, nil
 	} else {
-		cfg.Host = heapsterHost
-	}
-	log.Printf("Creating Heapster REST client for %s%s", cfg.Host, cfg.Prefix)
-	clientFactory := new(ClientFactoryImpl)
-	heapsterClient, err := clientFactory.New(&cfg)
-	if err != nil {
-		return nil, err
+		cfg := &client.Config{Host: heapsterHost}
+		restClient, err := client.New(cfg)
+		if err != nil {
+			return nil, err
+		}
+		log.Printf("Creating remote Heapster client for %s", heapsterHost)
+		return RemoteHeapsterClient{client: restClient.RESTClient}, nil
 	}
-	return heapsterClient.RESTClient, nil
 }

src/app/backend/replicationcontrollerpodsmetrics.go

@@ -89,8 +89,7 @@ func createMetricPath(namespace string, podNames []string, metricName string) st
 
 // Retrieves raw metrics from Heapster.
 func getRawMetrics(heapsterClient HeapsterClient, metricPath string) ([]byte, error) {
-
-	resultRaw, err := heapsterClient.Get().Suffix(metricPath).DoRaw()
+	resultRaw, err := heapsterClient.Get(metricPath).DoRaw()
 
 	if err != nil {
 		return make([]byte, 0), err