Fix 'kubectl proxy' to allow the /metrics page to be proxied, without breaking the previous proxy behavior

pkg/kubectl/cmd/proxy.go

@@ -38,9 +38,24 @@ $ kubectl proxy --api-prefix=/k8s-api`
 
 func NewCmdProxy(f *cmdutil.Factory, out io.Writer) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:     "proxy [--port=PORT] [--www=static-dir] [--www-prefix=prefix] [--api-prefix=prefix]",
-		Short:   "Run a proxy to the Kubernetes API server",
-		Long:    `Run a proxy to the Kubernetes API server. `,
+		Use:   "proxy [--port=PORT] [--www=static-dir] [--www-prefix=prefix] [--api-prefix=prefix]",
+		Short: "Run a proxy to the Kubernetes API server",
+		Long: `To proxy all of the kubernetes api and nothing else, use:
+
+kubectl proxy --api-prefix=/
+
+To proxy only part of the kubernetes api and also some static files:
+
+kubectl proxy --www=/my/files --www-prefix=/static/ --api-prefix=/api/
+
+The above lets you 'curl localhost:8001/api/v1/pods'.
+
+To proxy the entire kubernetes api at a different root, use:
+
+kubectl proxy --api-prefix=/custom/
+
+The above lets you 'curl localhost:8001/custom/api/v1/pods'
+`,
 		Example: proxy_example,
 		Run: func(cmd *cobra.Command, args []string) {
 			err := RunProxy(f, out, cmd)

pkg/kubectl/proxy_server.go

@@ -28,17 +28,18 @@ import (
 
 // ProxyServer is a http.Handler which proxies Kubernetes APIs to remote API server.
 type ProxyServer struct {
+	mux *http.ServeMux
 	httputil.ReverseProxy
 }
 
 // NewProxyServer creates and installs a new ProxyServer.
 // It automatically registers the created ProxyServer to http.DefaultServeMux.
 func NewProxyServer(filebase string, apiProxyPrefix string, staticPrefix string, cfg *client.Config) (*ProxyServer, error) {
-	prefix := cfg.Prefix
-	if prefix == "" {
-		prefix = "/api"
+	host := cfg.Host
+	if !strings.HasSuffix(host, "/") {
+		host = host + "/"
 	}
-	target, err := url.Parse(singleJoiningSlash(cfg.Host, prefix))
+	target, err := url.Parse(host)
 	if err != nil {
 		return nil, err
 	}
@@ -46,15 +47,22 @@ func NewProxyServer(filebase string, apiProxyPrefix string, staticPrefix string,
 	if proxy.Transport, err = client.TransportFor(cfg); err != nil {
 		return nil, err
 	}
-	http.Handle(apiProxyPrefix, http.StripPrefix(apiProxyPrefix, proxy))
-	http.Handle(staticPrefix, newFileHandler(staticPrefix, filebase))
+	if strings.HasPrefix(apiProxyPrefix, "/api") {
+		proxy.mux.Handle(apiProxyPrefix, proxy)
+	} else {
+		proxy.mux.Handle(apiProxyPrefix, http.StripPrefix(apiProxyPrefix, proxy))
+	}
+	proxy.mux.Handle(staticPrefix, newFileHandler(staticPrefix, filebase))
 	return proxy, nil
 }
 
 // Serve starts the server (http.DefaultServeMux) on given port, loops forever.
 func (s *ProxyServer) Serve(port int) error {
-	addr := fmt.Sprintf(":%d", port)
-	return http.ListenAndServe(addr, nil)
+	server := http.Server{
+		Addr:    fmt.Sprintf(":%d", port),
+		Handler: s.mux,
+	}
+	return server.ListenAndServe()
 }
 
 func newProxyServer(target *url.URL) *ProxyServer {
@@ -63,7 +71,10 @@ func newProxyServer(target *url.URL) *ProxyServer {
 		req.URL.Host = target.Host
 		req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
 	}
-	return &ProxyServer{ReverseProxy: httputil.ReverseProxy{Director: director}}
+	return &ProxyServer{
+		ReverseProxy: httputil.ReverseProxy{Director: director},
+		mux:          http.NewServeMux(),
+	}
 }
 
 func newFileHandler(prefix, base string) http.Handler {

pkg/kubectl/proxy_server_test.go

@@ -25,6 +25,8 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
 )
 
 func TestFileServing(t *testing.T) {
@@ -104,3 +106,55 @@ func TestAPIRequests(t *testing.T) {
 		}
 	}
 }
+
+func TestPathHandling(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprint(w, r.URL.Path)
+	}))
+	defer ts.Close()
+
+	table := []struct {
+		prefix     string
+		reqPath    string
+		expectPath string
+	}{
+		{"/api/", "/metrics", "404 page not found\n"},
+		{"/api/", "/api/metrics", "/api/metrics"},
+		{"/api/", "/api/v1/pods/", "/api/v1/pods/"},
+		{"/", "/metrics", "/metrics"},
+		{"/", "/api/v1/pods/", "/api/v1/pods/"},
+		{"/custom/", "/metrics", "404 page not found\n"},
+		{"/custom/", "/api/metrics", "404 page not found\n"},
+		{"/custom/", "/api/v1/pods/", "404 page not found\n"},
+		{"/custom/", "/custom/api/metrics", "/api/metrics"},
+		{"/custom/", "/custom/api/v1/pods/", "/api/v1/pods/"},
+	}
+
+	cc := &client.Config{
+		Host: ts.URL,
+	}
+
+	for _, item := range table {
+		func() {
+			p, err := NewProxyServer("", item.prefix, "/not/used/for/this/test", cc)
+			if err != nil {
+				t.Fatalf("%#v: %v", item, err)
+			}
+			pts := httptest.NewServer(p.mux)
+			defer pts.Close()
+
+			r, err := http.Get(pts.URL + item.reqPath)
+			if err != nil {
+				t.Fatalf("%#v: %v", item, err)
+			}
+			body, err := ioutil.ReadAll(r.Body)
+			r.Body.Close()
+			if err != nil {
+				t.Fatalf("%#v: %v", item, err)
+			}
+			if e, a := item.expectPath, string(body); e != a {
+				t.Errorf("%#v: Wanted %q, got %q", item, e, a)
+			}
+		}()
+	}
+}