Adds metrics to tokenreview

Signed-off-by: JoshVanL <vleeuwenjoshua@gmail.com>

Author: JoshVanL

pkg/proxy/tokenreview/tokenreview.go

@@ -9,11 +9,14 @@ import (
 	"time"
 
 	authv1 "k8s.io/api/authentication/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/kubernetes"
 	clientauthv1 "k8s.io/client-go/kubernetes/typed/authentication/v1"
 	"k8s.io/client-go/rest"
 
+	"github.com/jetstack/kube-oidc-proxy/pkg/metrics"
+	proxycontext "github.com/jetstack/kube-oidc-proxy/pkg/proxy/context"
 	"github.com/jetstack/kube-oidc-proxy/pkg/util"
 )
 
@@ -23,43 +26,73 @@ var (
 
 type TokenReview struct {
 	reviewRequester clientauthv1.TokenReviewInterface
+	metrics         *metrics.Metrics
 	audiences       []string
 }
 
-func New(restConfig *rest.Config, audiences []string) (*TokenReview, error) {
+func New(restConfig *rest.Config, metrics *metrics.Metrics, audiences []string) (*TokenReview, error) {
 	kubeclient, err := kubernetes.NewForConfig(restConfig)
 	if err != nil {
 		return nil, err
 	}
 
 	return &TokenReview{
 		reviewRequester: kubeclient.AuthenticationV1().TokenReviews(),
+		metrics:         metrics,
 		audiences:       audiences,
 	}, nil
 }
 
 func (t *TokenReview) Review(req *http.Request) (bool, error) {
+	var (
+		code          int
+		user          string
+		authenticated bool
+		err           error
+	)
+
+	// Start clock on metrics
+	tokenReviewDuration := time.Now()
+	req, remoteAddr := proxycontext.RemoteAddr(req)
+
 	token, ok := util.ParseTokenFromRequest(req)
 	if !ok {
 		return false, errors.New("bearer token not found in request")
 	}
-
 	review := t.buildReview(token)
 
+	// Setup metrics observation on defer
+	defer func() {
+		if err != nil {
+			if status := apierrors.APIStatus(nil); errors.As(err, &status) {
+				code = int(status.Status().Code)
+			}
+		}
+
+		t.metrics.ObserveTokenReivewLookup(authenticated, code, remoteAddr, user, time.Since(tokenReviewDuration))
+	}()
+
 	ctx, cancel := context.WithTimeout(req.Context(), timeout)
 	defer cancel()
 
-	resp, err := t.reviewRequester.Create(ctx, review, metav1.CreateOptions{})
+	var resp *authv1.TokenReview
+	resp, err = t.reviewRequester.Create(ctx, review, metav1.CreateOptions{})
 	if err != nil {
 		return false, err
 	}
 
+	// Since no error to the API server for token review, we have 200 response
+	// code.
+	code = 200
+	user = resp.Status.User.Username
+	authenticated = resp.Status.Authenticated
+
 	if len(resp.Status.Error) > 0 {
 		return false, fmt.Errorf("error authenticating using token review: %s",
 			resp.Status.Error)
 	}
 
-	return resp.Status.Authenticated, nil
+	return authenticated, nil
 }
 
 func (t *TokenReview) buildReview(token string) *authv1.TokenReview {

pkg/proxy/tokenreview/tokenreview_test.go

@@ -9,6 +9,7 @@ import (
 
 	authv1 "k8s.io/api/authentication/v1"
 
+	"github.com/jetstack/kube-oidc-proxy/pkg/metrics"
 	"github.com/jetstack/kube-oidc-proxy/pkg/proxy/tokenreview/fake"
 )
 
@@ -74,6 +75,7 @@ func TestReview(t *testing.T) {
 func runTest(t *testing.T, test testT) {
 	tReviewer := &TokenReview{
 		audiences:       nil,
+		metrics:         metrics.New(),
 		reviewRequester: fake.New().WithCreate(test.reviewResp, test.errResp),
 	}