fix: build clean config for externalmetrics provider if address is provided

Signed-off-by: Sanskar Jaiswal <jaiswalsanskar078@gmail.com>

pkg/metrics/providers/externalmetrics.go

@@ -47,19 +47,7 @@ func NewExternalMetricsProvider(
 		)
 	}
 
-	// clone to avoid mutating the shared config
-	restConfig := rest.CopyConfig(config)
-
-	// apply overrides from MetricTemplateProvider
-	if provider.Address != "" {
-		restConfig.Host = provider.Address
-	}
-	restConfig.TLSClientConfig.Insecure = provider.InsecureSkipVerify
-	if tokenBytes, ok := credentials["token"]; ok {
-		restConfig.BearerToken = string(tokenBytes)
-	}
-
-	restConfig.Timeout = 5 * time.Second
+	restConfig := externalMetricsRestConfig(provider, credentials, config)
 
 	client, err := externalmetrics_client.NewForConfig(restConfig)
 	if err != nil {
@@ -71,6 +59,29 @@ func NewExternalMetricsProvider(
 	}, nil
 }
 
+func externalMetricsRestConfig(
+	provider flaggerv1.MetricTemplateProvider,
+	credentials map[string][]byte,
+	config *rest.Config,
+) *rest.Config {
+	var restConfig *rest.Config
+	if provider.Address == "" {
+		restConfig = rest.CopyConfig(config)
+	} else {
+		restConfig = &rest.Config{
+			Host: provider.Address,
+		}
+	}
+
+	restConfig.TLSClientConfig.Insecure = provider.InsecureSkipVerify
+	if tokenBytes, ok := credentials["token"]; ok {
+		restConfig.BearerToken = strings.TrimSpace(string(tokenBytes))
+	}
+	restConfig.Timeout = 5 * time.Second
+
+	return restConfig
+}
+
 // RunQuery retrieves the ExternalMetricValue from the External Metrics API
 // at the ExternalMetricsProvider's address, using the provided query string,
 // and returns the *first* result as a float64.

pkg/metrics/providers/externalmetrics_test.go

@@ -18,6 +18,10 @@ package providers
 
 import (
 	"errors"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -99,6 +103,67 @@ func TestExternalMetrics_NewProvider_NilConfig(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestExternalMetrics_CustomProviderAddressDoesNotSendInheritedAuth(t *testing.T) {
+	tokenFile := filepath.Join(t.TempDir(), "token")
+	require.NoError(t, os.WriteFile(tokenFile, []byte("operator-file-token"), 0o600))
+
+	tests := []struct {
+		name              string
+		credentials       map[string][]byte
+		wantAuthorization string
+	}{
+		{
+			name:              "without credentials",
+			credentials:       nil,
+			wantAuthorization: "",
+		},
+		{
+			name: "with provider token",
+			credentials: map[string][]byte{
+				"token": []byte("provider-token"),
+			},
+			wantAuthorization: "Bearer provider-token",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			authHeaders := make(chan string, 1)
+			ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				authHeaders <- r.Header.Get("Authorization")
+				w.Header().Set("Content-Type", "application/json")
+				_, err := w.Write([]byte(`{
+					"kind": "ExternalMetricValueList",
+					"apiVersion": "external.metrics.k8s.io/v1beta1",
+					"metadata": {},
+					"items": []
+				}`))
+				require.NoError(t, err)
+			}))
+			defer ts.Close()
+
+			emp, err := NewExternalMetricsProvider(
+				flaggerv1.MetricTemplateProvider{
+					Address: ts.URL,
+				},
+				tt.credentials,
+				&rest.Config{
+					Host:            "https://kubernetes.default.svc",
+					BearerToken:     "operator-token",
+					BearerTokenFile: tokenFile,
+				},
+			)
+			require.NoError(t, err)
+
+			online, err := emp.IsOnline()
+			require.NoError(t, err)
+			assert.True(t, online)
+			require.Len(t, authHeaders, 1)
+			assert.Equal(t, tt.wantAuthorization, <-authHeaders)
+		})
+	}
+}
+
 func TestExternalMetrics_ParseQuery(t *testing.T) {
 	tests := []struct {
 		name              string