feat(scaler/prometheus): support authentication for Google Managed Pr…

…ometheus (kedacore#4675)

.pre-commit-config.yaml

@@ -12,6 +12,7 @@ repos:
     hooks:
       - id: trailing-whitespace
       - id: detect-private-key
+        exclude: pkg/scalers/prometheus_scaler_test.go
       - id: end-of-file-fixer
       - id: check-merge-conflict
       - id: mixed-line-ending

CHANGELOG.md

@@ -62,6 +62,7 @@ To learn more about active deprecations, we recommend checking [GitHub Discussio
 - **Security:** Enable secret scanning in GitHub repo
 - **RabbitMQ Scaler**: Add support for `unsafeSsl` in trigger metadata ([#4448](https://github.com/kedacore/keda/issues/4448))
 - **Prometheus Metrics**: Add new metric with KEDA build info ([#4647](https://github.com/kedacore/keda/issues/4647))
+- **Prometheus Scaler**: Add support for Google Managed Prometheus ([#4675](https://github.com/kedacore/keda/pull/4675))
 
 ### Fixes
 

pkg/scalers/gcp_common.go

@@ -1,37 +1,90 @@
 package scalers
 
 import (
-	"fmt"
+	"context"
+	"errors"
+	"net/http"
+	"os"
+
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google"
 
 	kedav1alpha1 "github.com/kedacore/keda/v2/apis/keda/v1alpha1"
 )
 
+var (
+	gcpScopeMonitoringRead = "https://www.googleapis.com/auth/monitoring.read"
+
+	errGoogleApplicationCrendentialsNotFound = errors.New("google application credentials not found")
+)
+
 type gcpAuthorizationMetadata struct {
 	GoogleApplicationCredentials     string
 	GoogleApplicationCredentialsFile string
 	podIdentityProviderEnabled       bool
 }
 
-func getGcpAuthorization(config *ScalerConfig, resolvedEnv map[string]string) (*gcpAuthorizationMetadata, error) {
-	metadata := config.TriggerMetadata
-	authParams := config.AuthParams
-	meta := gcpAuthorizationMetadata{}
-
-	switch {
-	case config.PodIdentity.Provider == kedav1alpha1.PodIdentityProviderGCP:
-		// do nothing, rely on underneath metadata google
-		meta.podIdentityProviderEnabled = true
-	case authParams["GoogleApplicationCredentials"] != "":
-		meta.GoogleApplicationCredentials = authParams["GoogleApplicationCredentials"]
-	default:
-		switch {
-		case metadata["credentialsFromEnv"] != "":
-			meta.GoogleApplicationCredentials = resolvedEnv[metadata["credentialsFromEnv"]]
-		case metadata["credentialsFromEnvFile"] != "":
-			meta.GoogleApplicationCredentialsFile = resolvedEnv[metadata["credentialsFromEnvFile"]]
-		default:
-			return nil, fmt.Errorf("GoogleApplicationCredentials not found")
+func (a *gcpAuthorizationMetadata) tokenSource(ctx context.Context, scopes ...string) (oauth2.TokenSource, error) {
+	if a.podIdentityProviderEnabled {
+		return google.DefaultTokenSource(ctx, scopes...)
+	}
+
+	if a.GoogleApplicationCredentials != "" {
+		creds, err := google.CredentialsFromJSON(ctx, []byte(a.GoogleApplicationCredentials), scopes...)
+		if err != nil {
+			return nil, err
 		}
+
+		return creds.TokenSource, nil
+	}
+
+	if a.GoogleApplicationCredentialsFile != "" {
+		data, err := os.ReadFile(a.GoogleApplicationCredentialsFile)
+		if err != nil {
+			return nil, err
+		}
+
+		creds, err := google.CredentialsFromJSON(ctx, data, scopes...)
+		if err != nil {
+			return nil, err
+		}
+
+		return creds.TokenSource, nil
+	}
+
+	return nil, errGoogleApplicationCrendentialsNotFound
+}
+
+func getGCPAuthorization(config *ScalerConfig) (*gcpAuthorizationMetadata, error) {
+	if config.PodIdentity.Provider == kedav1alpha1.PodIdentityProviderGCP {
+		return &gcpAuthorizationMetadata{podIdentityProviderEnabled: true}, nil
+	}
+
+	if creds := config.AuthParams["GoogleApplicationCredentials"]; creds != "" {
+		return &gcpAuthorizationMetadata{GoogleApplicationCredentials: creds}, nil
+	}
+
+	if creds := config.TriggerMetadata["credentialsFromEnv"]; creds != "" {
+		return &gcpAuthorizationMetadata{GoogleApplicationCredentials: config.ResolvedEnv[creds]}, nil
+	}
+
+	if credsFile := config.TriggerMetadata["credentialsFromEnvFile"]; credsFile != "" {
+		return &gcpAuthorizationMetadata{GoogleApplicationCredentialsFile: config.ResolvedEnv[credsFile]}, nil
 	}
-	return &meta, nil
+
+	return nil, errGoogleApplicationCrendentialsNotFound
+}
+
+func getGCPOAuth2HTTPTransport(config *ScalerConfig, base http.RoundTripper, scopes ...string) (http.RoundTripper, error) {
+	a, err := getGCPAuthorization(config)
+	if err != nil {
+		return nil, err
+	}
+
+	ts, err := a.tokenSource(context.Background(), scopes...)
+	if err != nil {
+		return nil, err
+	}
+
+	return &oauth2.Transport{Source: ts, Base: base}, nil
 }

pkg/scalers/gcp_pubsub_scaler.go

@@ -114,7 +114,7 @@ func parsePubSubMetadata(config *ScalerConfig, logger logr.Logger) (*pubsubMetad
 		meta.activationValue = activationValue
 	}
 
-	auth, err := getGcpAuthorization(config, config.ResolvedEnv)
+	auth, err := getGCPAuthorization(config)
 	if err != nil {
 		return nil, err
 	}

pkg/scalers/gcp_stackdriver_scaler.go

@@ -109,7 +109,7 @@ func parseStackdriverMetadata(config *ScalerConfig, logger logr.Logger) (*stackd
 		meta.activationTargetValue = activationTargetValue
 	}
 
-	auth, err := getGcpAuthorization(config, config.ResolvedEnv)
+	auth, err := getGCPAuthorization(config)
 	if err != nil {
 		return nil, err
 	}

pkg/scalers/gcp_storage_scaler.go

@@ -145,7 +145,7 @@ func parseGcsMetadata(config *ScalerConfig, logger logr.Logger) (*gcsMetadata, e
 		meta.blobPrefix = val
 	}
 
-	auth, err := getGcpAuthorization(config, config.ResolvedEnv)
+	auth, err := getGCPAuthorization(config)
 	if err != nil {
 		return nil, err
 	}

pkg/scalers/prometheus_scaler.go

@@ -3,6 +3,7 @@ package scalers
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"math"
@@ -67,12 +68,12 @@ type prometheusMetadata struct {
 
 type promQueryResult struct {
 	Status string `json:"status"`
-	Data   struct {
+
+	Data struct {
 		ResultType string `json:"resultType"`
 		Result     []struct {
-			Metric struct {
-			} `json:"metric"`
-			Value []interface{} `json:"value"`
+			Metric struct{}      `json:"metric"`
+			Value  []interface{} `json:"value"`
 		} `json:"result"`
 	} `json:"data"`
 }
@@ -109,16 +110,25 @@ func NewPrometheusScaler(config *ScalerConfig) (Scaler, error) {
 	} else {
 		// could be the case of azure managed prometheus. Try and get the roundtripper.
 		// If its not the case of azure managed prometheus, we will get both transport and err as nil and proceed assuming no auth.
-		transport, err := azure.TryAndGetAzureManagedPrometheusHTTPRoundTripper(config.PodIdentity, config.TriggerMetadata)
-
+		azureTransport, err := azure.TryAndGetAzureManagedPrometheusHTTPRoundTripper(config.PodIdentity, config.TriggerMetadata)
 		if err != nil {
 			logger.V(1).Error(err, "error while init Azure Managed Prometheus client http transport")
 			return nil, err
 		}
 
 		// transport should not be nil if its a case of azure managed prometheus
-		if transport != nil {
-			httpClient.Transport = transport
+		if azureTransport != nil {
+			httpClient.Transport = azureTransport
+		}
+
+		gcpTransport, err := getGCPOAuth2HTTPTransport(config, httpClient.Transport, gcpScopeMonitoringRead)
+		if err != nil && !errors.Is(err, errGoogleApplicationCrendentialsNotFound) {
+			logger.V(1).Error(err, "failed to get GCP client HTTP transport (either using Google application credentials or workload identity)")
+			return nil, err
+		}
+
+		if err == nil && gcpTransport != nil {
+			httpClient.Transport = gcpTransport
 		}
 	}
 
@@ -292,7 +302,7 @@ func (s *prometheusScaler) ExecutePromQuery(ctx context.Context) (float64, error
 	if err != nil {
 		return -1, err
 	}
-	_ = r.Body.Close()
+	defer r.Body.Close()
 
 	if !(r.StatusCode >= 200 && r.StatusCode <= 299) {
 		err := fmt.Errorf("prometheus query api returned error. status: %d response: %s", r.StatusCode, string(b))

pkg/scalers/prometheus_scaler_test.go

@@ -2,13 +2,19 @@ package scalers
 
 import (
 	"context"
+	"encoding/json"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
 	"github.com/go-logr/logr"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/oauth2"
 
 	kedav1alpha1 "github.com/kedacore/keda/v2/apis/keda/v1alpha1"
 )
@@ -363,3 +369,129 @@ func TestPrometheusScalerCustomHeaders(t *testing.T) {
 
 	assert.NoError(t, err)
 }
+
+func TestPrometheusScaler_ExecutePromQuery_WithGCPNativeAuthentication(t *testing.T) {
+	fakeGoogleOAuthServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, `{"token_type": "Bearer", "access_token": "fake_access_token"}`)
+	}))
+	defer fakeGoogleOAuthServer.Close()
+
+	fakeGCPCredsJSON, err := json.Marshal(map[string]string{
+		"type": "service_account",
+		"private_key": `-----BEGIN RSA PRIVATE KEY-----
+MIIBOwIBAAJBAOfgBHLEOcXo2X+8SSzF1rEsTewRzZIOZAak4XRULY+dBd1bsGBM
++dOb9a65cJbDuL3zmTZnfAxjmh2ueNTZvOcCAwEAAQJBAMwwibpG8llF48KInCfB
+UH5U9YmdY9nqskrnh2JZfoWnpBbGxtqg0vbdmvEL2bcbeUnudF25mPpoONw1F6G6
+5IECIQD0ouUBttDMacs5XqQppYCb8eAmiMkJxwgtJfPb9iGm0wIhAPKlXzNgIsMP
+v3sqXcOO3tNjEohptOpEyLWyCt3Htm0dAiB9w/CvfOjC7fCIQdtrfaYshaCSrueL
+m0Lc0xIXFuYd+QIgZ9DpkomnVd3/BytxQqJ2I+tXmpXfmfwkA9lRXOJ94uECIQC8
+IisErx3ap2o99Zn+Yotv/TGZkS+lfMLdbcOBr8a57Q==
+-----END RSA PRIVATE KEY-----`,
+		"token_uri": fakeGoogleOAuthServer.URL,
+	})
+	require.NoError(t, err)
+
+	fakeGCPCredsPath := filepath.Join(t.TempDir(), "fake_application_default_credentials.json")
+
+	f, err := os.Create(fakeGCPCredsPath)
+	require.NoError(t, err)
+	_, err = f.Write(fakeGCPCredsJSON)
+	require.NoError(t, err)
+	require.NoError(t, f.Close())
+
+	newFakeServer := func(t *testing.T) *httptest.Server {
+		t.Helper()
+		return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			assert.Equal(t, "/v1/projects/my-fake-project/location/global/prometheus/api/v1/query", r.URL.Path)
+			assert.True(t, r.URL.Query().Has("time"))
+			assert.Equal(t, "sum(rate(http_requests_total{instance=\"my-instance\"}[5m]))", r.URL.Query().Get("query"))
+
+			if !assert.Equal(t, "Bearer fake_access_token", r.Header.Get("Authorization")) {
+				w.WriteHeader(http.StatusUnauthorized)
+			}
+
+			assert.NoError(t, json.NewEncoder(w).Encode(map[string]any{
+				"status": "success",
+				"data": map[string]any{
+					"resultType": "vector",
+					"result": []map[string]any{
+						{"metric": map[string]string{}, "value": []any{1686063687, "777"}},
+					},
+				},
+			}))
+		}))
+	}
+
+	tests := map[string]struct {
+		config func(*testing.T, *ScalerConfig) *ScalerConfig
+	}{
+		"using GCP workload identity": {
+			config: func(t *testing.T, config *ScalerConfig) *ScalerConfig {
+				t.Setenv("GOOGLE_APPLICATION_CREDENTIALS", fakeGCPCredsPath)
+				config.PodIdentity = kedav1alpha1.AuthPodIdentity{
+					Provider: kedav1alpha1.PodIdentityProviderGCP,
+				}
+				return config
+			},
+		},
+
+		"with Google app credentials on auth params": {
+			config: func(t *testing.T, config *ScalerConfig) *ScalerConfig {
+				config.AuthParams = map[string]string{
+					"GoogleApplicationCredentials": string(fakeGCPCredsJSON),
+				}
+				return config
+			},
+		},
+
+		"with Google app credentials on envs": {
+			config: func(t *testing.T, config *ScalerConfig) *ScalerConfig {
+				config.TriggerMetadata["credentialsFromEnv"] = "GCP_APP_CREDENTIALS"
+				config.ResolvedEnv = map[string]string{
+					"GCP_APP_CREDENTIALS": string(fakeGCPCredsJSON),
+				}
+				return config
+			},
+		},
+
+		"with Google app credentials file on auth params": {
+			config: func(t *testing.T, config *ScalerConfig) *ScalerConfig {
+				config.TriggerMetadata["credentialsFromEnvFile"] = "GCP_APP_CREDENTIALS"
+				config.ResolvedEnv = map[string]string{
+					"GCP_APP_CREDENTIALS": fakeGCPCredsPath,
+				}
+				return config
+			},
+		},
+	}
+
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			server := newFakeServer(t)
+			defer server.Close()
+
+			baseConfig := &ScalerConfig{
+				TriggerMetadata: map[string]string{
+					"serverAddress": server.URL + "/v1/projects/my-fake-project/location/global/prometheus",
+					"query":         "sum(rate(http_requests_total{instance=\"my-instance\"}[5m]))",
+					"threshold":     "100",
+				},
+			}
+
+			require.NotNil(t, tt.config, "you must provide a config generator func")
+			config := tt.config(t, baseConfig)
+
+			scaler, err := NewPrometheusScaler(config)
+			require.NoError(t, err)
+
+			s, ok := scaler.(*prometheusScaler)
+			require.True(t, ok, "Scaler must be a Prometheus Scaler")
+			_, ok = s.httpClient.Transport.(*oauth2.Transport)
+			require.True(t, ok, "HTTP transport must be Google OAuth2")
+
+			got, err := s.ExecutePromQuery(context.TODO())
+			require.NoError(t, err)
+			assert.Equal(t, float64(777), got)
+		})
+	}
+}