Add GCP identity authentication when using Pubsub Scaler

CHANGELOG.md

@@ -27,6 +27,7 @@
 - Add Graphite Scaler ([#1628](https://github.com/kedacore/keda/pull/2092))
 - Add Cassandra Scaler ([#2211](https://github.com/kedacore/keda/pull/2211))
 - Improve Redis Scaler, upgrade library, add username and Sentinel support ([#2181](https://github.com/kedacore/keda/pull/2181))
+- Add GCP identity authentication when using Pubsub Scaler ([#2225](https://github.com/kedacore/keda/pull/2225))
 
 ### Improvements
 

go.mod

@@ -3,6 +3,7 @@ module github.com/kedacore/keda/v2
 go 1.16
 
 require (
+	cloud.google.com/go v0.97.0 // indirect
 	cloud.google.com/go/monitoring v1.0.0
 	github.com/Azure/azure-amqp-common-go/v3 v3.2.1
 	github.com/Azure/azure-event-hubs-go/v3 v3.3.16

go.sum

@@ -27,6 +27,8 @@ cloud.google.com/go v0.93.3/go.mod h1:8utlLll2EF5XMAV15woO4lSbWQlk8rer9aLOfLh7+Y
 cloud.google.com/go v0.94.1/go.mod h1:qAlAugsXlC+JWO+Bke5vCtc9ONxjQT3drlTTnAplMW4=
 cloud.google.com/go v0.96.0 h1:r9XIwQ9FrJspMjHulRm1kl1uanw5gSolzSK+dukeH0E=
 cloud.google.com/go v0.96.0/go.mod h1:GF7l59pYBVlXQIBLx3a761cZ41F9bBH3JUlihCt2Udc=
+cloud.google.com/go v0.97.0 h1:3DXvAyifywvq64LfkKaMOmkWPS1CikIQdMe2lY9vxU8=
+cloud.google.com/go v0.97.0/go.mod h1:GF7l59pYBVlXQIBLx3a761cZ41F9bBH3JUlihCt2Udc=
 cloud.google.com/go/bigquery v1.0.1/go.mod h1:i/xbL2UlR5RvWAURpBYZTtm/cXjCha9lbfbpx4poX+o=
 cloud.google.com/go/bigquery v1.3.0/go.mod h1:PjpwJnslEMmckchkHFfq+HTD2DmtT67aNFKH1/VBDHE=
 cloud.google.com/go/bigquery v1.4.0/go.mod h1:S8dzgnTigyfTmLBfrtrhyYhwRxG72rYxvftPBK2Dvzc=

pkg/scalers/gcp_pub_sub_scaler.go

@@ -12,6 +12,7 @@ import (
 	"k8s.io/metrics/pkg/apis/external_metrics"
 	logf "sigs.k8s.io/controller-runtime/pkg/log"
 
+	kedav1alpha1 "github.com/kedacore/keda/v2/apis/keda/v1alpha1"
 	kedautil "github.com/kedacore/keda/v2/pkg/util"
 )
 
@@ -23,6 +24,7 @@ const (
 type gcpAuthorizationMetadata struct {
 	GoogleApplicationCredentials string
 	podIdentityOwner             bool
+	podIdentityProviderEnabled   bool
 }
 
 type pubsubScaler struct {
@@ -74,7 +76,7 @@ func parsePubSubMetadata(config *ScalerConfig) (*pubsubMetadata, error) {
 		return nil, fmt.Errorf("no subscription name given")
 	}
 
-	auth, err := getGcpAuthorization(config.AuthParams, config.TriggerMetadata, config.ResolvedEnv)
+	auth, err := getGcpAuthorization(config, config.ResolvedEnv)
 	if err != nil {
 		return nil, err
 	}
@@ -153,7 +155,13 @@ func (s *pubsubScaler) GetMetrics(ctx context.Context, metricName string, metric
 // Stackdriver api
 func (s *pubsubScaler) GetSubscriptionSize(ctx context.Context) (int64, error) {
 	if s.client == nil {
-		client, err := NewStackDriverClient(ctx, s.metadata.gcpAuthorization.GoogleApplicationCredentials)
+		var client *StackDriverClient
+		var err error
+		if s.metadata.gcpAuthorization.podIdentityProviderEnabled {
+			client, err = NewStackDriverClientPodIdentity(ctx)
+		} else {
+			client, err = NewStackDriverClient(ctx, s.metadata.gcpAuthorization.GoogleApplicationCredentials)
+		}
 		if err != nil {
 			return -1, err
 		}
@@ -165,15 +173,21 @@ func (s *pubsubScaler) GetSubscriptionSize(ctx context.Context) (int64, error) {
 	return s.client.GetMetrics(ctx, filter)
 }
 
-func getGcpAuthorization(authParams, metadata, resolvedEnv map[string]string) (*gcpAuthorizationMetadata, error) {
+func getGcpAuthorization(config *ScalerConfig, resolvedEnv map[string]string) (*gcpAuthorizationMetadata, error) {
+	metadata := config.TriggerMetadata
+	authParams := config.AuthParams
 	meta := gcpAuthorizationMetadata{}
 	if metadata["identityOwner"] == "operator" {
 		meta.podIdentityOwner = false
 	} else if metadata["identityOwner"] == "" || metadata["identityOwner"] == "pod" {
 		meta.podIdentityOwner = true
-		if authParams["GoogleApplicationCredentials"] != "" {
+		switch {
+		case config.PodIdentity == kedav1alpha1.PodIdentityProviderGCP:
+			// do nothing, rely on underneath metadata google
+			meta.podIdentityProviderEnabled = true
+		case authParams["GoogleApplicationCredentials"] != "":
 			meta.GoogleApplicationCredentials = authParams["GoogleApplicationCredentials"]
-		} else {
+		default:
 			if metadata["credentialsFromEnv"] != "" {
 				meta.GoogleApplicationCredentials = resolvedEnv[metadata["credentialsFromEnv"]]
 			} else {

pkg/scalers/stackdriver_client.go

@@ -4,8 +4,10 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"net/http"
 	"time"
 
+	"cloud.google.com/go/compute/metadata"
 	monitoring "cloud.google.com/go/monitoring/apiv3/v2"
 	timestamp "github.com/golang/protobuf/ptypes/timestamp"
 	"google.golang.org/api/iterator"
@@ -18,6 +20,7 @@ import (
 type StackDriverClient struct {
 	metricsClient *monitoring.MetricClient
 	credentials   GoogleApplicationCredentials
+	projectID     string
 }
 
 // NewStackDriverClient creates a new stackdriver client with the credentials that are passed
@@ -41,6 +44,23 @@ func NewStackDriverClient(ctx context.Context, credentials string) (*StackDriver
 	}, nil
 }
 
+// NewStackDriverClient creates a new stackdriver client with the credentials underlying
+func NewStackDriverClientPodIdentity(ctx context.Context) (*StackDriverClient, error) {
+	client, err := monitoring.NewMetricClient(ctx)
+	if err != nil {
+		return nil, err
+	}
+	c := metadata.NewClient(&http.Client{})
+	project, err := c.ProjectID()
+	if err != nil {
+		return nil, err
+	}
+	return &StackDriverClient{
+		metricsClient: client,
+		projectID:     project,
+	}, nil
+}
+
 // GetMetrics fetches metrics from stackdriver for a specific filter for the last minute
 func (s StackDriverClient) GetMetrics(ctx context.Context, filter string) (int64, error) {
 	// Set the start time to 1 minute ago
@@ -50,19 +70,34 @@ func (s StackDriverClient) GetMetrics(ctx context.Context, filter string) (int64
 	endTime := time.Now().UTC()
 
 	// Create a request with the filter and the GCP project ID
-	req := &monitoringpb.ListTimeSeriesRequest{
-		Name:   "projects/" + s.credentials.ProjectID,
-		Filter: filter,
-		Interval: &monitoringpb.TimeInterval{
-			StartTime: &timestamp.Timestamp{
-				Seconds: startTime.Unix(),
+	var req *monitoringpb.ListTimeSeriesRequest
+	if len(s.projectID) > 0 {
+		req = &monitoringpb.ListTimeSeriesRequest{
+			Name:   "projects/" + s.projectID,
+			Filter: filter,
+			Interval: &monitoringpb.TimeInterval{
+				StartTime: &timestamp.Timestamp{
+					Seconds: startTime.Unix(),
+				},
+				EndTime: &timestamp.Timestamp{
+					Seconds: endTime.Unix(),
+				},
 			},
-			EndTime: &timestamp.Timestamp{
-				Seconds: endTime.Unix(),
+		}
+	} else {
+		req = &monitoringpb.ListTimeSeriesRequest{
+			Name:   "projects/" + s.credentials.ProjectID,
+			Filter: filter,
+			Interval: &monitoringpb.TimeInterval{
+				StartTime: &timestamp.Timestamp{
+					Seconds: startTime.Unix(),
+				},
+				EndTime: &timestamp.Timestamp{
+					Seconds: endTime.Unix(),
+				},
 			},
-		},
+		}
 	}
-
 	// Get an iterator with the list of time series
 	it := s.metricsClient.ListTimeSeries(ctx, req)