feat: add logic for prometheus scaler X-Scope-OrgID header (#2763)

Signed-off-by: Xoán Mallón <xoanmallon@gmail.com>

CHANGELOG.md

@@ -43,6 +43,7 @@
 - **Datadog Scaler:** Several improvements, including a new optional parameter `metricUnavailableValue` to fill data when no Datadog metric was returned ([#2657](https://github.com/kedacore/keda/issues/2657))
 - **GCP Pubsub Scaler** Adding e2e test for GCP PubSub scaler ([#1528](https://github.com/kedacore/keda/issues/1528))
 - **Kafka Scaler** Make "disable" a valid value for tls auth parameter ([#2608](https://github.com/kedacore/keda/issues/2608))
+- **Prometheus Scaler:** Support for `X-Scope-OrgID` header in Prometheus scaler ([#2667](https://github.com/kedacore/keda/issues/2667))
 - **RabbitMQ Scaler:** Include `vhost` for RabbitMQ when retrieving queue info with `useRegex` ([#2498](https://github.com/kedacore/keda/issues/2498))
 
 ### Breaking Changes

pkg/scalers/prometheus_scaler.go

@@ -22,11 +22,13 @@ import (
 )
 
 const (
-	promServerAddress = "serverAddress"
-	promMetricName    = "metricName"
-	promQuery         = "query"
-	promThreshold     = "threshold"
-	promNamespace     = "namespace"
+	promServerAddress    = "serverAddress"
+	promMetricName       = "metricName"
+	promQuery            = "query"
+	promThreshold        = "threshold"
+	promNamespace        = "namespace"
+	promCortexScopeOrgID = "cortexOrgID"
+	promCortexHeaderKey  = "X-Scope-OrgID"
 )
 
 type prometheusScaler struct {
@@ -42,6 +44,7 @@ type prometheusMetadata struct {
 	prometheusAuth *authentication.AuthMeta
 	namespace      string
 	scalerIndex    int
+	cortexOrgID    string
 }
 
 type promQueryResult struct {
@@ -118,6 +121,10 @@ func parsePrometheusMetadata(config *ScalerConfig) (meta *prometheusMetadata, er
 		meta.namespace = val
 	}
 
+	if val, ok := config.TriggerMetadata[promCortexScopeOrgID]; ok && val != "" {
+		meta.cortexOrgID = val
+	}
+
 	meta.scalerIndex = config.ScalerIndex
 
 	// parse auth configs from ScalerConfig
@@ -182,6 +189,10 @@ func (s *prometheusScaler) ExecutePromQuery(ctx context.Context) (float64, error
 		req.SetBasicAuth(s.metadata.prometheusAuth.Username, s.metadata.prometheusAuth.Password)
 	}
 
+	if s.metadata.cortexOrgID != "" {
+		req.Header.Add(promCortexHeaderKey, s.metadata.cortexOrgID)
+	}
+
 	r, err := s.httpClient.Do(req)
 	if err != nil {
 		return -1, err

pkg/scalers/prometheus_scaler_test.go

@@ -208,3 +208,34 @@ func TestPrometheusScalerExecutePromQuery(t *testing.T) {
 		})
 	}
 }
+
+func TestPrometheusScalerCortexHeader(t *testing.T) {
+	testData := prometheusQromQueryResultTestData{
+		name:           "no values",
+		bodyStr:        `{"data":{"result":[]}}`,
+		responseStatus: http.StatusOK,
+		expectedValue:  0,
+		isError:        false,
+	}
+	cortexOrgValue := "my-org"
+	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		reqHeader := request.Header.Get(promCortexHeaderKey)
+		assert.Equal(t, reqHeader, cortexOrgValue)
+		writer.WriteHeader(testData.responseStatus)
+		if _, err := writer.Write([]byte(testData.bodyStr)); err != nil {
+			t.Fatal(err)
+		}
+	}))
+
+	scaler := prometheusScaler{
+		metadata: &prometheusMetadata{
+			serverAddress: server.URL,
+			cortexOrgID:   cortexOrgValue,
+		},
+		httpClient: http.DefaultClient,
+	}
+
+	_, err := scaler.ExecutePromQuery(context.TODO())
+
+	assert.NoError(t, err)
+}