fix: Consider maxSessions in Selenium Grid Scaler

CHANGELOG.md

@@ -43,6 +43,7 @@
 - **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))
 - **RabbitMQ Scaler:** Include `vhost` for RabbitMQ when retrieving queue info with `useRegex` ([#2498](https://github.com/kedacore/keda/issues/2498))
+- **Selenium Grid Scaler** Consider `maxSession` grid info when scaling. ([#2618](https://github.com/kedacore/keda/issues/2618))
 
 ### Breaking Changes
 

pkg/scalers/selenium_grid_scaler.go

@@ -40,9 +40,14 @@ type seleniumResponse struct {
 }
 
 type data struct {
+	Grid         grid         `json:"grid"`
 	SessionsInfo sessionsInfo `json:"sessionsInfo"`
 }
 
+type grid struct {
+	MaxSession int `json:"maxSession"`
+}
+
 type sessionsInfo struct {
 	SessionQueueRequests []string          `json:"sessionQueueRequests"`
 	Sessions             []seleniumSession `json:"sessions"`
@@ -164,7 +169,7 @@ func (s *seleniumGridScaler) IsActive(ctx context.Context) (bool, error) {
 
 func (s *seleniumGridScaler) getSessionsCount(ctx context.Context) (*resource.Quantity, error) {
 	body, err := json.Marshal(map[string]string{
-		"query": "{ sessionsInfo { sessionQueueRequests, sessions { id, capabilities, nodeId } } }",
+		"query": "{ grid { maxSession }, sessionsInfo { sessionQueueRequests, sessions { id, capabilities, nodeId } } }",
 	})
 
 	if err != nil {
@@ -238,5 +243,11 @@ func getCountFromSeleniumResponse(b []byte, browserName string, browserVersion s
 		}
 	}
 
+	var gridMaxSession = int64(seleniumResponse.Data.Grid.MaxSession)
+
+	if gridMaxSession > 0 {
+		count = (count + gridMaxSession - 1) / gridMaxSession
+	}
+
 	return resource.NewQuantity(count, resource.DecimalSI), nil
 }

pkg/scalers/selenium_grid_scaler_test.go

@@ -42,6 +42,9 @@ func Test_getCountFromSeleniumResponse(t *testing.T) {
 			args: args{
 				b: []byte(`{
 					"data": {
+						"grid":{
+							"maxSession": 1
+						},
 						"sessionsInfo": {
 							"sessionQueueRequests": [],
 							"sessions": []
@@ -58,6 +61,9 @@ func Test_getCountFromSeleniumResponse(t *testing.T) {
 			args: args{
 				b: []byte(`{
 					"data": {
+						"grid":{
+							"maxSession": 1
+						},
 						"sessionsInfo": {
 							"sessionQueueRequests": ["{\n  \"browserName\": \"chrome\"\n}","{\n  \"browserName\": \"chrome\"\n}"],
 							"sessions": [
@@ -81,6 +87,9 @@ func Test_getCountFromSeleniumResponse(t *testing.T) {
 			args: args{
 				b: []byte(`{
 					"data": {
+						"grid":{
+							"maxSession": 1
+						},
 						"sessionsInfo": {
 							"sessionQueueRequests": ["{\n  \"browserName\": \"chrome\"\n}","{\n  \"browserName\": \"chrome\"\n}"],
 							"sessions": []
@@ -93,12 +102,35 @@ func Test_getCountFromSeleniumResponse(t *testing.T) {
 			want:    resource.NewQuantity(2, resource.DecimalSI),
 			wantErr: false,
 		},
+		{
+			name: "active sessions with matching browsername and maxSession=2 should return count as 1",
+			args: args{
+				b: []byte(`{
+					"data": {
+						"grid":{
+							"maxSession": 2
+						},
+						"sessionsInfo": {
+							"sessionQueueRequests": ["{\n  \"browserName\": \"chrome\",\n \"browserVersion\": \"91.0\"\n}","{\n  \"browserName\": \"chrome\"\n}"],
+							"sessions": []
+						}
+					}
+				}`),
+				browserName:    "chrome",
+				browserVersion: "latest",
+			},
+			want:    resource.NewQuantity(1, resource.DecimalSI),
+			wantErr: false,
+		},
 		{
 			name: "active sessions with matching browsername should return count as 3",
 			args: args{
 				b: []byte(`{
 					"data": {
 						"sessionsInfo": {
+							"grid":{
+								"maxSession": 1
+							},
 							"sessionQueueRequests": ["{\n  \"browserName\": \"chrome\"\n}","{\n  \"browserName\": \"chrome\"\n}"],
 							"sessions": [
 								{
@@ -121,6 +153,9 @@ func Test_getCountFromSeleniumResponse(t *testing.T) {
 			args: args{
 				b: []byte(`{
 					"data": {
+						"grid":{
+							"maxSession": 1
+						},
 						"sessionsInfo": {
 							"sessionQueueRequests": ["{\n  \"browserName\": \"chrome\",\n \"browserVersion\": \"91.0\"\n}","{\n  \"browserName\": \"chrome\"\n}"],
 							"sessions": [