fix: JetSteam scaler detects leader changes correctly

CHANGELOG.md

@@ -71,6 +71,7 @@ Here is an overview of all new **experimental** features:
 ### Fixes
 
 - **General**: Hashicorp Vault PKI doesn't fail with due to KeyPair mismatch ([#6028](https://github.com/kedacore/keda/issues/6028))
+- **JetStream**: Consumer leader change is correctly detected ([#6042](https://github.com/kedacore/keda/issues/6042))
 
 ### Deprecations
 

pkg/scalers/nats_jetstream_scaler.go

@@ -218,20 +218,6 @@ func (s *natsJetStreamScaler) getNATSJetstreamMonitoringData(ctx context.Context
 	}
 
 	if s.metadata.clusterSize > 1 {
-		// we know who the consumer leader and its monitoring url is, query it directly
-		if s.metadata.consumerLeader != "" && s.metadata.monitoringLeaderURL != "" {
-			natsJetStreamMonitoringLeaderURL := s.metadata.monitoringLeaderURL
-
-			jetStreamAccountResp, err = s.getNATSJetstreamMonitoringRequest(ctx, natsJetStreamMonitoringLeaderURL)
-			if err != nil {
-				return err
-			}
-
-			s.setNATSJetStreamMonitoringData(jetStreamAccountResp, natsJetStreamMonitoringLeaderURL)
-			return nil
-		}
-
-		// we haven't found the consumer yet, grab the list of hosts and try each one
 		natsJetStreamMonitoringServerURL, err := s.getNATSJetStreamMonitoringServerURL("")
 		if err != nil {
 			return err

pkg/scalers/nats_jetstream_scaler_test.go

@@ -440,22 +440,6 @@ func TestNATSJetStreamGetNATSJetstreamServerURL(t *testing.T) {
 	}
 }
 
-func TestInvalidateNATSJetStreamCachedMonitoringData(t *testing.T) {
-	meta, err := parseNATSJetStreamMetadata(&scalersconfig.ScalerConfig{TriggerMetadata: testNATSJetStreamGoodMetadata, TriggerIndex: 0})
-	if err != nil {
-		t.Fatal("Could not parse metadata:", err)
-	}
-
-	mockJetStreamScaler := natsJetStreamScaler{
-		stream:     nil,
-		metadata:   meta,
-		httpClient: http.DefaultClient,
-		logger:     InitializeLogger(&scalersconfig.ScalerConfig{TriggerMetadata: testNATSJetStreamGoodMetadata, TriggerIndex: 0}, "nats_jetstream_scaler"),
-	}
-
-	mockJetStreamScaler.invalidateNATSJetStreamCachedMonitoringData()
-}
-
 func TestNATSJetStreamClose(t *testing.T) {
 	mockJetStreamScaler, err := NewNATSJetStreamScaler(&scalersconfig.ScalerConfig{TriggerMetadata: testNATSJetStreamGoodMetadata, TriggerIndex: 0})
 	if err != nil {

tests/scalers/nats_jetstream/helper/nats_helper.go

@@ -100,6 +100,28 @@ spec:
         ]
       restartPolicy: OnFailure
   backoffLimit: 4
+  `
+
+	StepDownConsumer = `
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: step-down
+  namespace: {{.TestNamespace}}
+spec:
+  ttlSecondsAfterFinished: 15
+  template:
+    spec:
+      containers:
+      - name: stepdown
+        image: "natsio/nats-box:0.13.2"
+        imagePullPolicy: Always
+        command: [
+          'sh', '-c', 'nats context save local --server {{.NatsAddress}} --select &&
+          nats consumer cluster step-down {{.NatsStream}} {{.NatsConsumer}}'
+        ]
+      restartPolicy: OnFailure
+  backoffLimit: 4
   `
 
 	DeploymentTemplate = `

tests/scalers/nats_jetstream/nats_jetstream_cluster/nats_jetstream_cluster_test.go

@@ -234,6 +234,10 @@ func testActivation(t *testing.T, kc *k8s.Clientset, data nats.JetStreamDeployme
 
 func testScaleOut(t *testing.T, kc *k8s.Clientset, data nats.JetStreamDeploymentTemplateData) {
 	t.Log("--- testing scale out ---")
+	// We force the change of consumer leader to ensure that KEDA detects the change and
+	// handles it properly
+	KubectlApplyWithTemplate(t, data, "stepDownTemplate", nats.StepDownConsumer)
+
 	KubectlApplyWithTemplate(t, data, "publishJobTemplate", nats.PublishJobTemplate)
 
 	assert.True(t, WaitForDeploymentReplicaReadyCount(t, kc, deploymentName, testNamespace, maxReplicaCount, 60, 3),