With multiple triggers (CPU and HTTP) and minReplicaCount of 0, KEDA erroneously scales to 0.

[mengland-noaa]

Report

With CPU and the http-external-scaler together as triggers in the same scaled object, the http scaler is superseding the CPU scaler.
With CPU under heavy load and with http request(s) it scales up successfully, but KEDA subsequently intervenes and scales to 0 ignoring CPU.

Expected Behavior

Under heavy CPU load even with no http requests KEDA should not scale down to 0.

Actual Behavior

The HTTP add on appears to be overriding the CPU scaler.

Steps to Reproduce the Problem

1. Create an nginx or other deployment paired with a CPU load test side car or init container. The memory scaler behaves similarly.
2. Send an http request and watch as it initially scales up then scales back down to 0.

apiVersion: v1
kind: Service
metadata:
  name: my-service
  namespace: my-namespace
spec:
  selector:
    app: my-app
  type: ClusterIP
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
      name: http
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
  namespace: my-namespace
spec:
  replicas: 0
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: my-container
          image: nginx
          ports:
            - containerPort: 80
          resources:
            requests:
              cpu: "100m"
              memory: "100Mi"
            limits:
              cpu: "500m"
              memory: "100Mi"
        - name: stress-ng
          image: polinux/stress-ng:latest
          command: ["/bin/sh", "-c"]
          args:
            - "echo 'Running stress-ng'; stress-ng --cpu 1 --vm 1 --vm-bytes 64M --timeout 300s; echo 'stress-ng finished'; sleep 3600"
          resources:
            requests:
              cpu: "100m"
              memory: "100Mi"
            limits:
              cpu: "1000m"
              memory: "1000Mi"
---
kind: ScaledObject
apiVersion: keda.sh/v1alpha1
metadata:
  name: my-scaled-object
  namespace: my-namespace
spec:
  initialCooldownPeriod: 120
  cooldownPeriod: 30
  minReplicaCount: 0
  maxReplicaCount: 4
  pollingInterval: 5
  fallback:
    failureThreshold: 5
    replicas: 1
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-deployment
  advanced:
    horizontalPodAutoscalerConfig:
      name: custom-hpa-name
      behavior:
        scaleDown:
          stabilizationWindowSeconds: 300
  triggers:
    - type: cpu
      name: cpu_trig
      metricType: Utilization
      metadata:
        value: "10"
    - type: external
      name: http_trig
      metadata:
        httpScaledObject: my-scaled-object
        hosts: "myhost"
        scalerAddress: keda-add-ons-http-external-scaler.keda:9090
---
kind: HTTPScaledObject
apiVersion: http.keda.sh/v1alpha1
metadata:
  name: my-scaled-object
  namespace: my-namespace
  annotations:
      httpscaledobject.keda.sh/skip-scaledobject-creation: "true"
spec:
  hosts:
  - "myhost"
  scalingMetric:
    requestRate:
      granularity: 1s
      targetValue: 2
      window: 1m
  scaledownPeriod: 300
  scaleTargetRef:
      name: my-deployment
      service: my-service
      port: 80
  replicas:
      min: 0
      max: 4
  targetPendingRequests: 1
---
kind: Service
apiVersion: v1
metadata:
  name: keda-add-ons-http-interceptor-proxy
  namespace: my-namespace
spec:
  type: ExternalName
  externalName: keda-add-ons-http-interceptor-proxy.keda.svc.cluster.local

Logs from KEDA HTTP operator

No response

HTTP Add-on Version

0.10.0

Kubernetes Version

None

Platform

Any

Anything else?

No response