Horizontal Pod Scaling with custom metrics

Hpa.yaml

apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
  name: podname
  namespace: namespace
  annotations:
    metric-config.external.processed-events-per-second.prometheus/prometheus-server: http://prometheus.istio-system.svc
    metric-config.object.istio-requests-total.prometheus/per-replica: "true"
    metric-config.object.istio-requests-total.prometheus/query: |
      sum(
          rate(
              istio_requests_total{
                destination_workload="podname",
                destination_workload_namespace="namespace",
                reporter="destination"
              }[1m]
          )
      ) / count(container_memory_usage_bytes{namespace="namespace", container=~"podname.*"})
spec:
  maxReplicas: 50
  minReplicas: 1
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: podname
  metrics:
    - type: Object
      object:
        metricName: istio-requests-total
        target:
          apiVersion: v1
          kind: Pod
          name: podname
        targetValue: 30