Kubernetes HPA pod custom metrics shows as <unknown> - kubernetes

Question

I have managed to install Prometheus and it's adapter and I want to use one of the pod metrics for autoscaling
kubectl get --raw "/apis/custom.metrics.k8s.io/v1beta1" | jq . |grep "pods/http_request".
"name": "pods/http_request_duration_milliseconds_sum",
"name": "pods/http_request",
"name": "pods/http_request_duration_milliseconds",
"name": "pods/http_request_duration_milliseconds_count",
"name": "pods/http_request_in_flight",
Checking api I want to use pods/http_request and added it to my HPA configuration
---
apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
metadata:
name: app
namespace: app
spec:
scaleTargetRef:
apiVersion: apps/v1
kind: Deployment
name: app
minReplicas: 4
maxReplicas: 8
metrics:
- type: Pods
pods:
metric:
name: http_request
target:
type: AverageValue
averageValue: 200
After applying the yaml and check the hpa status it shows up as <unkown>
$ k apply -f app-hpa.yaml
$ k get hpa
NAME REFERENCE TARGETS
app Deployment/app 306214400/2000Mi, <unknown>/200 + 1 more...
But when using other pod metrics such as pods/memory_usage_bytes the value is properly detected
Is there a way to check the proper values for this metric? and how do I properly add it for my hpa configuration
Reference https://www.ibm.com/support/knowledgecenter/SSBS6K_3.2.0/manage_cluster/hpa.html

Answer 1

1st deploy metrics server, it should be up and running.
$ kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
Then in a few sec. metrics server deployed. check HPA it should resolved.
$ kubectl get deployment -A
NAMESPACE NAME READY UP-TO-DATE AVAILABLE AGE
.
.
kube-system metrics-server 1/1 1 1 34s
$ kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
ha-xxxx-deployment Deployment/xxxx-deployment 1%/5% 1 10 1 6h46m