Auto-scale based on resource usage #

So far, the HPA has not yet performed auto-scaling based on resource usage. Let’s do that now. First, we’ll try to create another HorizontalPodAutoscaler but, this time, we’ll target the StatefulSet that runs our MongoDB. So, let’s take a look at yet another YAML definition.

Create HPA #

cat scaling/go-demo-5-db-hpa.yml

The output is as follows.

apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
  name: db
  namespace: go-demo-5
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: StatefulSet
    name: db
  minReplicas: 3
  maxReplicas: 5
  metrics:
  - type: Resource
    resource:
      name: cpu
      targetAverageUtilization: 80
  - type: Resource
    resource:
      name: memory
      targetAverageUtilization: 80

That definition is almost the same as the one we used before. The only difference is that this time we’re targeting StatefulSet called db and that the minimum number of replicas should be 3.

Let’s apply it.

kubectl apply \
    -f scaling/go-demo-5-db-hpa.yml \
    --record

Let’s take another look at the HorizontalPodAutoscaler resources.

kubectl -n go-demo-5 get hpa

The output is as follows.

NAME REFERENCE      TARGETS                      MINPODS MAXPODS REPLICAS AGE
api  Deployment/api 41%/80%, 0%/80%              2       5       2        5m
db   StatefulSet/db <unknown>/80%, <unknown>/80% 3       5       0        20s

We can see that the second HPA was created and that the current utilization is unknown. That must be a similar situation as before. Should we give it some time for data to start flowing in? Wait for a few moments and retrieve HPAs again. Are the targets still unknown?

Resource utilization not getting shown #

There might be something wrong since the resource utilization continued being unknown. Let’s describe the newly created HPA and see whether we’ll be able to find the cause ...