Cron Scaling

2 minute read

Before you begin

You need to have a Kubernetes cluster with Kapacity installed.

Run sample workload

Download nginx-statefulset.yaml and run following command to run an NGINX workload:

kubectl apply -f nginx-statefulset.yaml

Check if the workload is running:

kubectl get po

NAME      READY   STATUS    RESTARTS   AGE
nginx-0   1/1     Running   0          5s

Create IHPA with cron portrait provider

Download cron-portrait-sample.yaml which looks like this:

apiVersion: autoscaling.kapacitystack.io/v1alpha1
kind: IntelligentHorizontalPodAutoscaler
metadata:
  name: cron-portrait-sample
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: StatefulSet
    name: nginx
  minReplicas: 1
  maxReplicas: 10
  portraitProviders:
  - type: Cron
    priority: 1
    cron:
      crons:
      - name: cron-1
        start: 0 * * * *
        end: 10 * * * *
        replicas: 1
      - name: cron-2
        start: 10 * * * *
        end: 20 * * * *
        replicas: 2
      - name: cron-3
        start: 20 * * * *
        end: 30 * * * *
        replicas: 3
      - name: cron-4
        start: 30 * * * *
        end: 40 * * * *
        replicas: 4
      - name: cron-5
        start: 40 * * * *
        end: 50 * * * *
        replicas: 5

Run following command to create the IHPA:

kubectl apply -f cron-portrait-sample.yaml

Verify results

You can see that the replica number of the workload is changing dynamically accroding to our configration by checking the events of the IHPA:

kubectl describe ihpa cron-portrait-sample

...
Events:
  Type     Reason                Age                From             Message
  ----     ------                ----               ----             -------
  Normal   CreateReplicaProfile  38m                ihpa_controller  create ReplicaProfile with onlineReplcas: 3, cutoffReplicas: 0, standbyReplicas: 0
  Normal   UpdateReplicaProfile  33m (x2 over 33m)  ihpa_controller  update ReplicaProfile with onlineReplcas: 3 -> 4, cutoffReplicas: 0 -> 0, standbyReplicas: 0 -> 0
  Normal   UpdateReplicaProfile  23m                ihpa_controller  update ReplicaProfile with onlineReplcas: 4 -> 5, cutoffReplicas: 0 -> 0, standbyReplicas: 0 -> 0
  Warning  NoValidPortraitValue  13m                ihpa_controller  no valid portrait value for now
  Normal   UpdateReplicaProfile  3m15s              ihpa_controller  update ReplicaProfile with onlineReplcas: 5 -> 1, cutoffReplicas: 0 -> 0, standbyReplicas: 0 -> 0

You can also verify it by directly watching the replica number of the workload.

Note

You can see a NoValidPortraitValue event because the cron expressions configured do not cover this period of time, and the replica number of the workload will remain unchanged at this time.

Cleanup

Run following command to cleanup all the resources:

kubectl delete -f cron-portrait-sample.yaml 
kubectl delete -f nginx-statefulset.yaml

Last modified October 30, 2023: overall doc tweak (b9c2658)