Kubernetes - Horizontal Pod autoscaling

Kubernetes has the ability to automatically scale resources as required by the current load. There are some prerequirements however. With a user-provisioned kubernetes cluster, there's most likely not going to be a metrics-server deployed:

 [archy@kube01 ~]$ kubectl -n kube-system get deployments -o wide

 NAME       READY  UP-TO-DATE  AVAILABLE  AGE  CONTAINERS    IMAGES                                 SELECTOR  
 coredns    2/2    2           2          154d coredns       k8s.gcr.io/coredns/coredns:v1.8.0      k8s-app=kube-dns

To deploy the metrics-server, go ahead and download the manifest from GitHub:

 [archy@kube01 ~]$ curl -k -L -o kubernetes/metrics-server.yml -X GET 'https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml'

In order to enable the metrics-server to communicate with the worker-nodes, we'll have to add the 'kubelet-insecure-tls' option to the manifest args and then apply it:

 [archy@kube01 ~]$ vim kubernetes/metrics-server.yml

   spec:  
     containers:  
     - args:  
       - --cert-dir=/tmp  
       - --secure-port=443  
       - --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname  
       - --kubelet-use-node-status-port  
       - --metric-resolution=15s  
 ++    - --kubelet-insecure-tls

 [archy@kube01 ~]$ kubectl apply -f kubernetes/metrics-server.yml

Now that the metrics server is deployed, you can create the autoscaler:

 [archy@kube01 ~]$ kubectl autoscale deployments/speedtest --min 2 --max 4 --cpu-percent 80

This will create autoscaling which will keep at least 2 pods with a maximum of up to 4 pods. The scaling here will depend on the pod's CPU usage.

Here's the autoscaling in yaml format:

 ---  
 apiVersion: autoscaling/v1  
 kind: HorizontalPodAutoscaler  
 metadata:  
  name: speedtest  
  namespace: default  
 spec:  
  maxReplicas: 4  
  minReplicas: 2  
  scaleTargetRef:  
   apiVersion: apps/v1  
   kind: Deployment  
   name: speedtest  
  targetCPUUtilizationPercentage: 80

Check if the autoscaler is present as expected:

 [archy@kube01 ~]$ kubectl get hpa -o wide

 NAME        REFERENCE             TARGETS  MINPODS  MAXPODS  REPLICAS  AGE  
 speedtest   Deployment/speedtest  0%/80%   2        4        2         7h49m

This concludes the autoscaler setup for kubernetes.

Feel free to comment and / or suggest a topic.

Comments

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