Day 24: Scaling Applications with Kubernetes HPA and Cluster Autoscaler

Welcome to Day 24 of the Zero to Platform Engineer in 30 Days challenge! 🚀 Today, we’re diving into autoscaling in Kubernetes, focusing on Horizontal Pod Autoscaler (HPA) and Cluster Autoscaler to efficiently manage workloads..

Feb 07, 20252 min readenpart 25 of 27

Why Autoscaling Matters in Kubernetes?

Autoscaling ensures that applications:

Adapt to demand by increasing or decreasing resources dynamically.
Improve cost efficiency by running only what’s needed.
Maintain performance under varying loads.

Two main types of autoscaling in Kubernetes:

HPA (Horizontal Pod Autoscaler) → Scales pods based on CPU, memory, or custom metrics.
Cluster Autoscaler → Adjusts the number of nodes dynamically based on pod scheduling needs.

Horizontal Pod Autoscaler (HPA)

Scales pods automatically based on CPU, memory, or custom metrics.
Works well for applications with fluctuating workloads.
Requires metrics-server to be installed.

Step 1: Enable Metrics Server

kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml

Step 2: Deploy a Sample Application

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        resources:
          requests:
            cpu: "100m`
          limits:
            cpu: "200m"

kubectl apply -f deployment.yaml

Step 3: Create an HPA for the Deployment

kubectl autoscale deployment nginx-deployment --cpu-percent=50 --min=1 --max=10

Step 4: Check HPA Status

kubectl get hpa

💡 HPA will increase/decrease pods based on CPU usage automatically.

Cluster Autoscaler

Scales nodes up/down when pods can’t be scheduled due to resource constraints.
Works with cloud providers like AWS, GCP, and Azure.

Step 1: Deploy Cluster Autoscaler on AWS EKS

helm repo add autoscaler https://kubernetes.github.io/autoscaler
helm repo update
helm install cluster-autoscaler autoscaler/cluster-autoscaler \
  --namespace kube-system \
  --set autoDiscovery.clusterName=my-cluster \
  --set awsRegion=us-west-2

Step 2: Verify Cluster Autoscaler

kubectl logs -f deployment/cluster-autoscaler -n kube-system

💡 Cluster Autoscaler ensures that Kubernetes adds/removes nodes as needed.

Activity for Today

Deploy HPA for a sample application.
Enable Cluster Autoscaler and scale up/down nodes.
Test autoscaling by generating load on your application.

What’s Next?

Tomorrow, we’ll explore safe deployments using Canary Releases and Feature Flags.

👉 Check it out here: Zero to Platform Engineer Repository

Feel free to clone the repo, experiment with the code, and even contribute if you’d like! 🚀

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