How to scale a Deployment?

Short answer

Scale a Deployment using kubectl scale, editing the manifest, or enabling the Horizontal Pod Autoscaler. All methods adjust the number of replicas to meet demand.

Steps

1. Manual scale with kubectl scale deployment <name> --replicas=5.
2. Update spec.replicas in the manifest and kubectl apply.
3. Create an HPA for automatic scaling.

Example

kubectl scale deployment web --replicas=5

HPA manifest:

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: web
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: web
  minReplicas: 2
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70

Tips

• Always set resource requests for HPA to work.
• Use cluster autoscaler to add nodes when Pods cannot be scheduled.
• Monitor scale events with kubectl get events.

Common issues

• Scaling beyond node capacity leaves Pods in Pending.
• HPA requires the metrics server to be installed.
• Rapid scaling can cause thundering herd problems.