recipes / zero-downtime-rollouts

Zero-downtime rolling updates

Rolling update strategy, a PodDisruptionBudget and spread across nodes so a deploy never drops requests.

With graceful shutdown and readiness probes in place, the last piece is telling the scheduler how many Pods may be unavailable at any time. The answer is zero.

Strategy

spec:
  replicas: 2
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 0
      maxSurge: 1

A new Pod must pass its readiness probe before an old one is terminated.

PodDisruptionBudget

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: app
spec:
  minAvailable: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: app

Node drains and cluster upgrades respect the budget. Without it, both replicas can be evicted at once.

Spread

spec:
  template:
    spec:
      topologySpreadConstraints:
        - maxSkew: 1
          topologyKey: kubernetes.io/hostname
          whenUnsatisfiable: ScheduleAnyway
          labelSelector:
            matchLabels:
              app.kubernetes.io/name: app

Notes

• replicas: 1 cannot be zero-downtime through a node drain, whatever else you set.
• minAvailable: 1 with two replicas blocks drains during a rollout for a moment. Use three replicas or maxUnavailable: 1 if drains stall.
• Watch a rollout with kubectl rollout status deployment/app.

See it applied

• examples/full/k8s/base in the repository
• examples/full - every recipe applied to one app

Updated 2026-09-10 · tags: rollout, pdb, availability · edit on GitHub