How do I achieve zero-downtime deployments for StatefulSets?

Achieving zero-downtime deployments for StatefulSets in Kubernetes is crucial for applications that require high availability and consistency. By leveraging various strategies like rolling updates, using the right service types, and ensuring your application is capable of handling graceful shutdowns, you can deploy updates without affecting the end-users. Below is a detailed example of how to achieve this:

apiVersion: apps/v1 kind: StatefulSet metadata: name: my-app spec: serviceName: "my-app" replicas: 3 selector: matchLabels: app: my-app template: metadata: labels: app: my-app spec: containers: - name: my-app image: my-app:v1 # Ensure to version the image ports: - containerPort: 80 readinessProbe: httpGet: path: /health port: 80 initialDelaySeconds: 5 periodSeconds: 10 terminationGracePeriodSeconds: 30 updateStrategy: type: RollingUpdate rollingUpdate: partition: 1 # This ensures only one pod is updated at a time

In this example:

  • The readinessProbe ensures that the pod is only marked as ready when it can handle traffic.
  • The TerminationGracePeriodSeconds allows existing connections to complete before terminating a pod.
  • The RollingUpdate strategy updates one pod at a time, ensuring that there is always at least one pod available to serve requests.

zero-downtime deployments Kubernetes StatefulSets rolling updates high availability graceful shutdowns

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