What approaches should be used if updating a Kubernetes cluster leads to service unavailability?

If a Kubernetes cluster update leads to service unavailability, the following approaches should be applied:

• Rolling Update: update pods one by one or in small batches to always keep available instances.
• Check readiness and liveness probes: ensure that probes are correctly configured so that Kubernetes does not route traffic to unready pods.
• Use update strategies with maxUnavailable and maxSurge: configure parameters to limit the number of pods that are unavailable at the same time.
• Check dependencies between services: ensure that the update does not break interactions between components.
• Monitoring and rollback: have the ability to quickly revert the update if problems occur.
• Test the update in a staging environment: reproduce the update process before production.

Example of rolling update configuration in Deployment:

strategy:
  type: RollingUpdate
  rollingUpdate:
    maxUnavailable: 1
    maxSurge: 1

This allows updating one pod at a time, minimizing service downtime.