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☑️ Ensure multiple replicas run on different nodes

Running multiple replicas won’t be very useful if all the replicas are running on the same node and the node becomes unavailable.
It is recommended to use pod anti-affinity to spread replicas across multiple worker nodes by running the application across multiple availability zones.

Targeted objects by this rule (types of kind): Deployment / Pod / DaemonSet / StatefulSet / ReplicaSet / CronJob / Job

Complexity: medium (What does this mean?)

Policy as code identifier: EKS_MISSING_KEY_TOPOLOGYKEY

This rule will fail​

If a podAffinityTerm is configured without a topologyKey:

podAntiAffinity:
  preferredDuringSchedulingIgnoredDuringExecution:
  - podAffinityTerm:
      labelSelector:
        matchExpressions:
        - key: app
          operator: In
          values:
          - web-server

Rule output in the CLI​

$ datree test *.yaml

>> File: failExample.yaml
❌ Ensure multiple replicas run on different nodes [1 occurrence]
💡 Missing key `topologyKey` - add it to ensure replicas are spread across multiple nodes

How to fix this failure​

podAntiAffinity:
  preferredDuringSchedulingIgnoredDuringExecution:
  - podAffinityTerm:
      labelSelector:
        matchExpressions:
        - key: app
          operator: In
          values:
          - web-server
      topologyKey: topology.kubernetes.io/zone

Read more​