Deployment without podAntiAffinity

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Metadata

Id: a31b7b82-d994-48c4-bd21-3bab6c31827a

Cloud Provider: k8s

Platform: Kubernetes

Severity: Low

Category: Resource Management

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Description

Deployments with more than two replicas should include a podAntiAffinity policy to prevent multiple Pods from being scheduled on the same node. The policy must be defined under spec.template.spec.affinity.podAntiAffinity and include at least one of preferredDuringSchedulingIgnoredDuringExecution or requiredDuringSchedulingIgnoredDuringExecution. Each affinity term’s podAffinityTerm.topologyKey must be set to ‘kubernetes.io/hostname’, and its labelSelector.matchLabels must match labels on the pod template.

Compliant Code Examples

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-server
spec:
  selector:
    matchLabels:
      app: web-store
  replicas: 3
  template:
    metadata:
      labels:
        app: web-store
    spec:
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - web-store
            topologyKey: "kubernetes.io/hostname"
      containers:
      - name: web-app
        image: nginx:1.16-alpine

Non-Compliant Code Examples

apiVersion: apps/v1
kind: Deployment
metadata:
  name: label-mismatch
spec:
  selector:
    matchLabels:
      app: web-store
  replicas: 3
  template:
    metadata:
      labels:
        app: web-shore
    spec:
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchLabels:
                app: web-store
            topologyKey: "kubernetes.io/hostname"
      containers:
      - name: web-app
        image: nginx:1.16-alpine
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: no-affinity
spec:
  selector:
    matchLabels:
      app: web-store
  replicas: 3
  template:
    metadata:
      labels:
        app: web-store
    spec:
      containers:
      - name: web-app
        image: nginx:1.16-alpine