Kubernetes pod affinity and anti affinity

https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#affinity-and-anti-affinity

• Elasticsearch PodAntiAffinity official example

0/11 nodes are available: 1 Insufficient cpu, 1 Too many pods, 10 nodes(s) didn't match Pod's node affinity/selector
0/2 nodes are available: 1 Too many pods, 1 nodes(s) didn't match Pod's node affinity/selector
0/2 nodes are available: 0/24 nodes are available: 1 node(s) didn't match pod anti-affinity rules, 1 node(s) were unschedulable, 2 node(s) had taint {node.kubernetes.io/not-ready}, that the pod did not tolerate, 20 node(s) didn't match Pod's node affinity/selector. 

Too many pods, 1 nodes(s) didn't match Pod's node affinity/selector

Official examples

apiVersion: v1
kind: Pod
metadata:
  name: with-node-affinity
spec:
  affinity: 
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: topology.kubernetes.io/zone
            operator: In
            values:
            - antarctica-east1
            - antarctica-west1
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 1
        preference:
          matchExpressions:
          - key: another-node-label-key
            operator: In
            values:
            - another-node-label-value
  containers:
  - name: with-node-affinity
    image: registry.k8s.io/pause:2.0
apiVersion: v1
kind: Pod
metadata:
  name: with-pod-affinity
spec:
  affinity:
    podAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:

          - key: security

            operator: In

            values:

           - S1

        topologyKey: topology.kubernetes.io/zone

    podAntiAffinity:

      preferredDuringSchedulingIgnoredDuringExecution:

      - weight: 100

       podAffinityTerm:

          labelSelector:

            matchExpressions:

            - key: security

              operator: In

              values:

              - S2

          topologyKey: topology.kubernetes.io/zone

  containers:

  - name: with-pod-affinity

    image: registry.k8s.io/pause:2.0

Related

• Kubernetes Pod Topology Spread Constraints
• default-scheduler
• Volume node affinity conflict

Activities

• https://aws.amazon.com/about-aws/whats-new/2022/04/amazon-eks-karpenter-v0-9-0-pod-affinity/

See also

• Kubernetes pod affinity and anti affinity, Kubernetes Node Affinity, default-scheduler, affinity:, NodeAffinity, spec.affinity.podAntiAffinity
• Pods: kubectl apply, kubectl [ pod get | top | delete | describe pods ], InitContainers, PodInitializing, CrashLoopBackOff, ImagePullPolicy:, NodeAffinity, NodeSelector, Terminated
• Karpenter, karpenter.sh, provisioners.karpenter.sh, Karpenter releases, best practices, karpenter.sh/capacity-type, karpenter.sh/discovery, kind: Provisioner, kind: AWSNodeTemplate, kubectl provisioner, TopologyKey, FailedDraining, Evict, DisruptionBlocked, Karpenter logs, controller., ttlSecondsUntilExpired, KEDA, NodePools, Kind: NodePool, Workload Consolidation, Disruption controls