openshift-docs/modules/virt-example-vm-node-placement-pod-affinity.adoc

// Module included in the following assemblies:
//
// * virt/virtual_machines/advanced_vm_management/virt-specifying-nodes-for-vms.adoc

:_mod-docs-content-type: REFERENCE
[id="virt-example-vm-node-placement-pod-affinity_{context}"]
= Example: VM node placement with pod affinity and pod anti-affinity

[role="_abstract"]
In this example, the VM must be scheduled on a node that has a running pod with the label `example-key-1 = example-value-1`. If there is no such pod running on any node, the VM is not scheduled.

If possible, the VM is not scheduled on a node that has any pod with the label `example-key-2 = example-value-2`. However, if all candidate nodes have a pod with this label, the scheduler ignores this constraint.

.Example VM manifest
====
[source,yaml]
----
metadata:
  name: example-vm-pod-affinity
apiVersion: kubevirt.io/v1
kind: VirtualMachine
spec:
  template:
    spec:
      affinity:
        podAffinity:
          requiredDuringSchedulingIgnoredDuringExecution: <1>
          - labelSelector:
              matchExpressions:
              - key: example-key-1
                operator: In
                values:
                - example-value-1
            topologyKey: kubernetes.io/hostname
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution: <2>
          - weight: 100
            podAffinityTerm:
              labelSelector:
                matchExpressions:
                - key: example-key-2
                  operator: In
                  values:
                  - example-value-2
              topologyKey: kubernetes.io/hostname
# ...
----
<1> If you use the `requiredDuringSchedulingIgnoredDuringExecution` rule type, the VM is not scheduled if the constraint is not met.
<2> If you use the `preferredDuringSchedulingIgnoredDuringExecution` rule type, the VM is still scheduled if the constraint is not met, as long as all required constraints are met.
====