148422597X Kubernetes Management Design Patterns [Vohra 2017-01-29] {E559F6BB}

Chapter 9 ■ Scheduling Pods on Nodes
The another-annotation-key: another-annotation-value setting implies that from the
nodes found suitable with the nodeAffinity condition, the node with the another-annotationkey:
another-annotation-value label should be preferred, which again is a hint for a preference
that may or may not be implemented. The another-annotation-key: another-annotation-value
is found to be implemented with requiredDuringSchedulingIgnoredDuringExecution and not with
preferredDuringSchedulingIgnoredDuringExecution. In addition to the In operator, the other supported
operators are NotIn, Exists, DoesNotExist, Gt and Lt.
Next, we shall discuss each of the node affinities with an example.
Setting requiredDuringSchedulingIgnoredDuringExecution
Create a pod definition file pod-node-affinity.yaml for a pod named with-labels and set the
nodeAffinity to requiredDuringSchedulingIgnoredDuringExecution with matching expressions for
nodeSelectorTerms to be a label kubernetes.io/image-name with value as one of nginx2 or hello-world2.
The another-annotation-key: another-annotation-value is kubernetes.io/image-name: nginx. The
container image is nginx.
apiVersion: v1
kind: Pod
metadata:
name: with-labels
annotations:
scheduler.alpha.kubernetes.io/affinity: >
{
"nodeAffinity": {
"requiredDuringSchedulingIgnoredDuringExecution": {
"nodeSelectorTerms": [
{
"matchExpressions": [
{
"key": "kubernetes.io/image-name",
"operator": "In",
"values": ["nginx2", "hello-world2"]
}
]
}
]
}
}
}
kubernetes.io/image-name: nginx
spec:
containers:
- name: with-labels
image: nginx
List the nodes, including labels. The resulting labels on nodes should not include the required labels
nginx2 or hello-world2, as shown in Figure 9-35.
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