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79 lines
2.7 KiB
Markdown
79 lines
2.7 KiB
Markdown
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# Create Pod Anti-Affinity
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In cases where you wish to run applications with multiple replicas, it may be required to ensure those Pods are separated from each other for availability purposes. While a `DaemonSet` resource would accomplish similar goals, your `Deployment` object may need fewer replicas than there are nodes. Pod anti-affinity rules ensures that Pods are separated from each other. Inversely, affinity rules ensure they are co-located.
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This sample policy configures all Deployments with Pod anti-affinity rules with the `preferredDuringSchedulingIgnoredDuringExecution` option. It requires the topology key exists on all nodes with the key name of `kubernetes.io/hostname` and requires that that label `app` is applied to the Deployment.
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In order to test the policy, you can use this sample Deployment manifest below.
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```yaml
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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labels:
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app: busybox
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distributed: required
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name: busybox
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spec:
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replicas: 2
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selector:
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matchLabels:
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app: busybox
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distributed: required
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template:
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metadata:
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labels:
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app: busybox
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distributed: required
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spec:
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containers:
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- image: busybox:1.28
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name: busybox
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command: ["sleep", "9999"]
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```
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## More Information
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* [Inter-pod affinity and anti-affinity](https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#inter-pod-affinity-and-anti-affinity)
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## Policy YAML
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[create_pod_antiaffinity.yaml](more/create_pod_antiaffinity.yaml)
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```yaml
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apiVersion: kyverno.io/v1
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kind: ClusterPolicy
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metadata:
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name: insert-podantiaffinity
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spec:
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rules:
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- name: insert-podantiaffinity
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match:
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resources:
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kinds:
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- Deployment
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preconditions:
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# This precondition ensures that the label `app` is applied to Pods within the Deployment resource.
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- key: "{{request.object.metadata.labels.app}}"
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operator: NotEquals
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value: ""
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mutate:
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patchStrategicMerge:
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spec:
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template:
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spec:
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# Add the `affinity` key and others if not already specified in the Deployment manifest.
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+(affinity):
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+(podAntiAffinity):
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+(preferredDuringSchedulingIgnoredDuringExecution):
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- weight: 1
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podAffinityTerm:
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topologyKey: "kubernetes.io/hostname"
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labelSelector:
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matchExpressions:
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- key: app
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operator: In
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values:
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- "{{request.object.metadata.labels.app}}"
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```
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