mirror of
https://github.com/kyverno/kyverno.git
synced 2025-03-05 15:37:19 +00:00
76 lines
2.4 KiB
Markdown
76 lines
2.4 KiB
Markdown
|
# Spread pods across topology
|
||
|
|
|
||
|
|
When having a Kubernetes cluster that spans multiple availability zones, it is often desired to spread your Pods out among them in a way which controls where they land. This can be advantageous in ensuring that, should one of those zones fail, your application continues to run in a more predictable way and with less potential loss.
|
||
|
|
|
||
|
|
This sample policy configures all Deployments having the label of `required: true` to be spread amongst hosts which are labeled with the key name of `zone`. It does this only to Deployments which do not already have the field `topologySpreadConstraints` set.
|
||
|
|
|
||
|
|
**NOTE:** When deploying this policy to a Kubernetes cluster less than version 1.19, some feature gate flags will need to be enabled. Please see the [More Information](#more-information) section below.
|
||
|
|
|
||
|
|
In order to test the policy, you can use this sample Deployment manifest below.
|
||
|
|
|
||
|
|
```yaml
|
||
|
|
apiVersion: apps/v1
|
||
|
|
kind: Deployment
|
||
|
|
metadata:
|
||
|
|
labels:
|
||
|
|
app: busybox
|
||
|
|
distributed: required
|
||
|
|
name: busybox
|
||
|
|
spec:
|
||
|
|
replicas: 2
|
||
|
|
selector:
|
||
|
|
matchLabels:
|
||
|
|
app: busybox
|
||
|
|
distributed: required
|
||
|
|
template:
|
||
|
|
metadata:
|
||
|
|
labels:
|
||
|
|
app: busybox
|
||
|
|
distributed: required
|
||
|
|
spec:
|
||
|
|
containers:
|
||
|
|
- image: busybox:1.28
|
||
|
|
name: busybox
|
||
|
|
command: ["sleep", "9999"]
|
||
|
|
```
|
||
|
|
|
||
|
|
## More Information
|
||
|
|
|
||
|
|
* [Pod Topology Spread Constraints](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/)
|
||
|
|
|
||
|
|
## Policy YAML
|
||
|
|
|
||
|
|
[spread_pods_across_topology.yaml](more/spread_pods_across_topology.yaml)
|
||
|
|
|
||
|
|
```yaml
|
||
|
|
apiVersion: kyverno.io/v1
|
||
|
|
kind: ClusterPolicy
|
||
|
|
metadata:
|
||
|
|
name: spread-pods
|
||
|
|
spec:
|
||
|
|
rules:
|
||
|
|
- name: spread-pods-across-nodes
|
||
|
|
# Matches any Deployment with the label `distributed=required`
|
||
|
|
match:
|
||
|
|
resources:
|
||
|
|
kinds:
|
||
|
|
- Deployment
|
||
|
|
selector:
|
||
|
|
matchLabels:
|
||
|
|
distributed: required
|
||
|
|
# Mutates the incoming Deployment.
|
||
|
|
mutate:
|
||
|
|
patchStrategicMerge:
|
||
|
|
spec:
|
||
|
|
template:
|
||
|
|
spec:
|
||
|
|
# Adds the topologySpreadConstraints field if non-existent in the request.
|
||
|
|
+(topologySpreadConstraints):
|
||
|
|
- maxSkew: 1
|
||
|
|
topologyKey: zone
|
||
|
|
whenUnsatisfiable: DoNotSchedule
|
||
|
|
labelSelector:
|
||
|
|
matchLabels:
|
||
|
|
distributed: required
|
||
|
|
```
|