topologySpreadConstraints¶

topologySpreadConstraints value enables defining of raw topologySpreadConstraings for Pod.

Note

By default topologySpreadConstraints is undefined.

In essence, these constraints provide a flexible alternative to Pod Affinity/Anti-Affinity. Topology spread constraints let you separate nodes into groups and assign Pods using a label selector. They also allow you to instruct the scheduler on how (un)evenly to distribute those Pods.

Topology spread constraints can overlap with other scheduling policies like Node Selector or taints.

Define custom topologySpreadConstraints rules

values.yaml
nameOverride: my-app
image:
  repository: nginx
  tag: latest

replicaCount: 5

toplologySpreadConstraints:
  - maxSkew: 1
    topologyKey: kubernetes.io/zone
    whenUnsatisfiable: DoNotSchedule
    labelSelector:
        matchLabels:
            app.kubernetes.io/name=my-app

Deploy command

helm install webapp sysbee/kubedeploy -f values.yaml

In the example above, with cluster deployed in only two availability zones, three Pods would be deployed in zone A and two Pods in zone B. See the Best practices link below for more info.

For more examples on custom topologySpreadCOnstraints, please read the official documentation.