Placement Groups

Keep Hetzner Cloud VMs on separate physical hosts so one hardware failure never takes down more than one node. A placement group of type spread schedules each node in the group onto a different physical machine.

This matters most for high-availability clusters, where you do not want several control-plane or worker nodes sharing a host that can fail as a unit.

Creating placement groups

In the Cluster resource, you can create placement groups in the spec.topology.variables section. The following example creates two placement groups:

yaml

		- name: hcloudPlacementGroups
  value:
    - name: myPlacementGroup1
      type: spread
    - name: myPlacementGroup2
      type: spread

Note

As of now, Hetzner Cloud only supports the spread placement group type. If you want to know more, you can read the Hetzner documentation⁠.

Adding placement groups to machine deployments

To add placement groups to your machine deployments, you can set them in variables.overrides:

yaml

		machineDeployments:
  - class: workeramd64hcloud
    name: md-0
    replicas: 5
    failureDomain: nbg1
    variables:
      overrides:
        - name: workerMachineTypeHcloud
          value: cpx42
        - name: workerMachinePlacementGroupNameHcloud
          value: myPlacementGroup1

The name should match an existing placement group, created in your Cluster resource topology.variables:

Adding placement groups to control plane nodes

You can set control plane placement groups in spec.topology.variables:

yaml

		- name: controlPlanePlacementGroupNameHcloud
  value: myPlacementGroup2

Here is an example of a complete Cluster resource with placement groups:

cluster.yamlyaml

		apiVersion: cluster.x-k8s.io/v1beta2
kind: Cluster
metadata:
  name: mycluster
spec:
  clusterNetwork:
    services:
      cidrBlocks: ["10.128.0.0/12"]
    pods:
      cidrBlocks: ["192.168.0.0/16"]
    serviceDomain: "cluster.local"
  topology:
    classRef:
      name: hetzner-apalla-1-34-v12
    version: v1.34.12
    controlPlane:
      replicas: 3
    variables:
      - name: hcloudPlacementGroups
        value:
          - name: myPlacementGroup1
            type: spread
          - name: myPlacementGroup2
            type: spread
      - name: controlPlanePlacementGroupNameHcloud
        value: myPlacementGroup2
    workers:
      machineDeployments:
        - class: workeramd64hcloud
          name: md-0
          replicas: 5
          failureDomain: nbg1
          variables:
            overrides:
              - name: workerMachineTypeHcloud
                value: cpx42
              - name: workerMachinePlacementGroupNameHcloud
                value: myPlacementGroup1

Migrate ARM servers to x86 in your cluster

Learn how to migrate ARM-based (CAX) nodes to x86 nodes in your Syself Autopilot cluster by updating machine deployment classes and server types.

Labelling and assign roles on nodes

Add labels to a worker pool so every node it creates carries them, and target that pool from pods.