Hetzner Cloud Placement Groups allow you to control how your Kubernetes nodes are distributed across physical hosts within Hetzner’s infrastructure. By assigning nodes to a placement group of type spread, you ensure that each node is scheduled on a different physical machine, increasing fault tolerance and availability.

This feature is especially useful for high-availability Kubernetes clusters, as it minimizes the risk of multiple nodes failing due to hardware issues on a single host.

## 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
```

{% callout type="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](https://docs.hetzner.com/cloud/placement-groups/overview).

{% /callout %}

## 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 controlplane 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:

```yaml
/// cluster.yaml
apiVersion: cluster.x-k8s.io/v1beta1
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:
    class: hetzner-apalla-1-34-v6
    version: v1.34.6
    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
```