fix: Volume requests are falsely scheduled to Robot servers

- See #400

chart/templates/core/storageclass.yaml

@@ -10,6 +10,13 @@ provisioner: csi.hetzner.cloud
 volumeBindingMode: WaitForFirstConsumer
 allowVolumeExpansion: true
 reclaimPolicy: {{ $val.reclaimPolicy | quote }}
+{{- if $val.includesRobotServers }}
+allowedTopologies:
+- matchLabelExpressions:
+  - key: instance.hetzner.cloud/is-root-server
+    values:
+    - "false"
+{{- end }}
 ---
 {{- end }}
 {{- end }}

chart/values.yaml

@@ -724,3 +724,4 @@ storageClasses:
   - name: hcloud-volumes
     defaultStorageClass: true
     reclaimPolicy: Delete
+    includesRobotServers: false 

docs/kubernetes/README.md

@@ -209,8 +209,26 @@ $ kubectl apply -f https://raw.githubusercontent.com/hetznercloud/csi-driver/v2.
 
 ## Integration with Root Servers
 
-Root servers can be part of the cluster, but the CSI plugin doesn't work there. Taint the root server as follows to skip that node for the DaemonSet.
+Root servers can be part of the cluster, but the CSI plugin doesn't work there and the current behaviour of the scheduler can cause Pods to be stuck in `Pending`. 
 
+Include topology key evaluation into storage class, by setting the helm chart value `includesRobotServers`:
+
+```yaml
+storageClasses:
+  - name: hcloud-volumes
+    defaultStorageClass: true
+    reclaimPolicy: Delete
+    includesRobotServers: true # <---
+```
+
+Label the nodes according to their type:
+
+**Cloud Servers**
+```bash
+kubectl label nodes <node name> instance.hetzner.cloud/is-root-server=false
+```
+
+**Root Servers**
 ```bash
 kubectl label nodes <node name> instance.hetzner.cloud/is-root-server=true
 ```

internal/driver/driver.go

@@ -9,4 +9,5 @@ const (
 	DefaultVolumeSize = MinVolumeSize
 
 	TopologySegmentLocation = PluginName + "/location"
+	IsRootServerLabel       = "instance.hetzner.cloud/is-root-server"
 )

internal/driver/node.go

@@ -178,6 +178,7 @@ func (s *NodeService) NodeGetInfo(_ context.Context, _ *proto.NodeGetInfoRequest
 		AccessibleTopology: &proto.Topology{
 			Segments: map[string]string{
 				TopologySegmentLocation: s.serverLocation,
+				IsRootServerLabel:       "false",
 			},
 		},
 	}