✨ Allow clusters without explicit availability zones

api/v1alpha3/conversion_test.go

@@ -199,6 +199,7 @@ func TestFuzzyConversion(t *testing.T) {
 				v1alpha5ClusterSpec.APIServerFixedIP = ""
 				v1alpha5ClusterSpec.AllowAllInClusterTraffic = false
 				v1alpha5ClusterSpec.DisableAPIServerFloatingIP = false
+				v1alpha5ClusterSpec.IgnoreAvailabilityZones = false
 			},
 			func(v1alpha5MachineSpec *infrav1.OpenStackMachineSpec, c fuzz.Continue) {
 				c.FuzzNoCustom(v1alpha5MachineSpec)

api/v1alpha4/conversion_test.go

@@ -318,6 +318,12 @@ func TestFuzzyConversion(t *testing.T) {
 				v1alpha5RootVolume.VolumeType = ""
 				v1alpha5RootVolume.AvailabilityZone = ""
 			},
+			// Don't test hub-spoke-hub conversion of v1alpha5 fields which are not in v1alpha4
+			func(v1alpha5ClusterSpec *infrav1.OpenStackClusterSpec, c fuzz.Continue) {
+				c.FuzzNoCustom(v1alpha5ClusterSpec)
+
+				v1alpha5ClusterSpec.IgnoreAvailabilityZones = false
+			},
 		}
 	}
 

api/v1alpha5/openstackcluster_types.go

@@ -123,6 +123,14 @@ type OpenStackClusterSpec struct {
 	// +optional
 	ControlPlaneEndpoint clusterv1.APIEndpoint `json:"controlPlaneEndpoint"`
 
+	// IgnoreAvailabilityZones disables the use of availability zones/failure domains,
+	// allowing Nova to schedule machines in any compatible AZ.
+	// This only affects control plane nodes - explicit failure domains can still be
+	// specified for worker nodes using MachineDeployment.spec.template.spec.failureDomain
+	// if desired.
+	// +optional
+	IgnoreAvailabilityZones bool `json:"ignoreAvailabilityZones"`
+
 	// ControlPlaneAvailabilityZones is the az to deploy control plane to
 	ControlPlaneAvailabilityZones []string `json:"controlPlaneAvailabilityZones,omitempty"`
 

config/crd/bases/infrastructure.cluster.x-k8s.io_openstackclusters.yaml

@@ -3063,6 +3063,13 @@ spec:
                 - kind
                 - name
                 type: object
+              ignoreAvailabilityZones:
+                description: IgnoreAvailabilityZones disables the use of availability
+                  zones/failure domains, allowing Nova to schedule machines in any
+                  compatible AZ. This only affects control plane nodes - explicit
+                  failure domains can still be specified for worker nodes using MachineDeployment.spec.template.spec.failureDomain
+                  if desired.
+                type: boolean
               managedSecurityGroups:
                 description: ManagedSecurityGroups determines whether OpenStack security
                   groups for the cluster will be managed by the OpenStack provider

config/crd/bases/infrastructure.cluster.x-k8s.io_openstackclustertemplates.yaml

@@ -1344,6 +1344,14 @@ spec:
                         - kind
                         - name
                         type: object
+                      ignoreAvailabilityZones:
+                        description: IgnoreAvailabilityZones disables the use of availability
+                          zones/failure domains, allowing Nova to schedule machines
+                          in any compatible AZ. This only affects control plane nodes
+                          - explicit failure domains can still be specified for worker
+                          nodes using MachineDeployment.spec.template.spec.failureDomain
+                          if desired.
+                        type: boolean
                       managedSecurityGroups:
                         description: ManagedSecurityGroups determines whether OpenStack
                           security groups for the cluster will be managed by the OpenStack

controllers/openstackcluster_controller.go

@@ -264,28 +264,30 @@ func reconcileNormal(ctx context.Context, scope *scope.Scope, patchHelper *patch
 		return reconcile.Result{}, err
 	}
 
-	availabilityZones, err := computeService.GetAvailabilityZones()
-	if err != nil {
-		return ctrl.Result{}, err
-	}
-
-	// Create a new list to remove any Availability
-	// Zones that have been removed from OpenStack
+	// Create a new list to remove any Availability Zones from our status that no longer exist in OpenStack
 	openStackCluster.Status.FailureDomains = make(clusterv1.FailureDomains)
-	for _, az := range availabilityZones {
-		found := true
-		// If Az given, then check whether it's in the allow list
-		// If no Az given, then by default put into allow list
-		if len(openStackCluster.Spec.ControlPlaneAvailabilityZones) > 0 {
-			if contains(openStackCluster.Spec.ControlPlaneAvailabilityZones, az.ZoneName) {
-				found = true
-			} else {
-				found = false
-			}
+	// Only populate the failure domains if we want them to be considered
+	if !openStackCluster.Spec.IgnoreAvailabilityZones {
+		availabilityZones, err := computeService.GetAvailabilityZones()
+		if err != nil {
+			return ctrl.Result{}, err
 		}
 
-		openStackCluster.Status.FailureDomains[az.ZoneName] = clusterv1.FailureDomainSpec{
-			ControlPlane: found,
+		for _, az := range availabilityZones {
+			found := true
+			// If Az given, then check whether it's in the allow list
+			// If no Az given, then by default put into allow list
+			if len(openStackCluster.Spec.ControlPlaneAvailabilityZones) > 0 {
+				if contains(openStackCluster.Spec.ControlPlaneAvailabilityZones, az.ZoneName) {
+					found = true
+				} else {
+					found = false
+				}
+			}
+
+			openStackCluster.Status.FailureDomains[az.ZoneName] = clusterv1.FailureDomainSpec{
+				ControlPlane: found,
+			}
 		}
 	}
 

controllers/openstackmachine_controller.go

@@ -421,10 +421,6 @@ func machineToInstanceSpec(openStackCluster *infrav1.OpenStackCluster, machine *
 		return nil, fmt.Errorf("create Options need be specified to create instace")
 	}
 
-	if machine.Spec.FailureDomain == nil {
-		return nil, fmt.Errorf("failure domain not set")
-	}
-
 	instanceSpec := compute.InstanceSpec{
 		Name:          openStackMachine.Name,
 		Image:         openStackMachine.Spec.Image,
@@ -434,13 +430,17 @@ func machineToInstanceSpec(openStackCluster *infrav1.OpenStackCluster, machine *
 		UserData:      userData,
 		Metadata:      openStackMachine.Spec.ServerMetadata,
 		ConfigDrive:   openStackMachine.Spec.ConfigDrive != nil && *openStackMachine.Spec.ConfigDrive,
-		FailureDomain: *machine.Spec.FailureDomain,
 		RootVolume:    openStackMachine.Spec.RootVolume,
 		Subnet:        openStackMachine.Spec.Subnet,
 		ServerGroupID: openStackMachine.Spec.ServerGroupID,
 		Trunk:         openStackMachine.Spec.Trunk,
 	}
 
+	// Add the failure domain only if specified
+	if machine.Spec.FailureDomain != nil {
+		instanceSpec.FailureDomain = *machine.Spec.FailureDomain
+	}
+
 	machineTags := []string{}
 
 	// Append machine specific tags

docs/book/src/clusteropenstack/configuration.md

@@ -107,9 +107,17 @@ Note: you need to set `clusterctl.cluster.x-k8s.io/move` label for the secret cr
 
 ## Availability zone
 
-The availability zone names must be exposed as an environment variable `OPENSTACK_FAILURE_DOMAIN`.
+When using the provided templates, the availability zone name must be exposed as an environment variable `OPENSTACK_FAILURE_DOMAIN`.
 
-By default, if `Availability zone` is not given, all `Availability zone` that defined in openstack will be a candidate to provision from, If administrator credential is used then `internal` Availability zone which is internal only Availability zone inside `nova` will be returned and can cause potential problem, see [PR 1165](https://github.com/kubernetes-sigs/cluster-api-provider-openstack/pull/1165) for further information. So we highly recommend to set `Availability zone` explicitly.
+However it is possible to provision clusters without using explicit availability zones, allowing Nova to select appropriate availability zones based on other scheduling constraints (e.g. flavor traits, host aggregates).
+
+For machine deployments (e.g. worker nodes), this can be achieved simply by not specifying a `failureDomain` in the machine template spec. For the control plane, the default behaviour is to explicitly schedule control plane nodes across all the availability zones. To disable this behaviour and allow control plane nodes _without_ explicit availability zones, you must set `OpenStackCluster.spec.ignoreAvailabilityZones: true`.
+
+> **WARNING**
+>
+> If an administrator credential is used then the `internal` availability zone will be returned, which can cause issues - see [PR 1165](https://github.com/kubernetes-sigs/cluster-api-provider-openstack/pull/1165) for further information.
+>
+> We highly recommend **not** using an administrator credential, but if it is required you should set your availability zones explicitly using `OpenStackCluster.spec.controlPlaneAvailabilityZones` and `MachineDeployment.spec.template.spec.failureDomain`.
 
 ## DNS server