Reconcile on libvirt domain events

Author: PhilippMatthes

internal/controller/hypervisor_controller.go

@@ -25,12 +25,16 @@ import (
 	"time"
 
 	kvmv1 "github.com/cobaltcore-dev/openstack-hypervisor-operator/api/v1"
+	golibvirt "github.com/digitalocean/go-libvirt"
 	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/event"
+	"sigs.k8s.io/controller-runtime/pkg/handler"
 	logger "sigs.k8s.io/controller-runtime/pkg/log"
+	"sigs.k8s.io/controller-runtime/pkg/source"
 
 	"github.com/cobaltcore-dev/kvm-node-agent/internal/certificates"
 	"github.com/cobaltcore-dev/kvm-node-agent/internal/evacuation"
@@ -48,6 +52,9 @@ type HypervisorReconciler struct {
 
 	osDescriptor     *systemd.Descriptor
 	evacuateOnReboot bool
+
+	// Channel that can be used to trigger reconcile events.
+	reconcileCh chan event.GenericEvent
 }
 
 const (
@@ -287,6 +294,39 @@ func (r *HypervisorReconciler) Reconcile(ctx context.Context, req ctrl.Request)
 	return ctrl.Result{RequeueAfter: 1 * time.Minute}, nil
 }
 
+// Start is called when the manager starts. It starts the libvirt
+// event subscription to receive events when the hypervisor needs to be
+// reconciled.
+func (r *HypervisorReconciler) Start(ctx context.Context) error {
+	log := logger.FromContext(ctx, "controller", "hypervisor")
+	log.Info("starting libvirt event subscription")
+
+	// Ensure we're connected to libvirt.
+	if err := r.Libvirt.Connect(); err != nil {
+		log.Error(err, "unable to connect to libvirt")
+		return err
+	}
+
+	// Reconcile the hypervisor resource when libvirt domain lifecycle events occur.
+	reconcile := func(ctx context.Context, _ any) {
+		r.reconcileCh <- event.GenericEvent{
+			Object: &kvmv1.Hypervisor{
+				TypeMeta: metav1.TypeMeta{
+					Kind:       "Hypervisor",
+					APIVersion: "kvm.cloud.sap/v1",
+				},
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      sys.Hostname,
+					Namespace: sys.Namespace,
+				},
+			},
+		}
+	}
+	r.Libvirt.Watch(golibvirt.DomainEventIDLifecycle, "rec-domain-lifecycle", reconcile)
+
+	return nil
+}
+
 // SetupWithManager sets up the controller with the Manager.
 func (r *HypervisorReconciler) SetupWithManager(mgr ctrl.Manager) error {
 	ctx := context.Background()
@@ -296,7 +336,17 @@ func (r *HypervisorReconciler) SetupWithManager(mgr ctrl.Manager) error {
 		return fmt.Errorf("unable to get Systemd hostname describe(): %w", err)
 	}
 
+	// Prepare an event channel that will trigger a reconcile event when
+	// the libvirt state changes.
+	r.reconcileCh = make(chan event.GenericEvent)
+	src := source.Channel(r.reconcileCh, &handler.EnqueueRequestForObject{})
+	// Run the Start(ctx context.Context) method when the manager starts.
+	if err := mgr.Add(r); err != nil {
+		return err
+	}
+
 	return ctrl.NewControllerManagedBy(mgr).
 		For(&kvmv1.Hypervisor{}).
+		WatchesRawSource(src).
 		Complete(r)
 }

internal/libvirt/interface.go

@@ -20,7 +20,10 @@ limitations under the License.
 package libvirt
 
 import (
+	"context"
+
 	v1 "github.com/cobaltcore-dev/openstack-hypervisor-operator/api/v1"
+	"github.com/digitalocean/go-libvirt"
 )
 
 type Interface interface {
@@ -30,6 +33,9 @@ type Interface interface {
 	// Close closes the connection to the libvirt daemon.
 	Close() error
 
+	// Watch libvirt changes and notify the provided handler.
+	Watch(eventId libvirt.DomainEventID, handlerId string, handler func(context.Context, any))
+
 	// Add information extracted from the libvirt socket to the hypervisor instance.
 	// If an error occurs, the instance is returned unmodified. The libvirt
 	// connection needs to be established before calling this function.