✨ Implement deletion lifecycle hooks

api/v1alpha3/machine_types.go

@@ -37,6 +37,18 @@ const (
 
 	// MachineDeploymentLabelName is the label set on machines if they're controlled by MachineDeployment
 	MachineDeploymentLabelName = "cluster.x-k8s.io/deployment-name"
+
+	// PreDrainDeleteHookAnnotationPrefix annotation specifies the prefix we
+	// search each annotation for during the pre-drain.delete lifecycle hook
+	// to pause reconciliation of deletion. These hooks will prevent removal of
+	// draining the associated node until all are removed.
+	PreDrainDeleteHookAnnotationPrefix = "pre-drain.delete.hook.machine.cluster.x-k8s.io"
+
+	// PreTerminateDeleteHookAnnotationPrefix annotation specifies the prefix we
+	// search each annotation for during the pre-terminate.delete lifecycle hook
+	// to pause reconciliation of deletion. These hooks will prevent removal of
+	// an instance from an infrastructure provider until all are removed.
+	PreTerminateDeleteHookAnnotationPrefix = "pre-terminate.delete.hook.machine.cluster.x-k8s.io"
 )
 
 // ANCHOR: MachineSpec

controllers/machine_controller.go

@@ -290,6 +290,11 @@ func (r *MachineReconciler) reconcileDelete(ctx context.Context, cluster *cluste
 	}
 
 	if isDeleteNodeAllowed {
+		// pre-drain.delete lifecycle hook
+		// Return early without error, will requeue if/when the hook owner removes the annotation.
+		if annotations.HasWithPrefix(clusterv1.PreDrainDeleteHookAnnotationPrefix, m.ObjectMeta.Annotations) {
+			return ctrl.Result{}, nil
+		}
 		// Drain node before deletion.
 		if _, exists := m.ObjectMeta.Annotations[clusterv1.ExcludeNodeDrainingAnnotation]; !exists {
 			logger.Info("Draining node", "node", m.Status.NodeRef.Name)
@@ -301,6 +306,12 @@ func (r *MachineReconciler) reconcileDelete(ctx context.Context, cluster *cluste
 		}
 	}
 
+	// pre-term.delete lifecycle hook
+	// Return early without error, will requeue if/when the hook owner removes the annotation.
+	if annotations.HasWithPrefix(clusterv1.PreTerminateDeleteHookAnnotationPrefix, m.ObjectMeta.Annotations) {
+		return ctrl.Result{}, nil
+	}
+
 	if ok, err := r.reconcileDeleteExternal(ctx, m); !ok || err != nil {
 		// Return early and don't remove the finalizer if we got an error or
 		// the external reconciliation deletion isn't ready.

docs/proposals/20200602-machine-deletion-phase-hooks.md

@@ -8,8 +8,8 @@ reviewers:
   - "@detiber"
   - "@ncdc"
 creation-date: 2020-06-02
-last-updated: 2020-06-02
-status: implementable
+last-updated: 2020-08-07
+status: implemented
 ---
 
 # Machine Deletion Phase Hooks

util/annotations/paused.go → util/annotations/helpers.go

@@ -17,6 +17,8 @@ limitations under the License.
 package annotations
 
 import (
+	"strings"
+
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	clusterv1 "sigs.k8s.io/cluster-api/api/v1alpha3"
 )
@@ -38,3 +40,12 @@ func HasPausedAnnotation(o metav1.Object) bool {
 	_, ok := annotations[clusterv1.PausedAnnotation]
 	return ok
 }
+
+func HasWithPrefix(prefix string, annotations map[string]string) bool {
+	for key := range annotations {
+		if strings.HasPrefix(key, prefix) {
+			return true
+		}
+	}
+	return false
+}