add component suspension (#418)

* add component suspension

* add suspension option to docs

Author: cbarbian-sap

pkg/component/component.go

@@ -77,6 +77,17 @@ func assertImpersonationConfiguration[T Component](component T) (ImpersonationCo
 	return nil, false
 }
 
+// Check if given component or its spec implements SuspensionConfiguration (and return it).
+func assertSuspensionConfiguration[T Component](component T) (SuspensionConfiguration, bool) {
+	if suspensionConfiguration, ok := Component(component).(SuspensionConfiguration); ok {
+		return suspensionConfiguration, true
+	}
+	if suspensionConfiguration, ok := getSpec(component).(SuspensionConfiguration); ok {
+		return suspensionConfiguration, true
+	}
+	return nil, false
+}
+
 // Check if given component or its spec implements RequeueConfiguration (and return it).
 func assertRequeueConfiguration[T Component](component T) (RequeueConfiguration, bool) {
 	if requeueConfiguration, ok := Component(component).(RequeueConfiguration); ok {
@@ -176,6 +187,11 @@ func (s *ImpersonationSpec) GetImpersonationGroups() []string {
 	return nil
 }
 
+// Implement the SuspensionConfiguration interface.
+func (s *SuspensionSpec) IsSuspended() bool {
+	return s.Suspend
+}
+
 // Implement the RequeueConfiguration interface.
 func (s *RequeueSpec) GetRequeueInterval() time.Duration {
 	if s.RequeueInterval != nil {

pkg/component/reconciler.go

@@ -76,6 +76,7 @@ const (
 	ReadyConditionReasonReady              = "Ready"
 	ReadyConditionReasonError              = "Error"
 	ReadyConditionReasonTimeout            = "Timeout"
+	ReadyConditionReasonSuspended          = "Suspended"
 	ReadyConditionReasonDeletionRetrying   = "DeletionRetrying"
 	ReadyConditionReasonDeletionBlocked    = "DeletionBlocked"
 	ReadyConditionReasonDeletionProcessing = "DeletionProcessing"
@@ -456,6 +457,13 @@ func (r *Reconciler[T]) Reconcile(ctx context.Context, req ctrl.Request) (result
 		return ctrl.Result{RequeueAfter: time.Millisecond}, nil
 	}
 
+	if component.GetDeletionTimestamp().IsZero() {
+		if suspensionConfiguration, ok := assertSuspensionConfiguration(component); ok && suspensionConfiguration.IsSuspended() {
+			status.SetState(StatePending, ReadyConditionReasonSuspended, "Reconciliation is suspended")
+			return ctrl.Result{RequeueAfter: r.backoff.Next(req, ReadyConditionReasonSuspended)}, nil
+		}
+	}
+
 	// resolve references
 	componentDigest, err = resolveReferences(ctx, r.client, r.hookClient, component)
 	if err != nil {

pkg/component/types.go

@@ -63,6 +63,14 @@ type ImpersonationConfiguration interface {
 	GetImpersonationGroups() []string
 }
 
+// The SuspensionConfiguration interface is meant to be implemented by components (or their spec) which offer
+// the ability to suspend reconciliation.
+type SuspensionConfiguration interface {
+	// Whether the reconciliation (apply) or the implementing component is supended. If true the component goes
+	// into Pending state with reason Suspended. Note that deletion is not affected by this suspension.
+	IsSuspended() bool
+}
+
 // The RequeueConfiguration interface is meant to be implemented by components (or their spec) which offer
 // tweaking the requeue interval (by default, it would be 10 minutes).
 type RequeueConfiguration interface {
@@ -170,6 +178,16 @@ var _ ImpersonationConfiguration = &ImpersonationSpec{}
 
 // +kubebuilder:object:generate=true
 
+// SuspensionSpec defines whether the reconciliation (apply) or the implementing component is suspended.
+// Components providing SuspensionConfiguration may include this into their spec.
+type SuspensionSpec struct {
+	Suspend bool `json:"suspend,omitempty"`
+}
+
+var _ SuspensionConfiguration = &SuspensionSpec{}
+
+// +kubebuilder:object:generate=true
+
 // RequeueSpec defines the requeue interval, that is, the interval after which components will be re-reconciled after a successful reconciliation.
 // Components providing RequeueConfiguration may include this into their spec.
 type RequeueSpec struct {

pkg/component/zz_generated.deepcopy.go

@@ -122,8 +122,21 @@ type ImpersonationConfiguration interface {
 
 to use different user/groups for the deployment of dependent objects.
 
-Note that, as mentioned above, the interfaces `PlacementConfiguration`, `ClientConfiguration` and `ImpersonationConfiguration` can be implemented by the component
-itself as well as by its spec type. In the theoretical case that both is the case, the implementation on the component level takes higher precedence.
+Sometimes it is desired to suspend the reconciliation of a component. In offer this, the compoent (or its spec) can implement the interface
+
+```go
+package component
+
+// The SuspensionConfiguration interface is meant to be implemented by components (or their spec) which offer
+// the ability to suspend reconciliation.
+type SuspensionConfiguration interface {
+	// Whether the reconciliation (apply) or the implementing component is supended. If true the component goes
+	// into Pending state with reason Suspended. Note that deletion is not affected by this suspension.
+	IsSuspended() bool
+}
+```
+
+Note that, as mentioned above, the interfaces `PlacementConfiguration`, `ClientConfiguration`, `ImpersonationConfiguration` and `SuspensionConfiguration` can be implemented by the component itself as well as by its spec type. In the theoretical case that both implement it, the component takes higher precedence.
 
 ## The Generator interface