Merge pull request #32 from embik/add-error

✨ Add `multicluster.ErrClusterNotFound` for providers

Author: k8s-ci-robot

pkg/builder/forked_controller.go

@@ -73,6 +73,8 @@ type TypedBuilder[request mcreconcile.ClusterAware[request]] struct {
 	ctrlOptions      controller.TypedOptions[request]
 	name             string
 	newController    func(name string, mgr mcmanager.Manager, options controller.TypedOptions[request]) (mccontroller.TypedController[request], error)
+
+	enableClusterNotFoundWrapper *bool
 }
 
 // ControllerManagedBy returns a new controller builder that will be started by the provided Manager.
@@ -260,6 +262,15 @@ func (blder *TypedBuilder[request]) WithLogConstructor(logConstructor func(*requ
 	return blder
 }
 
+// WithClusterNotFoundWrapper enables or disables a reconciler that is wrapped around the original reconciler
+// added to this builder. [reconcile.ClusterNotFoundWrapper] will stop reconcile results with [multicluster.ErrClusterNotFound]
+// as error from requeuing by marking them as successfully reconciled. This wrapper is enabled by default
+// and can be disabled with this builder method by setting it to false.
+func (blder *TypedBuilder[request]) WithClusterNotFoundWrapper(enabled bool) *TypedBuilder[request] {
+	blder.enableClusterNotFoundWrapper = ptr.To(enabled)
+	return blder
+}
+
 // Named sets the name of the controller to the given name. The name shows up
 // in metrics, among other things, and thus should be a prometheus compatible name
 // (underscores and alphanumeric characters only).
@@ -450,6 +461,11 @@ func (blder *TypedBuilder[request]) doController(r reconcile.TypedReconciler[req
 		ctrlOptions.Reconciler = r
 	}
 
+	// the ClusterNotFound wrapper is enabled by default, but can be disabled with WithClusterNotFoundWrapper(false).
+	if ptr.Deref(blder.enableClusterNotFoundWrapper, true) {
+		ctrlOptions.Reconciler = mcreconcile.NewClusterNotFoundWrapper(ctrlOptions.Reconciler)
+	}
+
 	// Retrieve the GVK from the object we're reconciling
 	// to pre-populate logger information, and to optionally generate a default name.
 	var gvk schema.GroupVersionKind

pkg/multicluster/errors.go

@@ -0,0 +1,29 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package multicluster
+
+import (
+	"errors"
+)
+
+var (
+	// ErrClusterNotFound can be returned by provider implementations if the cluster requested
+	// doesn't exist and cannot be constructed.
+	ErrClusterNotFound = errClusterNotFound()
+)
+
+func errClusterNotFound() error { return errors.New("cluster not found") }

pkg/multicluster/multicluster.go

@@ -54,7 +54,7 @@ type Provider interface {
 	// Get returns a cluster for the given identifying cluster name. Get
 	// returns an existing cluster if it has been created before.
 	// If no cluster is known to the provider under the given cluster name,
-	// an error should be returned.
+	// ErrClusterNotFound should be returned.
 	Get(ctx context.Context, clusterName string) (cluster.Cluster, error)
 
 	// IndexField indexes the given object by the given field on all engaged

pkg/reconcile/wrapper.go

@@ -0,0 +1,54 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package reconcile
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"sigs.k8s.io/controller-runtime/pkg/reconcile"
+
+	"sigs.k8s.io/multicluster-runtime/pkg/multicluster"
+)
+
+// ClusterNotFoundWrapper wraps an existing [reconcile.TypedReconciler] and ignores [multicluster.ErrClusterNotFound] errors.
+type ClusterNotFoundWrapper[request comparable] struct {
+	wrapped reconcile.TypedReconciler[request]
+}
+
+// NewClusterNotFoundWrapper creates a new [ClusterNotFoundWrapper].
+func NewClusterNotFoundWrapper[request comparable](w reconcile.TypedReconciler[request]) reconcile.TypedReconciler[request] {
+	return &ClusterNotFoundWrapper[request]{wrapped: w}
+}
+
+// Reconcile implements [reconcile.TypedReconciler].
+func (r *ClusterNotFoundWrapper[request]) Reconcile(ctx context.Context, req request) (reconcile.Result, error) {
+	res, err := r.wrapped.Reconcile(ctx, req)
+
+	// if the error returned by the reconciler is ErrClusterNotFound, we return without requeuing.
+	if errors.Is(err, multicluster.ErrClusterNotFound) {
+		return reconcile.Result{}, nil
+	}
+
+	return res, err
+}
+
+// String returns a string representation of the wrapped reconciler.
+func (r *ClusterNotFoundWrapper[request]) String() string {
+	return fmt.Sprintf("%v", r.wrapped)
+}

providers/cluster-api/provider.go

@@ -123,7 +123,7 @@ func (p *Provider) Get(_ context.Context, clusterName string) (cluster.Cluster,
 		return cl, nil
 	}
 
-	return nil, fmt.Errorf("cluster %s not found", clusterName)
+	return nil, multicluster.ErrClusterNotFound
 }
 
 // Run starts the provider and blocks.

providers/kind/provider.go

@@ -73,7 +73,7 @@ func (p *Provider) Get(ctx context.Context, clusterName string) (cluster.Cluster
 		return cl, nil
 	}
 
-	return nil, fmt.Errorf("cluster %s not found", clusterName)
+	return nil, multicluster.ErrClusterNotFound
 }
 
 // Run starts the provider and blocks.

providers/namespace/provider.go

@@ -134,7 +134,8 @@ func (p *Provider) Get(_ context.Context, clusterName string) (cluster.Cluster,
 	if cl, ok := p.clusters[clusterName]; ok {
 		return cl, nil
 	}
-	return nil, fmt.Errorf("cluster %s not found", clusterName)
+
+	return nil, multicluster.ErrClusterNotFound
 }
 
 // IndexField indexes a field on all clusters.

providers/nop/provider.go

@@ -18,7 +18,6 @@ package namespace
 
 import (
 	"context"
-	"fmt"
 
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/cluster"
@@ -45,7 +44,7 @@ func (p *Provider) Run(ctx context.Context, _ mcmanager.Manager) error {
 
 // Get returns an error for any cluster name.
 func (p *Provider) Get(_ context.Context, clusterName string) (cluster.Cluster, error) {
-	return nil, fmt.Errorf("cluster %s not found", clusterName)
+	return nil, multicluster.ErrClusterNotFound
 }
 
 // IndexField does nothing.

providers/single/provider.go

@@ -18,7 +18,6 @@ package namespace
 
 import (
 	"context"
-	"fmt"
 
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/cluster"
@@ -55,7 +54,7 @@ func (p *Provider) Get(_ context.Context, clusterName string) (cluster.Cluster,
 	if clusterName == p.name {
 		return p.cl, nil
 	}
-	return nil, fmt.Errorf("cluster %s not found", clusterName)
+	return nil, multicluster.ErrClusterNotFound
 }
 
 // IndexField calls IndexField on the single cluster.