implement support for APIExportEndpointSlices

On-behalf-of: @SAP [email protected]

Author: xrstf

cmd/api-syncagent/kcp.go

@@ -0,0 +1,293 @@
+/*
+Copyright 2025 The KCP 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 main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"regexp"
+
+	"github.com/kcp-dev/api-syncagent/internal/kcp"
+	"github.com/kcp-dev/logicalcluster/v3"
+
+	kcpdevv1alpha1 "github.com/kcp-dev/kcp/sdk/apis/apis/v1alpha1"
+	kcpdevcore "github.com/kcp-dev/kcp/sdk/apis/core"
+	kcpdevcorev1alpha1 "github.com/kcp-dev/kcp/sdk/apis/core/v1alpha1"
+
+	"k8s.io/apimachinery/pkg/fields"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/client-go/rest"
+	"sigs.k8s.io/controller-runtime/pkg/cache"
+	ctrlruntimeclient "sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/cluster"
+)
+
+// The agent has two potentially different kcp clusters:
+//
+//   endpointCluster - this is where the source of the virtual workspace URLs
+//                     live, i.e. where the APIExport/EndpointSlice.
+//   managedCluster  - this is where the APIExport and APIResourceSchemas
+//                     exist that are meant to be reconciled.
+//
+// The managedCluster always exists, the endpointCluster only if the workspace
+// for the virtual workspace source is different from the managed cluster.
+
+// setupEndpointKcpCluster sets up a plain, non-kcp-aware ctrl-runtime Cluster object
+// that is solvely used to watch whichever object holds the virtual workspace URLs,
+// either the APIExport or the APIExportEndpointSlice.
+func setupEndpointKcpCluster(endpoint *syncEndpoint) (cluster.Cluster, error) {
+	// no need for a dedicated endpoint cluster
+	if endpoint.APIExport.Cluster == endpoint.EndpointSlice.Cluster {
+		return nil, nil
+	}
+
+	scheme := runtime.NewScheme()
+
+	if err := kcpdevv1alpha1.AddToScheme(scheme); err != nil {
+		return nil, fmt.Errorf("failed to register scheme %s: %w", kcpdevv1alpha1.SchemeGroupVersion, err)
+	}
+
+	if err := kcpdevcorev1alpha1.AddToScheme(scheme); err != nil {
+		return nil, fmt.Errorf("failed to register scheme %s: %w", kcpdevcorev1alpha1.SchemeGroupVersion, err)
+	}
+
+	// RBAC in kcp might be very tight and might not allow to list/watch all objects;
+	// restrict the cache's selectors accordingly so we can still make use of caching.
+	byObject := map[ctrlruntimeclient.Object]cache.ByObject{
+		&kcpdevv1alpha1.APIExportEndpointSlice{}: {
+			Field: fields.SelectorFromSet(fields.Set{"metadata.name": endpoint.EndpointSlice.Name}),
+		},
+	}
+
+	return cluster.New(endpoint.EndpointSlice.Config, func(o *cluster.Options) {
+		o.Scheme = scheme
+		o.Cache = cache.Options{
+			Scheme:   scheme,
+			ByObject: byObject,
+		}
+	})
+}
+
+// setupManagedKcpCluster sets up a plain, non-kcp-aware ctrl-runtime Cluster object
+// that is solvely used to manage the APIExport and APIResourceSchemas.
+func setupManagedKcpCluster(endpoint *syncEndpoint) (cluster.Cluster, error) {
+	scheme := runtime.NewScheme()
+
+	if err := kcpdevv1alpha1.AddToScheme(scheme); err != nil {
+		return nil, fmt.Errorf("failed to register scheme %s: %w", kcpdevv1alpha1.SchemeGroupVersion, err)
+	}
+
+	if err := kcpdevcorev1alpha1.AddToScheme(scheme); err != nil {
+		return nil, fmt.Errorf("failed to register scheme %s: %w", kcpdevcorev1alpha1.SchemeGroupVersion, err)
+	}
+
+	// RBAC in kcp might be very tight and might not allow to list/watch all objects;
+	// restrict the cache's selectors accordingly so we can still make use of caching.
+	byObject := map[ctrlruntimeclient.Object]cache.ByObject{
+		&kcpdevv1alpha1.APIExport{}: {
+			Field: fields.SelectorFromSet(fields.Set{"metadata.name": endpoint.APIExport.Name}),
+		},
+	}
+
+	return cluster.New(endpoint.APIExport.Config, func(o *cluster.Options) {
+		o.Scheme = scheme
+		o.Cache = cache.Options{
+			Scheme:   scheme,
+			ByObject: byObject,
+		}
+	})
+}
+
+type qualifiedCluster struct {
+	Cluster logicalcluster.Name
+	Path    logicalcluster.Path
+	Config  *rest.Config
+}
+
+type qualifiedAPIExport struct {
+	*kcpdevv1alpha1.APIExport
+	qualifiedCluster
+}
+
+type qualifiedAPIExportEndpointSlice struct {
+	*kcpdevv1alpha1.APIExportEndpointSlice
+	qualifiedCluster
+}
+
+type syncEndpoint struct {
+	APIExport     qualifiedAPIExport
+	EndpointSlice *qualifiedAPIExportEndpointSlice
+}
+
+// resolveSyncEndpoint takes the user provided (usually via CLI flags) APIExportEndpointSliceRef and
+// APIExportRef and resolves, returning a consistent SyncEndpoint. The initialRestConfig must point
+// to the cluster where either of the two objects reside (i.e. if the APIExportRef is given, it
+// must point to the cluster where the APIExport lives, and vice versa for the endpoint slice;
+// however the endpoint slice references an APIExport in potentially another cluster, and for this
+// case the initialRestConfig will be rewritten accordingly).
+func resolveSyncEndpoint(ctx context.Context, initialRestConfig *rest.Config, endpointSliceRef string, apiExportRef string) (*syncEndpoint, error) {
+	// construct temporary, uncached client
+	scheme := runtime.NewScheme()
+	if err := kcpdevcorev1alpha1.AddToScheme(scheme); err != nil {
+		return nil, fmt.Errorf("failed to register scheme %s: %w", kcpdevcorev1alpha1.SchemeGroupVersion, err)
+	}
+	if err := kcpdevv1alpha1.AddToScheme(scheme); err != nil {
+		return nil, fmt.Errorf("failed to register scheme %s: %w", kcpdevv1alpha1.SchemeGroupVersion, err)
+	}
+
+	clientOpts := ctrlruntimeclient.Options{Scheme: scheme}
+	client, err := ctrlruntimeclient.New(initialRestConfig, clientOpts)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create service reader: %w", err)
+	}
+
+	se := &syncEndpoint{}
+
+	// When an endpoint ref is given, both the APIExportEndpointSlice and the APIExport must exist.
+	if endpointSliceRef != "" {
+		endpointSlice, err := resolveAPIExportEndpointSlice(ctx, client, endpointSliceRef)
+		if err != nil {
+			return nil, fmt.Errorf("failed to resolve APIExportEndpointSlice: %w", err)
+		}
+		endpointSlice.Config = initialRestConfig
+
+		// find the APIExport referenced not by the user (can't: both ref parameters to this function
+		// are mutually exclusive), but in the APIExportEndpointSlice.
+		restConfig, err := retargetRestConfig(initialRestConfig, endpointSlice.Spec.APIExport.Path)
+		if err != nil {
+			return nil, fmt.Errorf("failed to re-target the given kubeconfig to cluster %q: %w", endpointSlice.Spec.APIExport.Path, err)
+		}
+
+		client, err := ctrlruntimeclient.New(restConfig, clientOpts)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create service reader: %w", err)
+		}
+
+		apiExport, err := resolveAPIExport(ctx, client, endpointSlice.Spec.APIExport.Name)
+		if err != nil {
+			return nil, fmt.Errorf("failed to resolve APIExport: %w", err)
+		}
+		apiExport.Config = restConfig
+
+		se.APIExport = apiExport
+		se.EndpointSlice = &endpointSlice
+	} else { // if an export ref is given, the endpoint slice is optional (for compat with kcp <0.28)
+		apiExport, err := resolveAPIExport(ctx, client, apiExportRef)
+		if err != nil {
+			return nil, fmt.Errorf("failed to resolve APIExport: %w", err)
+		}
+		apiExport.Config = initialRestConfig
+
+		se.APIExport = apiExport
+
+		// try to find an endpoint slice in the same workspace with the same name as the APIExport
+		endpointSlice, err := resolveAPIExportEndpointSlice(ctx, client, apiExportRef)
+		if ctrlruntimeclient.IgnoreNotFound(err) != nil {
+			return nil, fmt.Errorf("failed to resolve APIExportEndpointSlice: %w", err)
+		} else if err == nil {
+			apiExport.Config = initialRestConfig
+			se.EndpointSlice = &endpointSlice
+		}
+	}
+
+	return se, nil
+}
+
+func resolveAPIExportEndpointSlice(ctx context.Context, client ctrlruntimeclient.Client, ref string) (qualifiedAPIExportEndpointSlice, error) {
+	endpointSlice := &kcpdevv1alpha1.APIExportEndpointSlice{}
+	key := types.NamespacedName{Name: ref}
+	if err := client.Get(ctx, key, endpointSlice); err != nil {
+		return qualifiedAPIExportEndpointSlice{}, fmt.Errorf("failed to get APIExportEndpointSlice %q: %w", ref, err)
+	}
+
+	lcName, lcPath, err := resolveCurrentCluster(ctx, client)
+	if err != nil {
+		return qualifiedAPIExportEndpointSlice{}, fmt.Errorf("failed to resolve APIExportEndpointSlice cluster: %w", err)
+	}
+
+	return qualifiedAPIExportEndpointSlice{
+		APIExportEndpointSlice: endpointSlice,
+		qualifiedCluster: qualifiedCluster{
+			Cluster: lcName,
+			Path:    lcPath,
+		},
+	}, nil
+}
+
+func resolveAPIExport(ctx context.Context, client ctrlruntimeclient.Client, ref string) (qualifiedAPIExport, error) {
+	apiExport := &kcpdevv1alpha1.APIExport{}
+	key := types.NamespacedName{Name: ref}
+	if err := client.Get(ctx, key, apiExport); err != nil {
+		return qualifiedAPIExport{}, fmt.Errorf("failed to get APIExport %q: %w", ref, err)
+	}
+
+	lcName, lcPath, err := resolveCurrentCluster(ctx, client)
+	if err != nil {
+		return qualifiedAPIExport{}, fmt.Errorf("failed to resolve APIExport cluster: %w", err)
+	}
+
+	return qualifiedAPIExport{
+		APIExport: apiExport,
+		qualifiedCluster: qualifiedCluster{
+			Cluster: lcName,
+			Path:    lcPath,
+		},
+	}, nil
+}
+
+func resolveCurrentCluster(ctx context.Context, client ctrlruntimeclient.Client) (logicalcluster.Name, logicalcluster.Path, error) {
+	lc := &kcpdevcorev1alpha1.LogicalCluster{}
+	if err := client.Get(ctx, types.NamespacedName{Name: kcp.IdentityClusterName}, lc); err != nil {
+		return "", logicalcluster.None, fmt.Errorf("failed to resolve current workspace: %w", err)
+	}
+
+	lcName := logicalcluster.From(lc)
+	lcPath := logicalcluster.NewPath(lc.Annotations[kcpdevcore.LogicalClusterPathAnnotationKey])
+
+	return lcName, lcPath, nil
+}
+
+var clusterFinder = regexp.MustCompile(`/clusters/([^/]+)`)
+
+func retargetRestConfig(cfg *rest.Config, destination string) (*rest.Config, error) {
+	// no change desired (use current cluster implicitly)
+	if destination == "" {
+		return cfg, nil
+	}
+
+	matches := clusterFinder.FindAllStringSubmatch(cfg.Host, -1)
+	if len(matches) == 0 {
+		return nil, errors.New("URL must point to a cluster/workspace")
+	}
+	if len(matches) > 1 {
+		return nil, errors.New("invalid URL: URL contains more than one cluster path")
+	}
+
+	current := matches[0][1]
+	if current == destination {
+		return cfg, nil
+	}
+
+	newCluster := fmt.Sprintf("/clusters/%s", destination)
+
+	newConfig := rest.CopyConfig(cfg)
+	newConfig.Host = clusterFinder.ReplaceAllString(cfg.Host, newCluster)
+
+	return newConfig, nil
+}