✨Wait until APIExport virtual workspace URLs are ready

main.go

@@ -22,30 +22,35 @@ import (
 	"fmt"
 	"os"
 
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/runtime"
-	"k8s.io/apimachinery/pkg/types"
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/apimachinery/pkg/watch"
 	"k8s.io/client-go/discovery"
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
 	"k8s.io/client-go/rest"
+	retrywatch "k8s.io/client-go/tools/watch"
 	"k8s.io/klog/v2"
-	"sigs.k8s.io/controller-runtime/pkg/client"
 
 	// Import all Kubernetes client auth plugins (e.g. Azure, GCP, OIDC, etc.)
 	// to ensure that exec-entrypoint and run can make use of them.
 	_ "k8s.io/client-go/plugin/pkg/client/auth"
+
 	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/healthz"
 	"sigs.k8s.io/controller-runtime/pkg/kcp"
 	"sigs.k8s.io/controller-runtime/pkg/log/zap"
 
-	datav1alpha1 "github.com/kcp-dev/controller-runtime-example/api/v1alpha1"
+	apisv1alpha1 "github.com/kcp-dev/kcp/pkg/apis/apis/v1alpha1"
+	"github.com/kcp-dev/kcp/pkg/apis/third_party/conditions/util/conditions"
 
 	// +kubebuilder:scaffold:imports
 
+	datav1alpha1 "github.com/kcp-dev/controller-runtime-example/api/v1alpha1"
 	"github.com/kcp-dev/controller-runtime-example/controllers"
-
-	apisv1alpha1 "github.com/kcp-dev/kcp/pkg/apis/apis/v1alpha1"
 )
 
 var (
@@ -67,7 +72,7 @@ func main() {
 	var enableLeaderElection bool
 	var probeAddr string
 	var apiExportName string
-	flag.StringVar(&apiExportName, "api-export-name", "", "The name of the APIExport.")
+	flag.StringVar(&apiExportName, "api-export-name", "data.my.domain", "The name of the APIExport.")
 	flag.StringVar(&metricsAddr, "metrics-bind-address", ":8080", "The address the metric endpoint binds to.")
 	flag.StringVar(&probeAddr, "health-probe-bind-address", ":8081", "The address the probe endpoint binds to.")
 	flag.BoolVar(&enableLeaderElection, "leader-elect", false,
@@ -161,48 +166,59 @@ func main() {
 // +kubebuilder:rbac:groups="apis.kcp.dev",resources=apiexports,verbs=get;list;watch
 
 // restConfigForAPIExport returns a *rest.Config properly configured to communicate with the endpoint for the
-// APIExport's virtual workspace.
+// APIExport's virtual workspace. It blocks until the controller APIExport VirtualWorkspaceURLsReady condition
+// becomes truthy, which happens when the APIExport is bound for the first time.
 func restConfigForAPIExport(ctx context.Context, cfg *rest.Config, apiExportName string) (*rest.Config, error) {
-	scheme := runtime.NewScheme()
-	if err := apisv1alpha1.AddToScheme(scheme); err != nil {
-		return nil, fmt.Errorf("error adding apis.kcp.dev/v1alpha1 to scheme: %w", err)
-	}
-
-	apiExportClient, err := client.New(cfg, client.Options{Scheme: scheme})
+	apiExportClient, err := client.NewWithWatch(cfg, client.Options{Scheme: scheme})
 	if err != nil {
 		return nil, fmt.Errorf("error creating APIExport client: %w", err)
 	}
 
-	var apiExport apisv1alpha1.APIExport
-
-	if apiExportName != "" {
-		if err := apiExportClient.Get(ctx, types.NamespacedName{Name: apiExportName}, &apiExport); err != nil {
-			return nil, fmt.Errorf("error getting APIExport %q: %w", apiExportName, err)
-		}
-	} else {
-		setupLog.Info("api-export-name is empty - listing")
-		exports := &apisv1alpha1.APIExportList{}
-		if err := apiExportClient.List(ctx, exports); err != nil {
-			return nil, fmt.Errorf("error listing APIExports: %w", err)
-		}
-		if len(exports.Items) == 0 {
-			return nil, fmt.Errorf("no APIExport found")
-		}
-		if len(exports.Items) > 1 {
-			return nil, fmt.Errorf("more than one APIExport found")
-		}
-		apiExport = exports.Items[0]
+	list := &apisv1alpha1.APIExportList{}
+	selector := fields.OneTermEqualSelector("metadata.name", apiExportName)
+	err = apiExportClient.List(ctx, list, client.MatchingFieldsSelector{Selector: selector})
+	if err != nil {
+		return nil, fmt.Errorf("error watching for APIExport: %w", err)
 	}
-
-	if len(apiExport.Status.VirtualWorkspaces) < 1 {
-		return nil, fmt.Errorf("APIExport %q status.virtualWorkspaces is empty", apiExportName)
+	if len(list.Items) > 0 && isAPIExportReady(&list.Items[0]) {
+		cfg = rest.CopyConfig(cfg)
+		// TODO: sharding support
+		cfg.Host = list.Items[0].Status.VirtualWorkspaces[0].URL
+		return cfg, nil
 	}
 
-	cfg = rest.CopyConfig(cfg)
-	// TODO(ncdc): sharding support
-	cfg.Host = apiExport.Status.VirtualWorkspaces[0].URL
+	setupLog.Info("Watching for APIExport to become ready", "name", apiExportName)
 
-	return cfg, nil
+	rw, err := retrywatch.NewRetryWatcher(list.ResourceVersion, watcher(apiExportClient.Watch).FilteredBy(selector))
+	if err != nil {
+		return nil, fmt.Errorf("error creating retry watcher for APIExport: %w", err)
+	}
+	defer rw.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case e := <-rw.ResultChan():
+			switch e.Type {
+			case watch.Error:
+				return nil, fmt.Errorf("error watching for APIExport: %w", apierrors.FromObject(e.Object))
+
+			case watch.Added, watch.Modified:
+				apiExport, ok := e.Object.(*apisv1alpha1.APIExport)
+				if !ok {
+					return nil, fmt.Errorf("unexpected event object: %v", e.Object)
+				}
+				if !isAPIExportReady(apiExport) {
+					continue
+				}
+				cfg = rest.CopyConfig(cfg)
+				// TODO: sharding support
+				cfg.Host = apiExport.Status.VirtualWorkspaces[0].URL
+				return cfg, nil
+			}
+		}
+	}
 }
 
 func kcpAPIsGroupPresent(restConfig *rest.Config) bool {
@@ -228,3 +244,29 @@ func kcpAPIsGroupPresent(restConfig *rest.Config) bool {
 	}
 	return false
 }
+
+func isAPIExportReady(apiExport *apisv1alpha1.APIExport) bool {
+	if !conditions.IsTrue(apiExport, apisv1alpha1.APIExportVirtualWorkspaceURLsReady) {
+		setupLog.Info("APIExport virtual workspace URLs are not ready", "APIExport", apiExport.Name)
+		return false
+	}
+
+	if len(apiExport.Status.VirtualWorkspaces) == 0 {
+		setupLog.Info("APIExport does not have any virtual workspace URLs", "APIExport", apiExport.Name)
+		return false
+	}
+
+	return true
+}
+
+type watcher func(ctx context.Context, obj client.ObjectList, opts ...client.ListOption) (watch.Interface, error)
+
+func (w watcher) Watch(options metav1.ListOptions) (watch.Interface, error) {
+	return w(context.TODO(), &apisv1alpha1.APIExportList{}, &client.ListOptions{Raw: &options})
+}
+
+func (w watcher) FilteredBy(selector fields.Selector) watcher {
+	return func(ctx context.Context, obj client.ObjectList, opts ...client.ListOption) (watch.Interface, error) {
+		return w(ctx, obj, append(opts, client.MatchingFieldsSelector{Selector: selector})...)
+	}
+}