Wait for kube api during init (#440)

* kubernetes: wait for KubeAPI to be reachable

bootstrapper/internal/kubernetes/kubeWaiter/waiter.go

@@ -0,0 +1,47 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package kubewaiter
+
+import (
+	"context"
+	"time"
+
+	corev1 "k8s.io/api/core/v1"
+
+	"github.com/edgelesssys/constellation/v2/internal/retry"
+)
+
+// KubernetesClient is an interface for the Kubernetes client.
+// It is used to check if the Kubernetes API is available.
+type KubernetesClient interface {
+	ListAllNamespaces(ctx context.Context) (*corev1.NamespaceList, error)
+}
+
+// CloudKubeAPIWaiter waits for the Kubernetes API to be available.
+type CloudKubeAPIWaiter struct{}
+
+// Wait waits for the Kubernetes API to be available.
+// Note that the kubernetesClient must have the kubeconfig already set.
+func (w *CloudKubeAPIWaiter) Wait(ctx context.Context, kubernetesClient KubernetesClient) error {
+	funcAlwaysRetriable := func(err error) bool { return true }
+
+	doer := &kubeDoer{kubeClient: kubernetesClient}
+	retrier := retry.NewIntervalRetrier(doer, 5*time.Second, funcAlwaysRetriable)
+	if err := retrier.Do(ctx); err != nil {
+		return doer.Do(context.Background())
+	}
+	return nil
+}
+
+type kubeDoer struct {
+	kubeClient KubernetesClient
+}
+
+func (d *kubeDoer) Do(ctx context.Context) error {
+	_, err := d.kubeClient.ListAllNamespaces(ctx)
+	return err
+}