csiaddonsNode: Recreate CSIAddonsNode with active sidecar(s)

This patch adds a watcher to csi-addons sidecar which is
responsible for re-creating CSIAddonNode(s) in case they
are deleted manually.

Signed-off-by: Niraj Yadav <niryadav@redhat.com>

Author: black-dragon74

sidecar/internal/csiaddonsnode/csiaddonsnode.go

@@ -30,8 +30,11 @@ import (
 
 	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/apimachinery/pkg/watch"
+	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/rest"
 	"k8s.io/klog/v2"
@@ -45,6 +48,11 @@ const (
 	nodeCreationRetry = time.Minute * 5
 	// nodeCreationTimeout is the time after which the context for node creation request is cancelled.
 	nodeCreationTimeout = time.Minute * 3
+
+	// watcherRetryCount is the number of times a watcher creation would be retried for.
+	watcherRetryCount = 10
+	// watcherRetryDelay is the amount of time to wait before trying recreation of a watcher.
+	watcherRetryDelay = time.Second * 5
 )
 
 var (
@@ -84,16 +92,10 @@ type Manager struct {
 	PodUID string
 }
 
-// Deploy creates CSIAddonsNode custom resource with all required information.
-// When information to create the CSIAddonsNode is missing, an error will be
-// returned immediately. If creating the CSIAddonsNode in the Kubernetes
-// cluster fails (missing CRD, RBAC limitations, ...), an error will be logged,
-// and creation will be retried.
-func (mgr *Manager) Deploy() error {
-	object, err := mgr.getCSIAddonsNode()
-	if err != nil {
-		return fmt.Errorf("failed to get csiaddonsNode object: %w", err)
-	}
+// deploy creates CSIAddonsNode custom resource with all required information.
+// If creating the CSIAddonsNode in the Kubernetes cluster fails (missing CRD, RBAC limitations, ...)
+// an error will be logged and creation will be retried.
+func (mgr *Manager) deploy(object *csiaddonsv1alpha1.CSIAddonsNode) error {
 
 	// loop until the CSIAddonsNode has been created
 	return wait.PollUntilContextTimeout(context.TODO(), nodeCreationRetry, nodeCreationTimeout, true, func(ctx context.Context) (bool, error) {
@@ -133,6 +135,10 @@ func (mgr *Manager) newCSIAddonsNode(node *csiaddonsv1alpha1.CSIAddonsNode) erro
 		},
 	}
 	_, err = controllerutil.CreateOrUpdate(ctx, cli, csiaddonNode, func() error {
+		if !csiaddonNode.DeletionTimestamp.IsZero() {
+			return errors.New("csiaddonnode is being deleted")
+		}
+
 		// update the resourceVersion
 		resourceVersion := csiaddonNode.ResourceVersion
 		if resourceVersion != "" {
@@ -275,3 +281,80 @@ func generateName(nodeID, namespace, ownerKind, ownerName string) (string, error
 
 	return base, nil
 }
+
+// watchCSIAddonsNode starts a watcher for a specific CSIAddonsNode resource identified by its name.
+// If a CSIAddonsNode is deleted, it logs a warning and attempts to recreate it using mgr.deploy()
+func (mgr *Manager) watchCSIAddonsNode(node *csiaddonsv1alpha1.CSIAddonsNode) error {
+	// Call deploy on start, this takes care of the cases where
+	// a watcher might exit due to an error while trying to
+	// recreate CSIAddonsNode in the cluster
+	err := mgr.deploy(node)
+	if err != nil {
+		klog.Fatalf("Failed to create csiaddonsnode: %v", err)
+	}
+
+	klog.Infof("Starting watcher for CSIAddonsNode: %s", node.Name)
+
+	dynamicClient, err := dynamic.NewForConfig(mgr.Config)
+	if err != nil {
+		return fmt.Errorf("failed to create dynamic client: %w", err)
+	}
+
+	gvr := schema.GroupVersionResource{
+		Group:    csiaddonsv1alpha1.GroupVersion.Group,
+		Version:  csiaddonsv1alpha1.GroupVersion.Version,
+		Resource: "csiaddonsnodes",
+	}
+
+	watcher, err := dynamicClient.Resource(gvr).Namespace(node.Namespace).Watch(context.Background(), v1.ListOptions{
+		FieldSelector: fmt.Sprintf("metadata.name=%s", node.Name),
+	})
+	if err != nil {
+		return fmt.Errorf("failed to watch CSIAddonsNode objects: %w", err)
+	}
+	defer watcher.Stop()
+
+	for event := range watcher.ResultChan() {
+		switch event.Type {
+		case watch.Deleted:
+			klog.Infof("WARNING: An active CSIAddonsNode: %s was deleted, it will be recreated", node.Name)
+
+			err := mgr.deploy(node)
+			if err != nil {
+				return fmt.Errorf("failed to recreate CSIAddonsNode: %w", err)
+			}
+			klog.Infof("CSIAddonsNode: %s recreated", node.Name)
+		}
+	}
+
+	// The channel was closed by the API server without any errors
+	// Simply log it here and return, the dispatcher is responsible
+	// for restarting the watcher
+	klog.Infof("Watcher for %s exited gracefully, will be restarted soon", node.Name)
+
+	return nil
+}
+
+// DispatchWatcher starts a watcher for the CSIAddonsNode and retries
+// if the watcher exits due to an error. It will retry up to a maximum number of
+// attempts defined by watcherRetryCount before returning an error.
+func (mgr *Manager) DispatchWatcher() error {
+	retryCount := 0
+	node, err := mgr.getCSIAddonsNode()
+	if err != nil {
+		return errors.New("failed to get CSIAddonsNode object")
+	}
+
+	for retryCount < int(watcherRetryCount) {
+		err := mgr.watchCSIAddonsNode(node)
+		if err != nil {
+			klog.Errorf("Watcher for %s exited, retrying (%d/%d), error: %v", node.Name, retryCount+1, watcherRetryCount, err)
+
+			retryCount++
+			time.Sleep(watcherRetryDelay * time.Duration(retryCount))
+		} else {
+			retryCount = 0
+		}
+	}
+	return fmt.Errorf("watcher for %s reached max retries, giving up", node.Name)
+}

sidecar/main.go

@@ -118,10 +118,15 @@ func main() {
 		PodNamespace: *podNamespace,
 		PodUID:       *podUID,
 	}
-	err = nodeMgr.Deploy()
-	if err != nil {
-		klog.Fatalf("Failed to create csiaddonsnode: %v", err)
-	}
+
+	// Start the watcher, it is responsible for fetching
+	// CSIAddonNode object and then calling deploy()
+	go func() {
+		err := nodeMgr.DispatchWatcher()
+		if err != nil {
+			klog.Fatalf("failed to start watcher due to error: %v", err)
+		}
+	}()
 
 	sidecarServer := server.NewSidecarServer(*controllerIP, *controllerPort, kubeClient, *enableAuthChecks)
 	sidecarServer.RegisterService(service.NewIdentityServer(csiClient.GetGRPCClient()))