syncer: add rolling update feature code annotation radondb#165

cluster/syncer/statefulset.go

@@ -97,6 +97,7 @@ func (s *StatefulSetSyncer) ObjectOwner() runtime.Object { return s.Unwrap() }
 func (s *StatefulSetSyncer) GetOwner() runtime.Object { return s.Unwrap() }
 
 // Sync persists data into the external store.
+// it's called by cluster controller, when return error, retry Reconcile(),when return nil, Exit this cycle
 // See https://github.com/presslabs/controller-util/blob/master/syncer/object.go#L68
 func (s *StatefulSetSyncer) Sync(ctx context.Context) (syncer.SyncResult, error) {
 	var err error
@@ -105,14 +106,19 @@ func (s *StatefulSetSyncer) Sync(ctx context.Context) (syncer.SyncResult, error)
 
 	result.Operation, err = s.createOrUpdate(ctx)
 
+	//get namespace
 	key := client.ObjectKeyFromObject(s.sfs)
+	//get groupVersionKind
 	gvk, gvkErr := apiutil.GVKForObject(s.sfs, s.cli.Scheme())
 	if gvkErr != nil {
 		kind = fmt.Sprintf("%T", s.sfs)
 	} else {
 		kind = gvk.String()
 	}
-
+	// print log
+	// Info: owner is deleted or ignored error
+	// Waring: other errors
+	// Normal: no error
 	switch {
 	case errors.Is(err, syncer.ErrOwnerDeleted):
 		log.Info(string(result.Operation), "key", key, "kind", kind, "error", err)
@@ -136,6 +142,7 @@ func (s *StatefulSetSyncer) Sync(ctx context.Context) (syncer.SyncResult, error)
 // see https://pkg.go.dev/sigs.k8s.io/[email protected]/pkg/controller/controllerutil?utm_source=gopls#CreateOrUpdate
 func (s *StatefulSetSyncer) createOrUpdate(ctx context.Context) (controllerutil.OperationResult, error) {
 	var err error
+	// check if sfs exist
 	if err = s.cli.Get(ctx, client.ObjectKeyFromObject(s.sfs), s.sfs); err != nil {
 		if !k8serrors.IsNotFound(err) {
 			return controllerutil.OperationResultNone, err
@@ -151,28 +158,28 @@ func (s *StatefulSetSyncer) createOrUpdate(ctx context.Context) (controllerutil.
 			return controllerutil.OperationResultCreated, nil
 		}
 	}
-
+	// deep copy the old sfs from StatefulSetSyncer
 	existing := s.sfs.DeepCopyObject()
+	// Sync data from cluster.spec to sfs
 	if err = s.mutate(); err != nil {
 		return controllerutil.OperationResultNone, err
 	}
-
+	// check if sfs changed
 	if equality.Semantic.DeepEqual(existing, s.sfs) {
 		return controllerutil.OperationResultNone, nil
 	}
-
+	// if changed, update sfs
 	if err := s.cli.Update(ctx, s.sfs); err != nil {
 		return controllerutil.OperationResultNone, err
 	}
-
+	// update every pods of sfs
 	if err := s.updatePod(ctx); err != nil {
 		return controllerutil.OperationResultNone, err
 	}
-
+	// update pvc
 	if err := s.updatePVC(ctx); err != nil {
 		return controllerutil.OperationResultNone, err
 	}
-
 	return controllerutil.OperationResultUpdated, nil
 }
 
@@ -199,7 +206,7 @@ func (s *StatefulSetSyncer) updatePod(ctx context.Context) error {
 	); err != nil {
 		return err
 	}
-
+	//update follower nodes first
 	var leaderPod corev1.Pod
 	var followerPods []corev1.Pod
 	for _, pod := range pods.Items {
@@ -438,6 +445,7 @@ func (s *StatefulSetSyncer) updatePVC(ctx context.Context) error {
 }
 
 func (s *StatefulSetSyncer) applyNWait(ctx context.Context, pod *corev1.Pod) error {
+	//check version, if not latest, delete node
 	if pod.ObjectMeta.Labels["controller-revision-hash"] == s.sfs.Status.UpdateRevision {
 		log.Info("pod is already updated", "pod name", pod.Name)
 	} else {