kube-controller之history

发表于
ControllerRevision

ControllerRevision 实现了一个不可变的状态数据快照。客户端负责序列化和反序列化包含其内部状态的对象
一旦成功创建了 ControllerRevision，就不能对其进行更新,但是可以被删除。APIServer会拒绝所有试图修改 Data 字段的请求。
ControllerRevision主要被 DaemonSet 和 StatefulSet 控制器用于更新和回滚。而且这个对象是beta的，在未来可能会发生变化，
客户端不应依赖其稳定性。因此ControllerRevision主要在内部控制器内使用。

源码分析
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// staging/src/k8s.io/api/apps/v1/types.go
type ControllerRevision struct {
	metav1.TypeMeta `json:",inline"`
	// Standard object's metadata.
	metav1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`

	// Data is the serialized representation of the state.
	Data runtime.RawExtension `json:"data,omitempty" protobuf:"bytes,2,opt,name=data"`

	// Revision indicates the revision of the state represented by Data.
	Revision int64 `json:"revision" protobuf:"varint,3,opt,name=revision"`
}

// pkg/controller/history/controller_history.go
func NewControllerRevision(parent metav1.Object,
	parentKind schema.GroupVersionKind,
	templateLabels map[string]string,
	data runtime.RawExtension,
	revision int64,
	collisionCount *int32) (*apps.ControllerRevision, error) {
	labelMap := make(map[string]string)
	for k, v := range templateLabels {
		labelMap[k] = v
	}
	cr := &apps.ControllerRevision{
		ObjectMeta: metav1.ObjectMeta{
			Labels:          labelMap,
            // 设置OwnerReferences
			OwnerReferences: []metav1.OwnerReference{*metav1.NewControllerRef(parent, parentKind)},
		},
		Data:     data,
		Revision: revision,
	}
    // 返回cr.Data的hash
	hash := HashControllerRevision(cr, collisionCount)
    // 设置cr.Name
	cr.Name = ControllerRevisionName(parent.GetName(), hash)
	cr.Labels[ControllerRevisionHashLabel] = hash
	return cr, nil
}

// pkg/controller/history/controller_history.go
func ControllerRevisionName(prefix string, hash string) string {
	if len(prefix) > 223 {
		prefix = prefix[:223]
	}

	return fmt.Sprintf("%s-%s", prefix, hash)
}


type realHistory struct {
	client clientset.Interface
	lister appslisters.ControllerRevisionLister
}

func NewHistory(client clientset.Interface, lister appslisters.ControllerRevisionLister) Interface {
	return &realHistory{client, lister}
}

// 返回ControllerRevision列表
func (rh *realHistory) ListControllerRevisions(parent metav1.Object, selector labels.Selector) ([]*apps.ControllerRevision, error) {
	// List all revisions in the namespace that match the selector
	history, err := rh.lister.ControllerRevisions(parent.GetNamespace()).List(selector)
	if err != nil {
		return nil, err
	}
	var owned []*apps.ControllerRevision
	for i := range history {
		ref := metav1.GetControllerOfNoCopy(history[i])
		if ref == nil ControllerRevisions|| ref.UID == parent.GetUID() {
			owned = append(owned, history[i])
		}

	}
	return owned, err
}

// 创建ControllerRevision
func (rh *realHistory) CreateControllerRevision(parent metav1.Object, revision *apps.ControllerRevision, collisionCount *int32) (*apps.ControllerRevision, error) {
	if collisionCount ControllerRevisions== nil {
		return nil, fmt.Errorf("collisionCount should not be nil")
	}

	// Clone the input
	clone := revision.DeepCopy()

	// Continue to attempt to create the revision updating the name with a new hash on each iteration
	for {
		hash := HashControllerRevision(revision, collisionCount)
		// Update the revisions name
		clone.Name = ControllerRevisionName(parent.GetName(), hash)
		ns := parent.GetNamespace()
		created, err := rh.client.AppsV1().ControllerRevisions(ns).Create(context.TODO(), clone, metav1.CreateOptions{})
		if errors.IsAlreadyExists(err) {
			exists, err := rh.client.AppsV1().ControllerRevisions(ns).Get(context.TODO(), clone.Name, metav1.GetOptions{})
			if err != nil {
				return nil, err
			}
			if bytes.Equal(exists.Data.Raw, clone.Data.Raw) {
				return exists, nil
			}
			*collisionCount++
			continue
		}
		return created, err
	}
}

// 更新ControllerRevision,Data字段不能更新
func (rh *realHistory) UpdateControllerRevision(revision *apps.ControllerRevision, newRevision int64) (*apps.ControllerRevision, error) {
	clone := revision.DeepCopy()
	err := retry.RetryOnConflict(retry.DefaultBackoff, func() error {
		if clone.Revision == newRevision {
			return nil
		}
		clone.Revision = newRevision
		updated, updateErr := rh.client.AppsV1().ControllerRevisions(clone.Namespace).Update(context.TODO(), clone, metav1.UpdateOptions{})
		if updateErr == nil {
			return nil
		}
		if updated != nil {
			clone = updated
		}
		if updated, err := rh.lister.ControllerRevisions(clone.Namespace).Get(clone.Name); err == nil {
			// make a copy so we don't mutate the shared cache
			clone = updated.DeepCopy()
		}
		return updateErr
	})
	return clone, err
}

// 删除ControllerRevision
func (rh *realHistory) DeleteControllerRevision(revision *apps.ControllerRevision) error {
	return rh.client.AppsV1().ControllerRevisions(revision.Namespace).Delete(context.TODO(), revision.Name, metav1.DeleteOptions{})
}


// pkg/controller/statefulset/stateful_set_control.go
func newRevision(set *apps.StatefulSet, revision int64, collisionCount *int32) (*apps.ControllerRevision, error) {
	patch, err := getPatch(set)
	if err != nil {
		return nil, err
	}
	cr, err := history.NewControllerRevision(set,
		controllerKind,
		set.Spec.Template.Labels,
		runtime.RawExtension{Raw: patch},
		revision,
		collisionCount)
	if err != nil {
		return nil, err
	}
	if cr.ObjectMeta.Annotations == nil {
		cr.ObjectMeta.Annotations = make(map[string]string)
	}
	for key, value := range set.Annotations {
		cr.ObjectMeta.Annotations[key] = value
	}
	return cr, nil
}

func (ssc *defaultStatefulSetControl) getStatefulSetRevisions(
	set *apps.StatefulSet,
	revisions []*apps.ControllerRevision) (*apps.ControllerRevision, *apps.ControllerRevision, int32, error) {
	...
	updateRevision, err := newRevision(set, nextRevision(revisions), &collisionCount)
    ...
}
小结

严格来说ControllerRevision history controller并不是一个真正的控制器，只是提供了创建ControlllerRevison和对ControllerRevision操作的一些方法，可以给其它的控制器使用，比如StatefulSet。

REF:
1.staging/src/k8s.io/api/apps/v1/types.go
2.pkg/controller/history/controller_history.go
3.pkg/controller/statefulset/stateful_set_control.go