k8s client-go源码分析 informer源码分析(5)-Controller&Processor源码分析

client-go之Controller&Processor源码分析

1.controller与Processor概述

Controller

Controller从DeltaFIFO中pop Deltas出来处理,根据对象的变化更新Indexer本地缓存,并通知Processor相关对象有变化事件发生。

Processor

Processor根据Controller的通知,即根据对象的变化事件类型,调用相应的ResourceEventHandler来处理对象的变化。

先通过一张informer概要架构图看一下Controller&Processor所处位置与概要功能。

《k8s client-go源码分析 informer源码分析(5)-Controller&Processor源码分析》

2.Controller初始化与启动分析

2.1 Cotroller初始化-New

New用于初始化Controller,方法比较简单。

// staging/src/k8s.io/client-go/tools/cache/controller.go
func New(c *Config) Controller {
	ctlr := &controller{
		config: *c,
		clock:  &clock.RealClock{},
	}
	return ctlr
}

2.2 Controller启动-controller.Run

controller.Run为controller的启动方法,这里主要看到几个点:
(1)调用NewReflector,初始化Reflector;
(2)调用r.Run,实际上是调用了Reflector的启动方法来启动Reflector(Reflector相关的分析前面的博客已经分析过了,这里不再重复);
(3)调用c.processLoop,开始controller的核心处理;

// staging/src/k8s.io/client-go/tools/cache/controller.go
func (c *controller) Run(stopCh <-chan struct{}) {
	defer utilruntime.HandleCrash()
	go func() {
		<-stopCh
		c.config.Queue.Close()
	}()
	r := NewReflector(
		c.config.ListerWatcher,
		c.config.ObjectType,
		c.config.Queue,
		c.config.FullResyncPeriod,
	)
	r.ShouldResync = c.config.ShouldResync
	r.clock = c.clock

	c.reflectorMutex.Lock()
	c.reflector = r
	c.reflectorMutex.Unlock()

	var wg wait.Group
	defer wg.Wait()

	wg.StartWithChannel(stopCh, r.Run)

	wait.Until(c.processLoop, time.Second, stopCh)
}

3.controller核心处理方法分析

controller.processLoop即为controller的核心处理方法。

controller.processLoop

controller的核心处理方法processLoop中,最重要的逻辑是循环调用c.config.Queue.Pop将DeltaFIFO中的队头元素给pop出来(实际上pop出来的是Deltas,是Delta的切片类型),然后调用c.config.Process方法来做处理,当处理出错时,再调用c.config.Queue.AddIfNotPresent将对象重新加入到DeltaFIFO中去。

func (c *controller) processLoop() {
	for {
		obj, err := c.config.Queue.Pop(PopProcessFunc(c.config.Process))
		if err != nil {
			if err == ErrFIFOClosed {
				return
			}
			if c.config.RetryOnError {
				// This is the safe way to re-enqueue.
				c.config.Queue.AddIfNotPresent(obj)
			}
		}
	}
}

根据前面sharedIndexInformer的初始化与启动分析(sharedIndexInformer.Run)可以得知,c.config.Process即为s.HandleDeltas方法,所以接下来看到s.HandleDeltas方法的分析。

c.config.Process/s.HandleDeltas

根据前面分析知道HandleDeltas要处理的是Deltas,是Delta的切片类型。

再来看到HandleDeltas方法的主要逻辑:
(1)循环遍历Deltas,拿到单个Delta;
(2)判断Delta的类型;
(3)如果是Added、Updated、Sync类型,则从indexer中获取该对象,存在则调用s.indexer.Update来更新indexer中的该对象,随后构造updateNotification struct,并调用s.processor.distribute方法;如果indexer中不存在该对象,则调用s.indexer.Add来往indexer中添加该对象,随后构造addNotification struct,并调用s.processor.distribute方法;
(4)如果是Deleted类型,则调用s.indexer.Delete来将indexer中的该对象删除,随后构造deleteNotification struct,并调用s.processor.distribute方法;

// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (s *sharedIndexInformer) HandleDeltas(obj interface{}) error {
	s.blockDeltas.Lock()
	defer s.blockDeltas.Unlock()

	// from oldest to newest
	for _, d := range obj.(Deltas) {
		switch d.Type {
		case Sync, Added, Updated:
			isSync := d.Type == Sync
			s.cacheMutationDetector.AddObject(d.Object)
			if old, exists, err := s.indexer.Get(d.Object); err == nil && exists {
				if err := s.indexer.Update(d.Object); err != nil {
					return err
				}
				s.processor.distribute(updateNotification{oldObj: old, newObj: d.Object}, isSync)
			} else {
				if err := s.indexer.Add(d.Object); err != nil {
					return err
				}
				s.processor.distribute(addNotification{newObj: d.Object}, isSync)
			}
		case Deleted:
			if err := s.indexer.Delete(d.Object); err != nil {
				return err
			}
			s.processor.distribute(deleteNotification{oldObj: d.Object}, false)
		}
	}
	return nil
}

type updateNotification struct {
	oldObj interface{}
	newObj interface{}
}

type addNotification struct {
	newObj interface{}
}

type deleteNotification struct {
	oldObj interface{}
}

至此,Controller的分析就结束了,用一张图来回忆一下Controller的功能与架构。

《k8s client-go源码分析 informer源码分析(5)-Controller&Processor源码分析》

4.processor核心处理方法分析

sharedIndexInformer.processor.distribute

接下来分析一下前面提到的s.processor.distribute方法。

可以看到distribute方法最终是将构造好的addNotification、updateNotification、deleteNotification对象写入到p.addCh中。

sync类型的对象写入到p.syncingListeners中,但informer中貌似没有启动p.syncingListeners或对p.syncingListeners做处理,所以sync类型的对象变化(也即list操作得到的对象所生成的对象变化)会被忽略?有待验证。

// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (p *sharedProcessor) distribute(obj interface{}, sync bool) {
	p.listenersLock.RLock()
	defer p.listenersLock.RUnlock()

	if sync {
		for _, listener := range p.syncingListeners {
			listener.add(obj)
		}
	} else {
		for _, listener := range p.listeners {
			listener.add(obj)
		}
	}
}

func (p *processorListener) add(notification interface{}) {
	p.addCh <- notification
}

sharedIndexInformer.processor.run

s.processor.run启动了processor,其中注意到listener.run与listener.pop两个核心方法。

这里可以看到processor的run方法中只启动了p.listeners,没有启动p.syncingListeners。

// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (p *sharedProcessor) run(stopCh <-chan struct{}) {
	func() {
		p.listenersLock.RLock()
		defer p.listenersLock.RUnlock()
		for _, listener := range p.listeners {
			p.wg.Start(listener.run)
			p.wg.Start(listener.pop)
		}
		p.listenersStarted = true
	}()
	<-stopCh
	p.listenersLock.RLock()
	defer p.listenersLock.RUnlock()
	for _, listener := range p.listeners {
		close(listener.addCh) // Tell .pop() to stop. .pop() will tell .run() to stop
	}
	p.wg.Wait() // Wait for all .pop() and .run() to stop
}

processorListener.pop

分析processorListener的pop方法可以得知,其逻辑实际上就是将p.addCh中的对象给拿出来,然后丢进了p.nextCh中。那么谁来处理p.nextCh呢?继续往下看。

// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (p *processorListener) pop() {
	defer utilruntime.HandleCrash()
	defer close(p.nextCh) // Tell .run() to stop

	var nextCh chan<- interface{}
	var notification interface{}
	for {
		select {
		case nextCh <- notification:
			// Notification dispatched
			var ok bool
			notification, ok = p.pendingNotifications.ReadOne()
			if !ok { // Nothing to pop
				nextCh = nil // Disable this select case
			}
		case notificationToAdd, ok := <-p.addCh:
			if !ok {
				return
			}
			if notification == nil { // No notification to pop (and pendingNotifications is empty)
				// Optimize the case - skip adding to pendingNotifications
				notification = notificationToAdd
				nextCh = p.nextCh
			} else { // There is already a notification waiting to be dispatched
				p.pendingNotifications.WriteOne(notificationToAdd)
			}
		}
	}
}

processorListener.run

在processorListener的run方法中,将循环读取p.nextCh,判断对象类型,是updateNotification则调用p.handler.OnUpdate方法,是addNotification则调用p.handler.OnAdd方法,是deleteNotification则调用p.handler.OnDelete方法做处理。

// staging/src/k8s.io/client-go/tools/cache/shared_informer.go
func (p *processorListener) run() {
	// this call blocks until the channel is closed.  When a panic happens during the notification
	// we will catch it, **the offending item will be skipped!**, and after a short delay (one second)
	// the next notification will be attempted.  This is usually better than the alternative of never
	// delivering again.
	stopCh := make(chan struct{})
	wait.Until(func() {
		// this gives us a few quick retries before a long pause and then a few more quick retries
		err := wait.ExponentialBackoff(retry.DefaultRetry, func() (bool, error) {
			for next := range p.nextCh {
				switch notification := next.(type) {
				case updateNotification:
					p.handler.OnUpdate(notification.oldObj, notification.newObj)
				case addNotification:
					p.handler.OnAdd(notification.newObj)
				case deleteNotification:
					p.handler.OnDelete(notification.oldObj)
				default:
					utilruntime.HandleError(fmt.Errorf("unrecognized notification: %T", next))
				}
			}
			// the only way to get here is if the p.nextCh is empty and closed
			return true, nil
		})

		// the only way to get here is if the p.nextCh is empty and closed
		if err == nil {
			close(stopCh)
		}
	}, 1*time.Minute, stopCh)
}

而p.handler.OnUpdate、p.handler.OnAdd、p.handler.OnDelete方法实际上就是自定义的的ResourceEventHandlerFuncs了。

informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
    AddFunc:    onAdd,
    UpdateFunc: onUpdate,
    DeleteFunc: onDelete,
  })
// staging/src/k8s.io/client-go/tools/cache/controller.go
type ResourceEventHandlerFuncs struct {
	AddFunc    func(obj interface{})
	UpdateFunc func(oldObj, newObj interface{})
	DeleteFunc func(obj interface{})
}

func (r ResourceEventHandlerFuncs) OnAdd(obj interface{}) {
	if r.AddFunc != nil {
		r.AddFunc(obj)
	}
}

func (r ResourceEventHandlerFuncs) OnUpdate(oldObj, newObj interface{}) {
	if r.UpdateFunc != nil {
		r.UpdateFunc(oldObj, newObj)
	}
}

func (r ResourceEventHandlerFuncs) OnDelete(obj interface{}) {
	if r.DeleteFunc != nil {
		r.DeleteFunc(obj)
	}
}

至此,Processor的分析也结束了,用一张图来回忆一下Processor的功能与架构。

《k8s client-go源码分析 informer源码分析(5)-Controller&Processor源码分析》

总结

Controller

Controller从DeltaFIFO中pop Deltas出来处理,根据对象的变化更新Indexer本地缓存,并通知Processor相关对象有变化事件发生:
(1)如果是Added、Updated、Sync类型,则从indexer中获取该对象,存在则调用s.indexer.Update来更新indexer中的该对象,随后构造updateNotification struct,并通知Processor;如果indexer中不存在该对象,则调用s.indexer.Add来往indexer中添加该对象,随后构造addNotification struct,并通知Processor;
(2)如果是Deleted类型,则调用s.indexer.Delete来将indexer中的该对象删除,随后构造deleteNotification struct,并通知Processor;

Processor

Processor根据Controller的通知,即根据对象的变化事件类型(addNotification、updateNotification、deleteNotification),调用相应的ResourceEventHandler(addFunc、updateFunc、deleteFunc)来处理对象的变化。

informer架构中的Controller&Processor

《k8s client-go源码分析 informer源码分析(5)-Controller&Processor源码分析》

在对informer中的Controller与Processor分析完之后,接下来将分析informer中的Indexer。

    原文作者:良凯尔
    原文地址: https://www.cnblogs.com/lianngkyle/p/16343460.html
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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