k8s-client-go源码剖析(二)

{"type":"doc","content":[{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"简介：云原生社区活动---Kubernetes源码剖析第一期第二周"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本周是K8S源码研习社第一期第二周，学习内容是学习Informer机制，本文以这个课题进行展开。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本周研习社社长挺忙的，将本次课程推迟到下一周结束，任何事情都是这样，计划总有可能会被其他事情打破，但最终只要能够回归到对应的主线上，就不是什么问题。就像参与开源一样，最开始的开放源代码只是开始，需要的是能够坚持下去，而这一点往往是很重要的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"好了，开始正文。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"本文主题："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"numberedlist","attrs":{"start":null,"normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"Informer机制架构设计总览"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"Reflector理解"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","text":"DeltaFIFO理解"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":4,"align":null,"origin":null},"content":[{"type":"text","text":"Indexer理解"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果涉及到资源的内容，本文以Deployment资源进行相关内容讲述。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Informer机制架构设计总览"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面是我根据理解画的一个数据流转图,从全局视角看一下数据的整体走向是怎么样的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其中虚线的表示的是代码中的方法。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/cd/cdfa3b3ec2e148308bc37db0d5931277.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先讲一个结论："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通过Informer机制获取数据的情况下，在初始化的时候会从Kubernetes API Server获取对应Resource的全部Object，后续只会通过Watch机制接收API Server推送过来的数据，不会再主动从API Server拉取数据，直接使用本地缓存中的数据以减少API Server的压力。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Watch机制基于HTTP的Chunk实现，维护一个长连接，这是一个优化点，减少请求的数据量。第二个优化点是SharedInformer,它可以让同一种资源使用的是同一个Informer，例如v1版本的Deployment和v1beta1版本的Deployment同时存在的时候，共享一个Informer。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上面图中可以看到Informer分为三个部分，可以理解为三大逻辑。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其中Reflector主要是把从API Server数据获取到的数据放到DeltaFIFO队列中，充当生产者角色。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"SharedInformer主要是从DeltaFIFIO队列中获取数据并分发数据，充当消费者角色。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最后Indexer是作为本地缓存的存储组件存在。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Reflector理解"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Reflector中主要看Run、ListAndWatch、watchHandler三个地方就足够了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"源码位置是 tools/cache/reflector.go"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"// Ruvn starts a watch and handles watch events. Will restart the watch if it is closed.\n// Run will exit when stopCh is closed.\n//开始时执行Run，上一层调用的地方是 controller.go中的Run方法\nfunc (r *Reflector) Run(stopCh 0 {\n\t\t... \n //pop消息\n \n\t\tf.cond.Broadcast()\n\t...\n\treturn nil\n}"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Pop方法："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"func (f *DeltaFIFO) Pop(process PopProcessFunc) (interface{}, error) {\n\tf.lock.Lock()\n\tdefer f.lock.Unlock()\n\tfor {\n\t\tfor len(f.queue) == 0 {\n\t\t\t//阻塞 直到调用了f.cond.Broadcast()\n\t\t\tf.cond.Wait()\n\t\t}\n//取出第一个元素\n\t\tid := f.queue[0]\n\t\tf.queue = f.queue[1:]\n\t\t...\n\t\titem, ok := f.items[id]\n...\n delete(f.items, id)\n\t\t//这个process可以在controller.go中的processLoop()找到\n\t\t//初始化是在shared_informer.go的Run\n\t\t//最终执行到shared_informer.go的HandleDeltas方法\n\t\terr := process(item)\n\t\t//如果处理出错了重新放回队列中\n\t\tif e, ok := err.(ErrRequeue); ok {\n\t\t\tf.addIfNotPresent(id, item)\n\t\t\terr = e.Err\n\t\t}\n\t\t ...\n\t}\n}"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Resync机制："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"小总结：每次从本地缓存Indexer中获取数据重新放到DeltaFIFO中执行任务逻辑。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"启动的Resync地方是reflector.go的resyncChan()方法，在reflector.go的ListAndWatch方法中的调用开始定时执行。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"go func() {\n //启动定时任务\n\t\tresyncCh, cleanup := r.resyncChan()\n\t\tdefer func() {\n\t\t\tcleanup() // Call the last one written into cleanup\n\t\t}()\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase %s\\n\", idx+1, deploy.Name)\n\t}\n\n\t