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<!DOCTYPE HTML>
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<title>replicaset controller 源码分析 · 田飞雨</title>
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<li class="chapter " data-level="1.1" data-path="../">
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<b>1.1.</b>
Introduction
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job controller 源码分析
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garbage collector controller 源码分析
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daemonset controller 源码分析
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<b>1.2.7.</b>
statefulset controller 源码分析
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<b>1.2.8.</b>
deployment controller 源码分析
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<b>1.2.9.</b>
replicaset controller 源码分析
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kube-scheduler 源码分析
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<b>1.2.11.</b>
kube-scheduler predicates 与 priorities 调度算法源码分析
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<b>1.2.12.</b>
kube-scheduler 优先级与抢占机制源码分析
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<b>1.2.13.</b>
kubernetes service 原理解析
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kube-proxy 源码分析
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kube-proxy iptables 模式源码分析
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kube-proxy ipvs 模式源码分析
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<b>1.2.17.</b>
kubelet 架构浅析
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<b>1.2.18.</b>
kubelet 启动流程分析
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<b>1.2.19.</b>
kubelet 创建 pod 的流程
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<b>1.2.20.</b>
kubelet 状态上报的方式
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<b>1.2.21.</b>
kubelet 中事件处理机制
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kubelet statusManager 源码分析
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kubernetes 中 Qos 的设计与实现
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<b>1.2.24.</b>
kubelet 中垃圾回收机制的设计与实现
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<b>1.2.25.</b>
kubernetes 中 Evicted pod 是如何产生的
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<b>1.2.26.</b>
Kubernetes 中 Descheduler 组件的使用与扩展
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在 minkube 上部署 knative
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knative serving 组件分析
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blkio cgroup
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pid cgroup
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golang 中函数使用值返回与指针返回的区别，底层原理分析
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<li><a href="#replicasetcontroller-源码分析">ReplicaSetController 源码分析</a><ul>
<li><a href="#启动流程">启动流程</a></li>
<li><a href="#eventhandler">EventHandler</a><ul>
<li><a href="#addpod">addPod</a></li>
<li><a href="#updatepod">updatePod</a></li>
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<li><a href="#addrs-和-deleters">AddRS 和 DeleteRS</a></li>
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<li><a href="#satisfiedexpectations">SatisfiedExpectations</a></li>
<li><a href="#managereplicas">manageReplicas</a></li>
<li><a href="#calculatestatus">calculateStatus</a></li>
</ul>
</li>
<li><a href="#expectations-机制">expectations 机制</a></li>
</ul>
</li>
<li><a href="#总结">总结</a></li>
</ul>
<p>在前面的文章中已经介绍了 deployment controller 的设计与实现，deployment 控制的是 replicaset，而 replicaset 控制 pod 的创建与删除，deployment 通过控制 replicaset 实现了滚动更新、回滚等操作。而 replicaset 会直接控制 pod 的创建与删除，本文会继续从源码层面分析 replicaset 的设计与实现。</p>
<p>在分析源码前先考虑一下 replicaset 的使用场景，在平时的操作中其实我们并不会直接操作 replicaset，replicaset 也仅有几个简单的操作，创建、删除、更新等，但其地位是非常重要的，replicaset 的主要功能就是通过 add/del pod 来达到期望的状态。</p>
<h3 id="replicasetcontroller-源码分析"><a name="replicasetcontroller-源码分析" class="anchor-navigation-ex-anchor" href="#replicasetcontroller-源码分析"><i class="fa fa-link" aria-hidden="true"></i></a>ReplicaSetController 源码分析</h3>
<blockquote>
<p>kubernetes 版本: v1.16</p>
</blockquote>
<h4 id="启动流程"><a name="启动流程" class="anchor-navigation-ex-anchor" href="#启动流程"><i class="fa fa-link" aria-hidden="true"></i></a>启动流程</h4>
<p>首先来看 replicaSetController 对象初始化以及启动的代码，在 startReplicaSetController 中有两个比较重要的变量：</p>
<ul>
<li>BurstReplicas：用来控制在一个 syncLoop 过程中 rs 最多能创建的 pod 数量，设置上限值是为了避免单个 rs 影响整个系统，默认值为 500；</li>
<li>ConcurrentRSSyncs：指的是需要启动多少个 goroutine 处理 informer 队列中的对象，默认值为 5；</li>
</ul>
<p><code>k8s.io/kubernetes/cmd/kube-controller-manager/app/apps.go:69</code></p>
<pre class="language-"><code>func startReplicaSetController(ctx ControllerContext) (http.Handler, bool, error) {
if !ctx.AvailableResources[schema.GroupVersionResource{Group: "apps", Version: "v1", Resource: "replicasets"}] {
return nil, false, nil
}
go replicaset.NewReplicaSetController(
ctx.InformerFactory.Apps().V1().ReplicaSets(),
ctx.InformerFactory.Core().V1().Pods(),
ctx.ClientBuilder.ClientOrDie("replicaset-controller"),
replicaset.BurstReplicas,
).Run(int(ctx.ComponentConfig.ReplicaSetController.ConcurrentRSSyncs), ctx.Stop)
return nil, true, nil
}
</code></pre><p>下面是 replicaSetController 初始化的具体步骤，可以看到其会监听 pod 以及 rs 两个对象的事件。</p>
<p><code>k8s.io/kubernetes/pkg/controller/replicaset/replica_set.go:109</code></p>
<pre class="language-"><code>func NewReplicaSetController(......) *ReplicaSetController {
......
// 1、此处调用 NewBaseController
return NewBaseController(rsInformer, podInformer, kubeClient, burstReplicas,
apps.SchemeGroupVersion.WithKind("ReplicaSet"),
"replicaset_controller",
"replicaset",
controller.RealPodControl{
KubeClient: kubeClient,
Recorder: eventBroadcaster.NewRecorder(scheme.Scheme, v1.EventSource{Component: "replicaset-controller"}),
},
)
}
func NewBaseController(......) *ReplicaSetController {
......
// 2、ReplicaSetController 初始化
rsc := &ReplicaSetController{
GroupVersionKind: gvk,
kubeClient: kubeClient,
podControl: podControl,
burstReplicas: burstReplicas,
// 3、expectations 的初始化
expectations: controller.NewUIDTrackingControllerExpectations(controller.NewControllerExpectations()),
queue: workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), queueName),
}
// 4、rsInformer 中注册的 EventHandler
rsInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
AddFunc: rsc.enqueueReplicaSet,
UpdateFunc: rsc.updateRS,
DeleteFunc: rsc.enqueueReplicaSet,
})
......
// 5、podInformer 中注册的 EventHandler
podInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
AddFunc: rsc.addPod,
UpdateFunc: rsc.updatePod,
DeleteFunc: rsc.deletePod,
})
......
return rsc
}
</code></pre><p>replicaSetController 初始化完成后会调用 <code>Run</code> 方法启动 5 个 goroutine 处理 informer 队列中的事件并进行 sync 操作，kube-controller-manager 中每个 controller 的启动操作都是如下所示流程。</p>
<p><code>k8s.io/kubernetes/pkg/controller/replicaset/replica_set.go:177</code></p>
<pre class="language-"><code>func (rsc *ReplicaSetController) Run(workers int, stopCh <-chan struct{}) {
......
// 1、等待 informer 同步缓存
if !cache.WaitForNamedCacheSync(rsc.Kind, stopCh, rsc.podListerSynced, rsc.rsListerSynced) {
return
}
// 2、启动 5 个 goroutine 执行 worker 方法
for i := 0; i < workers; i++ {
go wait.Until(rsc.worker, time.Second, stopCh)
}
<-stopCh
}
// 3、worker 方法中调用 rocessNextWorkItem
func (rsc *ReplicaSetController) worker() {
for rsc.processNextWorkItem() {
}
}
func (rsc *ReplicaSetController) processNextWorkItem() bool {
// 4、从队列中取出对象
key, quit := rsc.queue.Get()
if quit {
return false
}
defer rsc.queue.Done(key)
// 5、执行 sync 操作
err := rsc.syncHandler(key.(string))
......
return true
}
</code></pre><h4 id="eventhandler"><a name="eventhandler" class="anchor-navigation-ex-anchor" href="#eventhandler"><i class="fa fa-link" aria-hidden="true"></i></a>EventHandler</h4>
<p>初始化 replicaSetController 时，其中有一个 <code>expectations</code> 字段，这是 rs 中一个比较特殊的机制，为了说清楚 expectations，先来看一下 controller 中所注册的 eventHandler，replicaSetController 会 watch pod 和 replicaSet 两个对象，eventHandler 中注册了对这两种对象的 add、update、delete 三个操作。</p>
<h5 id="addpod"><a name="addpod" class="anchor-navigation-ex-anchor" href="#addpod"><i class="fa fa-link" aria-hidden="true"></i></a>addPod</h5>
<ul>
<li>1、判断 pod 是否处于删除状态；</li>
<li>2、获取该 pod 关联的 rs 以及 rsKey，入队 rs 并更新 rsKey 的 expectations；</li>
<li>3、若 pod 对象没体现出关联的 rs 则为孤儿 pod，遍历 rsList 查找匹配的 rs，若该 rs.Namespace == pod.Namespace 并且 rs.Spec.Selector 匹配 pod.Labels，则说明该 pod 应该与此 rs 关联，将匹配的 rs 入队；</li>
</ul>
<p><code>k8s.io/kubernetes/pkg/controller/replicaset/replica_set.go:255</code></p>
<pre class="language-"><code>func (rsc *ReplicaSetController) addPod(obj interface{}) {
pod := obj.(*v1.Pod)
if pod.DeletionTimestamp != nil {
rsc.deletePod(pod)
return
}
// 1、获取 pod 所关联的 rs
if controllerRef := metav1.GetControllerOf(pod); controllerRef != nil {
rs := rsc.resolveControllerRef(pod.Namespace, controllerRef)
if rs == nil {
return
}