kubernetes hpa源码分析

最新推荐文章于 2025-02-13 15:23:36 发布

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最新推荐文章于 2025-02-13 15:23:36 发布 · 809 阅读

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#kubernetes #hpa

本文详细解析了Kubernetes中Horizontal Pod Autoscaler (HPA)的工作原理，包括其启动过程、核心组件及工作流程。从HPA的初始化到实际的Pod扩缩容逻辑均有涉及，尤其深入分析了如何根据不同的度量标准来计算所需Pod副本数。

初始化

文件位置:cmd/kube-controller-manager/app/controllermanager.go

func NewControllerInitializers(loopMode ControllerLoopMode) map[string]InitFunc {
	...
	controllers["horizontalpodautoscaling"] = startHPAController
	...
}

HPA Controller和其他的Controller一样，都在NewControllerInitializers方法中进行注册，然后通过startHPAController来启动。

startHPAController

|-> startHPAControllerWithRESTClient

    |-> startHPAControllerWithMetricsClient

        |-> NewHorizontalController

文件位置：/pkg/controller/podautoscaler/horizontal.go

// NewHorizontalController creates a new HorizontalController.
func NewHorizontalController(
	evtNamespacer v1core.EventsGetter,
	scaleNamespacer scaleclient.ScalesGetter,
	hpaNamespacer autoscalingclient.HorizontalPodAutoscalersGetter,
	mapper apimeta.RESTMapper,
	metricsClient metricsclient.MetricsClient,
	hpaInformer autoscalinginformers.HorizontalPodAutoscalerInformer,
	podInformer coreinformers.PodInformer,
	resyncPeriod time.Duration,
	downscaleStabilisationWindow time.Duration,
	tolerance float64,
	cpuInitializationPeriod,
	delayOfInitialReadinessStatus time.Duration,

) *HorizontalController {
	broadcaster := record.NewBroadcaster()
	broadcaster.StartStructuredLogging(0)
	broadcaster.StartRecordingToSink(&v1core.EventSinkImpl{Interface: evtNamespacer.Events("")})
	recorder := broadcaster.NewRecorder(scheme.Scheme, v1.EventSource{Component: "horizontal-pod-autoscaler"})

  ...

	hpaInformer.Informer().AddEventHandlerWithResyncPeriod(
		cache.ResourceEventHandlerFuncs{
			AddFunc:    hpaController.enqueueHPA,
			UpdateFunc: hpaController.updateHPA,
			DeleteFunc: hpaController.deleteHPA,
		},
		resyncPeriod,
	)
  ...

	return hpaController
}

核心逻辑是监听hpa对象的事件，分别对应hpaController.unqueueHPA，hpaController.updateHPA和hpaController.deleteHPA。enqueueHPA本质上就是把hpa对象注册到HorizontalController的队列里，updateHPA是更新hpa对象，deleteHPA是删除对象。hpa对象存在hpaController的workqueue中。

代码见下文

文件位置：/pkg/controller/podautoscaler/horizontal.go

// obj could be an *v1.HorizontalPodAutoscaler, or a DeletionFinalStateUnknown marker item.
func (a *HorizontalController) updateHPA(old, cur interface{}) {
	a.enqueueHPA(cur)
}

// obj could be an *v1.HorizontalPodAutoscaler, or a DeletionFinalStateUnknown marker item.
func (a *HorizontalController) enqueueHPA(obj interface{}) {
	key, err := controller.KeyFunc(obj)
	if err != nil {
		utilruntime.HandleError(fmt.Errorf("couldn't get key for object %+v: %v", obj, err))
		return
	}

	// Requests are always added to queue with resyncPeriod delay.  If there's already
	// request for the HPA in the queue then a new request is always dropped. Requests spend resync
	// interval in queue so HPAs are processed every resync interval.
	a.queue.AddRateLim