KubernetesHPAController怎么使用
这篇文章主要讲解了“Kubernetes HPA Controller怎么使用”,文中的讲解内容简单清晰,易于学习与理解,下面请大家跟着小编的思路慢慢深入,一起来研究和学习“Kubernetes HPA Controller怎么使用”吧!
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源码目录结构分析
HorizontalPodAutoscaler(以下简称HPA)的主要代码如下,主要涉及的文件不多。
cmd/kube-controller-manager/app/autoscaling.go // HPA Controller的启动代码 /pkg/controller/podautoscaler . ├── BUILD ├── OWNERS ├── doc.go ├── horizontal.go // podautoscaler的核心代码,包括其创建和运行的代码 ├── horizontal_test.go ├── metrics │ ├── BUILD │ ├── metrics_client.go │ ├── metrics_client_test.go │ ├── metrics_client_test.go.orig │ ├── metrics_client_test.go.rej │ └── utilization.go ├── replica_calculator.go // ReplicaCaculator的创建,以及根据cpu/metrics计算replicas的方法 └── replica_calculator_test.go
其中,horizontal.go和replica_calculator.go是最核心的文件,他们对应的Structure如下:
horizontal.go
replica_calculator.go
源码分析
HPA Controller同其他Controller一样,都是在kube-controller-manager启动时完成初始化并启动的,如下代码所示。
cmd/kube-controller-manager/app/controllermanager.go:224 func newControllerInitializers() map[string]InitFunc { controllers := map[string]InitFunc{} ... controllers["horizontalpodautoscaling"] = startHPAController ... return controllers }
kube-controller-manager启动时会initial一堆的controllers,对于HPA controller,它的启动就交给startHPAController了。
cmd/kube-controller-manager/app/autoscaling.go:29 func startHPAController(ctx ControllerContext) (bool, error) { ... // HPA Controller需要集群已经部署Heapster,由Heapster提供监控数据,来进行replicas的计算。 metricsClient := metrics.NewHeapsterMetricsClient( hpaClient, metrics.DefaultHeapsterNamespace, metrics.DefaultHeapsterScheme, metrics.DefaultHeapsterService, metrics.DefaultHeapsterPort, ) // 创建ReplicaCaculator,后面会用它来计算desired replicas。 replicaCalc := podautoscaler.NewReplicaCalculator(metricsClient, hpaClient.Core()) // 创建HPA Controller,并启动goroutine执行其Run方法,开始工作。 go podautoscaler.NewHorizontalController( hpaClient.Core(), hpaClient.Extensions(), hpaClient.Autoscaling(), replicaCalc, ctx.Options.HorizontalPodAutoscalerSyncPeriod.Duration, ).Run(ctx.Stop) return true, nil }
首先我们来看看NewHorizontalController创建HPA Controller的代码。
pkg/controller/podautoscaler/horizontal.go:112 func NewHorizontalController(evtNamespacer v1core.EventsGetter, scaleNamespacer unversionedextensions.ScalesGetter, hpaNamespacer unversionedautoscaling.HorizontalPodAutoscalersGetter, replicaCalc *ReplicaCalculator, resyncPeriod time.Duration) *HorizontalController { ... // 构建HPA Controller controller := &HorizontalController{ replicaCalc: replicaCalc, eventRecorder: recorder, scaleNamespacer: scaleNamespacer, hpaNamespacer: hpaNamespacer, } // 创建Informer,配置对应的ListWatch Func,及其对应的EventHandler,用来监控HPA Resource的Add和Update事件。newInformer是HPA的核心代码入口。 store, frameworkController := newInformer(controller, resyncPeriod) controller.store = store controller.controller = frameworkController return controller }
我们有必要来看看HPA Controller struct的定义:
pkg/controller/podautoscaler/horizontal.go:59 type HorizontalController struct { scaleNamespacer unversionedextensions.ScalesGetter hpaNamespacer unversionedautoscaling.HorizontalPodAutoscalersGetter replicaCalc *ReplicaCalculator eventRecorder record.EventRecorder // A store of HPA objects, populated by the controller. store cache.Store // Watches changes to all HPA objects. controller *cache.Controller }
scaleNamespacer其实是一个ScaleInterface,包括Scale subresource的Get和Update接口。
hpaNamespacer是HorizontalPodAutoscalerInterface,包括HorizontalPodAutoscaler的Create, Update, UpdateStatus, Delete, Get, List, Watch等接口。
replicaCalc根据Heapster提供的监控数据,计算对应desired replicas。
pkg/controller/podautoscaler/replica_calculator.go:31 type ReplicaCalculator struct { metricsClient metricsclient.MetricsClient podsGetter v1core.PodsGetter }
store和controller:controller用来watch HPA objects,并更新到store这个cache中。
上面提到了Scale subresource,那是个什么东西?好吧,我们得看看Scale的定义。
pkg/apis/extensions/v1beta1/types.go:56 // represents a scaling request for a resource. type Scale struct { metav1.TypeMeta `json:",inline"` // Standard object metadata; More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#metadata. // +optional v1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"` // defines the behavior of the scale. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#spec-and-status. // +optional Spec ScaleSpec `json:"spec,omitempty" protobuf:"bytes,2,opt,name=spec"` // current status of the scale. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#spec-and-status. Read-only. // +optional Status ScaleStatus `json:"status,omitempty" protobuf:"bytes,3,opt,name=status"` } // describes the attributes of a scale subresource type ScaleSpec struct { // desired number of instances for the scaled object. Replicas int `json:"replicas,omitempty"` } // represents the current status of a scale subresource. type ScaleStatus struct { // actual number of observed instances of the scaled object. Replicas int `json:"replicas"` // label query over pods that should match the replicas count. Selector map[string]string `json:"selector,omitempty"` }
Scale struct作为一次scale动作的请求数据。
其中Spec定义的是desired replicas number。
ScaleStatus定义了current replicas number。
看完了HorizontalController的结构后,接着看看NewHorizontalController中调用的newInformer。在上面的注释中,我提到newInformer是整个HPA的核心代码入口。
pkg/controller/podautoscaler/horizontal.go:75 func newInformer(controller *HorizontalController, resyncPeriod time.Duration) (cache.Store, *cache.Controller) { return cache.NewInformer( // 配置ListFucn和WatchFunc,用来定期List和watch HPA resource。 &cache.ListWatch{ ListFunc: func(options v1.ListOptions) (runtime.Object, error) { return controller.hpaNamespacer.HorizontalPodAutoscalers(v1.NamespaceAll).List(options) }, WatchFunc: func(options v1.ListOptions) (watch.Interface, error) { return controller.hpaNamespacer.HorizontalPodAutoscalers(v1.NamespaceAll).Watch(options) }, }, // 定义期望收到的object为HorizontalPodAutoscaler &autoscaling.HorizontalPodAutoscaler{}, // 定义定期List的周期 resyncPeriod, // 配置HPA resource event的Handler(AddFunc, UpdateFunc) cache.ResourceEventHandlerFuncs{ AddFunc: func(obj interface{}) { hpa := obj.(*autoscaling.HorizontalPodAutoscaler) hasCPUPolicy := hpa.Spec.TargetCPUUtilizationPercentage != nil _, hasCustomMetricsPolicy := hpa.Annotations[HpaCustomMetricsTargetAnnotationName] if !hasCPUPolicy && !hasCustomMetricsPolicy { controller.eventRecorder.Event(hpa, v1.EventTypeNormal, "DefaultPolicy", "No scaling policy specified - will use default one. See documentation for details") } // 根据监控调整hpa的数据 err := controller.reconcileAutoscaler(hpa) if err != nil { glog.Warningf("Failed to reconcile %s: %v", hpa.Name, err) } }, UpdateFunc: func(old, cur interface{}) { hpa := cur.(*autoscaling.HorizontalPodAutoscaler) // 根据监控调整hpa的数据 err := controller.reconcileAutoscaler(hpa) if err != nil { glog.Warningf("Failed to reconcile %s: %v", hpa.Name, err) } }, // We are not interested in deletions. }, ) }
newInformer的代码也不长嘛,简单说来,就是配置了HPA resource的ListWatch的Func,注册HPA resource 的Add和Update Event的handler Func。
最终通过调用reconcileAutoscaler来矫正hpa的数据。
上面代码中,将HPA resource的ListWatch Func注册为HorizontalPodAutoscaler Interface定义的List和Watch接口。
等等,说了这么多,怎么还没看到HorizontalPodAutoscaler struct的定义呢!好吧,下面就来看看,正好HorizontalPodAutoscaler Interface中出现了。
pkg/apis/autoscaling/v1/types.go:76 // configuration of a horizontal pod autoscaler. type HorizontalPodAutoscaler struct { metav1.TypeMeta `json:",inline"` // Standard object metadata. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#metadata // +optional v1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"` // behaviour of autoscaler. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#spec-and-status. // +optional Spec HorizontalPodAutoscalerSpec `json:"spec,omitempty" protobuf:"bytes,2,opt,name=spec"` // current information about the autoscaler. // +optional Status HorizontalPodAutoscalerStatus `json:"status,omitempty" protobuf:"bytes,3,opt,name=status"` }
Spec HorizontalPodAutoscalerSpec
存的是hpa的描述信息,是可以通过kube-controller-manager配置对应flag的信息。包括最小副本数MinReplicas,最大副本数MaxReplicas,hpa对应的所有pods的平均的百分比形式的目标CPU利用率TargetCPUUtilizationPercentage。pkg/apis/autoscaling/v1/types.go:36 // specification of a horizontal pod autoscaler. type HorizontalPodAutoscalerSpec struct { // reference to scaled resource; horizontal pod autoscaler will learn the current resource consumption // and will set the desired number of pods by using its Scale subresource. ScaleTargetRef CrossVersionObjectReference `json:"scaleTargetRef" protobuf:"bytes,1,opt,name=scaleTargetRef"` // lower limit for the number of pods that can be set by the autoscaler, default 1. // +optional MinReplicas *int32 `json:"minReplicas,omitempty" protobuf:"varint,2,opt,name=minReplicas"` // upper limit for the number of pods that can be set by the autoscaler; cannot be smaller than MinReplicas. MaxReplicas int32 `json:"maxReplicas" protobuf:"varint,3,opt,name=maxReplicas"` // target average CPU utilization (represented as a percentage of requested CPU) over all the pods; // if not specified the default autoscaling policy will be used. // +optional TargetCPUUtilizationPercentage *int32 `json:"targetCPUUtilizationPercentage,omitempty" protobuf:"varint,4,opt,name=targetCPUUtilizationPercentage"` }
Status HorizontalPodAutoscalerStatu
存的是HPA的当前状态数据,包括前后两次scale的时间间隔ObservedGeneration,上一次scale的时间戳LastScaleTime,当前副本数CurrentReplicas,期望副本数DesiredReplicas,hpa对应的所有pods的平均的百分比形式的当前CPU利用率。pkg/apis/autoscaling/v1/types.go:52 // current status of a horizontal pod autoscaler type HorizontalPodAutoscalerStatus struct { // most recent generation observed by this autoscaler. // +optional ObservedGeneration *int64 `json:"observedGeneration,omitempty" protobuf:"varint,1,opt,name=observedGeneration"` // last time the HorizontalPodAutoscaler scaled the number of pods; // used by the autoscaler to control how often the number of pods is changed. // +optional LastScaleTime *metav1.Time `json:"lastScaleTime,omitempty" protobuf:"bytes,2,opt,name=lastScaleTime"` // current number of replicas of pods managed by this autoscaler. CurrentReplicas int32 `json:"currentReplicas" protobuf:"varint,3,opt,name=currentReplicas"` // desired number of replicas of pods managed by this autoscaler. DesiredReplicas int32 `json:"desiredReplicas" protobuf:"varint,4,opt,name=desiredReplicas"` // current average CPU utilization over all pods, represented as a percentage of requested CPU, // e.g. 70 means that an average pod is using now 70% of its requested CPU. // +optional CurrentCPUUtilizationPercentage *int32 `json:"currentCPUUtilizationPercentage,omitempty" protobuf:"varint,5,opt,name=currentCPUUtilizationPercentage"` }
newInformer的代码可见,不管hpa resource的event为Add或者update,最终都是调用reconcileAutoscaler来触发HorizontalPodAutoscaler数据的更新。
pkg/controller/podautoscaler/horizontal.go:272 func (a *HorizontalController) reconcileAutoscaler(hpa *autoscaling.HorizontalPodAutoscaler) error { ... // 获取对应resource的scale subresource数据。 scale, err := a.scaleNamespacer.Scales(hpa.Namespace).Get(hpa.Spec.ScaleTargetRef.Kind, hpa.Spec.ScaleTargetRef.Name) ... // 得到当前副本数 currentReplicas := scale.Status.Replicas cpuDesiredReplicas := int32(0) cpuCurrentUtilization := new(int32) cpuTimestamp := time.Time{} cmDesiredReplicas := int32(0) cmMetric := "" cmStatus := "" cmTimestamp := time.Time{} desiredReplicas := int32(0) rescaleReason := "" timestamp := time.Now() rescale := true // 如果期望副本数为0,这不进行scale操作。 if scale.Spec.Replicas == 0 { // Autoscaling is disabled for this resource desiredReplicas = 0 rescale = false } // 期望副本数不能超过hpa中配置的最大副本数 else if currentReplicas > hpa.Spec.MaxReplicas { rescaleReason = "Current number of replicas above Spec.MaxReplicas" desiredReplicas = hpa.Spec.MaxReplicas } // 期望副本数不能低于配置的最小副本数 else if hpa.Spec.MinReplicas != nil && currentReplicas < *hpa.Spec.MinReplicas { rescaleReason = "Current number of replicas below Spec.MinReplicas" desiredReplicas = *hpa.Spec.MinReplicas } // 期望副本数最少为1 else if currentReplicas == 0 { rescaleReason = "Current number of replicas must be greater than 0" desiredReplicas = 1 } // 如果当前副本数在Min和Max之间,则需要根据cpu或者custom metrics(如果加了对应的Annotation)数据进行算法计算得到期望副本数。 else { // All basic scenarios covered, the state should be sane, lets use metrics. cmAnnotation, cmAnnotationFound := hpa.Annotations[HpaCustomMetricsTargetAnnotationName] if hpa.Spec.TargetCPUUtilizationPercentage != nil || !cmAnnotationFound { // 根据cpu利用率计算期望副本数 cpuDesiredReplicas, cpuCurrentUtilization, cpuTimestamp, err = a.computeReplicasForCPUUtilization(hpa, scale) if err != nil { // 更新hpa的当前副本数 a.updateCurrentReplicasInStatus(hpa, currentReplicas) return fmt.Errorf("failed to compute desired number of replicas based on CPU utilization for %s: %v", reference, err) } } if cmAnnotationFound { // 根据custom metrics数据计算期望副本数 cmDesiredReplicas, cmMetric, cmStatus, cmTimestamp, err = a.computeReplicasForCustomMetrics(hpa, scale, cmAnnotation) if err != nil { // 更新hpa的当前副本数 a.updateCurrentReplicasInStatus(hpa, currentReplicas) return fmt.Errorf("failed to compute desired number of replicas based on Custom Metrics for %s: %v", reference, err) } } // 取cpu和custom metric得到的期望副本数的最大值作为最终的desired replicas,并且要在min和max范围内。 rescaleMetric := "" if cpuDesiredReplicas > desiredReplicas { desiredReplicas = cpuDesiredReplicas timestamp = cpuTimestamp rescaleMetric = "CPU utilization" } if cmDesiredReplicas > desiredReplicas { desiredReplicas = cmDesiredReplicas timestamp = cmTimestamp rescaleMetric = cmMetric } if desiredReplicas > currentReplicas { rescaleReason = fmt.Sprintf("%s above target", rescaleMetric) } if desiredReplicas < currentReplicas { rescaleReason = "All metrics below target" } if hpa.Spec.MinReplicas != nil && desiredReplicas < *hpa.Spec.MinReplicas { desiredReplicas = *hpa.Spec.MinReplicas } // never scale down to 0, reserved for disabling autoscaling if desiredReplicas == 0 { desiredReplicas = 1 } if desiredReplicas > hpa.Spec.MaxReplicas { desiredReplicas = hpa.Spec.MaxReplicas } // Do not upscale too much to prevent incorrect rapid increase of the number of master replicas caused by // bogus CPU usage report from heapster/kubelet (like in issue #32304). if desiredReplicas > calculateScaleUpLimit(currentReplicas) { desiredReplicas = calculateScaleUpLimit(currentReplicas) } // 根据currentReplicas和desiredReplicas的对比,以及scale时间是否满足配置间隔要求,决定是否此时需要rescale rescale = shouldScale(hpa, currentReplicas, desiredReplicas, timestamp) } if rescale { scale.Spec.Replicas = desiredReplicas // 执行ScaleInterface的Update接口,触发调用API Server的对应resource的scale subresource的数据更新。其实最终会去修改对应rc或者deployment的replicas,然后由rc或deployment Controller去最终扩容或者缩容,使得副本数达到新的期望值。 _, err = a.scaleNamespacer.Scales(hpa.Namespace).Update(hpa.Spec.ScaleTargetRef.Kind, scale) if err != nil { a.eventRecorder.Eventf(hpa, v1.EventTypeWarning, "FailedRescale", "New size: %d; reason: %s; error: %v", desiredReplicas, rescaleReason, err.Error()) return fmt.Errorf("failed to rescale %s: %v", reference, err) } a.eventRecorder.Eventf(hpa, v1.EventTypeNormal, "SuccessfulRescale", "New size: %d; reason: %s", desiredReplicas, rescaleReason) glog.Infof("Successfull rescale of %s, old size: %d, new size: %d, reason: %s", hpa.Name, currentReplicas, desiredReplicas, rescaleReason) } else { desiredReplicas = currentReplicas } // 更新hpa resource的status数据 return a.updateStatus(hpa, currentReplicas, desiredReplicas, cpuCurrentUtilization, cmStatus, rescale) }
上面reconcileAutoscaler的代码很重要,把想说的都写到对应的注释了。其中computeReplicasForCPUUtilization
和computeReplicasForCustomMetrics
需要单独提出来看看,因为这两个方法是HPA算法的体现,实际上最终算法是在pkg/controller/podautoscaler/replica_calculator.go:45#GetResourceReplicas
和pkg/controller/podautoscaler/replica_calculator.go:153#GetMetricReplicas
实现的:
pkg/controller/podautoscaler/replica_calculator.go:45#GetResourceReplicas
负责根据heapster提供的cpu利用率数据计算得到desired replicas number。pkg/controller/podautoscaler/replica_calculator.go:153#GetMetricReplicas
负责根据heapster提供的custom raw metric数据计算得到desired replicas number。
具体关于HPA算法的源码分析,我后续会单独写一篇博客,有兴趣的可以关注(对于绝大部分同学来说没必要关注,除非需要定制HPA算法时,才会具体去分析)。
总而言之,根据cpu和custom metric数据分别计算得到desired replicas后,取两者最大的值,但不能超过配置的Max Replicas。
稍等稍等,计算出了desired replicas还还够,我们还要通过shouldScale
看看现在距离上一次弹性伸缩的时间间隔是否满足条件:
两次缩容的间隔不得小于5min。
两次扩容的间隔不得小于3min。
shouldScale
的代码如下:
pkg/controller/podautoscaler/horizontal.go:387 ... var downscaleForbiddenWindow = 5 * time.Minute var upscaleForbiddenWindow = 3 * time.Minute ... func shouldScale(hpa *autoscaling.HorizontalPodAutoscaler, currentReplicas, desiredReplicas int32, timestamp time.Time) bool { if desiredReplicas == currentReplicas { return false } if hpa.Status.LastScaleTime == nil { return true } // Going down only if the usageRatio dropped significantly below the target // and there was no rescaling in the last downscaleForbiddenWindow. if desiredReplicas < currentReplicas && hpa.Status.LastScaleTime.Add(downscaleForbiddenWindow).Before(timestamp) { return true } // Going up only if the usage ratio increased significantly above the target // and there was no rescaling in the last upscaleForbiddenWindow. if desiredReplicas > currentReplicas && hpa.Status.LastScaleTime.Add(upscaleForbiddenWindow).Before(timestamp) { return true } return false }
只有满足这个条件后,接着才会调用Scales.Update接口与API Server交互,完成Scale对应的RC的replicas的设置。以rc Controller为例(deployment Controller的雷同),API Server对应的Scales.Update接口的实现逻辑如下:
pkg/registry/core/rest/storage_core.go:91 func (c LegacyRESTStorageProvider) NewLegacyRESTStorage(restOptionsGetter generic.RESTOptionsGetter) (LegacyRESTStorage, genericapiserver.APIGroupInfo, error) { ... if autoscalingGroupVersion := (schema.GroupVersion{Group: "autoscaling", Version: "v1"}); registered.IsEnabledVersion(autoscalingGroupVersion) { apiGroupInfo.SubresourceGroupVersionKind["replicationcontrollers/scale"] = autoscalingGroupVersion.WithKind("Scale") } ... restStorageMap := map[string]rest.Storage{ ... "replicationControllers": controllerStorage.Controller, "replicationControllers/status": controllerStorage.Status, ... } return restStorage, apiGroupInfo, nil } pkg/registry/core/controller/etcd/etcd.go:124 func (r *ScaleREST) Update(ctx api.Context, name string, objInfo rest.UpdatedObjectInfo) (runtime.Object, bool, error) { rc, err := r.registry.GetController(ctx, name, &metav1.GetOptions{}) if err != nil { return nil, false, errors.NewNotFound(autoscaling.Resource("replicationcontrollers/scale"), name) } oldScale := scaleFromRC(rc) obj, err := objInfo.UpdatedObject(ctx, oldScale) if err != nil { return nil, false, err } if obj == nil { return nil, false, errors.NewBadRequest("nil update passed to Scale") } scale, ok := obj.(*autoscaling.Scale) if !ok { return nil, false, errors.NewBadRequest(fmt.Sprintf("wrong object passed to Scale update: %v", obj)) } if errs := validation.ValidateScale(scale); len(errs) > 0 { return nil, false, errors.NewInvalid(autoscaling.Kind("Scale"), scale.Name, errs) } // 设置rc对应spec.replicas为Scale中的期望副本数 rc.Spec.Replicas = scale.Spec.Replicas rc.ResourceVersion = scale.ResourceVersion // 更新到etcd rc, err = r.registry.UpdateController(ctx, rc) if err != nil { return nil, false, err } return scaleFromRC(rc), false, nil }
了解kubernetes rc Controller的同学很清楚,修改rc的replicas后,会被rc Controller watch到,然后触发rc Controller去执行创建或者销毁对应差额数量的replicas,最终使得其副本数达到HPA计算得到的期望值。也就是说,最终由rc controller去执行具体的扩容或缩容动作。
最后,来看看HorizontalController的Run方法:
pkg/controller/podautoscaler/horizontal.go:130 func (a *HorizontalController) Run(stopCh <-chan struct{}) { defer utilruntime.HandleCrash() glog.Infof("Starting HPA Controller") go a.controller.Run(stopCh) <-stopCh glog.Infof("Shutting down HPA Controller") }
很简单,就是负责 HPA Resource的ListWatch,将change更新到对应的store(cache)。
HPA Resource的同步周期通过
--horizontal-pod-autoscaler-sync-period
设置,默认值为30s。
感谢各位的阅读,以上就是“Kubernetes HPA Controller怎么使用”的内容了,经过本文的学习后,相信大家对Kubernetes HPA Controller怎么使用这一问题有了更深刻的体会,具体使用情况还需要大家实践验证。这里是创新互联,小编将为大家推送更多相关知识点的文章,欢迎关注!
文章名称:KubernetesHPAController怎么使用
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