kube-scheduler framework

调度框架用来保存配置的插件，并在调度算法中被执行遍历插件，其实现了如下接口

type Framework interface {
	//提供了插件获取调度框架里数据的接口和抢占接口，见下面注释
	Handle

	//返回排序函数，用在调度队列中，用来给pod排序
	QueueSortFunc() LessFunc

	//用来执行配置的PreFilter插件
	RunPreFilterPlugins(ctx context.Context, state *CycleState, pod *v1.Pod) *Status

	//用来执行配置的PostFilter插件
	RunPostFilterPlugins(ctx context.Context, state *CycleState, pod *v1.Pod, filteredNodeStatusMap NodeToStatusMap) (*PostFilterResult, *Status)

	//用来执行配置的PreBind插件
	RunPreBindPlugins(ctx context.Context, state *CycleState, pod *v1.Pod, nodeName string) *Status

	//用来执行配置的PostBind插件
	RunPostBindPlugins(ctx context.Context, state *CycleState, pod *v1.Pod, nodeName string)

	//用来执行配置的Reserve插件的Reserve方法
	RunReservePluginsReserve(ctx context.Context, state *CycleState, pod *v1.Pod, nodeName string) *Status

	//用来执行配置的Reserve插件的Unreserve方法
	RunReservePluginsUnreserve(ctx context.Context, state *CycleState, pod *v1.Pod, nodeName string)

	//用来执行配置的Permit插件
	RunPermitPlugins(ctx context.Context, state *CycleState, pod *v1.Pod, nodeName string) *Status

	//如果pod是一个等待pod，则堵塞，直到等待pod返回拒绝或者允许
	WaitOnPermit(ctx context.Context, pod *v1.Pod) *Status

	//用来执行配置的Bind插件
	RunBindPlugins(ctx context.Context, state *CycleState, pod *v1.Pod, nodeName string) *Status

	//返回是否配置了Filter插件
	HasFilterPlugins() bool

	//返回是否配置了PostFilter插件
	HasPostFilterPlugins() bool

	//返回是否配置了Score插件
	HasScorePlugins() bool

	//获取map，key为扩展点名字，value为扩展点上配置的插件
	ListPlugins() *config.Plugins

	//返回此framework的名字，由此可见，一个framework对应一个profile
	ProfileName() string
}

type Handle interface {
	//抽象了操作提名pod的函数，会在抢占流程中讲解
	PodNominator
	//抽象了运行插件的函数
	PluginsRunner
	
	SnapshotSharedLister() SharedLister

	IterateOverWaitingPods(callback func(WaitingPod))

	//根据pod UID获取WaitingPod，目前只在抢占插件中被调用
	GetWaitingPod(uid types.UID) WaitingPod

	//拒绝WaitingPod，即让WaitingPod不可调度，目前只在抢占插件中被调用
	RejectWaitingPod(uid types.UID) bool

	//获取和apiserver交互的接口，比如bind插件和apiserver交互来bind pod
	ClientSet() clientset.Interface

	KubeConfig() *restclient.Config

	EventRecorder() events.EventRecorder

	//有些插件需要从informer获取数据
	SharedInformerFactory() informers.SharedInformerFactory

	//为提名pod运行Filter插件，此函数在抢占流程和正常调度流程都会被调用，后面会详细讲解此函数
	RunFilterPluginsWithNominatedPods(ctx context.Context, state *CycleState, pod *v1.Pod, info *NodeInfo) *Status

	//暂时忽略
	Extenders() []Extender

	//获取并行个数
	Parallelizer() parallelize.Parallelizer
}

//官网说此接口是抢占插件(PostFilter)用来评估当某些运行的pod被抢占后，调度成功的可行性。
//但目前RunPreScorePlugins和RunScorePlugins只用在正常调度，RunFilterPlugins用在正常调度和抢占流程，其他两个只用在抢占流程
type PluginsRunner interface {
	//执行PreScore插件
	RunPreScorePlugins(context.Context, *CycleState, *v1.Pod, []*v1.Node) *Status
	//执行Score插件
	RunScorePlugins(context.Context, *CycleState, *v1.Pod, []*v1.Node) (PluginToNodeScores, *Status)
	//执行Filter插件
	RunFilterPlugins(context.Context, *CycleState, *v1.Pod, *NodeInfo) PluginToStatus
	//调用插件的AddPod函数，只用在抢占流程 
	RunPreFilterExtensionAddPod(ctx context.Context, state *CycleState, podToSchedule *v1.Pod, podInfoToAdd *PodInfo, nodeInfo *NodeInfo) *Status
	//调用插件的RemovePod函数，只用在抢占流程 
	RunPreFilterExtensionRemovePod(ctx context.Context, state *CycleState, podToSchedule *v1.Pod, podInfoToRemove *PodInfo, nodeInfo *NodeInfo) *Status
}

frameworkImpl为调度框架的具体实现，其实现了上面的接口

// frameworkImpl is the component responsible for initializing and running scheduler
// plugins.
type frameworkImpl struct {
	//支持的所有插件，保存后好像也没用到
	registry             Registry
	snapshotSharedLister framework.SharedLister
	//用来保存waitingPod
	waitingPods          *waitingPodsMap
	//保存score插件的权重
	scorePluginWeight    map[string]int
	//这里保存了每个扩展点上的插件
	queueSortPlugins     []framework.QueueSortPlugin
	preFilterPlugins     []framework.PreFilterPlugin
	filterPlugins        []framework.FilterPlugin
	postFilterPlugins    []framework.PostFilterPlugin
	preScorePlugins      []framework.PreScorePlugin
	scorePlugins         []framework.ScorePlugin
	reservePlugins       []framework.ReservePlugin
	preBindPlugins       []framework.PreBindPlugin
	bindPlugins          []framework.BindPlugin
	postBindPlugins      []framework.PostBindPlugin
	permitPlugins        []framework.PermitPlugin

	//和apiserver通信的接口
	clientSet       clientset.Interface
	kubeConfig      *restclient.Config
	eventRecorder   events.EventRecorder
	//informer获取数据接口
	informerFactory informers.SharedInformerFactory

	metricsRecorder *metricsRecorder
	//一个profiler对应一个调用框架的实现frameworkImpl
	profileName     string

	extenders []framework.Extender
	framework.PodNominator

	parallelizer parallelize.Parallelizer

	// Indicates that RunFilterPlugins should accumulate all failed statuses and not return
	// after the first failure.
	runAllFilters bool
}

调度框架初始化

//r为所有的插件
//profile为一个调度器的配置
func NewFramework(r Registry, profile *config.KubeSchedulerProfile, opts ...Option) (framework.Framework, error) {
	options := defaultFrameworkOptions()
	for _, opt := range opts {
		opt(&options)
	}

	f := &frameworkImpl{
		registry:             r,
		snapshotSharedLister: options.snapshotSharedLister,
		scorePluginWeight:    make(map[string]int),
		waitingPods:          newWaitingPodsMap(),
		clientSet:            options.clientSet,
		kubeConfig:           options.kubeConfig,
		eventRecorder:        options.eventRecorder,
		informerFactory:      options.informerFactory,
		metricsRecorder:      options.metricsRecorder,
		runAllFilters:        options.runAllFilters,
		extenders:            options.extenders,
		PodNominator:         options.podNominator,
		parallelizer:         options.parallelizer,
	}

	if profile == nil {
		return f, nil
	}

	f.profileName = profile.SchedulerName
	if profile.Plugins == nil {
		return f, nil
	}
	...
	//获取每个扩展点上使能的插件。
	//因为一个插件可能在多个扩展点上，这里通过map结构进行去重，map的key为插件名字，value为插件，
	//为什么去重？因为后面会调用factory初始化插件对象，一个插件初始化一次即可
	pg := f.pluginsNeeded(profile.Plugins)

	//将插件参数保存到pluginConfig，key为插件名字，value为插件参数
	pluginConfig := make(map[string]runtime.Object, len(profile.PluginConfig))
	for i := range profile.PluginConfig {
		name := profile.PluginConfig[i].Name
		if _, ok := pluginConfig[name]; ok {
			return nil, fmt.Errorf("repeated config for plugin %s", name)
		}
		pluginConfig[name] = profile.PluginConfig[i].Args
	}
	...
	//pluginsMap用来保存初始化后的插件对象
	pluginsMap := make(map[string]framework.Plugin)
	//遍历所有插件
	for name, factory := range r {
		//跳过没使能的插件
		if _, ok := pg[name]; !ok {
			continue
		}

		args := pluginConfig[name]
		...
		//调用插件的初始化函数，将f作为参数传给插件，这样插件就可以获取调度框架的数据
		//比如pkg/scheduler/framework/plugins/serviceaffinity/service_affinity.go:New()
		p, err := factory(args, f)
		if err != nil {
			return nil, fmt.Errorf("initializing plugin %q: %w", name, err)
		}
		pluginsMap[name] = p

		// Update ClusterEventMap in place.
		fillEventToPluginMap(p, options.clusterEventMap)
	}

	//因为一个插件可能在多个扩展点，这里将初始化后的插件对象保存到各个扩展点上
	for _, e := range f.getExtensionPoints(profile.Plugins) {
		if err := updatePluginList(e.slicePtr, *e.plugins, pluginsMap); err != nil {
			return nil, err
		}
	}
	...
	//排序插件个数不能为0
	if len(f.queueSortPlugins) == 0 {
		return nil, fmt.Errorf("no queue sort plugin is enabled")
	}
	//排序插件个数不能大于1，所以一个调度器只能使能一个排序插件
	if len(f.queueSortPlugins) > 1 {
		return nil, fmt.Errorf("only one queue sort plugin can be enabled")
	}
	//bind插件个数不能为0
	if len(f.bindPlugins) == 0 {
		return nil, fmt.Errorf("at least one bind plugin is needed")
	}
	...

	return f, nil
}

RunPreFilterPlugins
执行配置在PreFilter扩展点上的插件

func (f *frameworkImpl) RunPreFilterPlugins(ctx context.Context, state *framework.CycleState, pod *v1.Pod) (status *framework.Status) {
	startTime := time.Now()
	defer func() {
		metrics.FrameworkExtensionPointDuration.WithLabelValues(preFilter, status.Code().String(), f.profileName).Observe(metrics.SinceInSeconds(startTime))
	}()
	//遍历扩展点上的插件
	for _, pl := range f.preFilterPlugins {
		status = f.runPreFilterPlugin(ctx, pl, state, pod)
		if !status.IsSuccess() {
			status.SetFailedPlugin(pl.Name())
			if status.IsUnschedulable() {
				return status
			}
			return framework.AsStatus(fmt.Errorf("running PreFilter plugin %q: %w", pl.Name(), status.AsError())).WithFailedPlugin(pl.Name())
		}
	}

	return nil
}

RunFilterPlugins
执行配置在Filter扩展点上的插件

func (f *frameworkImpl) RunFilterPlugins(
	ctx context.Context,
	state *framework.CycleState,
	pod *v1.Pod,
	nodeInfo *framework.NodeInfo,
) framework.PluginToStatus {
	statuses := make(framework.PluginToStatus)
	//遍历扩展点上的插件
	for _, pl := range f.filterPlugins {
		pluginStatus := f.runFilterPlugin(ctx, pl, state, pod, nodeInfo)
		if !pluginStatus.IsSuccess() {
			if !pluginStatus.IsUnschedulable() {
				// Filter plugins are not supposed to return any status other than
				// Success or Unschedulable.
				errStatus := framework.AsStatus(fmt.Errorf("running %q filter plugin: %w", pl.Name(), pluginStatus.AsError())).WithFailedPlugin(pl.Name())
				return map[string]*framework.Status{pl.Name(): errStatus}
			}
			pluginStatus.SetFailedPlugin(pl.Name())
			statuses[pl.Name()] = pluginStatus
			if !f.runAllFilters {
				// Exit early if we don't need to run all filters.
				return statuses
			}
		}
	}

	return statuses
}

RunFilterPluginsWithNominatedPods
这里先说几个概念
successpod: 调度成功，并且bind到node成功的pod
assumepod：调度成功，假定pod运行在node上，bind异步执行中
failedpod：调度失败的pod
NominatedPods：当一个pod调度失败后，在PostFilter中执行抢占插件流程，看是否能抢占某个node上的其他低优先级的pod，如果能抢占成功，则此pod在后面调度周期很可能会被调度到此node上，这种pod被称为NominatedPods，NominatedPods虽然还没真正运行在抢占的node上，但后续的调度周期必须考虑这些pod。NominatedPods肯定是failedpod
victimpod：牺牲的pod，这些pod是被高优先级pod抢占的pod，在运行的node上被驱逐，再重新调度

此函数在正常调度流程和抢占流程被调用，目的是确认目标pod(参数pod)是否能运行在指定node(参数info)上。
正常调度被调用时：在nodeinfo(successpod+assumepod)中加上比目标pod优先级高的NominatedPods后，对目标pod执行Filter扩展点上的插件，如果返回失败，则目标pod肯定不能运行在指定node上。
抢占流程被调用时：在nodeinfo(successpod+assumepod-victimpod)中加上比目标pod优先级高的NominatedPods后，对目标pod执行Filter扩展点上的插件，如果返回失败，则目标pod肯定不能运行在指定node上。

// RunFilterPluginsWithNominatedPods runs the set of configured filter plugins
// for nominated pod on the given node.
// This function is called from two different places: Schedule and Preempt.
// When it is called from Schedule, we want to test whether the pod is
// schedulable on the node with all the existing pods on the node plus higher
// and equal priority pods nominated to run on the node.
// When it is called from Preempt, we should remove the victims of preemption
// and add the nominated pods. Removal of the victims is done by
// SelectVictimsOnNode(). Preempt removes victims from PreFilter state and
// NodeInfo before calling this function.
func (f *frameworkImpl) RunFilterPluginsWithNominatedPods(ctx context.Context, state *framework.CycleState, pod *v1.Pod, info *framework.NodeInfo) *framework.Status {
	var status *framework.Status

	podsAdded := false
	//有些场景下需要执行两次filters. 如果node上有比目标pod优先级高或者相等的nominated pod，会将这些pod资源添加到node上，执行filters。
	//如果所有的filters都通过了，还要不加这些nominatedpod资源，再次执行filters，因为有些filters(比如pod亲和性filter)在
	//不加nominated pod时可能会失败。
	
	//如果没有比目标pod优先级高或者相等的nominated pod或者第一次执行失败了，不会再执行第二次。
	
	//这里为什么只考虑比目标pod优先级高或者相等的nominated pod呢，因为这些pod本身不占用node资源，并且在抢占流程中会将这些pod的提名node删除，
	//从而进行正常调度，可参考函数prepareCandidate。
	
	//为什么要执行两次来保证目标pod在加和不加nominated pod时都能被调度呢，这是一个保守的决定：有些filter(比如pod间反亲和性filter)可能在
	//加了nominated pod时失败，有些filter(比如pod间亲和性filter)可能在不加nominated pod时失败。我们不能假定nominated pod已经运行在node
	//上了，因为他们还没真正调度到此node上，而且最终还有可能被调度到其他node上。
	for i := 0; i < 2; i++ {
		stateToUse := state
		nodeInfoToUse := info
		//第一轮执行，加上抢占成功的pod
		if i == 0 {
			var err error
			//将node上优先级比目标pod高的抢占成功的pod的资源考虑进去保存到nodeInfoToUse
			//如果有这样的pod，则podsAdded为true
			podsAdded, stateToUse, nodeInfoToUse, err = addNominatedPods(ctx, f, pod, state, info)
			if err != nil {
				return framework.AsStatus(err)
			}
		//如果没有抢占pod，或者第一轮执行失败
		} else if !podsAdded || !status.IsSuccess() {
			break
		}

		statusMap := f.RunFilterPlugins(ctx, stateToUse, pod, nodeInfoToUse)
		status = statusMap.Merge()
		if !status.IsSuccess() && !status.IsUnschedulable() {
			return status
		}
	}

	return status
}