Scheduler结构
Scheduler 是整个 kube-scheduler 的一个 structure，提供了 kube-scheduler 运行所需的组件。
type Scheduler struct {
// Cache是一个抽象，会缓存pod的信息，作为scheduler进行查找，操作是基于Pod进行增加
Cache internalcache.Cache
// Extenders 算是调度框架中提供的调度插件，会影响kubernetes中的调度策略
Extenders []framework.Extender
// NextPod 作为一个函数提供，会阻塞获取下一个ke'diao'du
NextPod func() *framework.QueuedPodInfo
// Error is called if there is an error. It is passed the pod in
// question, and the error
Error func(*framework.QueuedPodInfo, error)
// SchedulePod 尝试将给出的pod调度到Node。
SchedulePod func(ctx context.Context, fwk framework.Framework, state *framework.CycleState, pod *v1.Pod) (ScheduleResult, error)
// 关闭scheduler的信号
StopEverything <-chan struct{}
// SchedulingQueue保存要调度的Pod
SchedulingQueue internalqueue.SchedulingQueue
// Profiles中是多个调度框架
Profiles profile.Map
client clientset.Interface
nodeInfoSnapshot *internalcache.Snapshot
percentageOfNodesToScore int32
nextStartNodeIndex int
}
作为实际执行的两个核心，SchedulingQueue ，与 scheduleOne 将会分析到这两个
SchedulingQueue
在知道 kube-scheduler 初始化过程后，需要对 kube-scheduler 的整个 structure 和 workflow 进行分析
在 Run 中，运行的是 一个 SchedulingQueue 与 一个 scheduleOne ，从结构上看是属于 Scheduler
func (sched *Scheduler) Run(ctx context.Context) {
sched.SchedulingQueue.Run()
// We need to start scheduleOne loop in a dedicated goroutine,
// because scheduleOne function hangs on getting the next item
// from the SchedulingQueue.
// If there are no new pods to schedule, it will be hanging there
// and if done in this goroutine it will be blocking closing
// SchedulingQueue, in effect causing a deadlock on shutdown.
go wait.UntilWithContext(ctx, sched.scheduleOne, 0)
<-ctx.Done()
sched.SchedulingQueue.Close()
}
SchedulingQueue 是一个队列的抽象，用于存储等待调度的Pod。该接口遵循类似于 cache.FIFO 和 cache.Heap 的模式。
type SchedulingQueue interface {
framework.PodNominator
Add(pod *v1.Pod) error
// Activate moves the given pods to activeQ iff they're in unschedulablePods or backoffQ.
// The passed-in pods are originally compiled from plugins that want to activate Pods,
// by injecting the pods through a reserved CycleState struct (PodsToActivate).
Activate(pods map[string]*v1.Pod)
// 将不可调度的Pod重入到队列中
AddUnschedulableIfNotPresent(pod *framework.QueuedPodInfo, podSchedulingCycle int64) error
// SchedulingCycle returns the current number of scheduling cycle which is
// cached by scheduling queue. Normally, incrementing this number whenever
// a pod is popped (e.g. called Pop()) is enough.
SchedulingCycle() int64
// Pop会弹出一个pod，并从head优先级队列中删除
Pop() (*framework.QueuedPodInfo, error)
Update(oldPod, newPod *v1.Pod) error
Delete(pod *v1.Pod) error
MoveAllToActiveOrBackoffQueue(event framework.ClusterEvent, preCheck PreEnqueueCheck)
AssignedPodAdded(pod *v1.Pod)
AssignedPodUpdated(pod *v1.Pod)
PendingPods() []*v1.Pod
// Close closes the SchedulingQueue so that the goroutine which is
// waiting to pop items can exit gracefully.
Close()
// Run starts the goroutines managing the queue.
Run()
}
而 PriorityQueue 是 SchedulingQueue 的实现，该部分的核心构成是两个子队列与一个数据结构，即 activeQ、backoffQ 和 unschedulablePods
activeQ：是一个 heap 类型的优先级队列，是 sheduler 从中获得优先级最高的Pod进行调度backoffQ：也是一个 heap 类型的优先级队列，存放的是不可调度的PodunschedulablePods：保存确定不可被调度的Pod
type SchedulingQueue interface {
framework.PodNominator
Add(pod *v1.Pod) error
// Activate moves the given pods to activeQ iff they're in unschedulablePods or backoffQ.
// The passed-in pods are originally compiled from plugins that want to activate Pods,
// by injecting the pods through a reserved CycleState struct (PodsToActivate).
Activate(pods map[string]*v1.Pod)
// AddUnschedulableIfNotPresent adds an unschedulable pod back to scheduling queue.
// The podSchedulingCycle represents the current scheduling cycle number which can be
// returned by calling SchedulingCycle().
AddUnschedulableIfNotPresent(pod *framework.QueuedPodInfo, podSchedulingCycle int64) error
// SchedulingCycle returns the current number of scheduling cycle which is
// cached by scheduling queue. Normally, incrementing this number whenever
// a pod is popped (e.g. called Pop()) is enough.
SchedulingCycle() int64
// Pop removes the head of the queue and returns it. It blocks if the
// queue is empty and waits until a new item is added to the queue.
Pop() (*framework.QueuedPodInfo, error)
Update(oldPod, newPod *v1.Pod) error
Delete(pod *v1.Pod) error
MoveAllToActiveOrBackoffQueue(event framework.ClusterEvent, preCheck PreEnqueueCheck)
AssignedPodAdded(pod *v1.Pod)
AssignedPodUpdated(pod *v1.Pod)
PendingPods() []*v1.Pod
// Close closes the SchedulingQueue so that the goroutine which is
// waiting to pop items can exit gracefully.
Close()
// Run starts the goroutines managing the queue.
Run()
}
在New scheduler 时可以看到会初始化这个queue
podQueue := internalqueue.NewSchedulingQueue(
// 实现pod对比的一个函数即less
profiles[options.profiles[0].SchedulerName].QueueSortFunc(),
informerFactory,
internalqueue.WithPodInitialBackoffDuration(time.Duration(options.podInitialBackoffSeconds)*time.Second),
internalqueue.WithPodMaxBackoffDuration(time.Duration(options.podMaxBackoffSeconds)*time.Second),
internalqueue.WithPodNominator(nominator),
internalqueue.WithClusterEventMap(clusterEventMap),
internalqueue.WithPodMaxInUnschedulablePodsDuration(options.podMaxInUnschedulablePodsDuration),
)
而 NewSchedulingQueue 则是初始化这个 PriorityQueue
// NewSchedulingQueue initializes a priority queue as a new scheduling queue.
func NewSchedulingQueue(
lessFn framework.LessFunc,
informerFactory informers.SharedInformerFactory,
opts ...Option) SchedulingQueue {
return NewPriorityQueue(lessFn, informerFactory, opts...)
}
// NewPriorityQueue creates a PriorityQueue object.
func NewPriorityQueue(
lessFn framework.LessFunc,
informerFactory informers.SharedInformerFactory,
opts ...Option,
) *PriorityQueue {
options := defaultPriorityQueueOptions
for _, opt := range opts {
opt(&options)
}
// 这个就是 less函数，作为打分的一部分
comp := func(podInfo1, podInfo2 interface{}) bool {
pInfo1 := podInfo1.(*framework.QueuedPodInfo)
pInfo2 := podInfo2.(*framework.QueuedPodInfo)
return lessFn(pInfo1, pInfo2)
}
if options.podNominator == nil {
options.podNominator = NewPodNominator(informerFactory.Core().V1().Pods().Lister())
}
pq := &PriorityQueue{
PodNominator: options.podNominator,
clock: options.clock,
stop: make(chan struct{}),
podInitialBackoffDuration: options.podInitialBackoffDuration,
podMaxBackoffDuration: options.podMaxBackoffDuration,
podMaxInUnschedulablePodsDuration: options.podMaxInUnschedulablePodsDuration,
activeQ: heap.NewWithRecorder(podInfoKeyFunc, comp, metrics.NewActivePodsRecorder()),
unschedulablePods: newUnschedulablePods(metrics.NewUnschedulablePodsRecorder()),
moveRequestCycle: -1,
clusterEventMap: options.clusterEventMap,
}
pq.cond.L = &pq.lock
pq.podBackoffQ = heap.NewWithRecorder(podInfoKeyFunc, pq.podsCompareBackoffCompleted, metrics.NewBackoffPodsRecorder())
pq.nsLister = informerFactory.Core().V1().Namespaces().Lister()
return pq
}
了解了Queue的结构，就需要知道 入队列与出队列是在哪里操作的。在初始化时，需要注册一个 addEventHandlerFuncs 这个时候，会注入三个动作函数，也就是controller中的概念；而在AddFunc中可以看到会入队列。
注入是对 Pod 的informer注入的，注入的函数 addPodToSchedulingQueue 就是入栈
Handler: cache.ResourceEventHandlerFuncs{
AddFunc: sched.addPodToSchedulingQueue,
UpdateFunc: sched.updatePodInSchedulingQueue,
DeleteFunc: sched.deletePodFromSchedulingQueue,
},
func (sched *Scheduler) addPodToSchedulingQueue(obj interface{}) {
pod := obj.(*v1.Pod)
klog.V(3).InfoS("Add event for unscheduled pod", "pod", klog.KObj(pod))
if err := sched.SchedulingQueue.Add(pod); err != nil {
utilruntime.HandleError(fmt.Errorf("unable to queue %T: %v", obj, err))
}
}
而这个 SchedulingQueue 的实现就是 PriorityQueue ，而Add中则对 activeQ进行的操作
func (p *PriorityQueue) Add(pod *v1.Pod) error {
p.lock.Lock()
defer p.lock.Unlock()
// 格式化入栈数据，包含podinfo，里会包含v1.Pod
// 初始化的时间，创建的时间，以及不能被调度时的记录其plugin的名称
pInfo := p.newQueuedPodInfo(pod)
// 入栈
if err := p.activeQ.Add(pInfo); err != nil {
klog.ErrorS(err, "Error adding pod to the active queue", "pod", klog.KObj(pod))
return err
}
if p.unschedulablePods.get(pod) != nil {
klog.ErrorS(nil, "Error: pod is already in the unschedulable queue", "pod", klog.KObj(pod))
p.unschedulablePods.delete(pod)
}
// Delete pod from backoffQ if it is backing off
if err := p.podBackoffQ.Delete(pInfo); err == nil {
klog.ErrorS(nil, "Error: pod is already in the podBackoff queue", "pod", klog.KObj(pod))
}
metrics.SchedulerQueueIncomingPods.WithLabelValues("active", PodAdd).Inc()
p.PodNominator.AddNominatedPod(pInfo.PodInfo, nil)
p.cond.Broadcast()
return nil
}
在上面看 scheduler 结构时，可以看到有一个 nextPod的，nextPod就是从队列中弹出一个pod，这个在scheduler 时会传入 MakeNextPodFunc 就是这个 nextpod
func MakeNextPodFunc(queue SchedulingQueue) func() *framework.QueuedPodInfo {
return func() *framework.QueuedPodInfo {
podInfo, err := queue.Pop()
if err == nil {
klog.V(4).InfoS("About to try and schedule pod", "pod", klog.KObj(podInfo.Pod))
for plugin := range podInfo.UnschedulablePlugins {
metrics.UnschedulableReason(plugin, podInfo.Pod.Spec.SchedulerName).Dec()
}
return podInfo
}
klog.ErrorS(err, "Error while retrieving next pod from scheduling queue")
return nil
}
}
而这个 queue.Pop() 对应的就是 PriorityQueue 的 Pop() ，在这里会将作为 activeQ 的消费端
func (p *PriorityQueue) Pop() (*framework.QueuedPodInfo, error) {
p.lock.Lock()
defer p.lock.Unlock()
for p.activeQ.Len() == 0 {
// When the queue is empty, invocation of Pop() is blocked until new item is enqueued.
// When Close() is called, the p.closed is set and the condition is broadcast,
// which causes this loop to continue and return from the Pop().
if p.closed {
return nil, fmt.Errorf(queueClosed)
}
p.cond.Wait()
}
obj, err := p.activeQ.Pop()
if err != nil {
return nil, err
}
pInfo := obj.(*framework.QueuedPodInfo)
pInfo.Attempts++
p.schedulingCycle++
return pInfo, nil
}
在上面入口部分也看到了，scheduleOne 和 scheduler，scheduleOne 就是去消费一个Pod，他会调用 NextPod，NextPod就是在初始化传入的 MakeNextPodFunc ，至此回到对应的 Pop来做消费。
schedulerOne是为一个Pod做调度的流程。
func (sched *Scheduler) scheduleOne(ctx context.Context) {
podInfo := sched.NextPod()
// pod could be nil when schedulerQueue is closed
if podInfo == nil || podInfo.Pod == nil {
return
}
pod := podInfo.Pod
fwk, err := sched.frameworkForPod(pod)
if err != nil {
// This shouldn't happen, because we only accept for scheduling the pods
// which specify a scheduler name that matches one of the profiles.
klog.ErrorS(err, "Error occurred")
return
}
if sched.skipPodSchedule(fwk, pod) {
return
}
...
调度上下文
当了解了scheduler结构后，下面分析下调度上下文的过程。看看扩展点是怎么工作的。这个时候又需要提到官网的调度上下文的图。
调度框架
调度框架 (scheduling framework SF ) 是kubernetes为 scheduler设计的一个pluggable的架构。SF 将scheduler设计为 Plugin 式的 API，API将上一章中提到的一些列调度策略实现为 Plugin。
在 SF 中，定义了一些扩展点 （extension points EP ），而被实现为Plugin的调度程序将被注册在一个或多个 EP 中，换句话来说，在这些 EP 的执行过程中如果注册在多个 EP 中，将会在多个 EP 被调用。
每次调度都分为两个阶段，调度周期（Scheduling Cycel）与绑定周期（Binding Cycle）。
- SC 表示为，为Pod选择一个节点；SC 是串行运行的。
- BC 表示为，将 SC 决策结果应用于集群中；BC 可以同时运行。
调度周期与绑定周期结合一起，被称为调度上下文 （Scheduling Context）,下图则是调度上下文的工作流
扩展点
扩展点（Extension points）是指在调度上下文中的每个可扩展API，通过图提现为[图1]。其中 Filter 相当于 Predicate 而 Scoring 相当于 Priority。
对于调度阶段会通过以下扩展点：
Sort：该插件提供了排序功能，用于对在调度队列中待处理 Pod 进行排序。一次只能启用一个队列排序。preFilter：该插件用于在过滤之前预处理或检查 Pod 或集群的相关信息。这里会终止调度filter：该插件相当于调度上下文中的Predicates，用于排除不能运行 Pod 的节点。Filter 会按配置的顺序进行调用。如果有一个filter将节点标记位不可用，则将 Pod 标记为不可调度（即不会向下执行）。postFilter：当没有为 pod 找到FN时，该插件会按照配置的顺序进行调用。如果任何postFilter插件将 Pod 标记为schedulable，则不会调用其余插件。即filter成功后不会进行这步骤preScore：可用于进行预Score工作（通知性的扩展点）。score：该插件为每个通过filter阶段的Node提供打分服务。然后Scheduler将选择具有最高加权分数总和的Node。reserve：因为绑定事件时异步发生的，该插件是为了避免Pod在绑定到节点前时，调度到新的Pod，使节点使用资源超过可用资源情况。如果后续阶段发生错误或失败，将触发UnReserve回滚（通知性扩展点）。这也是作为调度周期中最后一个状态，要么成功到postBind，要么失败触发UnReserve。permit：该插件可以阻止或延迟 Pod 的绑定，一般情况下这步骤会做三件事：appove：调度器继续绑定过程Deny：如果任何一个Premit拒绝了Pod与节点的绑定，那么将触发UnReserve，并重入队列Wait： 如果 Permit 插件返回Wait，该 Pod 将保留在内部WaitPod 列表中，直到被Appove。如果发生超时，wait变为deny，将Pod放回至调度队列中，并触发Unreserve回滚 。
preBind：该插件用于在 bind Pod 之前执行所需的前置工作。如，preBind可能会提供一个网络卷并将其挂载到目标节点上。如果在该步骤中的任意插件返回错误，则Pod 将被deny并放置到调度队列中。bind：在所有的preBind完成后，该插件将用于将Pod绑定到Node，并按顺序调用绑定该步骤的插件。如果有一个插件处理了这个事件，那么则忽略其余所有插件。postBind：该插件在绑定 Pod 后调用，可用于清理相关资源（通知性的扩展点）。multiPoint：这是一个仅配置字段，允许同时为所有适用的扩展点启用或禁用插件。
而 scheduler 对于调度上下文在代码中的实现就是 scheduleOne ，下面就是看这个调度上下文
Sort
Sort 插件提供了排序功能，用于对在调度队列中待处理 Pod 进行排序。一次只能启用一个队列排序。
在进入 scheduleOne 后，NextPod 从 activeQ 中队列中得到一个Pod，然后的 frameworkForPod 会做打分的动作就是调度上下文的第一个扩展点 sort
func (sched *Scheduler) scheduleOne(ctx context.Context) {
podInfo := sched.NextPod()
// pod could be nil when schedulerQueue is closed
if podInfo == nil || podInfo.Pod == nil {
return
}
pod := podInfo.Pod
fwk, err := sched.frameworkForPod(pod)
...
func (sched *Scheduler) frameworkForPod(pod *v1.Pod) (framework.Framework, error) {
// 获取指定的profile
fwk, ok := sched.Profiles[pod.Spec.SchedulerName]
if !ok {
return nil, fmt.Errorf("profile not found for scheduler name %q", pod.Spec.SchedulerName)
}
return fwk, nil
}
回顾，因为在New scheduler时会初始化这个 sort 函数
podQueue := internalqueue.NewSchedulingQueue(
profiles[options.profiles[0].SchedulerName].QueueSortFunc(),
informerFactory,
internalqueue.WithPodInitialBackoffDuration(time.Duration(options.podInitialBackoffSeconds)*time.Second),
internalqueue.WithPodMaxBackoffDuration(time.Duration(options.podMaxBackoffSeconds)*time.Second),
internalqueue.WithPodNominator(nominator),
internalqueue.WithClusterEventMap(clusterEventMap),
internalqueue.WithPodMaxInUnschedulablePodsDuration(options.podMaxInUnschedulablePodsDuration),
)
preFilter
preFilter作为第一个扩展点，是用于在过滤之前预处理或检查 Pod 或集群的相关信息。这里会终止调度
func (sched *Scheduler) scheduleOne(ctx context.Context) {
podInfo := sched.NextPod()
// pod could be nil when schedulerQueue is closed
if podInfo == nil || podInfo.Pod == nil {
return
}
pod := podInfo.Pod
fwk, err := sched.frameworkForPod(pod)
if err != nil {
// This shouldn't happen, because we only accept for scheduling the pods
// which specify a scheduler name that matches one of the profiles.
klog.ErrorS(err, "Error occurred")
return
}
if sched.skipPodSchedule(fwk, pod) {
return
}
klog.V(3).InfoS("Attempting to schedule pod", "pod", klog.KObj(pod))
// Synchronously attempt to find a fit for the pod.
start := time.Now()
state := framework.NewCycleState()
state.SetRecordPluginMetrics(rand.Intn(100) < pluginMetricsSamplePercent)
// Initialize an empty podsToActivate struct, which will be filled up by plugins or stay empty.
podsToActivate := framework.NewPodsToActivate()
state.Write(framework.PodsToActivateKey, podsToActivate)
schedulingCycleCtx, cancel := context.WithCancel(ctx)
defer cancel()
// 这里将进入prefilter
scheduleResult, err := sched.SchedulePod(schedulingCycleCtx, fwk, state, pod)
schedulePod 尝试将给定的 pod 调度到节点列表中的节点之一。如果成功，它将返回节点的名称。
func (sched *Scheduler) schedulePod(ctx context.Context, fwk framework.Framework, state *framework.CycleState, pod *v1.Pod) (result ScheduleResult, err error) {
trace := utiltrace.New("Scheduling", utiltrace.Field{Key: "namespace", Value: pod.Namespace}, utiltrace.Field{Key: "name", Value: pod.Name})
defer trace.LogIfLong(100 * time.Millisecond)
// 用于将cache更新为当前内容
if err := sched.Cache.UpdateSnapshot(sched.nodeInfoSnapshot); err != nil {
return result, err
}
trace.Step("Snapshotting scheduler cache and node infos done")
if sched.nodeInfoSnapshot.NumNodes() == 0 {
return result, ErrNoNodesAvailable
}
// 找到一个合适的pod时，会执行扩展点
feasibleNodes, diagnosis, err := sched.findNodesThatFitPod(ctx, fwk, state, pod)
...
findNodesThatFitPod 会执行对应的过滤插件来找到最适合的Node，包括备注，以及方法名都可以看到，这里运行的插件😁😁，后面会分析算法内容，只对workflow学习。
func (sched *Scheduler) findNodesThatFitPod(ctx context.Context, fwk framework.Framework, state *framework.CycleState, pod *v1.Pod) ([]*v1.Node, framework.Diagnosis, error) {
diagnosis := framework.Diagnosis{
NodeToStatusMap: make(framework.NodeToStatusMap),
UnschedulablePlugins: sets.NewString(),
}
// Run "prefilter" plugins.
preRes, s := fwk.RunPreFilterPlugins(ctx, state, pod)
allNodes, err := sched.nodeInfoSnapshot.NodeInfos().List()
if err != nil {
return nil, diagnosis, err
}
if !s.IsSuccess() {
if !s.IsUnschedulable() {
return nil, diagnosis, s.AsError()
}
// All nodes will have the same status. Some non trivial refactoring is
// needed to avoid this copy.
for _, n := range allNodes {
diagnosis.NodeToStatusMap[n.Node().Name] = s
}
// Status satisfying IsUnschedulable() gets injected into diagnosis.UnschedulablePlugins.
if s.FailedPlugin() != "" {
diagnosis.UnschedulablePlugins.Insert(s.FailedPlugin())
}
return nil, diagnosis, nil
}
// "NominatedNodeName" can potentially be set in a previous scheduling cycle as a result of preemption.
// This node is likely the only candidate that will fit the pod, and hence we try it first before iterating over all nodes.
if len(pod.Status.NominatedNodeName) > 0 {
feasibleNodes, err := sched.evaluateNominatedNode(ctx, pod, fwk, state, diagnosis)
if err != nil {
klog.ErrorS(err, "Evaluation failed on nominated node", "pod", klog.KObj(pod), "node", pod.Status.NominatedNodeName)
}
// Nominated node passes all the filters, scheduler is good to assign this node to the pod.
if len(feasibleNodes) != 0 {
return feasibleNodes, diagnosis, nil
}
}
nodes := allNodes
if !preRes.AllNodes() {
nodes = make([]*framework.NodeInfo, 0, len(preRes.NodeNames))
for n := range preRes.NodeNames {
nInfo, err := sched.nodeInfoSnapshot.NodeInfos().Get(n)
if err != nil {
return nil, diagnosis, err
}
nodes = append(nodes, nInfo)
}
}
feasibleNodes, err := sched.findNodesThatPassFilters(ctx, fwk, state, pod, diagnosis, nodes)
if err != nil {
return nil, diagnosis, err
}
feasibleNodes, err = findNodesThatPassExtenders(sched.Extenders, pod, feasibleNodes, diagnosis.NodeToStatusMap)
if err != nil {
return nil, diagnosis, err
}
return feasibleNodes, diagnosis, nil
}
filter
filter插件相当于调度上下文中的 Predicates，用于排除不能运行 Pod 的节点。Filter 会按配置的顺序进行调用。如果有一个filter将节点标记位不可用，则将 Pod 标记为不可调度（即不会向下执行）。
对于代码中来讲，filter还是处于 findNodesThatFitPod 函数中，findNodesThatPassFilters 就是获取到 FN，即可行节点，而这个过程就是 filter 扩展点
func (sched *Scheduler) findNodesThatFitPod(ctx context.Context, fwk framework.Framework, state *framework.CycleState, pod *v1.Pod) ([]*v1.Node, framework.Diagnosis, error) {
...
feasibleNodes, err := sched.findNodesThatPassFilters(ctx, fwk, state, pod, diagnosis, nodes)
if err != nil {
return nil, diagnosis, err
}
feasibleNodes, err = findNodesThatPassExtenders(sched.Extenders, pod, feasibleNodes, diagnosis.NodeToStatusMap)
if err != nil {
return nil, diagnosis, err
}
return feasibleNodes, diagnosis, nil
}
Postfilter
当没有为 pod 找到FN时，该插件会按照配置的顺序进行调用。如果任何postFilter插件将 Pod 标记为schedulable，则不会调用其余插件。即 filter 成功后不会进行这步骤，那我们来验证下这里把😊
还是在 scheduleOne 中，当我们运行的 SchedulePod 完成后（成功或失败），这时会返回一个err，而 postfilter 会根据这个 err进行选择执行或不执行，符合官方给出的说法。
scheduleResult, err := sched.SchedulePod(schedulingCycleCtx, fwk, state, pod)
if err != nil {
// SchedulePod() may have failed because the pod would not fit on any host, so we try to
// preempt, with the expectation that the next time the pod is tried for scheduling it
// will fit due to the preemption. It is also possible that a different pod will schedule
// into the resources that were preempted, but this is harmless.
var nominatingInfo *framework.NominatingInfo
if fitError, ok := err.(*framework.FitError); ok {
if !fwk.HasPostFilterPlugins() {
klog.V(3).InfoS("No PostFilter plugins are registered, so no preemption will be performed")
} else {
// Run PostFilter plugins to try to make the pod schedulable in a future scheduling cycle.
result, status := fwk.RunPostFilterPlugins(ctx, state, pod, fitError.Diagnosis.NodeToStatusMap)
if status.Code() == framework.Error {
klog.ErrorS(nil, "Status after running PostFilter plugins for pod", "pod", klog.KObj(pod), "status", status)
} else {
fitError.Diagnosis.PostFilterMsg = status.Message()
klog.V(5).InfoS("Status after running PostFilter plugins for pod", "pod", klog.KObj(pod), "status", status)
}
if result != nil {
nominatingInfo = result.NominatingInfo
}
}
// Pod did not fit anywhere, so it is counted as a failure. If preemption
// succeeds, the pod should get counted as a success the next time we try to
// schedule it. (hopefully)
metrics.PodUnschedulable(fwk.ProfileName(), metrics.SinceInSeconds(start))
} else if err == ErrNoNodesAvailable {
nominatingInfo = clearNominatedNode
// No nodes available is counted as unschedulable rather than an error.
metrics.PodUnschedulable(fwk.ProfileName(), metrics.SinceInSeconds(start))
} else {
nominatingInfo = clearNominatedNode
klog.ErrorS(err, "Error selecting node for pod", "pod", klog.KObj(pod))
metrics.PodScheduleError(fwk.ProfileName(), metrics.SinceInSeconds(start))
}
sched.handleSchedulingFailure(ctx, fwk, podInfo, err, v1.PodReasonUnschedulable, nominatingInfo)
return
}
PreScore,Score
可用于进行预Score工作，作为通知性的扩展点，会在在filter完之后直接会关联 preScore 插件进行继续工作，而不是返回，如果配置的这些插件有任何一个返回失败，则Pod将被拒绝。
func (sched *Scheduler) schedulePod(ctx context.Context, fwk framework.Framework, state *framework.CycleState, pod *v1.Pod) (result ScheduleResult, err error) {
trace := utiltrace.New("Scheduling", utiltrace.Field{Key: "namespace", Value: pod.Namespace}, utiltrace.Field{Key: "name", Value: pod.Name})
defer trace.LogIfLong(100 * time.Millisecond)
if err := sched.Cache.UpdateSnapshot(sched.nodeInfoSnapshot); err != nil {
return result, err
}
trace.Step("Snapshotting scheduler cache and node infos done")
if sched.nodeInfoSnapshot.NumNodes() == 0 {
return result, ErrNoNodesAvailable
}
feasibleNodes, diagnosis, err := sched.findNodesThatFitPod(ctx, fwk, state, pod)
if err != nil {
return result, err
}
trace.Step("Computing predicates done")
if len(feasibleNodes) == 0 {
return result, &framework.FitError{
Pod: pod,
NumAllNodes: sched.nodeInfoSnapshot.NumNodes(),
Diagnosis: diagnosis,
}
}
// When only one node after predicate, just use it.
if len(feasibleNodes) == 1 {
return ScheduleResult{
SuggestedHost: feasibleNodes[0].Name,
EvaluatedNodes: 1 + len(diagnosis.NodeToStatusMap),
FeasibleNodes: 1,
}, nil
}
// 这里会完成prescore，score
priorityList, err := prioritizeNodes(ctx, sched.Extenders, fwk, state, pod, feasibleNodes)
if err != nil {
return result, err
}
host, err := selectHost(priorityList)
trace.Step("Prioritizing done")
return ScheduleResult{
SuggestedHost: host,
EvaluatedNodes: len(feasibleNodes) + len(diagnosis.NodeToStatusMap),
FeasibleNodes: len(feasibleNodes),
}, err
}
priorityNodes 会通过配置的插件给Node打分，并返回每个Node的分数，将每个插件打分结果计算总和获得Node的分数，最后获得节点的加权总分数。
func prioritizeNodes(
ctx context.Context,
extenders []framework.Extender,
fwk framework.Framework,
state *framework.CycleState,
pod *v1.Pod,
nodes []*v1.Node,
) (framework.NodeScoreList, error) {
// If no priority configs are provided, then all nodes will have a score of one.
// This is required to generate the priority list in the required format
if len(extenders) == 0 && !fwk.HasScorePlugins() {
result := make(framework.NodeScoreList, 0, len(nodes))
for i := range nodes {
result = append(result, framework.NodeScore{
Name: nodes[i].Name,
Score: 1,
})
}
return result, nil
}
// Run PreScore plugins.
preScoreStatus := fwk.RunPreScorePlugins(ctx, state, pod, nodes)
if !preScoreStatus.IsSuccess() {
return nil, preScoreStatus.AsError()
}
// Run the Score plugins.
scoresMap, scoreStatus := fwk.RunScorePlugins(ctx, state, pod, nodes)
if !scoreStatus.IsSuccess() {
return nil, scoreStatus.AsError()
}
// Additional details logged at level 10 if enabled.
klogV := klog.V(10)
if klogV.Enabled() {
for plugin, nodeScoreList := range scoresMap {
for _, nodeScore := range nodeScoreList {
klogV.InfoS("Plugin scored node for pod", "pod", klog.KObj(pod), "plugin", plugin, "node", nodeScore.Name, "score", nodeScore.Score)
}
}
}
// Summarize all scores.
result := make(framework.NodeScoreList, 0, len(nodes))
for i := range nodes {
result = append(result, framework.NodeScore{Name: nodes[i].Name, Score: 0})
for j := range scoresMap {
result[i].Score += scoresMap[j][i].Score
}
}
if len(extenders) != 0 && nodes != nil {
var mu sync.Mutex
var wg sync.WaitGroup
combinedScores := make(map[string]int64, len(nodes))
for i := range extenders {
if !extenders[i].IsInterested(pod) {
continue
}
wg.Add(1)
go func(extIndex int) {
metrics.SchedulerGoroutines.WithLabelValues(metrics.PrioritizingExtender).Inc()
defer func() {
metrics.SchedulerGoroutines.WithLabelValues(metrics.PrioritizingExtender).Dec()
wg.Done()
}()
prioritizedList, weight, err := extenders[extIndex].Prioritize(pod, nodes)
if err != nil {
// Prioritization errors from extender can be ignored, let k8s/other extenders determine the priorities
klog.V(5).InfoS("Failed to run extender's priority function. No score given by this extender.", "error", err, "pod", klog.KObj(pod), "extender", extenders[extIndex].Name())
return
}
mu.Lock()
for i := range *prioritizedList {
host, score := (*prioritizedList)[i].Host, (*prioritizedList)[i].Score
if klogV.Enabled() {
klogV.InfoS("Extender scored node for pod", "pod", klog.KObj(pod), "extender", extenders[extIndex].Name(), "node", host, "score", score)
}
combinedScores[host] += score * weight
}
mu.Unlock()
}(i)
}
// wait for all go routines to finish
wg.Wait()
for i := range result {
// MaxExtenderPriority may diverge from the max priority used in the scheduler and defined by MaxNodeScore,
// therefore we need to scale the score returned by extenders to the score range used by the scheduler.
result[i].Score += combinedScores[result[i].Name] * (framework.MaxNodeScore / extenderv1.MaxExtenderPriority)
}
}
if klogV.Enabled() {
for i := range result {
klogV.InfoS("Calculated node's final score for pod", "pod", klog.KObj(pod), "node", result[i].Name, "score", result[i].Score)
}
}
return result, nil
}
Reserve
Reserve 因为绑定事件时异步发生的，该插件是为了避免Pod在绑定到节点前时，调度到新的Pod，使节点使用资源超过可用资源情况。如果后续阶段发生错误或失败，将触发 UnReserve 回滚（通知性扩展点）。这也是作为调度周期中最后一个状态，要么成功到 postBind ，要么失败触发 UnReserve。
// Run the Reserve method of reserve plugins.
if sts := fwk.RunReservePluginsReserve(schedulingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost); !sts.IsSuccess() { // 当处理不成功时
metrics.PodScheduleError(fwk.ProfileName(), metrics.SinceInSeconds(start))
// 触发 un-reserve 来清理相关Pod的状态
fwk.RunReservePluginsUnreserve(schedulingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost)
if forgetErr := sched.Cache.ForgetPod(assumedPod); forgetErr != nil {
klog.ErrorS(forgetErr, "Scheduler cache ForgetPod failed")
}
sched.handleSchedulingFailure(ctx, fwk, assumedPodInfo, sts.AsError(), SchedulerError, clearNominatedNode)
return
}
permit
Permit 插件可以阻止或延迟 Pod 的绑定
// Run "permit" plugins.
runPermitStatus := fwk.RunPermitPlugins(schedulingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost)
if !runPermitStatus.IsWait() && !runPermitStatus.IsSuccess() {
var reason string
if runPermitStatus.IsUnschedulable() {
metrics.PodUnschedulable(fwk.ProfileName(), metrics.SinceInSeconds(start))
reason = v1.PodReasonUnschedulable
} else {
metrics.PodScheduleError(fwk.ProfileName(), metrics.SinceInSeconds(start))
reason = SchedulerError
}
// 只要其中一个插件返回的状态不是 success 或者 wait
fwk.RunReservePluginsUnreserve(schedulingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost)
// 从cache中忘掉pod
if forgetErr := sched.Cache.ForgetPod(assumedPod); forgetErr != nil {
klog.ErrorS(forgetErr, "Scheduler cache ForgetPod failed")
}
sched.handleSchedulingFailure(ctx, fwk, assumedPodInfo, runPermitStatus.AsError(), reason, clearNominatedNode)
return
}
Binding Cycle
在选择好 FN 后则做一个假设绑定，并更新到cache中，接下来回去执行真正的bind操作，也就是 binding cycle
func (sched *Scheduler) scheduleOne(ctx context.Context) {
...
...
// binding cycle 是一个异步的操作，这里表现就是go协程
go func() {
bindingCycleCtx, cancel := context.WithCancel(ctx)
defer cancel()
metrics.SchedulerGoroutines.WithLabelValues(metrics.Binding).Inc()
defer metrics.SchedulerGoroutines.WithLabelValues(metrics.Binding).Dec()
// 运行WaitOnPermit插件，如果失败则，unReserve回滚
waitOnPermitStatus := fwk.WaitOnPermit(bindingCycleCtx, assumedPod)
if !waitOnPermitStatus.IsSuccess() {
var reason string
if waitOnPermitStatus.IsUnschedulable() {
metrics.PodUnschedulable(fwk.ProfileName(), metrics.SinceInSeconds(start))
reason = v1.PodReasonUnschedulable
} else {
metrics.PodScheduleError(fwk.ProfileName(), metrics.SinceInSeconds(start))
reason = SchedulerError
}
// trigger un-reserve plugins to clean up state associated with the reserved Pod
fwk.RunReservePluginsUnreserve(bindingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost)
if forgetErr := sched.Cache.ForgetPod(assumedPod); forgetErr != nil {
klog.ErrorS(forgetErr, "scheduler cache ForgetPod failed")
} else {
// "Forget"ing an assumed Pod in binding cycle should be treated as a PodDelete event,
// as the assumed Pod had occupied a certain amount of resources in scheduler cache.
// TODO(#103853): de-duplicate the logic.
// Avoid moving the assumed Pod itself as it's always Unschedulable.
// It's intentional to "defer" this operation; otherwise MoveAllToActiveOrBackoffQueue() would
// update `q.moveRequest` and thus move the assumed pod to backoffQ anyways.
defer sched.SchedulingQueue.MoveAllToActiveOrBackoffQueue(internalqueue.AssignedPodDelete, func(pod *v1.Pod) bool {
return assumedPod.UID != pod.UID
})
}
sched.handleSchedulingFailure(ctx, fwk, assumedPodInfo, waitOnPermitStatus.AsError(), reason, clearNominatedNode)
return
}
// 运行Prebind 插件
preBindStatus := fwk.RunPreBindPlugins(bindingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost)
if !preBindStatus.IsSuccess() {
metrics.PodScheduleError(fwk.ProfileName(), metrics.SinceInSeconds(start))
// trigger un-reserve plugins to clean up state associated with the reserved Pod
fwk.RunReservePluginsUnreserve(bindingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost)
if forgetErr := sched.Cache.ForgetPod(assumedPod); forgetErr != nil {
klog.ErrorS(forgetErr, "scheduler cache ForgetPod failed")
} else {
// "Forget"ing an assumed Pod in binding cycle should be treated as a PodDelete event,
// as the assumed Pod had occupied a certain amount of resources in scheduler cache.
// TODO(#103853): de-duplicate the logic.
sched.SchedulingQueue.MoveAllToActiveOrBackoffQueue(internalqueue.AssignedPodDelete, nil)
}
sched.handleSchedulingFailure(ctx, fwk, assumedPodInfo, preBindStatus.AsError(), SchedulerError, clearNominatedNode)
return
}
// bind是真正的绑定操作
err := sched.bind(bindingCycleCtx, fwk, assumedPod, scheduleResult.SuggestedHost, state)
if err != nil {
metrics.PodScheduleError(fwk.ProfileName(), metrics.SinceInSeconds(start))
// 如果失败了就触发 un-reserve plugins
fwk.RunReservePluginsUnreserve(bindingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost)
if err := sched.Cache.ForgetPod(assumedPod); err != nil {
klog.ErrorS(err, "scheduler cache ForgetPod failed")
} else {
// "Forget"ing an assumed Pod in binding cycle should be treated as a PodDelete event,
// as the assumed Pod had occupied a certain amount of resources in scheduler cache.
// TODO(#103853): de-duplicate the logic.
sched.SchedulingQueue.MoveAllToActiveOrBackoffQueue(internalqueue.AssignedPodDelete, nil)
}
sched.handleSchedulingFailure(ctx, fwk, assumedPodInfo, fmt.Errorf("binding rejected: %w", err), SchedulerError, clearNominatedNode)
return
}
// Calculating nodeResourceString can be heavy. Avoid it if klog verbosity is below 2.
klog.V(2).InfoS("Successfully bound pod to node", "pod", klog.KObj(pod), "node", scheduleResult.SuggestedHost, "evaluatedNodes", scheduleResult.EvaluatedNodes, "feasibleNodes", scheduleResult.FeasibleNodes)
metrics.PodScheduled(fwk.ProfileName(), metrics.SinceInSeconds(start))
metrics.PodSchedulingAttempts.Observe(float64(podInfo.Attempts))
metrics.PodSchedulingDuration.WithLabelValues(getAttemptsLabel(podInfo)).Observe(metrics.SinceInSeconds(podInfo.InitialAttemptTimestamp))
// 运行 "postbind" 插件
// 是通知性的扩展点，该插件在绑定 Pod 后调用，可用于清理相关资源（）。
fwk.RunPostBindPlugins(bindingCycleCtx, state, assumedPod, scheduleResult.SuggestedHost)
// At the end of a successful binding cycle, move up Pods if needed.
if len(podsToActivate.Map) != 0 {
sched.SchedulingQueue.Activate(podsToActivate.Map)
// Unlike the logic in scheduling cycle, we don't bother deleting the entries
// as `podsToActivate.Map` is no longer consumed.
}
}()
}
调度上下文中的失败流程
上面说到的都是正常的请求，下面会对失败的请求是如何重试的进行分析，而 scheduler 中关于失败处理方面相关的属性会涉及到上面 scheduler 结构中的 backoffQ 与 unschedulablePods
backoffQ：也是一个 heap 类型的优先级队列，存放的是不可调度的PodunschedulablePods：保存确定不可被调度的Pod，一个map类型
backoffQ 与 unschedulablePods 会在初始化 scheduler 时初始化，
func NewPriorityQueue(
lessFn framework.LessFunc,
informerFactory informers.SharedInformerFactory,
opts ...Option,
) *PriorityQueue {
options := defaultPriorityQueueOptions
for _, opt := range opts {
opt(&options)
}
comp := func(podInfo1, podInfo2 interface{}) bool {
pInfo1 := podInfo1.(*framework.QueuedPodInfo)
pInfo2 := podInfo2.(*framework.QueuedPodInfo)
return lessFn(pInfo1, pInfo2)
}
if options.podNominator == nil {
options.podNominator = NewPodNominator(informerFactory.Core().V1().Pods().Lister())
}
pq := &PriorityQueue{
PodNominator: options.podNominator,
clock: options.clock,
stop: make(chan struct{}),
podInitialBackoffDuration: options.podInitialBackoffDuration,
podMaxBackoffDuration: options.podMaxBackoffDuration,
podMaxInUnschedulablePodsDuration: options.podMaxInUnschedulablePodsDuration,
activeQ: heap.NewWithRecorder(podInfoKeyFunc, comp, metrics.NewActivePodsRecorder()),
unschedulablePods: newUnschedulablePods(metrics.NewUnschedulablePodsRecorder()),
moveRequestCycle: -1,
clusterEventMap: options.clusterEventMap,
}
pq.cond.L = &pq.lock
// 初始化backoffQ
// NewWithRecorder作为一个可选的 metricRecorder 的 Heap 对象。
// podInfoKeyFunc是一个函数，返回错误与字符串
// pq.podsCompareBackoffCompleted 比较两个pod的回退时间，如果第一个在第二个之前为true，
// 反之 false
pq.podBackoffQ = heap.NewWithRecorder(podInfoKeyFunc, pq.podsCompareBackoffCompleted, metrics.NewBackoffPodsRecorder())
pq.nsLister = informerFactory.Core().V1().Namespaces().Lister()
return pq
}
对于初始化 backoffQ 会产生的两个函数，getBackoffTime 与 calculateBackoffDuration
// getBackoffTime returns the time that podInfo completes backoff
func (p *PriorityQueue) getBackoffTime(podInfo *framework.QueuedPodInfo) time.Time {
duration := p.calculateBackoffDuration(podInfo)
backoffTime := podInfo.Timestamp.Add(duration)
return backoffTime
}
// calculateBackoffDuration is a helper function for calculating the backoffDuration
// based on the number of attempts the pod has made.
func (p *PriorityQueue) calculateBackoffDuration(podInfo *framework.QueuedPodInfo) time.Duration {
duration := p.podInitialBackoffDuration
for i := 1; i < podInfo.Attempts; i++ {
// Use subtraction instead of addition or multiplication to avoid overflow.
if duration > p.podMaxBackoffDuration-duration {
return p.podMaxBackoffDuration
}
duration += duration
}
return duration
}
对于整个故障错误会按照如下流程进行，在初始化 scheduler 会注册一个 Error 函数，这个函数用作对不可调度Pod进行处理，实际上被注册的函数是 MakeDefaultErrorFunc。这个函数将作为 Error 函数被调用。
sched := newScheduler(
schedulerCache,
extenders,
internalqueue.MakeNextPodFunc(podQueue),
MakeDefaultErrorFunc(client, podLister, podQueue, schedulerCache),
stopEverything,
podQueue,
profiles,
client,
snapshot,
options.percentageOfNodesToScore,
)
而在 调度周期中，也就是 scheduleOne 可以看到，每个扩展点操作失败后都会调用 handleSchedulingFailure 而该函数，使用了注册的 Error 函数来处理Pod
func (sched *Scheduler) scheduleOne(ctx context.Context) {
...
defer cancel()
scheduleResult, err := sched.SchedulePod(schedulingCycleCtx, fwk, state, pod)
if err != nil {
var nominatingInfo *framework.NominatingInfo
if fitError, ok := err.(*framework.FitError); ok {
if !fwk.HasPostFilterPlugins() {
klog.V(3).InfoS("No PostFilter plugins are registered, so no preemption will be performed")
} else {
result, status := fwk.RunPostFilterPlugins(ctx, state, pod, fitError.Diagnosis.NodeToStatusMap)
if status.Code() == framework.Error {
klog.ErrorS(nil, "Status after running PostFilter plugins for pod", "pod", klog.KObj(pod), "status", status)
} else {
fitError.Diagnosis.PostFilterMsg = status.Message()
klog.V(5).InfoS("Status after running PostFilter plugins for pod", "pod", klog.KObj(pod), "status", status)
}
if result != nil {
nominatingInfo = result.NominatingInfo
}
}
metrics.PodUnschedulable(fwk.ProfileName(), metrics.SinceInSeconds(start))
} else if err == ErrNoNodesAvailable {
nominatingInfo = clearNominatedNode
// No nodes available is counted as unschedulable rather than an error.
metrics.PodUnschedulable(fwk.ProfileName(), metrics.SinceInSeconds(start))
} else {
nominatingInfo = clearNominatedNode
klog.ErrorS(err, "Error selecting node for pod", "pod", klog.KObj(pod))
metrics.PodScheduleError(fwk.ProfileName(), metrics.SinceInSeconds(start))
}
// 处理不可调度Pod
sched.handleSchedulingFailure(ctx, fwk, podInfo, err, v1.PodReasonUnschedulable, nominatingInfo)
return
}
来到了注册的 Error 函数 MakeDefaultErrorFunc
func MakeDefaultErrorFunc(client clientset.Interface, podLister corelisters.PodLister, podQueue internalqueue.SchedulingQueue, schedulerCache internalcache.Cache) func(*framework.QueuedPodInfo, error) {
return func(podInfo *framework.QueuedPodInfo, err error) {
pod := podInfo.Pod
if err == ErrNoNodesAvailable {
klog.V(2).InfoS("Unable to schedule pod; no nodes are registered to the cluster; waiting", "pod", klog.KObj(pod))
} else if fitError, ok := err.(*framework.FitError); ok {
// Inject UnschedulablePlugins to PodInfo, which will be used later for moving Pods between queues efficiently.
podInfo.UnschedulablePlugins = fitError.Diagnosis.UnschedulablePlugins
klog.V(2).InfoS("Unable to schedule pod; no fit; waiting", "pod", klog.KObj(pod), "err", err)
} else if apierrors.IsNotFound(err) {
klog.V(2).InfoS("Unable to schedule pod, possibly due to node not found; waiting", "pod", klog.KObj(pod), "err", err)
if errStatus, ok := err.(apierrors.APIStatus); ok && errStatus.Status().Details.Kind == "node" {
nodeName := errStatus.Status().Details.Name
// when node is not found, We do not remove the node right away. Trying again to get
// the node and if the node is still not found, then remove it from the scheduler cache.
_, err := client.CoreV1().Nodes().Get(context.TODO(), nodeName, metav1.GetOptions{})
if err != nil && apierrors.IsNotFound(err) {
node := v1.Node{ObjectMeta: metav1.ObjectMeta{Name: nodeName}}
if err := schedulerCache.RemoveNode(&node); err != nil {
klog.V(4).InfoS("Node is not found; failed to remove it from the cache", "node", node.Name)
}
}
}
} else {
klog.ErrorS(err, "Error scheduling pod; retrying", "pod", klog.KObj(pod))
}
// Check if the Pod exists in informer cache.
cachedPod, err := podLister.Pods(pod.Namespace).Get(pod.Name)
if err != nil {
klog.InfoS("Pod doesn't exist in informer cache", "pod", klog.KObj(pod), "err", err)
return
}
// In the case of extender, the pod may have been bound successfully, but timed out returning its response to the scheduler.
// It could result in the live version to carry .spec.nodeName, and that's inconsistent with the internal-queued version.
if len(cachedPod.Spec.NodeName) != 0 {
klog.InfoS("Pod has been assigned to node. Abort adding it back to queue.", "pod", klog.KObj(pod), "node", cachedPod.Spec.NodeName)
return
}
// As <cachedPod> is from SharedInformer, we need to do a DeepCopy() here.
podInfo.PodInfo = framework.NewPodInfo(cachedPod.DeepCopy())
// 添加到unschedulable队列中
if err := podQueue.AddUnschedulableIfNotPresent(podInfo, podQueue.SchedulingCycle()); err != nil {
klog.ErrorS(err, "Error occurred")
}
}
}
下面来到 AddUnschedulableIfNotPresent ，这个也是操作 backoffQ 和 unschedulablePods 的真正的动作
AddUnschedulableIfNotPresent 函数会吧无法调度的 pod 插入队列，除非它已经在队列中。通常情况下，PriorityQueue 将不可调度的 Pod 放在 unschedulablePods 中。但如果最近有 move request，则将 pod 放入 podBackoffQ 中。
func (p *PriorityQueue) AddUnschedulableIfNotPresent(pInfo *framework.QueuedPodInfo, podSchedulingCycle int64) error {
p.lock.Lock()
defer p.lock.Unlock()
pod := pInfo.Pod
// 如果已经存在则不添加
if p.unschedulablePods.get(pod) != nil {
return fmt.Errorf("Pod %v is already present in unschedulable queue", klog.KObj(pod))
}
// 检查是否在activeQ中
if _, exists, _ := p.activeQ.Get(pInfo); exists {
return fmt.Errorf("Pod %v is already present in the active queue", klog.KObj(pod))
}
// 检查是否在podBackoffQ中
if _, exists, _ := p.podBackoffQ.Get(pInfo); exists {
return fmt.Errorf("Pod %v is already present in the backoff queue", klog.KObj(pod))
}
// 在重新添加时，会刷新 Pod时间为最新操作的时间
pInfo.Timestamp = p.clock.Now()
for plugin := range pInfo.UnschedulablePlugins {
metrics.UnschedulableReason(plugin, pInfo.Pod.Spec.SchedulerName).Inc()
}
// 如果接受到move request那么则放入BackoffQ
if p.moveRequestCycle >= podSchedulingCycle {
if err := p.podBackoffQ.Add(pInfo); err != nil {
return fmt.Errorf("error adding pod %v to the backoff queue: %v", pod.Name, err)
}
metrics.SchedulerQueueIncomingPods.WithLabelValues("backoff", ScheduleAttemptFailure).Inc()
} else {
// 否则将放入到 unschedulablePods
p.unschedulablePods.addOrUpdate(pInfo)
metrics.SchedulerQueueIncomingPods.WithLabelValues("unschedulable", ScheduleAttemptFailure).Inc()
}
p.PodNominator.AddNominatedPod(pInfo.PodInfo, nil)
return nil
}
在启动 scheduler 时，会将这两个队列异步启用两个loop来操作队列。表现在 Run()
func (p *PriorityQueue) Run() {
go wait.Until(p.flushBackoffQCompleted, 1.0*time.Second, p.stop)
go wait.Until(p.flushUnschedulablePodsLeftover, 30*time.Second, p.stop)
}
可以看到 flushBackoffQCompleted 作为 BackoffQ 实现；而 flushUnschedulablePodsLeftover 作为 UnschedulablePods 实现。
flushBackoffQCompleted 是用于将所有已完成回退的 pod 从 backoffQ 移到 activeQ 中
func (p *PriorityQueue) flushBackoffQCompleted() {
p.lock.Lock()
defer p.lock.Unlock()
broadcast := false
for { // 这就是heap实现的方法，窥视下，但不弹出
rawPodInfo := p.podBackoffQ.Peek()
if rawPodInfo == nil {
break
}
pod := rawPodInfo.(*framework.QueuedPodInfo).Pod
boTime := p.getBackoffTime(rawPodInfo.(*framework.QueuedPodInfo))
if boTime.After(p.clock.Now()) {
break
}
_, err := p.podBackoffQ.Pop() // 弹出一个
if err != nil {
klog.ErrorS(err, "Unable to pop pod from backoff queue despite backoff completion", "pod", klog.KObj(pod))
break
}
p.activeQ.Add(rawPodInfo) // 放入到活动队列中
metrics.SchedulerQueueIncomingPods.WithLabelValues("active", BackoffComplete).Inc()
broadcast = true
}
if broadcast {
p.cond.Broadcast()
}
}
flushUnschedulablePodsLeftover 函数用于将在 unschedulablePods 中的存放时间超过 podMaxInUnschedulablePodsDuration 值的 pod 移动到 backoffQ 或 activeQ 中。
podMaxInUnschedulablePodsDuration 会根据配置传入，当没有传入，也就是使用了 Deprecated 那么会为5分钟。
func NewOptions() *Options {
o := &Options{
SecureServing: apiserveroptions.NewSecureServingOptions().WithLoopback(),
Authentication: apiserveroptions.NewDelegatingAuthenticationOptions(),
Authorization: apiserveroptions.NewDelegatingAuthorizationOptions(),
Deprecated: &DeprecatedOptions{
PodMaxInUnschedulablePodsDuration: 5 * time.Minute,
},
对于 flushUnschedulablePodsLeftover 就是做一个时间对比，然后添加到对应的队列中
func (p *PriorityQueue) flushUnschedulablePodsLeftover() {
p.lock.Lock()
defer p.lock.Unlock()
var podsToMove []*framework.QueuedPodInfo
currentTime := p.clock.Now()
for _, pInfo := range p.unschedulablePods.podInfoMap {
lastScheduleTime := pInfo.Timestamp
if currentTime.Sub(lastScheduleTime) > p.podMaxInUnschedulablePodsDuration {
podsToMove = append(podsToMove, pInfo)
}
}
if len(podsToMove) > 0 {
p.movePodsToActiveOrBackoffQueue(podsToMove, UnschedulableTimeout)
}
}
总结调度上下文流程
- 在构建一个 scheduler 时经历如下步骤：
- 准备cache，informer，queue，错误处理函数等
- 添加事件函数，会监听资源（如Pod），当有变动则触发对应事件函数，这是入站
activeQ
- 构建完成后会 run，run时会run一个
SchedulingQueue，这个是作为不可调度队列BackoffQUnschedulablePods- 不可调度队列会根据注册时定期消费队列中Pod将其添加到
activeQ中
- 启动一个
scheduleOne的loop，这个是调度上下文中所有的扩展点的执行，也是activeQ的消费端scheduleOne获取 pod- 执行各个扩展点，如果出错则 Error 函数
MakeDefaultErrorFunc将其添加到不可调度队列中 - 回到不可调度队列中消费部分