1. 前言
转载请说明原文出处, 尊重他人劳动成果!
本文将分析调度器中的预选方法, 主要涉及
pkg/scheduler/algorithm/predicate/predicates.go和pkg/scheduler/algorithm/type.go
源码位置: https://github.com/nicktming/kubernetes
分支: tming-v1.13 (基于v1.13版本)
2. 预选方法定义(predicate)
type FitPredicate func(pod *v1.Pod, meta PredicateMetadata, nodeInfo *schedulercache.NodeInfo) (bool, []PredicateFailureReason, error)
// PredicateMetadataProducer is a function that computes predicate metadata for a given pod.
type PredicateMetadataProducer func(pod *v1.Pod, nodeNameToInfo map[string]*schedulercache.NodeInfo) PredicateMetadata
// PredicateMetadata interface represents anything that can access a predicate metadata.
type PredicateMetadata interface {
ShallowCopy() PredicateMetadata
AddPod(addedPod *v1.Pod, nodeInfo *schedulercache.NodeInfo) error
RemovePod(deletedPod *v1.Pod) error
}
可以看到
FitPredicate就是预选方法
pod: 需要调度的pod.
meta: 一个PredicateMetadata(对predicateMetadata目前可以不用在意, 因为不会影响到整个对预选方法的理解, 会在后面有分析)
nodeInfo: 就是节点信息
返回该pod在该节点nodeInfo是否可以通过, 如果不通过, 理由也会返回.
所以接下来就分析几个常见的预选方法. 因为在[k8s源码分析][kube-scheduler]scheduler/algorithmprovider之注册default-scheduler 已经有涉及到, 所以直接就从
pkg/scheduler/algorithmprovider/defaults/defaults.go中选几个简单看看就可以了.
3. 预选方法
3.1 PodFitsHostPorts
判断该节点中使用了的port是否与requested pod ports有冲突
func PodFitsHostPorts(pod *v1.Pod, meta algorithm.PredicateMetadata, nodeInfo *schedulercache.NodeInfo) (bool, []algorithm.PredicateFailureReason, error) {
var wantPorts []*v1.ContainerPort
// 如果meta可以转成predicateMetadata 就从meta中取
// 这里不用太在意meta, 因为该meta如果不为nil的话 其实就是从该pod中做了一些操作而已
if predicateMeta, ok := meta.(*predicateMetadata); ok {
wantPorts = predicateMeta.podPorts
} else {
// We couldn't parse metadata - fallback to computing it.
wantPorts = schedutil.GetContainerPorts(pod)
}
if len(wantPorts) == 0 {
return true, nil, nil
}
// 从该节点信息中拿到该节点已经使用过的端口
existingPorts := nodeInfo.UsedPorts()
// try to see whether existingPorts and wantPorts will conflict or not
//判断是否有冲突
if portsConflict(existingPorts, wantPorts) {
return false, []algorithm.PredicateFailureReason{ErrPodNotFitsHostPorts}, nil
}
return true, nil, nil
}
3.2 PodFitsResources
判断资源是否充足
func PodFitsResources(pod *v1.Pod, meta algorithm.PredicateMetadata, nodeInfo *schedulercache.NodeInfo) (bool, []algorithm.PredicateFailureReason, error) {
node := nodeInfo.Node()
if node == nil {
return false, nil, fmt.Errorf("node not found")
}
var predicateFails []algorithm.PredicateFailureReason
allowedPodNumber := nodeInfo.AllowedPodNumber()
// 如果该节点所可以容纳的pod数量达到上限时
if len(nodeInfo.Pods())+1 > allowedPodNumber {
predicateFails = append(predicateFails, NewInsufficientResourceError(v1.ResourcePods, 1, int64(len(nodeInfo.Pods())), int64(allowedPodNumber)))
}
// No extended resources should be ignored by default.
ignoredExtendedResources := sets.NewString()
var podRequest *schedulercache.Resource
if predicateMeta, ok := meta.(*predicateMetadata); ok {
podRequest = predicateMeta.podRequest
if predicateMeta.ignoredExtendedResources != nil {
ignoredExtendedResources = predicateMeta.ignoredExtendedResources
}
} else {
// We couldn't parse metadata - fallback to computing it.
podRequest = GetResourceRequest(pod)
}
if podRequest.MilliCPU == 0 &&
podRequest.Memory == 0 &&
podRequest.EphemeralStorage == 0 &&
len(podRequest.ScalarResources) == 0 {
return len(predicateFails) == 0, predicateFails, nil
}
allocatable := nodeInfo.AllocatableResource()
// 判断cpu部分 都是按request计算的
if allocatable.MilliCPU < podRequest.MilliCPU+nodeInfo.RequestedResource().MilliCPU {
predicateFails = append(predicateFails, NewInsufficientResourceError(v1.ResourceCPU, podRequest.MilliCPU, nodeInfo.RequestedResource().MilliCPU, allocatable.MilliCPU))
}
// 判断memory部分 都是按request计算的
if allocatable.Memory < podRequest.Memory+nodeInfo.RequestedResource().Memory {
predicateFails = append(predicateFails, NewInsufficientResourceError(v1.ResourceMemory, podRequest.Memory, nodeInfo.RequestedResource().Memory, allocatable.Memory))
}
if allocatable.EphemeralStorage < podRequest.EphemeralStorage+nodeInfo.RequestedResource().EphemeralStorage {
predicateFails = append(predicateFails, NewInsufficientResourceError(v1.ResourceEphemeralStorage, podRequest.EphemeralStorage, nodeInfo.RequestedResource().EphemeralStorage, allocatable.EphemeralStorage))
}
// 判断扩展的资源 比如利用device_plugin注册的资源
for rName, rQuant := range podRequest.ScalarResources {
if v1helper.IsExtendedResourceName(rName) {
// If this resource is one of the extended resources that should be
// ignored, we will skip checking it.
if ignoredExtendedResources.Has(string(rName)) {
continue
}
}
if allocatable.ScalarResources[rName] < rQuant+nodeInfo.RequestedResource().ScalarResources[rName] {
predicateFails = append(predicateFails, NewInsufficientResourceError(rName, podRequest.ScalarResources[rName], nodeInfo.RequestedResource().ScalarResources[rName], allocatable.ScalarResources[rName]))
}
}
if klog.V(10) {
if len(predicateFails) == 0 {
// We explicitly don't do klog.V(10).Infof() to avoid computing all the parameters if this is
// not logged. There is visible performance gain from it.
klog.Infof("Schedule Pod %+v on Node %+v is allowed, Node is running only %v out of %v Pods.",
podName(pod), node.Name, len(nodeInfo.Pods()), allowedPodNumber)
}
}
return len(predicateFails) == 0, predicateFails, nil
}
3.3 PodFitsHost (HostNamePred = "HostName")
判断
pod.Spec.NodeName是否匹配当前节点名称.
如果pod.Spec.NodeName为空或者等于当前节点名称, 就返回true.
否则返回false.
func PodFitsHost(pod *v1.Pod, meta algorithm.PredicateMetadata, nodeInfo *schedulercache.NodeInfo) (bool, []algorithm.PredicateFailureReason, error) {
if len(pod.Spec.NodeName) == 0 {
return true, nil, nil
}
node := nodeInfo.Node()
if node == nil {
return false, nil, fmt.Errorf("node not found")
}
if pod.Spec.NodeName == node.Name {
return true, nil, nil
}
return false, []algorithm.PredicateFailureReason{ErrPodNotMatchHostName}, nil
}
4. 总结
简单介绍了几个常见的预选方法
PodFitsHostPorts,PodFitsResources和HostName. 主要是为了能理解预选方法的工作性质是什么即可.
