专题-亲和性调度(Author - XiaoYang)

简介

在未分析和深入理解scheduler源码逻辑之前，本人在操作配置亲和性上，由于官方和第三方文档者说明不清楚等原因，在亲和性理解上有遇到过一些困惑，如：

1. 亲和性的operator的 “In”底层是什么匹配操作？正则匹配吗？“Gt/Lt”底层又是什么操作实现的？

2. 所有能查到的文档描述pod亲和性的topoloykey有三个：kubernetes.io/hostnamefailure-domain.beta.kubernetes.io/zonefailure-domain.beta.kubernetes.io/region为什么？真的只支持这三个key？不能自定义？

3. Pod与Node亲和性两种类型的差异是什么？而Pod亲和性正真要去匹配的是什么，其内在逻辑是？不知道你们是否有同样类似的问题或困惑呢？当你清晰的理解了代码逻辑实现后，那么你会觉得一切是那么的清楚明确了，不再有“隐性知识”问题存在。所以我希望本文所述内容能给大家在kubernetes亲和性的解惑上有所帮助。

约束调度

在展开源码分析之前为更好的理解亲和性代码逻辑，补充一些kubernetes调度相关的基础知识：

1. 亲和性目的是为了实现用户可以按需将pod调度到指定Node上，我称之为“约束调度”。
2. 约束调度操作上常用以下三类：

• NodeSelector / NodeName node标签选择器 和 “nodeName”匹配
• Affinity (Node/Pod/Service） 亲和性
• Taint / Toleration 污点和容忍

1. 本文所述主题是亲和性，亲和性分为三种类型Node、Pod、Service亲和，以下是亲和性预选和优选阶段代码实现的策略对应表（后面有详细分析）：

Labels.selector标签选择器

labels selector是亲和性代码底层使用最基础的代码工具，不论是nodeAffinity还是podAffinity都是需要用到它。在使用yml类型deployment定义一个pod，配置其亲和性时须指定匹配表达式，其根本的匹配都是要对Node或pod的labels标签进行条件匹配。而这些labels标签匹配计算就必须要用到labels.selector工具(公共使用部分)。 所以在将此块最底层的匹配计算分析部分放在最前面，以便于后面源码分析部分更容易理解。

labels.selector接口定义，关键的方法是Matchs()

!FILENAME vendor/k8s.io/apimachinery/pkg/labels/selector.go:36

type Selector interface {
    Matches(Labels) bool  
    Empty() bool
    String() string
    Add(r ...Requirement) Selector
    Requirements() (requirements Requirements, selectable bool)
    DeepCopySelector() Selector
}

看一下调用端，如下面的几个实例的func，调用labels.NewSelector()实例化一个labels.selector对象返回.

func LabelSelectorAsSelector(ps *LabelSelector) (labels.Selector, error) {
  ...
    selector := labels.NewSelector()   
  ...
}
func NodeSelectorRequirementsAsSelector(nsm []v1.NodeSelectorRequirement) (labels.Selector, error) {
    ...
    selector := labels.NewSelector() 
    ...
    }
func TopologySelectorRequirementsAsSelector(tsm []v1.TopologySelectorLabelRequirement) (labels.Selector, error) {
  ...
    selector := labels.NewSelector()  
  ...
}

NewSelector返回的是一个InternelSelector类型，而InternelSelector类型是一个Requirement（必要条件）

类型的列表。

!FILENAME vendor/k8s.io/apimachinery/pkg/labels/selector.go:79

func NewSelector() Selector {
    return internalSelector(nil)
}
type internalSelector []Requirement

InternelSelector类的Matches()底层实现是遍历调用requirement.Matches()

!FILENAME vendor/k8s.io/apimachinery/pkg/labels/selector.go:340

func (lsel internalSelector) Matches(l Labels) bool {
    for ix := range lsel {
      // internalSelector[ix]为Requirement
        if matches := lsel[ix].Matches(l); !matches {
            return false
        }
    }
    return true
}

再来看下requirment结构定义(key、操作符、值 ) “这就是配置的亲和匹配条件表达式”

!FILENAME vendor/k8s.io/apimachinery/pkg/labels/selector.go:114

type Requirement struct {
    key      string
    operator selection.Operator
    // In huge majority of cases we have at most one value here.
    // It is generally faster to operate on a single-element slice
    // than on a single-element map, so we have a slice here.
    strValues []string
}

requirment.matchs() 真正的条件表达式操作实现,基于表达式operator,计算key/value,返回匹配与否

!FILENAME vendor/k8s.io/apimachinery/pkg/labels/selector.go:192

func (r *Requirement) Matches(ls Labels) bool {
    switch r.operator {
    case selection.In, selection.Equals, selection.DoubleEquals:
        if !ls.Has(r.key) {                       //IN
            return false
        }
        return r.hasValue(ls.Get(r.key))
    case selection.NotIn, selection.NotEquals:   //NotIn
        if !ls.Has(r.key) {
            return true
        }
        return !r.hasValue(ls.Get(r.key))        
    case selection.Exists:                       //Exists
        return ls.Has(r.key)
    case selection.DoesNotExist:                 //NotExists
        return !ls.Has(r.key)
    case selection.GreaterThan, selection.LessThan: // GT、LT
        if !ls.Has(r.key) {
            return false
        }
        lsValue, err := strconv.ParseInt(ls.Get(r.key), 10, 64)   //能转化为数值的”字符数值“
        if err != nil {
            klog.V(10).Infof("ParseInt failed for value %+v in label %+v, %+v", ls.Get(r.key), ls, err)
            return false
        }
        // There should be only one strValue in r.strValues, and can be converted to a integer.
        if len(r.strValues) != 1 {
            klog.V(10).Infof("Invalid values count %+v of requirement %#v, for 'Gt', 'Lt' operators, exactly one value is required", len(r.strValues), r)
            return false
        }
        var rValue int64
        for i := range r.strValues {
            rValue, err = strconv.ParseInt(r.strValues[i], 10, 64)
            if err != nil {
                klog.V(10).Infof("ParseInt failed for value %+v in requirement %#v, for 'Gt', 'Lt' operators, the value must be an integer", r.strValues[i], r)
                return false
            }
        }
        return (r.operator == selection.GreaterThan && lsValue > rValue) || (r.operator == selection.LessThan && lsValue < rValue)
    default:
        return false
    }
}

注：除了LabelsSelector外还有NodeSelector 、FieldsSelector、PropertySelector等，但基本都是类似的Selector接口实现，逻辑上都基本一致，后在源码分析过程有相应的说明。

Node亲和性

Node亲和性基础描述:

yml配置实例sample：

---
apiVersion:v1
kind: Pod
metadata:
  name: with-node-affinity
spec:
  affinity:
    nodeAffinity:    #pod实例部署在prd-zone-A 或 prd-zone-B
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: kubernetes.io/prd-zone-name
            operator: In
            values:
            - prd-zone-A
            - prd-zone-B
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 1
        preference:
          matchExpressions:
          - key: securityZone
            operator: In
            values:
            - BussinssZone
  containers:
  - name: with-node-affinity
    image: gcr.io/google_containers/pause:2.0

Node亲和性预选策略MatchNodeSelectorPred

策略说明：

基于NodeSelector和NodeAffinity定义为被调度的pod选择相匹配的Node（Nodes Labels）

适用NodeAffinity配置项：

NodeAffinity.RequiredDuringSchedulingIgnoredDuringExecution

预选策略源码分析：

1. 策略注册： defaults.init()注册了一条名为“MatchNodeSelectorPred”预选策略项,策略Func是PodMatchNodeSelector()

!FILENAME pkg/scheduler/algorithmprovider/defaults/defaults.go:78

func init() {
  ...
factory.RegisterFitPredicate(predicates.MatchNodeSelectorPred, predicates.PodMatchNodeSelector)
  ...
}

1. 策略Func: PodMatchNodeSelector()

获取目标Node信息,调用podMatchesNodeSelectorAndAffinityTerms()对被调度pod和目标node进行亲和性匹配。 如果符合则返回true,反之false并记录错误信息。

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:853

func PodMatchNodeSelector(pod *v1.Pod, meta algorithm.PredicateMetadata, nodeInfo *schedulercache.NodeInfo) (bool, []algorithm.PredicateFailureReason, error) {
  // 获取node信息
    node := nodeInfo.Node()
    if node == nil {
        return false, nil, fmt.Errorf("node not found")
    }
  // 关键子逻辑func
  // 输入参数:被调度的pod和前面获取的node(被检测的node)
    if podMatchesNodeSelectorAndAffinityTerms(pod, node) {
        return true, nil, nil
    }
    return false, []algorithm.PredicateFailureReason{ErrNodeSelectorNotMatch}, nil
}

​ podMatchesNodeSelectorAndAffinityTerms()

​ NodeSelector和NodeAffinity定义的”必要条件”配置匹配检测

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:807

func podMatchesNodeSelectorAndAffinityTerms(pod *v1.Pod, node *v1.Node) bool {
  // 如果设置了NodeSelector,则检测Node labels是否满足NodeSelector所定义的所有terms项.   
    if len(pod.Spec.NodeSelector) > 0 {
        selector := labels.SelectorFromSet(pod.Spec.NodeSelector)
        if !selector.Matches(labels.Set(node.Labels)) {
            return false
        }
    }
  //如果设置了NodeAffinity，则进行Node亲和性匹配  nodeMatchesNodeSelectorTerms() *[后面有详细分析]* 
    nodeAffinityMatches := true
    affinity := pod.Spec.Affinity
    if affinity != nil && affinity.NodeAffinity != nil {
        nodeAffinity := affinity.NodeAffinity
        if nodeAffinity.RequiredDuringSchedulingIgnoredDuringExecution == nil {
            return true
        }
        if nodeAffinity.RequiredDuringSchedulingIgnoredDuringExecution != nil {
            nodeSelectorTerms := nodeAffinity.RequiredDuringSchedulingIgnoredDuringExecution.NodeSelectorTerms
            klog.V(10).Infof("Match for RequiredDuringSchedulingIgnoredDuringExecution node selector terms %+v", nodeSelectorTerms)
      // 关键处理func: nodeMatchesNodeSelectorTerms()                             
            nodeAffinityMatches = nodeAffinityMatches && nodeMatchesNodeSelectorTerms(node, nodeSelectorTerms)
        }
    }
    return nodeAffinityMatches
}

注：

• NodeSelector和NodeAffinity.Require… 都存在配置则都需True；

• 如果NodeSelector失败则直接false,不处理NodeAffinity;

• 如果指定了多个 NodeSelectorTerms，那 node只要满足其中一个条件;

• 如果指定了多个 MatchExpressions，那必须要满足所有条件.

nodeMatchesNodeSelectorTerms()调用v1helper.MatchNodeSelectorTerms()进行NodeSelectorTerm定义的必要条件进行检测是否符合。关键的配置定义分为两类(matchExpressions/matchFileds)：-“requiredDuringSchedulingIgnoredDuringExecution.matchExpressions”定义检测(匹配key与value)-“requiredDuringSchedulingIgnoredDuringExecution.matchFileds”定义检测(不匹配key，只value)

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:797

func nodeMatchesNodeSelectorTerms(node *v1.Node, nodeSelectorTerms []v1.NodeSelectorTerm) bool {
    nodeFields := map[string]string{}
  // 获取检测目标node的Filelds
    for k, f := range algorithm.NodeFieldSelectorKeys {
        nodeFields[k] = f(node)
    }
  // 调用v1helper.MatchNodeSelectorTerms()
  // 参数：nodeSelectorTerms  亲和性配置的必要条件Terms
  //      labels             被检测的目标node的label列表 
  //      fields             被检测的目标node filed列表
    return v1helper.MatchNodeSelectorTerms(nodeSelectorTerms, labels.Set(node.Labels), fields.Set(nodeFields))
}
// pkg/apis/core/v1/helper/helpers.go:302
func MatchNodeSelectorTerms( nodeSelectorTerms []v1.NodeSelectorTerm,
    nodeLabels labels.Set, nodeFields fields.Set,) bool {
    for _, req := range nodeSelectorTerms {
        // nil or empty term selects no objects
        if len(req.MatchExpressions) == 0 && len(req.MatchFields) == 0 {
            continue
        }
    // MatchExpressions条件表达式匹配                                             ① 
        if len(req.MatchExpressions) != 0 {
            labelSelector, err := NodeSelectorRequirementsAsSelector(req.MatchExpressions)
            if err != nil || !labelSelector.Matches(nodeLabels) {
                continue
            }
        }
    // MatchFields条件表达式匹配                                                   ②
        if len(req.MatchFields) != 0 {
            fieldSelector, err := NodeSelectorRequirementsAsFieldSelector(req.MatchFields)
            if err != nil || !fieldSelector.Matches(nodeFields) {
                continue
            }
        }
        return true
    }
    return false
}

① NodeSelectorRequirementAsSelector()是对“requiredDuringSchedulingIgnoredDuringExecution.matchExpressions”所配置的表达式进行Selector表达式进行格式化加工，返回一个labels.Selector实例化对象. [本文开头1.2章节有分析]

!FILENAME pkg/apis/core/v1/helper/helpers.go:222

func NodeSelectorRequirementsAsSelector(nsm []v1.NodeSelectorRequirement) (labels.Selector, error) {
    if len(nsm) == 0 {
        return labels.Nothing(), nil
    }
    selector := labels.NewSelector()
    for _, expr := range nsm {
        var op selection.Operator
        switch expr.Operator {
        case v1.NodeSelectorOpIn:
            op = selection.In
        case v1.NodeSelectorOpNotIn:
            op = selection.NotIn
        case v1.NodeSelectorOpExists:
            op = selection.Exists
        case v1.NodeSelectorOpDoesNotExist:
            op = selection.DoesNotExist
        case v1.NodeSelectorOpGt:
            op = selection.GreaterThan
        case v1.NodeSelectorOpLt:
            op = selection.LessThan
        default:
            return nil, fmt.Errorf("%q is not a valid node selector operator", expr.Operator)
        }
        // 表达式的三个关键要素： expr.Key, op, expr.Values 
        r, err := labels.NewRequirement(expr.Key, op, expr.Values)
        if err != nil {
            return nil, err
        }
        selector = selector.Add(*r)
    }
    return selector, nil
}

② NodeSelectorRequirementAsFieldSelector()是对“requiredDuringSchedulingIgnoredDuringExecution.matchFields”所配置的表达式进行Selector表达式进行格式化加工，返回一个Fields.Selector实例化对象.

!FILENAME pkg/apis/core/v1/helper/helpers.go:256

func NodeSelectorRequirementsAsFieldSelector(nsm []v1.NodeSelectorRequirement) (fields.Selector, error) {
    if len(nsm) == 0 {
        return fields.Nothing(), nil
    }
    selectors := []fields.Selector{}
    for _, expr := range nsm {
        switch expr.Operator {
        case v1.NodeSelectorOpIn:
            if len(expr.Values) != 1 {
                return nil, fmt.Errorf("unexpected number of value (%d) for node field selector operator %q",
                    len(expr.Values), expr.Operator)
            }
            selectors = append(selectors, fields.OneTermEqualSelector(expr.Key, expr.Values[0]))
        case v1.NodeSelectorOpNotIn:
            if len(expr.Values) != 1 {
                return nil, fmt.Errorf("unexpected number of value (%d) for node field selector operator %q",
                    len(expr.Values), expr.Operator)
            }
            selectors = append(selectors, fields.OneTermNotEqualSelector(expr.Key, expr.Values[0]))
        default:
            return nil, fmt.Errorf("%q is not a valid node field selector operator", expr.Operator)
        }
    }
    return fields.AndSelectors(selectors...), nil
}

1. 关键数据结构NodeSelector相关结构的定义

!FILENAME vendor/k8s.io/api/core/v1/types.go:2436

type NodeSelector struct {
    NodeSelectorTerms []NodeSelectorTerm `json:"nodeSelectorTerms" protobuf:"bytes,1,rep,name=nodeSelectorTerms"`
}
type NodeSelectorTerm struct {
    MatchExpressions []NodeSelectorRequirement `json:"matchExpressions,omitempty" protobuf:"bytes,1,rep,name=matchExpressions"`
    MatchFields []NodeSelectorRequirement `json:"matchFields,omitempty" protobuf:"bytes,2,rep,name=matchFields"`
}
type NodeSelectorRequirement struct {
    Key string `json:"key" protobuf:"bytes,1,opt,name=key"`
    Operator NodeSelectorOperator `json:"operator" protobuf:"bytes,2,opt,name=operator,casttype=NodeSelectorOperator"`
    Values []string `json:"values,omitempty" protobuf:"bytes,3,rep,name=values"`
}
type NodeSelectorOperator string
const (
    NodeSelectorOpIn           NodeSelectorOperator = "In"
    NodeSelectorOpNotIn        NodeSelectorOperator = "NotIn"
    NodeSelectorOpExists       NodeSelectorOperator = "Exists"
    NodeSelectorOpDoesNotExist NodeSelectorOperator = "DoesNotExist"
    NodeSelectorOpGt           NodeSelectorOperator = "Gt"
    NodeSelectorOpLt           NodeSelectorOperator = "Lt"
)

FieldsSelector实现类的结构定义（Match value)

!FILENAME vendor/k8s.io/apimachinery/pkg/fields/selector.go:78

type hasTerm struct {
    field, value string
}
func (t *hasTerm) Matches(ls Fields) bool {
    return ls.Get(t.field) == t.value
}
type notHasTerm struct {
    field, value string
}
func (t *notHasTerm) Matches(ls Fields) bool {
    return ls.Get(t.field) != t.value
}

Node亲和性优选策略NodeAffinityPriority

策略说明：

通过被调度的pod亲和性配置定义条件，对潜在可被调度运行的Nodes进行亲和性匹配并评分.

适用NodeAffinity配置项：

NodeAffinity.PreferredDuringSchedulingIgnoredDuringExecution

预选策略源码分析：

1. 策略注册：defaultPriorities()注册了一条名为“NodeAffinityPriority”优选策略项.并注册了策略的两个方法Map/Reduce：

   • CalculateNodeAffinityPriorityMap() map计算， 对潜在被调度Node进行亲和匹配，并为其计权重得分.
   • CalculateNodeAffinityPriorityReduce() reduce计算，重新统计得分,取值区间0~10.

!FILENAME pkg/scheduler/algorithmprovider/defaults/defaults.go:266

//k8s.io/kubernetes/pkg/scheduler/algorithmprovider/defaults/defaults.go/algorithmprovider/defaults.go 
func defaultPriorities() sets.String {
  ...
factory.RegisterPriorityFunction2("NodeAffinityPriority", priorities.CalculateNodeAffinityPriorityMap, priorities.CalculateNodeAffinityPriorityReduce, 1),
  ...
}

1. 策略Func:

   map计算 CalculateNodeAffinityPriorityMap()

      遍历affinity.NodeAffinity.PreferredDuringSchedulingIgnoredDuringExecution所 定义的Terms解NodeSelector对象(labels.selector)后，对潜在被调度Node的labels进行Match匹配检测，如果匹配则将条件所给定的Weight权重值累计。 最后将返回各潜在的被调度Node最后分值。 

!FILENAME pkg/scheduler/algorithm/priorities/node_affinity.go:34

func CalculateNodeAffinityPriorityMap(pod *v1.Pod, meta interface{}, nodeInfo *schedulercache.NodeInfo) (schedulerapi.HostPriority, error) {
    // 获取被检测的Node信息
  node := nodeInfo.Node()
    if node == nil {
        return schedulerapi.HostPriority{}, fmt.Errorf("node not found")
    }
    // 默认为Spec配置的Affinity
    affinity := pod.Spec.Affinity
    if priorityMeta, ok := meta.(*priorityMetadata); ok {
        // We were able to parse metadata, use affinity from there.
        affinity = priorityMeta.affinity
    }
    var count int32
    if affinity != nil && affinity.NodeAffinity != nil && affinity.NodeAffinity.PreferredDuringSchedulingIgnoredDuringExecution != nil {
    // 遍历PreferredDuringSchedulingIgnoredDuringExecution定义的`必要条件项`(Terms)
        for i := range affinity.NodeAffinity.PreferredDuringSchedulingIgnoredDuringExecution {
            preferredSchedulingTerm := &affinity.NodeAffinity.PreferredDuringSchedulingIgnoredDuringExecution[i]
            if preferredSchedulingTerm.Weight == 0 {  //注意前端的配置，如果weight为0则不做任何处理
                continue
            }
            // TODO: Avoid computing it for all nodes if this becomes a performance problem.
      // 获取node亲和MatchExpression表达式条件，实例化label.Selector对象.  
            nodeSelector, err := v1helper.NodeSelectorRequirementsAsSelector(preferredSchedulingTerm.Preference.MatchExpressions)
            if err != nil {
                return schedulerapi.HostPriority{}, err
            }
            if nodeSelector.Matches(labels.Set(node.Labels)) {
                count += preferredSchedulingTerm.Weight
            }
        }
    }
     // 返回Node得分
    return schedulerapi.HostPriority{
        Host:  node.Name,
        Score: int(count),
    }, nil
}

再次看到前面(预选策略分析时)分析过的NodeSelectorRequirementAsSelector()返回一个labels.Selector实例对象 使用selector.Matches对node.Labels进行匹配是否符合条件.

reduce计算 CalculateNodeAffinityPriorityReduce()

将各个node的最后得分重新计算分布区间在0〜10.

代码内给定一个NormalizeReduce()方法，MaxPriority值为10,reverse取反false关闭

!FILENAME pkg/scheduler/algorithm/priorities/node_affinity.go:77

const    MaxPriority = 10
var CalculateNodeAffinityPriorityReduce = NormalizeReduce(schedulerapi.MaxPriority, false)

NormalizeReduce()

• 结果评分取值0〜MaxPriority
• reverse取反为true时，最终评分=(MaxPriority-其原评分值）

!FILENAME pkg/scheduler/algorithm/priorities/reduce.go:29

func NormalizeReduce(maxPriority int, reverse bool) algorithm.PriorityReduceFunction {
    return func(
        _ *v1.Pod,
        _ interface{},
        _ map[string]*schedulercache.NodeInfo,
        result schedulerapi.HostPriorityList) error {
        var maxCount int
        // 取出最大的值
        for i := range result {
            if result[i].Score > maxCount {
                maxCount = result[i].Score
            }
        }
    // 如果最大的值为0，且取反设为真，则将所有的评分设置为MaxPriority
        if maxCount == 0 {
            if reverse {
                for i := range result {
                    result[i].Score = maxPriority
                }
            }
            return nil
        }
        // 计算后得分 = maxPrority * 原分值 / 最大值
        // 如果取反为真则 maxPrority - 计算后得分
        for i := range result {
            score := result[i].Score
            score = maxPriority * score / maxCount
            if reverse {
                score = maxPriority - score
            }
            result[i].Score = score
        }
        return nil
    }
}

Pod亲和性

Pod亲和性基础描述:

yml配置实例sample：

---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: affinity
  labels:
    app: affinity
spec:
  replicas: 3
  template:
    metadata:
      labels:
        app: affinity
        role: lab-web
    spec:
      containers:
      - name: nginx
        image: nginx:1.9.0
        ports:
        - containerPort: 80
          name: nginx_web_Lab
      affinity:                     #为实现高可用，三个pod应该分布在不同Node上
        podAntiAffinity: 
          requiredDuringSchedulingIgnoredDuringExecution:  
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - prod-pod
            topologyKey: kubernetes.io/hostname

Pod亲和性预选策略MatchInterPodAffinityPred

策略说明：

对需被调度的Pod进行亲和/反亲和配置匹配检测目标Pods，然后获取满足亲和条件的Pods所运行的Nodes​的 TopologyKey的值(亲和性pod定义topologyKey)与目标 Nodes进行一一匹配是否符合条件.

适用NodeAffinity配置项：PodAffinity.RequiredDuringSchedulingIgnoredDuringExecutionPodAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution

预选策略源码分析：

1. 策略注册：defaultPredicates()注册了一条名为“MatchInterPodAffinity”预选策略项.

!FILENAME pkg/scheduler/algorithmprovider/defaults/defaults.go:143

func defaultPredicates() sets.String {
  ...
factory.RegisterFitPredicateFactory(
            predicates.MatchInterPodAffinityPred,
            func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
                return predicates.NewPodAffinityPredicate(args.NodeInfo, args.PodLister)
            },
  ...
}

1. 策略Func: checker.InterPodAffinityMatches()Func是通过NewPodAffinityProdicate()实例化PodAffinityChecker类对象后返回。

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1138

type PodAffinityChecker struct {
    info      NodeInfo
    podLister algorithm.PodLister
}
func NewPodAffinityPredicate(info NodeInfo, podLister algorithm.PodLister) algorithm.FitPredicate {
    checker := &PodAffinityChecker{
        info:      info,
        podLister: podLister,
    }
    return checker.InterPodAffinityMatches  //返回策略func
}

InterPodAffinityMatches()检测一个pod是否满足调度到特定的（符合pod亲和或反亲和配置）Node上。

1. satisfiesExistingPodsAntiAffinity() 满足存在的Pods反亲和配置.
2. satisfiesPodsAffinityAntiAffinity() 满足Pods亲和与反亲和配置.

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1155

func (c *PodAffinityChecker) InterPodAffinityMatches(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")
    }     
                                          //①
    if failedPredicates, error := c.satisfiesExistingPodsAntiAffinity(pod, meta, nodeInfo); failedPredicates != nil {
        failedPredicates := append([]algorithm.PredicateFailureReason{ErrPodAffinityNotMatch}, failedPredicates)
        return false, failedPredicates, error
    }
    // Now check if <pod> requirements will be satisfied on this node.
    affinity := pod.Spec.Affinity
    if affinity == nil || (affinity.PodAffinity == nil && affinity.PodAntiAffinity == nil) {
        return true, nil, nil
    }   
                                         //② 
    if failedPredicates, error := c.satisfiesPodsAffinityAntiAffinity(pod, meta, nodeInfo, affinity); failedPredicates != nil {
        failedPredicates := append([]algorithm.PredicateFailureReason{ErrPodAffinityNotMatch}, failedPredicates)
        return false, failedPredicates, error
    }
    return true, nil, nil
}

① satisfiesExistingPodsAntiAffinity()检测当pod被调度到目标node上是否触犯了其它pods所定义的反亲和配置.即：当调度一个pod到目标Node上，而某个或某些Pod定义了反亲和配置与被 调度的Pod相匹配(触犯)，那么就不应该将此Node加入到可选的潜在调度Nodes列表内.

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1293

func (c *PodAffinityChecker) satisfiesExistingPodsAntiAffinity(pod *v1.Pod, meta algorithm.PredicateMetadata, nodeInfo *schedulercache.NodeInfo) (algorithm.PredicateFailureReason, error) {
    node := nodeInfo.Node()
    if node == nil {
        return ErrExistingPodsAntiAffinityRulesNotMatch, fmt.Errorf("Node is nil")
    }
    var topologyMaps *topologyPairsMaps
  //如果存在预处理的MetaData则直接获取topologyPairsAntiAffinityPodsMap
    if predicateMeta, ok := meta.(*predicateMetadata); ok {
        topologyMaps = predicateMeta.topologyPairsAntiAffinityPodsMap
    } else {
    //  不存在预处理的MetaData处理逻辑.
    //  过滤掉pod的nodeName等于NodeInfo.Node.Name,且不存在于nodeinfo中.
    //  即运行在其它Nodes上的Pods
        filteredPods, err := c.podLister.FilteredList(nodeInfo.Filter, labels.Everything())
        if err != nil {
            errMessage := fmt.Sprintf("Failed to get all pods, %+v", err)
            klog.Error(errMessage)
            return ErrExistingPodsAntiAffinityRulesNotMatch, errors.New(errMessage)
        }
    // 获取被调度Pod与其它存在反亲和配置的Pods匹配的topologyMaps
        if topologyMaps, err = c.getMatchingAntiAffinityTopologyPairsOfPods(pod, filteredPods); err != nil {
            errMessage := fmt.Sprintf("Failed to get all terms that pod %+v matches, err: %+v", podName(pod), err)
            klog.Error(errMessage)
            return ErrExistingPodsAntiAffinityRulesNotMatch, errors.New(errMessage)
        }
    }
  // 遍历所有topology pairs(所有反亲和topologyKey/Value)，检测Node是否有影响.
    for topologyKey, topologyValue := range node.Labels {
        if topologyMaps.topologyPairToPods[topologyPair{key: topologyKey, value: topologyValue}] != nil {
            klog.V(10).Infof("Cannot schedule pod %+v onto node %v", podName(pod), node.Name)
            return ErrExistingPodsAntiAffinityRulesNotMatch, nil
        }
    }
    return nil, nil
}

getMatchingAntiAffinityTopologyPairsOfPods()获取被调度Pod与其它存在反亲和配置的Pods匹配的topologyMaps

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1270

func (c *PodAffinityChecker) getMatchingAntiAffinityTopologyPairsOfPods(pod *v1.Pod, existingPods []*v1.Pod) (*topologyPairsMaps, error) {
    topologyMaps := newTopologyPairsMaps()
   // 遍历所有存在Pods,获取pod所运行的Node信息
    for _, existingPod := range existingPods {
        existingPodNode, err := c.info.GetNodeInfo(existingPod.Spec.NodeName)
        if err != nil {
            if apierrors.IsNotFound(err) {
                klog.Errorf("Node not found, %v", existingPod.Spec.NodeName)
                continue
            }
            return nil, err
        }
    // 依据被调度的pod、目标pod、目标Node信息(上面获取得到)获取TopologyPairs。
    // getMatchingAntiAffinityTopologyPairsOfPod()下面详述
        existingPodTopologyMaps, err := getMatchingAntiAffinityTopologyPairsOfPod(pod, existingPod, existingPodNode)
        if err != nil {
            return nil, err
        }
        topologyMaps.appendMaps(existingPodTopologyMaps)
    }
    return topologyMaps, nil
}
//1)是否ExistingPod定义了反亲和配置，如果没有直接返回
//2)如果有定义，是否有任务一个反亲和Term匹配需被调度的pod.
//  如果配置则将返回term定义的TopologyKey和Node的topologyValue.
func getMatchingAntiAffinityTopologyPairsOfPod(newPod *v1.Pod, existingPod *v1.Pod, node *v1.Node) (*topologyPairsMaps, error) {
    affinity := existingPod.Spec.Affinity
    if affinity == nil || affinity.PodAntiAffinity == nil {
        return nil, nil
    }
    topologyMaps := newTopologyPairsMaps()
    for _, term := range GetPodAntiAffinityTerms(affinity.PodAntiAffinity) {
        namespaces := priorityutil.GetNamespacesFromPodAffinityTerm(existingPod, &term)
        selector, err := metav1.LabelSelectorAsSelector(term.LabelSelector)
        if err != nil {
            return nil, err
        }
        if priorityutil.PodMatchesTermsNamespaceAndSelector(newPod, namespaces, selector) {
            if topologyValue, ok := node.Labels[term.TopologyKey]; ok {
                pair := topologyPair{key: term.TopologyKey, value: topologyValue}
                topologyMaps.addTopologyPair(pair, existingPod)
            }
        }
    }
    return topologyMaps, nil
}

② satisfiesPodsAffinityAntiAffinity()满足Pods亲和与反亲和配置.我们先看一下代码结构，我将共分为两个部分if{}部分,else{}部分,依赖于是否指定了预处理的预选metadata.

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1367

func (c *PodAffinityChecker) satisfiesPodsAffinityAntiAffinity(pod *v1.Pod,
    meta algorithm.PredicateMetadata, nodeInfo *schedulercache.NodeInfo,
    affinity *v1.Affinity) (algorithm.PredicateFailureReason, error) {
    node := nodeInfo.Node()
    if node == nil {
        return ErrPodAffinityRulesNotMatch, fmt.Errorf("Node is nil")
    }
    if predicateMeta, ok := meta.(*predicateMetadata); ok {
      ...    //partI
    } else { 
    ...    //partII  
    }
    return nil, nil
}

partI if{…}

• 如果指定了预处理metadata，则使用此逻辑，否则跳至else{…}
• 获取所有pod亲和性定义AffinityTerms，如果存在亲和性定义，基于指定的metadata判断AffinityTerms所定义的nodeTopoloykey与值是否所有都存在于metadata.topologyPairsPotentialAffinityPods之内（潜在匹配亲和定义的pod list）。
• 获取所有pod亲和性定义AntiAffinityTerms，如果存在反亲和定义，基于指定的metadata判断AntiAffinityTerms所定义的nodeTopoloykey与值 是否有一个存在于 metadata.topologyPairsPotentialAntiAffinityPods之内的情况（潜在匹配anti反亲和定义的pod list）。

    if predicateMeta, ok := meta.(*predicateMetadata); ok {
        // 检测所有affinity terms.
        topologyPairsPotentialAffinityPods := predicateMeta.topologyPairsPotentialAffinityPods
        if affinityTerms := GetPodAffinityTerms(affinity.PodAffinity); len(affinityTerms) > 0 {
            matchExists := c.nodeMatchesAllTopologyTerms(pod, topologyPairsPotentialAffinityPods, nodeInfo, affinityTerms)
            if !matchExists {
                if !(len(topologyPairsPotentialAffinityPods.topologyPairToPods) == 0 && targetPodMatchesAffinityOfPod(pod, pod)) {
                    klog.V(10).Infof("Cannot schedule pod %+v onto node %v, because of PodAffinity",
                        podName(pod), node.Name)
                    return ErrPodAffinityRulesNotMatch, nil
                }
            }
        }
        // 检测所有anti-affinity terms.
        topologyPairsPotentialAntiAffinityPods := predicateMeta.topologyPairsPotentialAntiAffinityPods
        if antiAffinityTerms := GetPodAntiAffinityTerms(affinity.PodAntiAffinity); len(antiAffinityTerms) > 0 {
            matchExists := c.nodeMatchesAnyTopologyTerm(pod, topologyPairsPotentialAntiAffinityPods, nodeInfo, antiAffinityTerms)
            if matchExists {
                klog.V(10).Infof("Cannot schedule pod %+v onto node %v, because of PodAntiAffinity",
                    podName(pod), node.Name)
                return ErrPodAntiAffinityRulesNotMatch, nil
            }
        }
 }

以下说明继续if{…}内所用的各个子逻辑函数分析(按代码位置的先后顺序)：

GetPodAffinityTerms()如果存在podAffinity硬件配置，获取所有”匹配必要条件”Terms

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1217

func GetPodAffinityTerms(podAffinity *v1.PodAffinity) (terms []v1.PodAffinityTerm) {
    if podAffinity != nil {
        if len(podAffinity.RequiredDuringSchedulingIgnoredDuringExecution) != 0 {
            terms = podAffinity.RequiredDuringSchedulingIgnoredDuringExecution
        }
    }
    return terms
}

nodeMatchesAllTopologyTerms()判断目标Node是否匹配所有亲和性配置的定义Terms的topology值.

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1336

// 目标Node须匹配所有Affinity terms所定义的TopologyKey，且值须与nodes(运行被亲和匹配表达式匹配的Pods)
// 的TopologyKey和值相匹配。
// 注：此逻辑内metadata预计算了topologyPairs
func (c *PodAffinityChecker) nodeMatchesAllTopologyTerms(pod *v1.Pod, topologyPairs *topologyPairsMaps, nodeInfo *schedulercache.NodeInfo, terms []v1.PodAffinityTerm) bool {
    node := nodeInfo.Node()
    for _, term := range terms {
    // 判断目标node上是否存在亲和配置定义的TopologyKey的key，取出其topologykey值
    // 根据key与值创建topologyPair
    // 基于metadata.topologyPairsPotentialAffinityPods(潜在亲和pods的topologyPairs)判断\
       //目标node上的ToplogyKey与value是否相互匹配.
        if topologyValue, ok := node.Labels[term.TopologyKey]; ok {
            pair := topologyPair{key: term.TopologyKey, value: topologyValue}
            if _, ok := topologyPairs.topologyPairToPods[pair]; !ok {
                return false // 一项不满足则为false
            }
        } else {
            return false
        }
    }
    return true
}
// topologyPairsMaps结构定义
type topologyPairsMaps struct {
    topologyPairToPods    map[topologyPair]podSet
    podToTopologyPairs    map[string]topologyPairSet
}

targetPodMatchesAffinityOfPod()根据pod的亲和定义检测目标pod的NameSpace是否符合条件以及 Labels.selector条件表达式是否匹配.

!FILENAME pkg/scheduler/algorithm/predicates/metadata.go:498

func targetPodMatchesAffinityOfPod(pod, targetPod *v1.Pod) bool {
    affinity := pod.Spec.Affinity
    if affinity == nil || affinity.PodAffinity == nil {
        return false
    }
    affinityProperties, err := getAffinityTermProperties(pod, GetPodAffinityTerms(affinity.PodAffinity))   // ① 
    if err != nil {
        klog.Errorf("error in getting affinity properties of Pod %v", pod.Name)
        return false
    }                                          // ② 
    return podMatchesAllAffinityTermProperties(targetPod, affinityProperties)
}
// ① 获取affinityTerms所定义所有的namespaces 和 selector 列表，
//    返回affinityTermProperites数组. 数组的每项定义{namesapces,selector}.
func getAffinityTermProperties(pod *v1.Pod, terms []v1.PodAffinityTerm) (properties []*affinityTermProperties, err error) {
    if terms == nil {
        return properties, nil
    }
    for _, term := range terms {
        namespaces := priorityutil.GetNamespacesFromPodAffinityTerm(pod, &term)
    // 基于定义的亲和性term，创建labels.selector
        selector, err := metav1.LabelSelectorAsSelector(term.LabelSelector) 
        if err != nil {
            return nil, err
        }
        // 返回 namespaces 和 selector
        properties = append(properties, &affinityTermProperties{namespaces: namespaces, selector: selector})
    }
    return properties, nil
}
// 返回Namespace列表（如果term未指定Namespace则使用被调度pod的Namespace）.
func GetNamespacesFromPodAffinityTerm(pod *v1.Pod, podAffinityTerm *v1.PodAffinityTerm) sets.String {
    names := sets.String{}
    if len(podAffinityTerm.Namespaces) == 0 {
        names.Insert(pod.Namespace)
    } else {
        names.Insert(podAffinityTerm.Namespaces...)
    }
    return names
}
// ② 遍历properties所有定义的namespaces 和 selector 列表，调用PodMatchesTermsNamespaceAndSelector()进行一一匹配.
func podMatchesAllAffinityTermProperties(pod *v1.Pod, properties []*affinityTermProperties) bool {
    if len(properties) == 0 {
        return false
    }
    for _, property := range properties {
        if !priorityutil.PodMatchesTermsNamespaceAndSelector(pod, property.namespaces, property.selector) {
            return false
        }
    }
    return true
}
//  检测NameSpaces一致性和Labels.selector是否匹配.
//  - 如果pod.Namespaces不相等于指定的NameSpace值则返回false，如果true则继续labels match.
//  - 如果pod.labels不能Match Labels.selector选择器，则返回false,反之true
func PodMatchesTermsNamespaceAndSelector(pod *v1.Pod, namespaces sets.String, selector labels.Selector) bool {
    if !namespaces.Has(pod.Namespace) {
        return false
    }
    if !selector.Matches(labels.Set(pod.Labels)) {
        return false
    }
    return true
}

GetPodAntiAffinityTerms()获取pod反亲和配置所有的必要条件Terms

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1231

func GetPodAntiAffinityTerms(podAntiAffinity *v1.PodAntiAffinity) (terms []v1.PodAffinityTerm) {
    if podAntiAffinity != nil {
        if len(podAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution) != 0 {
            terms = podAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution
        }
    }
    return terms
}

nodeMatchesAnyTopologyTerm()判断目标Node是否有匹配了反亲和的定义Terms的topology值*.

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1353

//  Node只须匹配任何一条AnitAffinity terms所定义的TopologyKey则为True
//  逻辑等同于nodeMatchesAllTopologyTerms(),只是匹配一条则返回为true.
func (c *PodAffinityChecker) nodeMatchesAnyTopologyTerm(pod *v1.Pod, topologyPairs *topologyPairsMaps, nodeInfo *schedulercache.NodeInfo, terms []v1.PodAffinityTerm) bool {
    node := nodeInfo.Node()
    for _, term := range terms {
        if topologyValue, ok := node.Labels[term.TopologyKey]; ok {
            pair := topologyPair{key: term.TopologyKey, value: topologyValue}
            if _, ok := topologyPairs.topologyPairToPods[pair]; ok {
                return true // 一项满足则为true
            }
        }
    }
    return false
}

partII else{…}

• 如果没有预处理的Metadata，则通过指定podFilter过滤器获取满足条件的pod列表
• 获取所有亲和配置定义，如果存在则，通过获取PodAffinity所定义的所有namespaces和标签条件表达式进行匹配”目标pod”,完全符合则获取此目标pod的运行node的topologykey（此为affinity指定的topologykey）的 值和”潜在Node”的topologykey的值比对是否一致。
• 与上类似，获取所有anti反亲和配置定义，如果存在则，通过获取PodAntiAffinity所定义的所有namespaces和标签条件表达式进行匹配”目标pod”,完全符合则获取此目标pod的运行node的topologykey（此为AntiAffinity指定的topologykey）的值和”潜在Node”的topologykey的值比对是否一致。

else { 
  // We don't have precomputed metadata. We have to follow a slow path to check affinity terms.
        filteredPods, err := c.podLister.FilteredList(nodeInfo.Filter, labels.Everything())
        if err != nil {
            return ErrPodAffinityRulesNotMatch, err
        }
    //获取亲和、反亲和配置定义的"匹配条件"Terms
        affinityTerms := GetPodAffinityTerms(affinity.PodAffinity)
        antiAffinityTerms := GetPodAntiAffinityTerms(affinity.PodAntiAffinity)
        matchFound, termsSelectorMatchFound := false, false
        for _, targetPod := range filteredPods {
            // 遍历所有目标Pod,检测所有亲和性配置"匹配条件"Terms
            if !matchFound && len(affinityTerms) > 0 {
        // podMatchesPodAffinityTerms()对namespaces和标签条件表达式进行匹配目标pod【详解后述】
                affTermsMatch, termsSelectorMatch, err := c.podMatchesPodAffinityTerms(pod, targetPod, nodeInfo, affinityTerms)
                if err != nil {
                    errMessage := fmt.Sprintf("Cannot schedule pod %+v onto node %v, because of PodAffinity, err: %v", podName(pod), node.Name, err)
                    klog.Error(errMessage)
                    return ErrPodAffinityRulesNotMatch, errors.New(errMessage)
                }
                if termsSelectorMatch {
                    termsSelectorMatchFound = true
                }
                if affTermsMatch {
                    matchFound = true
                }
            }
            // 同上，遍历所有目标Pod,检测所有Anti反亲和配置"匹配条件"Terms.
            if len(antiAffinityTerms) > 0 {
                antiAffTermsMatch, _, err := c.podMatchesPodAffinityTerms(pod, targetPod, nodeInfo, antiAffinityTerms)
                if err != nil || antiAffTermsMatch {
                    klog.V(10).Infof("Cannot schedule pod %+v onto node %v, because of PodAntiAffinityTerm, err: %v",
                        podName(pod), node.Name, err)
                    return ErrPodAntiAffinityRulesNotMatch, nil
                }
            }
        }
        if !matchFound && len(affinityTerms) > 0 {
            if termsSelectorMatchFound {
                klog.V(10).Infof("Cannot schedule pod %+v onto node %v, because of PodAffinity",
                    podName(pod), node.Name)
                return ErrPodAffinityRulesNotMatch, nil
            }
            // Check if pod matches its own affinity properties (namespace and label selector).
            if !targetPodMatchesAffinityOfPod(pod, pod) {
                klog.V(10).Infof("Cannot schedule pod %+v onto node %v, because of PodAffinity",
                    podName(pod), node.Name)
                return ErrPodAffinityRulesNotMatch, nil
            }
        }
    }

以下说明继续else{…}内所用的子逻辑函数分析：

podMatchesPodAffinityTerms()通过获取亲和配置定义的所有namespaces和标签条件表达式进行匹配目标pod,完全符合则获取此目标pod的运行node的topologykey（此为affinity指定的topologykey）的值和潜在Node的topologykey的值比对是否一致.

!FILENAME pkg/scheduler/algorithm/predicates/predicates.go:1189

func (c *PodAffinityChecker) podMatchesPodAffinityTerms(pod, targetPod *v1.Pod, nodeInfo *schedulercache.NodeInfo, terms []v1.PodAffinityTerm) (bool, bool, error) {
    if len(terms) == 0 {
        return false, false, fmt.Errorf("terms array is empty")
    }
    // 获取{namespaces,selector}列表
    props, err := getAffinityTermProperties(pod, terms)
    if err != nil {
        return false, false, err
    }
    // 匹配目标pod是否在affinityTerm定义的{namespaces,selector}列表内所有项，如果不匹配则返回false,
    // 如果匹配则获取此pod的运行node信息(称为目标Node)，
    // 通过“目标Node”所定义的topologykey（此为affinity指定的topologykey）的值来匹配“潜在被调度的Node”的topologykey是否一致。
    if !podMatchesAllAffinityTermProperties(targetPod, props) {
        return false, false, nil
    }
    // Namespace and selector of the terms have matched. Now we check topology of the terms.
    targetPodNode, err := c.info.GetNodeInfo(targetPod.Spec.NodeName)
    if err != nil {
        return false, false, err
    }
    for _, term := range terms {
        if len(term.TopologyKey) == 0 {
            return false, false, fmt.Errorf("empty topologyKey is not allowed except for PreferredDuringScheduling pod anti-affinity")
        }
        if !priorityutil.NodesHaveSameTopologyKey(nodeInfo.Node(), targetPodNode, term.TopologyKey) {
            return false, true, nil
        }
    }
    return true, true, nil
}

priorityutil.NodesHaveSameTopologyKey() 正真的toplogykey比较实现的逻辑代码块。*从此代码可以看出deployment的yml对topologykey设定的可以支持自定义的

!FILENAME pkg/scheduler/algorithm/priorities/util/topologies.go:53

// 判断两者的topologyKey定义的值是否一致。
func NodesHaveSameTopologyKey(nodeA, nodeB *v1.Node, topologyKey string) bool {
    if len(topologyKey) == 0 {
        return false
    }
    if nodeA.Labels == nil || nodeB.Labels == nil {
        return false
    }
    nodeALabel, okA := nodeA.Labels[topologyKey]   //取Node一个被意义化的“Label”的值value
    nodeBLabel, okB := nodeB.Labels[topologyKey]
    // If found label in both nodes, check the label
    if okB && okA {                                  
        return nodeALabel == nodeBLabel             //比对  
    }
    return false
}

Pod亲和性优选策略InterPodAffinityPriority

策略说明：并发遍历所有潜在的目标Nodes，对Pods与需被调度Pod的亲和和反亲性检测，对亲性匹配则增，对反亲性匹配则减， 最终对每个Node进行统计分数。

适用NodeAffinity配置项：PodAffinity.PreferredDuringSchedulingIgnoredDuringExecutionPodAntiAffinity.PreferredDuringSchedulingIgnoredDuringExecution

预选策略源码分析：

1. 策略注册：defaultPriorities()注册了一条名为“InterPodAffinityPriority”优选策略项.

!FILENAME pkg/scheduler/algorithmprovider/defaults/defaults.go:145

// k8s.io/kubernetes/pkg/scheduler/algorithmprovider/defaults/defaults.go
func defaultPriorities() sets.String {
  ...
    factory.RegisterPriorityConfigFactory(
            "InterPodAffinityPriority",
            factory.PriorityConfigFactory{
                Function: func(args factory.PluginFactoryArgs) algorithm.PriorityFunction {
                    return priorities.NewInterPodAffinityPriority(args.NodeInfo, args.NodeLister, args.PodLister, args.HardPodAffinitySymmetricWeight)
                },
                Weight: 1,
            },
        ),
  ...
}

1. 策略Func: interPodAffinity.CalculateInterPodAffinityPriority()通过NewPodAffinityPriority()实例化interPodAffinityod类对象及CalculateInterPodAffinityPriority()策略Func返回。

!FILENAME pkg/scheduler/algorithm/priorities/interpod_affinity.go:45

func NewInterPodAffinityPriority(
    info predicates.NodeInfo,
    nodeLister algorithm.NodeLister,
    podLister algorithm.PodLister,
    hardPodAffinityWeight int32) algorithm.PriorityFunction {
    interPodAffinity := &InterPodAffinity{
        info:                  info,
        nodeLister:            nodeLister,
        podLister:             podLister,
        hardPodAffinityWeight: hardPodAffinityWeight,
    }
    return interPodAffinity.CalculateInterPodAffinityPriority
}

CalculateInterPodAffinityPriority()基于pod亲和性配置匹配”必要条件项”Terms,并发处理所有目标nodes,为其目标node统计亲和weight得分.我们先来看一下它的代码结构：

• processPod := func(existingPod *v1.Pod) error {… pm.processTerms()}
• processNode := func(i int) {…}
• workqueue.ParallelizeUntil(context.TODO(), 16, len(allNodeNames), processNode)
• fScore = float64(schedulerapi.MaxPriority) * ((pm.counts[node.Name] - minCount) / (maxCount - minCount))

此代码逻辑需理解几个定义：pod 一个”需被调度的Pod”hasAffinityConstraints “被调度的pod”是否有定义亲和配置hasAntiAffinityConstraints “被调度的pod”是否有定义亲和配置existingPod 一个待处理的”亲和目标pod“existingPodNode 运行此“亲和目标pod”的节点—“目标Node”existingHasAffinityConstraints “亲和目标pod”是否存在亲和约束existingHasAntiAffinityConstraints “亲和目标pod”是否存在反亲和约束

!FILENAME pkg/scheduler/algorithm/priorities/interpod_affinity.go:119

func (ipa *InterPodAffinity) CalculateInterPodAffinityPriority(pod *v1.Pod, nodeNameToInfo map[string]*schedulercache.NodeInfo, nodes []*v1.Node) (schedulerapi.HostPriorityList, error) {
    affinity := pod.Spec.Affinity
  //"需被调度Pod"是否存在亲和、反亲和约束配置
    hasAffinityConstraints := affinity != nil && affinity.PodAffinity != nil
    hasAntiAffinityConstraints := affinity != nil && affinity.PodAntiAffinity != nil
    allNodeNames := make([]string, 0, len(nodeNameToInfo))
    for name := range nodeNameToInfo {
        allNodeNames = append(allNodeNames, name)
    }
    var maxCount float64
    var minCount float64
    pm := newPodAffinityPriorityMap(nodes)
  // processPod()主要处理pod亲和和反亲和weight累计的逻辑代码。                     ②
  // 调用了Terms处理方法：processTerms()
    processPod := func(existingPod *v1.Pod) error {     
        ...
       // 亲和性检测逻辑代码                                                    ① 
       pm.processTerms(terms, pod, existingPod, existingPodNode, 1)
    ...
    }
  //ProcessNode()通过一个判断是否存在亲和性配置选择调用processPod()                ③
    processNode := func(i int) {  
            ...
                    if err := processPod(existingPod); err != nil {
                        pm.setError(err)
                    }
        ...
    }
  // 并发多线程处理调用ProcessNode()
    workqueue.ParallelizeUntil(context.TODO(), 16, len(allNodeNames), processNode)
  ...
    for _, node := range nodes {
        if pm.counts[node.Name] > maxCount {
            maxCount = pm.counts[node.Name]
        }
        if pm.counts[node.Name] < minCount {
            minCount = pm.counts[node.Name]
        }
    }
    result := make(schedulerapi.HostPriorityList, 0, len(nodes))
    for _, node := range nodes {
        fScore := float64(0)
        if (maxCount - minCount) > 0 {           //reduce计算fScore分             ④ 
            fScore = float64(schedulerapi.MaxPriority) * ((pm.counts[node.Name] - minCount) / (maxCount - minCount))
        }
        result = append(result, schedulerapi.HostPriority{
                                 Host: node.Name, 
                                 Score: int(fScore)
                                 })  
        }
    }
    return result, nil
}