kubernetes的PodAffinity的不解

PodAffinity

字数统计: 553阅读时长: 2 min

 2018/06/02 

官方文档来看是下面的说法,摘自官方文档https://kubernetes.io/docs/concepts/configuration/assign-pod-node/

An example of a pod that uses pod affinity:

apiVersion: v1
kind: Pod
metadata:
  name: with-pod-affinity
spec:
  affinity:
    podAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: security
            operator: In
            values:
            - S1
        topologyKey: failure-domain.beta.kubernetes.io/zone
    podAntiAffinity:
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 100
        podAffinityTerm:
          labelSelector:
            matchExpressions:
            - key: security
              operator: In
              values:
              - S2
          topologyKey: kubernetes.io/hostname
  containers:
  - name: with-pod-affinity
    image: k8s.gcr.io/pause:2.0

More precisely, the pod is eligible to run on node N if node N has a label with key failure-domain.beta.kubernetes.io/zone and some value V such that there is at least one node in the cluster with key failure-domain.beta.kubernetes.io/zone and value V that is running a pod that has a label with key “security” and value “S1”

pod能够落在的node N 必须满足：N有一个key为failure-domain.beta.kubernetes.io/zone并且value为某个值V的标签，这样集群中就至少有一个node拥有这个标签，并且有一个 key 为 “security” 并且 value 为 “S1” 的标签的 pod 在之上运行

这里的demo的yaml里根本就没有判断failure-domain.beta.kubernetes.io/zone的值，文档里却说and value V
顺着官方的说法也就是说存在这个键的node去判断

但是现实里使用的更多是去根据值去判断node,例如

area: beijing
area: shanghai
disktype: ide
disktype: ssd

甚至自己的label都用这样值去区分

[root@k8s-m1 k8s]# kubectl get nodes --show-labels 
NAME      STATUS    ROLES     AGE       VERSION   LABELS
k8s-m1    Ready     master    6d        v1.10.3   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=k8s-m1,node-role.kubernetes.io/master=
k8s-m2    Ready     master    6d        v1.10.3   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=k8s-m2,node-role.kubernetes.io/master=
k8s-m3    Ready     master    6d        v1.10.3   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=k8s-m3,node-role.kubernetes.io/master=
k8s-n1    Ready     node      6d        v1.10.3   beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/hostname=k8s-n1,node-role.kubernetes.io/node=

那按照官方的这个去使用就是下面的这样的标签了

1 2	disktype-ssd: true disktype-ide: true

这样很反人类了
如果说有这样一个需求:
把该pod亲和到ssd硬盘的node上

1	topologyKey: disktype-ssd

还不如下面好用

topology: 
  key: disktype
  operator: In
  value: ssd

搜索了下一大堆人在哪瞎扯,说topologyKey是zone,事实我给node加上一个lable都可以亲和上去,而不是看值的

原文作者：Zhangguanzhang

原文链接：http://zhangguanzhang.github.io/2018/06/02/kubernetes-nodeSelector/

发表日期：June 2nd 2018, 8:24:46 pm

更新日期：June 2nd 2018, 8:24:46 pm

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