Node Affinity / Taints /Tolerations

[root@k8s-master cka]# cat multi-expression-in-term.yaml
apiVersion: v1
kind: Pod
metadata:
  name: node-affinity-allmatch
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: role
            operator: In
            values:
             - master
          - key: role
            operator: In
            values:
             - node
  containers:
  - name: with-node-affinity
    image: nginx

 Warning   FailedScheduling   default-scheduler    0/2 nodes are available: 2 node(s) didn't match node selector.

在一个matchexpression部分中的多条件是 AND关系

[root@k8s-master cka]# cat multi-terms.yaml
apiVersion: v1
kind: Pod
metadata:
  name: node-affinity-ifany
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: role
            operator: In
            values:
             - master
        - matchExpressions:
          - key: role
            operator: In
            values:
             - node
  containers:
  - name: with-node-affinity
    image: nginx

多nodeselectorterm是 或，任意一个匹配即可

[root@k8s-master cka]# cat prefer-affinity.yaml
apiVersion: v1
kind: Pod
metadata:
  name: node-affinity-ifany
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: owner
            operator: In
            values:
             - lj
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 10
        preference:
          matchExpressions:
          - key: role
            operator: In
            values:
             - node
  containers:
  - name: with-node-affinity
    image: nginx

2018-08-11 13:17:44 +0800 CST   2018-08-11 13:17:44 +0800 CST   1         node-affinity-ifany.1549bcbc3b670aef   Pod                 Normal    Scheduled   default-scheduler   Successfully assigned node-affinity-ifany to k8s-node1
2018-08-11 13:17:45 +0800 CST   2018-08-11 13:17:45 +0800 CST   1         node-affinity-ifany.1549bcbc733d4529   Pod                 Normal    SuccessfulMountVolume   kubelet, k8s-node1   MountVolume.SetUp succeeded for volume "default-token-gt88m"
2018-08-11 13:17:47 +0800 CST   2018-08-11 13:17:47 +0800 CST   1         node-affinity-ifany.1549bcbcd5bfb3af   Pod       spec.containers{with-node-affinity}   Normal    Pulling   kubelet, k8s-node1   pulling image "nginx"
2018-08-11 13:17:55 +0800 CST   2018-08-11 13:17:55 +0800 CST   1         node-affinity-ifany.1549bcbecd747893   Pod       spec.containers{with-node-affinity}   Normal    Pulled    kubelet, k8s-node1   Successfully pulled image "nginx"
2018-08-11 13:17:55 +0800 CST   2018-08-11 13:17:55 +0800 CST   1         node-affinity-ifany.1549bcbeda6e3ece   Pod       spec.containers{with-node-affinity}   Normal    Created   kubelet, k8s-node1   Created container
2018-08-11 13:17:56 +0800 CST   2018-08-11 13:17:56 +0800 CST   1         node-affinity-ifany.1549bcbee47f163c   Pod       spec.containers{with-node-affinity}   Normal    Started   kubelet, k8s-node1   Started container

required首先要满足，在同时多个node满足的情况下，使用prefer，preference下只能配置一个matchexpression，如果匹配则给node加weight（因为此时scheduler还需根据很多其它条件来排序可用的nodes，增加分值可以增加选择概率）

Taints, 用在node上，格式为key=value:effect，例如

edge=true:NoSchedule
gpu=true:NoSchedule
bigdata=true:NoExcute
dev=team3:PreferNoSschedule
最后的effect指明了这个taint的动作，拒绝被调度，拒绝pod在其上执行，不优先考虑被调度。如果一个node有了Noschedule的taint，那么只有当pod声明了对应的key/value/effect的tolerations时，这个pod才可以被调度到这个node上。

所以这个方法一般用来保护一个node，确保node上只调度那些期望的pods。

一个node包含多个taints，tolerations会挨个根据自己的tolerations去匹配过滤，都能被toleration了就可以调度，如果有剩余的taints没被匹配，那么根据这个剩余的taints本身的效果来决定。

tolerations:
- key: "key"
  operator: "Exists" 匹配key的任意effect都可以被容忍

tolerations:
- operator: "Exists"
表示容忍所有。 Existsccc操作本身不需要配置value