K8s（三）Pod资源——pod亲和性与反亲和性，pod重启策略
目录
pod亲和性与反亲和性
pod亲和性
pod反亲和性
pod状态与重启策略
pod状态
pod重启策略
本文主要介绍了pod资源与pod相关的亲和性，以及pod的重启策略
pod亲和性与反亲和性
pod亲和性（podAffinity）有两种 1.podaffinity，即联系比较紧密的pod更倾向于使用同一个区域 比如tomcat和nginx这样资源的利用效率更高
2.podunaffinity，即两套完全相同，或两套完全不同功能的服务 为了不互相影响容灾效果，或者让服务之间不会互相影响，更倾向于不适用同一个区域
那么如何判断是不是“同一个区域”就非常重要
#查看帮助
kubectl explain pods.spec.affinity.podAffinity
preferredDuringSchedulingIgnoredDuringExecution #软亲和性，尽可能在一起
requiredDuringSchedulingIgnoredDuringExecution #硬亲和性，一定要在一起pod亲和性
#硬亲和性
kubectl explain pods.spec.affinity.podAffinity.requiredDuringSchedulingIgnoredDuringExecutionlabelSelector <Object> #以标签为筛选条件，选择一组亲和的podnamespaceSelector <Object> #以命名空间为筛选条件，选择一组亲和的podnamespaces <[]string> #确定命名空间的位置topologyKey <string> -required- #拓扑逻辑键，根据xx判断是否是同一位置cat > qinhe-pod1.yaml << EOF
apiVersion: v1
kind: Pod
metadata:name: qinhe1namespace: defaultlabels:user: ws
spec:containers:- name: qinhe1image: docker.io/library/nginximagePullPolicy: IfNotPresent
EOF
kubectl apply -f qinhe-pod1.yaml #定义一个初始的pod，后面的pod可以依次为参照echo "
apiVersion: v1
kind: Pod
metadata:name: qinhe2labels:app: app1
spec:containers:- name: qinhe2image: docker.io/library/nginximagePullPolicy: IfNotPresentaffinity:podAffinity: # 和pod亲和性requiredDuringSchedulingIgnoredDuringExecution:- labelSelector: # 以标签为筛选条件matchExpressions: # 以表达式进行匹配- {key: user, operator: In, values: ["ws"]}topologyKey: kubernetes.io/hostname
#带有kubernetes.io/hostname标签相同的被认为是同一个区域，即以主机名区分
#标签的node被认为是统一位置
" > qinhe-pod2.yaml
kubectl apply -f qinhe-pod2.yamlkubectl get pods -owide #因为hostname node1和node2不同，所以只会调度到node1
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
qinhe1 1/1 Running 0 68s 10.10.179.9 ws-k8s-node1 <none> <none>
qinhe2 1/1 Running 0 21s 10.10.179.10 ws-k8s-node1 <none> <none>#修改
...topologyKey: beta.kubernetes.io/arch
... #node1和node2这两个标签都相同
kubectl delete -f qinhe-pod2.yaml
kubectl apply -f qinhe-pod2.yaml
kubectl get pods -owide #再查看时会发现qinhe2分到了node2
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
qinhe1 1/1 Running 0 4m55s 10.10.179.9 ws-k8s-node1 <none> <none>
qinhe2 1/1 Running 0 15s 10.10.234.68 ws-k8s-node2 <none> <none>#清理环境
kubectl delete -f qinhe-pod1.yaml
kubectl delete -f qinhe-pod2.yaml
pod反亲和性
kubectl explain pods.spec.affinity.podAntiAffinity
preferredDuringSchedulingIgnoredDuringExecution <[]Object>
requiredDuringSchedulingIgnoredDuringExecution <[]Object>#硬亲和性
#创建qinhe-pod3.yaml
cat > qinhe-pod3.yaml << EOF
apiVersion: v1
kind: Pod
metadata:name: qinhe3namespace: defaultlabels:user: ws
spec:containers:- name: qinhe3image: docker.io/library/nginximagePullPolicy: IfNotPresent
EOF#创建qinhe-pod4.yaml
echo "
apiVersion: v1
kind: Pod
metadata:name: qinhe4labels:app: app1
spec:containers:- name: qinhe4image: docker.io/library/nginximagePullPolicy: IfNotPresentaffinity:podAntiAffinity: # 和pod亲和性requiredDuringSchedulingIgnoredDuringExecution:- labelSelector: # 以标签为筛选条件matchExpressions: # 以表达式进行匹配- {key: user, operator: In, values: ["ws"]} #表达式user=wstopologyKey: kubernetes.io/hostname #以hostname作为区分是否同个区域
" > qinhe-pod4.yaml
kubectl apply -f qinhe-pod3.yaml
kubectl apply -f qinhe-pod4.yaml
#分配到了不同的node
kubectl get pods -owide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
qinhe3 1/1 Running 0 9s 10.10.179.11 ws-k8s-node1 <none> <none>
qinhe4 1/1 Running 0 8s 10.10.234.70 ws-k8s-node2 <none> <none>#修改topologyKey
pod4修改为topologyKey: user
kubectl label nodes ws-k8s-node1 user=xhy
kubectl label nodes ws-k8s-node2 user=xhy
#现在node1和node2都会被pod4识别为同一位置，因为node的label中user值相同kubectl delete -f qinhe-pod4.yaml
kubectl apply -f qinhe-pod4.yaml
#直接显示离线
kubectl get pods -owide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
qinhe3 1/1 Running 0 9m59s 10.10.179.12 ws-k8s-node1 <none> <none>
qinhe4 0/1 Pending 0 2s <none> <none> <none> <none>
#查看日志
Warning FailedScheduling 74s default-scheduler 0/4 nodes are available: 2 node(s) didn't match pod anti-affinity rules, 2 node(s) had untolerated taint {node-role.kubernetes.io/control-plane: }. preemption: 0/4 nodes are available: 2 No preemption victims found for incoming pod, 2 Preemption is not helpful for scheduling..#pod反亲和性的软亲和性与node亲和性的软亲和性同理#清理环境
kubectl label nodes ws-k8s-node1 user-
kubectl label nodes ws-k8s-node2 user-
kubectl delete -f qinhe-pod3.yaml
kubectl delete -f qinhe-pod4.yaml
pod状态与重启策略
参考文档：Pod 的生命周期 | Kubernetes
pod状态
1.pending——挂起
（1）正在创建pod，检查存储、网络、下载镜像等问题
（2）条件不满足，比如硬亲和性，污点等调度条件不满足
2.failed——失败
至少有一个容器因为失败而停止，即非0状态退出
3.unknown——未知
apiserver连不上node节点的kubelet，通常是网络问题
4.Error——错误
5.succeeded——成功
pod所有容器成功终止
6.Unschedulable
pod不能被调度
7.PodScheduled
正在调度中
8.Initialized
pod初始化完成
9.ImagePullBackOff
容器拉取失败
10.evicted
node节点资源不足
11.CrashLoopBackOff
容器曾经启动，但又异常退出了
pod重启策略
当容器异常时，可以通过设置RestartPolicy字段，设置pod重启策略来对pod进行重启等操作
#查看帮助
kubectl explain pod.spec.restartPolicy
KIND: Pod
VERSION: v1
FIELD: restartPolicy <string>
DESCRIPTION:Restart policy for all containers within the pod. One of Always, OnFailure,Never. Default to Always. More info:<https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy>Possible enum values:- `"Always"` #只要异常退出，立即自动重启- `"Never"` #不会重启容器- `"OnFailure"`#容器错误退出，即退出码不为0时，则自动重启#测试Always策略，创建always.yaml
cat > always.yaml << EOF
apiVersion: v1
kind: Pod
metadata:name: always-podnamespace: default
spec:restartPolicy: Alwayscontainers:- name: test-podimage: docker.io/library/tomcatimagePullPolicy: IfNotPresent
EOF
kubectl apply -f always.yaml
kubectl get po #查看状态
NAME READY STATUS RESTARTS AGE
always-pod 1/1 Running 0 22s
#进入容器去关闭容器
kubectl exec -it always-pod -- /bin/bash
shutdown.sh
#查看当前状态，可以看到always-pod重启计数器为1
kubectl get po
NAME READY STATUS RESTARTS AGE
always-pod 1/1 Running 1 (5s ago) 70s#测试never策略，创建never.yaml
cat > never.yaml << EOF
apiVersion: v1
kind: Pod
metadata:name: never-podnamespace: default
spec:restartPolicy: Nevercontainers:- name: test-podimage: docker.io/library/tomcatimagePullPolicy: IfNotPresent
EOF
kubectl apply -f never.yaml
kubectl exec -it never-pod -- /bin/bash
shutdown.sh
#不会重启，状态为completed
kubectl get pods | grep never
never-pod 0/1 Completed 0 73s#测试OnFailure策略，创建onfailure.yaml
cat > onfailure.yaml << EOF
apiVersion: v1
kind: Pod
metadata:name: onfailure-podnamespace: default
spec:restartPolicy: OnFailurecontainers:- name: test-podimage: docker.io/library/tomcatimagePullPolicy: IfNotPresent
EOF
kubectl apply -f onfailure.yaml
#进去后进行异常退出
kubectl exec -it onfailure-pod -- /bin/bash
kill 1
#查看pods状态，已经重启
kubectl get po | grep onfailure
onfailure-pod 1/1 Running 1 (43s ago) 2m11s
#进入后进行正常退出
kubectl exec -it onfailure-pod -- /bin/bash
shutdown.sh
#查看pods状态，没有重启，进入completed状态
kubectl get po | grep onfailure
onfailure-pod 0/1 Completed 1 3m58s#清理环境
kubectl delete -f always.yaml
kubectl delete -f never.yaml
kubectl delete -f onfailure.yaml