环境说明:

主机名 操作系统版本 ip docker version kubelet version 配置 备注
master Centos 7.6.1810 172.27.9.131 Docker 18.09.6 V1.14.2 2C2G master主机
node01 Centos 7.6.1810 172.27.9.135 Docker 18.09.6 V1.14.2 2C2G node节点
node02 Centos 7.6.1810 172.27.9.136 Docker 18.09.6 V1.14.2 2C2G node节点

 

k8s集群部署详见:Centos7.6部署k8s(v1.14.2)集群

k8s学习资料详见:基本概念、kubectl命令和资料分享

emptyDir详见:存储卷和数据持久化(Volumes and Persistent Storage)

k8s高可用集群部署详见:Centos7.6部署k8s v1.16.4高可用集群(主备模式)

一、背景

当node节点进行如打补丁、操作系统升级等操作时,需停机维护,这就涉及pod驱逐迁移,本文将详细介绍node节点维护的整个过程。

二、pdb简介

  • pdb为poddisruptionbudgets缩写,意为主动驱逐保护;
  • 没有pdb。当进行节点维护时,如果某个服务的多个pod在该节点上,则节点的停机可能会造成服务中断或者服务降级。举个例子,某服务有5个pod,最低3个pod能保证服务质量,否则会造成响应慢等影响,此时该服务的4个pod在node01上,如果对node01进行停机维护,此时只有1个pod能正常对外服务,在node01的4个pod迁移过程中,就会影响该服务正常响应;
  • pdb能保证应用在节点维护时不低于一定数量的pod运行,从而保持服务质量;

三、准备工作

1.新建pod

[root@master ~]# more nginx-master.yml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx-master
spec:
  replicas: 10 
  template:
    metadata:
      labels:
        app: nginx
    spec:
      restartPolicy: Always
      containers:
      - name: nginx
        image: nginx:latest
[root@master ~]# kubectl apply -f nginx-master.yml 
deployment.extensions/nginx-master created
[root@master ~]# kubectl get po -o wide
NAME                           READY   STATUS    RESTARTS   AGE   IP             NODE     NOMINATED NODE   READINESS GATES
nginx-master-9d4cf4f77-47vfj   1/1     Running   0          28s   10.244.0.129   master   <none>           <none>
nginx-master-9d4cf4f77-69jn6   1/1     Running   0          28s   10.244.2.206   node02   <none>           <none>
nginx-master-9d4cf4f77-6drhg   1/1     Running   0          28s   10.244.1.218   node01   <none>           <none>
nginx-master-9d4cf4f77-b7zfd   1/1     Running   0          28s   10.244.1.219   node01   <none>           <none>
nginx-master-9d4cf4f77-fxsjd   1/1     Running   0          28s   10.244.2.204   node02   <none>           <none>
nginx-master-9d4cf4f77-ktnvk   1/1     Running   0          28s   10.244.0.128   master   <none>           <none>
nginx-master-9d4cf4f77-mzrx7   1/1     Running   0          28s   10.244.1.217   node01   <none>           <none>
nginx-master-9d4cf4f77-pcznk   1/1     Running   0          28s   10.244.2.203   node02   <none>           <none>
nginx-master-9d4cf4f77-px98b   1/1     Running   0          28s   10.244.2.205   node02   <none>           <none>
nginx-master-9d4cf4f77-wtcwt   1/1     Running   0          28s   10.244.1.220   node01   <none>           <none>

新建pod,镜像为最新版的nginx,deployment为nginx-master,数量为10。可以看到10个pod分布在node01、node02和master 3台不同主机上。

2.新建pdb

[root@master ~]# more pdb-nginx.yaml 
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
  name: pdb-nginx
spec:
  minAvailable: 9
  selector:
    matchLabels:
      app: nginx
[root@master ~]# kubectl apply -f pdb-nginx.yaml 
poddisruptionbudget.policy/pdb-nginx created
[root@master ~]# kubectl get pdb
NAME        MIN AVAILABLE   MAX UNAVAILABLE   ALLOWED DISRUPTIONS   AGE
pdb-nginx   9               N/A               1                     8s

新建pdb pdb-nginx,Label Selector和deployment一样都为app: nginx,minAvailable: 9意为存活的nginx pod至少为9个。

四、节点维护

本文以节点node02维护为例介绍。

1.设置节点不可调度

[root@master ~]# kubectl cordon node02
node/node02 cordoned
[root@master ~]# kubectl get node
NAME     STATUS                     ROLES    AGE    VERSION
master   Ready                      master   184d   v1.14.2
node01   Ready                      <none>   183d   v1.14.2
node02   Ready,SchedulingDisabled   <none>   182d   v1.14.2
[root@master ~]# kubectl get po -o wide
NAME                           READY   STATUS    RESTARTS   AGE   IP             NODE     NOMINATED NODE   READINESS GATES
nginx-master-9d4cf4f77-47vfj   1/1     Running   0          30m   10.244.0.129   master   <none>           <none>
nginx-master-9d4cf4f77-69jn6   1/1     Running   0          30m   10.244.2.206   node02   <none>           <none>
nginx-master-9d4cf4f77-6drhg   1/1     Running   0          30m   10.244.1.218   node01   <none>           <none>
nginx-master-9d4cf4f77-b7zfd   1/1     Running   0          30m   10.244.1.219   node01   <none>           <none>
nginx-master-9d4cf4f77-fxsjd   1/1     Running   0          30m   10.244.2.204   node02   <none>           <none>
nginx-master-9d4cf4f77-ktnvk   1/1     Running   0          30m   10.244.0.128   master   <none>           <none>
nginx-master-9d4cf4f77-mzrx7   1/1     Running   0          30m   10.244.1.217   node01   <none>           <none>
nginx-master-9d4cf4f77-pcznk   1/1     Running   0          30m   10.244.2.203   node02   <none>           <none>
nginx-master-9d4cf4f77-px98b   1/1     Running   0          30m   10.244.2.205   node02   <none>           <none>
nginx-master-9d4cf4f77-wtcwt   1/1     Running   0          30m   10.244.1.220   node01   <none>           <none>

设置node02不可调度,查看各节点状态,发现node02为SchedulingDisabled,此时master不会将新的pod调度到该节点上,但是node02上pod还是正常运行。

2.驱逐节点上的pod

[root@master ~]# kubectl drain node02 --delete-local-data --ignore-daemonsets --force 
node/node02 already cordoned

图片.png

参数说明:

  • --delete-local-data 即使pod使用了emptyDir也删除
  • --ignore-daemonsets 忽略deamonset控制器的pod,如果不忽略,deamonset控制器控制的pod被删除后可能马上又在此节点上启动起来,会成为死循环;
  • --force 不加force参数只会删除该NODE上由ReplicationController, ReplicaSet, DaemonSet,StatefulSet or Job创建的Pod,加了后还会删除'裸奔的pod'(没有绑定到任何replication controller)

可以看到同一时刻只有一个pod进行迁移,对外提供服务的pod始终有9个。

图片.png

迁移pod nginx-master-9d4cf4f77-pcznk到node01

图片.png

迁移pod nginx-master-9d4cf4f77-px98b到master,此时前一个pod nginx-master-9d4cf4f77-pcznk已经迁移完成。

图片.png

迁移pod nginx-master-9d4cf4f77-69jn6到master

图片.png

迁移pod nginx-master-9d4cf4f77-fxsjd到master

这个也再次验证了同一时刻只有一个pod迁移,nginx服务始终有9个pod对外提供服务。

3.维护结束

[root@master ~]# kubectl uncordon node02
node/node02 uncordoned
[root@master ~]# kubectl get nodes      
NAME     STATUS   ROLES    AGE    VERSION
master   Ready    master   184d   v1.14.2
node01   Ready    <none>   183d   v1.14.2
node02   Ready    <none>   183d   v1.14.2

维护结束,重新将node02节点置为可调度状态。

五、pod回迁

pod回迁貌似还没什么好的办法,这里采用delete然后重建的方式回迁。

[root@master ~]# kubectl get po -o wide
NAME                           READY   STATUS    RESTARTS   AGE   IP             NODE     NOMINATED NODE   READINESS GATES
nginx-master-9d4cf4f77-2vnvk   1/1     Running   0          33m   10.244.1.222   node01   <none>           <none>
nginx-master-9d4cf4f77-47vfj   1/1     Running   0          73m   10.244.0.129   master   <none>           <none>
nginx-master-9d4cf4f77-6drhg   1/1     Running   0          73m   10.244.1.218   node01   <none>           <none>
nginx-master-9d4cf4f77-7n7pt   1/1     Running   0          32m   10.244.0.131   master   <none>           <none>
nginx-master-9d4cf4f77-b7zfd   1/1     Running   0          73m   10.244.1.219   node01   <none>           <none>
nginx-master-9d4cf4f77-ktnvk   1/1     Running   0          73m   10.244.0.128   master   <none>           <none>
nginx-master-9d4cf4f77-mzrx7   1/1     Running   0          73m   10.244.1.217   node01   <none>           <none>
nginx-master-9d4cf4f77-pdkst   1/1     Running   0          32m   10.244.0.130   master   <none>           <none>
nginx-master-9d4cf4f77-pskmp   1/1     Running   0          32m   10.244.0.132   master   <none>           <none>
nginx-master-9d4cf4f77-wtcwt   1/1     Running   0          73m   10.244.1.220   node01   <none>           <none>
[root@master ~]# kubectl delete po nginx-master-9d4cf4f77-47vfj
pod "nginx-master-9d4cf4f77-47vfj" deleted
[root@master ~]# kubectl delete po nginx-master-9d4cf4f77-2vnvk
pod "nginx-master-9d4cf4f77-2vnvk" deleted
[root@master ~]# kubectl get po -o wide
NAME                           READY   STATUS    RESTARTS   AGE   IP             NODE     NOMINATED NODE   READINESS GATES
nginx-master-9d4cf4f77-6drhg   1/1     Running   0          76m   10.244.1.218   node01   <none>           <none>
nginx-master-9d4cf4f77-7n7pt   1/1     Running   0          35m   10.244.0.131   master   <none>           <none>
nginx-master-9d4cf4f77-b7zfd   1/1     Running   0          76m   10.244.1.219   node01   <none>           <none>
nginx-master-9d4cf4f77-f92hp   1/1     Running   0          44s   10.244.2.207   node02   <none>           <none>
nginx-master-9d4cf4f77-ktnvk   1/1     Running   0          76m   10.244.0.128   master   <none>           <none>
nginx-master-9d4cf4f77-mzrx7   1/1     Running   0          76m   10.244.1.217   node01   <none>           <none>
nginx-master-9d4cf4f77-pdkst   1/1     Running   0          35m   10.244.0.130   master   <none>           <none>
nginx-master-9d4cf4f77-pskmp   1/1     Running   0          35m   10.244.0.132   master   <none>           <none>
nginx-master-9d4cf4f77-tdghn   1/1     Running   0          15s   10.244.2.208   node02   <none>           <none>
nginx-master-9d4cf4f77-wtcwt   1/1     Running   0          76m   10.244.1.220   node01   <none>           <none>

在业务低峰delete pod nginx-master-9d4cf4f77-47vfj和nginx-master-9d4cf4f77-2vnvk,由于node02上的pod之前都被驱逐,此时资源使用率最低,所以pod重建时会调度值该节点,完成pod回迁。

六、节点删除

1.删除节点

实际运维过程中可能会删除某个node节点,本文还是以node02为例,介绍如果删除节点。

[root@master ~]# kubectl cordon node02
[root@master ~]# kubectl drain node02 --delete-local-data --ignore-daemonsets --force 
[root@master ~]# kubectl delete node node02

图片.png

[root@node02 ~]# kubeadm reset

图片.png

2.节点重新加入

master节点上运行

[root@master ~]# kubeadm token create --print-join-command
kubeadm join 172.27.9.131:6443 --token kpz40z.tuxb4t4m1q37vwl1     --discovery-token-ca-cert-hash sha256:5f656ae26b5e7d4641a979cbfdffeb7845cc5962bbfcd1d5435f00a25c02ea50 

node02重新加入集群

[root@node02 ~]# kubeadm join 172.27.9.131:6443 --token svrip0.lajrfl4jgal0ul6i     --discovery-token-ca-cert-hash sha256:5f656ae26b5e7d4641a979cbfdffeb7845cc5962bbfcd1d5435f00a25c02ea50 

图片.png

查看node

图片.png

本文所有脚本和配置文件已上传:Pode Eviction and Node Manage