文章目录

• 一、StatefulSet简介
• 二、示例
• • 1.代码演示
  • 2.补充
• 三、statefullset部署mysql主从部署

一、StatefulSet简介

• StatefulSet将应用状态抽象成了两种情况：
  拓扑状态：应用实例必须按照某种顺序启动。新创建的Pod必须和原来Pod的网络标识一样
  存储状态：应用的多个实例分别绑定了不同存储数据。

• StatefulSet给所有的Pod进行了编号，编号规则是：(statefulset名称)−(statefulset名称)-(statefulset名称)−(序号)，从0开始。

• StatefulSet还会为每一个Pod分配并创建一个同样编号的PVC。这样，kubernetes就可以通过Persistent Volume机制为这个PVC绑定对应的PV，从而保证每一个Pod都拥有一个独立的Volume。

• Pod被删除后重建，重建Pod的网络标识也不会改变,Pod的拓扑状态按照Pod的“名字+编号”的方式固定下来,并且为每个Pod提供了一个固定且唯一的访问入口,即Pod对应的DNS记录。

二、示例

1.代码演示

[root@k8s2 statefulset]# vim headless.yaml                                        ##目录位置任意
apiVersion: v1
kind: Service
metadata:name: nginx-svclabels:app: nginx
spec:ports:- port: 80name: webclusterIP: Noneselector:app: nginx
[root@k8s2 statefulset]# kubectl apply -f headless.yaml
[root@k8s2 statefulset]# kubectl get svc
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1            443/TCP   6d23h
nginx-svc    ClusterIP   None                 80/TCP    2s[root@k8s2 statefulset]# vim statefulset.yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:name: web
spec:serviceName: "nginx-svc"replicas: 3selector:matchLabels:app: nginxtemplate:metadata:labels:app: nginxspec:containers:- name: nginximage: nginxvolumeMounts:- name: wwwmountPath: /usr/share/nginx/htmlvolumeClaimTemplates:- metadata:name: wwwspec:storageClassName: nfs-clientaccessModes:- ReadWriteOnceresources:requests:storage: 1Gi[root@k8s2 statefulset]# kubectl apply -f statefulset.yaml
[root@k8s2 statefulset]# kubectl get pod
NAME    READY   STATUS    RESTARTS   AGE
web-0   1/1     Running   0          75s
web-1   1/1     Running   0          5s
web-2   1/1     Running   0          4s

在nfs输出目录创建测试页

[root@k8s2 statefulset]# kubectl run demo --image busyboxplus -it
/ # curl  web-0.nginx-svc
web-0
/ # curl  web-1.nginx-svc
web-1
/ # curl  web-2.nginx-svc
web-2statefulset有序回收
kubectl scale statefulsets web --replicas=0
[root@k8s2 statefulset]# kubectl delete -f statefulset.yaml
[root@k8s2 mysql]# kubectl delete pvc --all

2.补充

• kubectl 弹缩
  首先,想要弹缩的StatefulSet. 需先清楚是否能弹缩该应用.
  $ kubectl get statefulsets
  改变StatefulSet副本数量:
  $ kubectl scale statefulsets --replicas=

• 如果StatefulSet开始由 kubectl apply 或 kubectl create --save-config 创建,更新StatefulSet manifests中的 .spec.replicas, 然后执行命令 kubectl apply:
  $ kubectl apply -f

• 也可以通过命令 kubectl edit 编辑该字段:
  $ kubectl edit statefulsets

• 使用 kubectl patch:
  $ kubectl patch statefulsets -p ‘{“spec”:{“replicas”:}}’

三、statefullset部署mysql主从部署

官网：https://v1-25.docs.kubernetes.io/zh-cn/docs/tasks/run-application/run-replicated-stateful-application/
首先上传镜像，确保仓库中有以下两个镜像

[root@k8s2 mysql]# vim configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:name: mysqllabels:app: mysqlapp.kubernetes.io/name: mysql
data:primary.cnf: |[mysqld]log-binreplica.cnf: |[mysqld]super-read-only
[root@k8s2 mysql]# kubectl apply -f configmap.yaml[root@k8s2 mysql]# vim svc.yaml
apiVersion: v1
kind: Service
metadata:name: mysqllabels:app: mysqlapp.kubernetes.io/name: mysql
spec:ports:- name: mysqlport: 3306clusterIP: Noneselector:app: mysql
---
apiVersion: v1
kind: Service
metadata:name: mysql-readlabels:app: mysqlapp.kubernetes.io/name: mysqlreadonly: "true"
spec:ports:- name: mysqlport: 3306selector:app: mysql
[root@k8s2 mysql]# kubectl apply -f svc.yaml
[root@k8s2 mysql]# kubectl get svc
NAME         TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
kubernetes   ClusterIP   10.96.0.1              443/TCP    7d
mysql        ClusterIP   None                   3306/TCP   23m
mysql-read   ClusterIP   10.98.32.113           3306/TCP   23m

[root@k8s2 mysql]# vim statefulset.yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:name: mysql
spec:selector:matchLabels:app: mysqlapp.kubernetes.io/name: mysqlserviceName: mysqlreplicas: 0template:metadata:labels:app: mysqlapp.kubernetes.io/name: mysqlspec:initContainers:- name: init-mysqlimage: mysql:5.7command:- bash- "-c"- |set -ex# 基于 Pod 序号生成 MySQL 服务器的 ID。[[ $HOSTNAME =~ -([0-9]+)$ ]] || exit 1ordinal=${BASH_REMATCH[1]}echo [mysqld] > /mnt/conf.d/server-id.cnf# 添加偏移量以避免使用 server-id=0 这一保留值。echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf# 将合适的 conf.d 文件从 config-map 复制到 emptyDir。if [[ $ordinal -eq 0 ]]; thencp /mnt/config-map/primary.cnf /mnt/conf.d/elsecp /mnt/config-map/replica.cnf /mnt/conf.d/fivolumeMounts:- name: confmountPath: /mnt/conf.d- name: config-mapmountPath: /mnt/config-map- name: clone-mysqlimage: xtrabackup:1.0command:- bash- "-c"- |set -ex# 如果已有数据，则跳过克隆。[[ -d /var/lib/mysql/mysql ]] && exit 0# 跳过主实例（序号索引 0）的克隆。[[ `hostname` =~ -([0-9]+)$ ]] || exit 1ordinal=${BASH_REMATCH[1]}[[ $ordinal -eq 0 ]] && exit 0# 从原来的对等节点克隆数据。ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql# 准备备份。xtrabackup --prepare --target-dir=/var/lib/mysqlvolumeMounts:- name: datamountPath: /var/lib/mysqlsubPath: mysql- name: confmountPath: /etc/mysql/conf.dcontainers:- name: mysqlimage: mysql:5.7env:- name: MYSQL_ALLOW_EMPTY_PASSWORDvalue: "1"ports:- name: mysqlcontainerPort: 3306volumeMounts:- name: datamountPath: /var/lib/mysqlsubPath: mysql- name: confmountPath: /etc/mysql/conf.dresources:requests:cpu: 500mmemory: 512MilivenessProbe:exec:command: ["mysqladmin", "ping"]initialDelaySeconds: 30periodSeconds: 10timeoutSeconds: 5readinessProbe:exec:# 检查我们是否可以通过 TCP 执行查询（skip-networking 是关闭的）。command: ["mysql", "-h", "127.0.0.1", "-e", "SELECT 1"]initialDelaySeconds: 5periodSeconds: 2timeoutSeconds: 1- name: xtrabackupimage: xtrabackup:1.0ports:- name: xtrabackupcontainerPort: 3307command:- bash- "-c"- |set -excd /var/lib/mysql# 确定克隆数据的 binlog 位置（如果有的话）。if [[ -f xtrabackup_slave_info && "x$( change_master_to.sql.in# 在这里要忽略 xtrabackup_binlog_info （它是没用的）。rm -f xtrabackup_slave_info xtrabackup_binlog_infoelif [[ -f xtrabackup_binlog_info ]]; then# 我们直接从主实例进行克隆。解析 binlog 位置。[[ `cat xtrabackup_binlog_info` =~ ^(.*?)[[:space:]]+(.*?)$ ]] || exit 1rm -f xtrabackup_binlog_info xtrabackup_slave_infoecho "CHANGE MASTER TO MASTER_LOG_FILE='${BASH_REMATCH[1]}',\MASTER_LOG_POS=${BASH_REMATCH[2]}" > change_master_to.sql.infi# 检查我们是否需要通过启动复制来完成克隆。if [[ -f change_master_to.sql.in ]]; thenecho "Waiting for mysqld to be ready (accepting connections)"until mysql -h 127.0.0.1 -e "SELECT 1"; do sleep 1; doneecho "Initializing replication from clone position"mysql -h 127.0.0.1 \-e "$(

连接测试
[root@k8s2 mysql]# kubectl  run demo --image mysql:5.7 -it -- bash
If you don't see a command prompt, try pressing enter.
bash-4.2# mysql -h mysql-0.mysqlmysql> show databases;
...回收
[root@k8s2 mysql]# kubectl delete -f statefulset.yaml
[root@k8s2 mysql]# kubectl delete pvc --all