Docker(二十)--Docker k8s--Kubernetes存储--Volumes配置管理--持久卷--StatefulSet

1. 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：$(statefulset名称)-$(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。

2. 示例

## 1. 清理环境
[root@server2 nfs-client]# kubectl delete -f demo.yaml   
[root@server2 nfs-client]# kubectl delete -f pvc.yaml 

## 2. 配置
[root@server2 volumes]# pwd
/root/volumes
[root@server2 volumes]# mkdir statefulset
[root@server2 volumes]# cd statefulset/
[root@server2 statefulset]# vim service.yaml 
[root@server2 statefulset]# cat service.yaml     ##实验文件
apiVersion: v1          ##StatefulSet如何通过Headless Service维持Pod的拓扑状态
kind: Service
metadata:
 name: nginx-svc
 labels:
  app: nginx
spec:
 ports:
 - port: 80
   name: web
 clusterIP: None     ##无头服务
 selector:
  app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
 name: web
spec:
 serviceName: "nginx-svc"
 replicas: 2               ##副本数,如果只删除pod可以改为0。全部删除需要删除控制器
 selector:
  matchLabels:
   app: nginx
 template:
  metadata:
   labels:
    app: nginx
  spec:
   containers:
   - name: nginx
     image: myapp:v1           ##myapp其实就是nginx
     ports:
     - containerPort: 80
       name: web
     volumeMounts:          #PV和PVC的设计，使得StatefulSet对存储状态的管理成为了可能:
       - name: www
         mountPath: /usr/share/nginx/html
 volumeClaimTemplates:
  - metadata:
     name: www
    spec:
     storageClassName: managed-nfs-storage    ##sc
     accessModes:
     - ReadWriteOnce
     resources:
      requests:
       storage: 1Gi

[root@server2 statefulset]# kubectl apply -f service.yaml 
service/nginx-svc created
statefulset.apps/web created
[root@server2 statefulset]# kubectl get pod
NAME    READY   STATUS    RESTARTS   AGE
web-0   1/1     Running   0          9s
web-1   1/1     Running   0          5s
[root@server2 statefulset]# kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM               STORAGECLASS          REASON   AGE
pvc-25c0739c-3a00-442e-8287-2b2f216cb676   1Gi        RWO            Delete           Bound    default/www-web-0   managed-nfs-storage            15s
pvc-dde9af65-ae0a-4412-b704-e5b7f1abfe59   1Gi        RWO            Delete           Bound    default/www-web-1   managed-nfs-storage            11s
[root@server2 statefulset]# kubectl get pvc
NAME        STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS          AGE
www-web-0   Bound    pvc-25c0739c-3a00-442e-8287-2b2f216cb676   1Gi        RWO            managed-nfs-storage   17s
www-web-1   Bound    pvc-dde9af65-ae0a-4412-b704-e5b7f1abfe59   1Gi        RWO            managed-nfs-storage   13s
[root@server2 statefulset]# kubectl describe svc nginx-svc    ##查看svc详细信息
[root@server2 statefulset]# dig -t A web-0.nginx-svc.default.svc.cluster.local @10.96.0.10           ##可以通过dig查看
[root@server2 statefulset]# dig -t A nginx-svc.default.svc.cluster.local @10.96.0.10
## 3. 测试
[root@server1 nfsdata]# pwd
/nfsdata
[root@server1 nfsdata]# ls
archived-pvc-2262d8b4-c660-4301-aad5-2ec59516f14e
archived-pvc-bc952d4e-47a5-4ac4-9d95-5cd2e6132ebf
default-www-web-0-pvc-25c0739c-3a00-442e-8287-2b2f216cb676
default-www-web-1-pvc-dde9af65-ae0a-4412-b704-e5b7f1abfe59

[root@server1 nfsdata]# echo web-0 > default-www-web-0-pvc-25c0739c-3a00-442e-8287-2b2f216cb676/index.html
[root@server1 nfsdata]# echo web-1 > default-www-web-1-pvc-dde9af65-ae0a-4412-b704-e5b7f1abfe59/index.html

[root@server2 statefulset]# kubectl run demo --image=busyboxplus -it   ##测试
/ # nslookup nginx-svc
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
Name:      nginx-svc
Address 1: 10.244.22.11 web-0.nginx-svc.default.svc.cluster.local
Address 2: 10.244.141.211 web-1.nginx-svc.default.svc.cluster.local
/ # curl web-0.nginx-svc
web-0
/ # curl web-1.nginx-svc
web-1

2.1 环境清理

2.2 配置

2.3 测试

2.4 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 <stateful-set-name>
  改变StatefulSet副本数量:
  $ kubectl scale statefulsets <stateful-set-name> --replicas=<new-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 <stateful-set-file-updated>

• 也可以通过命令 kubectl edit 编辑该字段:
  $ kubectl edit statefulsets <stateful-set-name>

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

3. statefullset部署mysql主从集群

官网代码

[root@server2 mysql]# cat configmap.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql
  labels:
    app: mysql
data:
  master.cnf: |
    # Apply this config only on the master.
    [mysqld]
    log-bin    
  slave.cnf: |
    # Apply this config only on slaves.
    [mysqld]
    super-read-only
[root@server2 mysql]# cat services.yaml 
apiVersion: v1
kind: Service
metadata:
  name: mysql
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  clusterIP: None
  selector:
    app: mysql
---
apiVersion: v1
kind: Service
metadata:
  name: mysql-read
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  selector:
    app: mysql
[root@server2 mysql]# cat statefulset.yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  serviceName: mysql
  replicas: 3
  template:
    metadata:
      labels:
        app: mysql
    spec:
      initContainers:
      - name: init-mysql
        image: mysql:5.7
        command:
        - bash
        - "-c"
        - |
          set -ex
          # Generate mysql server-id from pod ordinal index.
          [[ `hostname` =~ -([0-9]+)$ ]] || exit 1
          ordinal=${
    
    BASH_REMATCH[1]}
          echo [mysqld] > /mnt/conf.d/server-id.cnf
          # Add an offset to avoid reserved server-id=0 value.
          echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf
          # Copy appropriate conf.d files from config-map to emptyDir.
          if [[ $ordinal -eq 0 ]]; then
            cp /mnt/config-map/master.cnf /mnt/conf.d/
          else
            cp /mnt/config-map/slave.cnf /mnt/conf.d/
          fi          
        volumeMounts:
        - name: conf
          mountPath: /mnt/conf.d
        - name: config-map
          mountPath: /mnt/config-map
      - name: clone-mysql
        image: xtrabackup:1.0
        command:
        - bash
        - "-c"
        - |
          set -ex
          # Skip the clone if data already exists.
          [[ -d /var/lib/mysql/mysql ]] && exit 0
          # Skip the clone on master (ordinal index 0).
          [[ `hostname` =~ -([0-9]+)$ ]] || exit 1
          ordinal=${
    
    BASH_REMATCH[1]}
          [[ $ordinal -eq 0 ]] && exit 0
          # Clone data from previous peer.
          ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql
          # Prepare the backup.
          xtrabackup --prepare --target-dir=/var/lib/mysql          
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
      containers:
      - name: mysql
        image: mysql:5.7
        env:
        - name: MYSQL_ALLOW_EMPTY_PASSWORD
          value: "1"
        ports:
        - name: mysql
          containerPort: 3306
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
        resources:
          requests:
            cpu: 500m
            memory: 512Mi
        livenessProbe:
          exec:
            command: ["mysqladmin", "ping"]
          initialDelaySeconds: 30
          periodSeconds: 10
          timeoutSeconds: 5
        readinessProbe:
          exec:
            # Check we can execute queries over TCP (skip-networking is off).
            command: ["mysql", "-h", "127.0.0.1", "-e", "SELECT 1"]
          initialDelaySeconds: 5
          periodSeconds: 2
          timeoutSeconds: 1      
      - name: xtrabackup
        image: xtrabackup:1.0
        ports:
        - name: xtrabackup
          containerPort: 3307
        command:
        - bash
        - "-c"
        - |
          set -ex
          cd /var/lib/mysql

          # Determine binlog position of cloned data, if any.
          if [[ -f xtrabackup_slave_info && "x$(<xtrabackup_slave_info)" != "x" ]]; then
            # XtraBackup already generated a partial "CHANGE MASTER TO" query
            # because we're cloning from an existing slave. (Need to remove the tailing semicolon!)
            cat xtrabackup_slave_info | sed -E 's/;$//g' > change_master_to.sql.in
            # Ignore xtrabackup_binlog_info in this case (it's useless).
            rm -f xtrabackup_slave_info xtrabackup_binlog_info
          elif [[ -f xtrabackup_binlog_info ]]; then
            # We're cloning directly from master. Parse binlog position.
            [[ `cat xtrabackup_binlog_info` =~ ^(.*?)[[:space:]]+(.*?)$ ]] || exit 1
            rm -f xtrabackup_binlog_info xtrabackup_slave_info
            echo "CHANGE MASTER TO MASTER_LOG_FILE='${BASH_REMATCH[1]}',\
                  MASTER_LOG_POS=${BASH_REMATCH[2]}" > change_master_to.sql.in
          fi

          # Check if we need to complete a clone by starting replication.
          if [[ -f change_master_to.sql.in ]]; then
            echo "Waiting for mysqld to be ready (accepting connections)"
            until mysql -h 127.0.0.1 -e "SELECT 1"; do sleep 1; done

            echo "Initializing replication from clone position"
            mysql -h 127.0.0.1 \
                  -e "$(<change_master_to.sql.in), \
                          MASTER_HOST='mysql-0.mysql', \
                          MASTER_USER='root', \
                          MASTER_PASSWORD='', \
                          MASTER_CONNECT_RETRY=10; \
                        START SLAVE;" || exit 1
            # In case of container restart, attempt this at-most-once.
            mv change_master_to.sql.in change_master_to.sql.orig
          fi

          # Start a server to send backups when requested by peers.
          exec ncat --listen --keep-open --send-only --max-conns=1 3307 -c \
            "xtrabackup --backup --slave-info --stream=xbstream --host=127.0.0.1 --user=root"          
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
        resources:
          requests:
            cpu: 100m
            memory: 100Mi
      volumes:
      - name: conf
        emptyDir: {
    
    }
      - name: config-map
        configMap:
          name: mysql
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes: ["ReadWriteOnce"]
      resources:
        requests:
          storage: 5Gi

##镜像拉取
[root@server1 nfsdata]# docker pull mysql:5.7
[root@server1 nfsdata]# docker tag mysql:5.7 reg.westos.org/library/mysql:5.7
[root@server1 nfsdata]# docker push reg.westos.org/library/mysql:5.7 


[root@server1 nfsdata]# docker pull yizhiyong/xtrabackup
[root@server1 nfsdata]# docker tag yizhiyong/xtrabackup:latest reg.westos.org/library/xtrabackup:1.0
[root@server1 nfsdata]# docker push reg.westos.org/library/xtrabackup:1.0

[root@server2 mysql]# kubectl apply -f configmap.yaml 
configmap/mysql created
[root@server2 mysql]# kubectl describe cm mysql 
Name:         mysql
Namespace:    default
Labels:       app=mysql
Annotations:  <none>

Data
====
master.cnf:
----
# Apply this config only on the master.
[mysqld]
log-bin    

slave.cnf:
----
# Apply this config only on slaves.
[mysqld]
super-read-only

Events:  <none>


[root@server2 mysql]# kubectl apply -f services.yaml 
service/mysql created
service/mysql-read created
[root@server2 mysql]# kubectl get svc
NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
kubernetes   ClusterIP   10.96.0.1        <none>        443/TCP    6d5h
mysql        ClusterIP   None             <none>        3306/TCP   6s
mysql-read   ClusterIP   10.109.234.245   <none>        3306/TCP   6s


[root@server2 mysql]# yum install mariadb -y   ##需要安装数据库
[root@server2 mysql]# kubectl apply -f statefulset.yaml  ##
[root@server2 mysql]# kubectl get pod  
[root@server2 mysql]# kubectl get pvc
[root@server2 mysql]# kubectl get pv

3.1 配置

3.2 测试