使用StatefulSet搭建MySQL8集群

因为MySQL是一个有状态的应用，使用Deployment的方式部署不是很方便

参考了官方文档，修改为MySQL8版本。

创建ConfigMap

apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql
  labels:
    app: mysql
data:
  master.cnf: |
    # Apply this config only on the master.
    [client]
    default-character-set=utf8mb4

    [mysql]
    default-character-set=utf8mb4

    [mysqld]
    # 打开binlog日志
    log-bin
    binlog_expire_logs_seconds=2592000
    max_connections=10000
    # 在容器里面需要设置下时区
    default-time-zone='+8:00'
    character-set-client-handshake=FALSE
    character-set-server=utf8mb4
    collation-server=utf8mb4_unicode_ci
    init_connect='SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci'
  slave.cnf: |
    # Apply this config only on slaves.
    [client]
    default-character-set=utf8mb4

    [mysql]
    default-character-set=utf8mb4

    [mysqld]
    # 机器设置只读
    super-read-only
    max_connections=10000
    default-time-zone='+8:00'
    character-set-client-handshake=FALSE
    character-set-server=utf8mb4
    collation-server=utf8mb4_unicode_ci
    init_connect='SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci'

$ kubectl create -f configmap.yml

这个ConfigMap分别提供了my.cnf的覆盖，可以独立控制 MySQL 主服务器和从服务器的配置。

创建Service

apiVersion: v1
kind: Service
metadata:
  name: mysql-svc-master
  labels:
    app: mysql
spec:
  selector:
    app: mysql
  ports:
  - port: 3306
    name: mysql
  clusterIP: None

$ kubectl create -f service.yml

需要先创建一个Headless Service，用于从机去访问主机。从机可以通过<pod-name>.mysql-svc-master去访问到指定的pod。

创建StorageClass

这一步可以不需要。如果有创建好的StorageClass可以直接使用，这里主要是给StatefulSet创建PV使用。

StatefulSet

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql-ss
spec: 
  selector: 
    matchLabels: 
      app: mysql # 匹配 .spec.template.metadata.labels
  serviceName: mysql-svc-master
  replicas: 3
  template: 
    metadata:
      labels:
        app: mysql # 匹配 .spec.selector.matchLabels
    spec:
      initContainers:
      - name: init-mysql
        image: mysql:8.0
        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: mzmuer/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-ss-$(($ordinal-1)).mysql-svc-master 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:8.0
        args: ["--default-authentication-plugin=mysql_native_password"]
        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: 250m
            memory: 256Mi
          limits:
            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: mzmuer/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 [[ -s xtrabackup_slave_info ]]; then
            # XtraBackup already generated a partial "CHANGE MASTER TO" query
            # because we're cloning from an existing slave.
            mv xtrabackup_slave_info change_master_to.sql.in

            # Ignore xtrabackup_binlog_info in this case (it's useless).
            rm -f 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 xtrabackup_binlog_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"
            # In case of container restart, attempt this at-most-once.
            mv change_master_to.sql.in change_master_to.sql.orig
            mysql -h 127.0.0.1 <<EOF
          $(<change_master_to.sql.orig),
            MASTER_HOST='mysql-ss-0.mysql-svc-master',
            MASTER_USER='root',
            MASTER_PASSWORD='',
            MASTER_CONNECT_RETRY=10;
          START SLAVE;
          EOF
          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
          limits: 
            cpu: 200m
            memory: 200Mi
      volumes:
      - name: conf
        emptyDir: {}
      - name: config-map
        configMap:
          name: mysql
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
     # 这里需要注意下，要修改为自己的StorageClass的名称
      storageClassName: mysql-sc
      accessModes:
        - ReadWriteOnce
      resources:
        requests:
          storage: 10Gi

$ kubectl create -f statefulclass.yml

这个编排文分为一下几块：

• init-mysql
  初始化配置文件和server-id文件，分别给主机和从机不同的配置文件。
• clone-mysql
  初始化mysql。如果是从机需要先用xtrabackup做一次全量的备份，备份的数据来自于前一个pod。
• mysql
  按照配置启动mysql
• xtrabackup
  执行命令启动slave，并利用ncat启动监听，如果扩展新的节点，传输数据到新节点。

最后

kubectl get pods -l app=mysql

NAME         READY   STATUS    RESTARTS   AGE
mysql-ss-0   2/2     Running   0          5h6m
mysql-ss-1   2/2     Running   0          5h6m
mysql-ss-2   2/2     Running   1          5h5m

官方文档是MySQL5.7。修改为MySQL8主要需要解决的是xtrabackup的版本问题 ，这里自己做一个xtrabackup8的镜像。
所有编排文件都在 https://github.com/mzmuer/k8s-yml/tree/master/mysql