【从入门到放弃-Kubernetes】Kubernetes入门-部署MySQL

前言

上文【从入门到放弃-Kubernetes】Kubernetes入门-有状态应用扩缩容中，介绍了如何部署有状态应用。有状态应用中，MySQL是我们最常见也是最常用的。本文我们就实战部署一个一组多从的MySQL集群。

配置准备

configMap

#application/mysql/mysql-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

configMap可以将配置文件和镜像解耦开。
上面的配置意思是，创建一个master.cnf文件配置内容为：log-bin，即开启bin-log日志，供主节点使用。
创建一个slave.cnf文件配置内容为：super-read-only，设为该节点只读，供备用节点使用。

service

# application/mysql/mysql-services.yaml # Headless service for stable DNS entries of StatefulSet members. apiVersion: v1 kind: Service metadata: name: mysql labels: app: mysql spec: ports: - name: mysql port: 3306 clusterIP: None selector: app: mysql --- # Client service for connecting to any MySQL instance for reads. # For writes, you must instead connect to the master: mysql-0.mysql. apiVersion: v1 kind: Service metadata: name: mysql-read labels: app: mysql spec: ports: - name: mysql port: 3306 selector: app: mysql

创建一个服务名为mysql的headless类型的service。
创建一个服务名为mysql-read的service

StatefulSet

#application/mysql/mysql-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: # 设置初始化容器，进行一些准备工作 initContainers: - name: init-mysql image: mysql:5.7 # 为每个MySQL节点配置service-id # 如果节点序号是0，则使用master的配置， 其余节点使用slave的配置 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 [[ $ordinal -eq 0 ]]; then cp /mnt/config-map/master.cnf /mnt/conf.d/ else cp /mnt/config-map/slave.cnf /mnt/conf.d/ fi volumeMounts: - name: conf mountPath: /mnt/conf.d - name: config-map mountPath: /mnt/config-map - name: clone-mysql image: gcr.io/google-samples/xtrabackup:1.0 # 为除了节点序号为0的主节点外的其它节点，备份前一个节点的数据 command: - bash - "-c" - | set -ex # Skip the clone if data already exists. [[ -d /var/lib/mysql/mysql ]] && exit 0 # Skip the clone on master (ordinal index 0). [[ `hostname` =~ -([0-9]+)$ ]] || exit 1 ordinal=${BASH_REMATCH[1]} [[ $ordinal -eq 0 ]] && exit 0 # Clone data from previous peer. ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql # Prepare the backup. xtrabackup --prepare --target-dir=/var/lib/mysql volumeMounts: - name: data mountPath: /var/lib/mysql subPath: mysql - name: conf mountPath: /etc/mysql/conf.d containers: - name: mysql image: mysql:5.7 # 设置支持免密登录 env: - name: MYSQL_ALLOW_EMPTY_PASSWORD value: "1" ports: - name: mysql containerPort: 3306 volumeMounts: - name: data mountPath: /var/lib/mysql subPath: mysql - name: conf mountPath: /etc/mysql/conf.d resources: # 设置启动pod需要的资源，官方文档上需要500m cpu，1Gi memory。 # 我本地测试的时候，会因为资源不足，报1 Insufficient cpu, 1 Insufficient memory错误，所以我改小了点 requests: # m是千分之一的意思，100m表示需要0.1个cpu cpu: 100m # Mi是兆的意思，需要100M 内存 memory: 100Mi livenessProbe: # 使用mysqladmin ping命令，对MySQL节点进行探活检测 # 在节点部署完30秒后开始，每10秒检测一次，超时时间为5秒 exec: command: ["mysqladmin", "ping"] initialDelaySeconds: 30 periodSeconds: 10 timeoutSeconds: 5 readinessProbe: # 对节点服务可用性进行检测， 启动5秒后开始，每2秒检测一次，超时时间1秒 exec: # Check we can execute queries over TCP (skip-networking is off). command: ["mysql", "-h", "127.0.0.1", "-e", "SELECT 1"] initialDelaySeconds: 5 periodSeconds: 2 timeoutSeconds: 1 - name: xtrabackup image: gcr.io/google-samples/xtrabackup:1.0 ports: - name: xtrabackup containerPort: 3307 # 开始进行备份文件校验、解析和开始同步 command: - bash - "-c" - | set -ex cd /var/lib/mysql # Determine binlog position of cloned data, if any. if [[ -f xtrabackup_slave_info && "x$(<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 # 设置PVC volumeClaimTemplates: - metadata: name: data spec: accessModes: ["ReadWriteOnce"] resources: requests: storage: 1Gi

主从节点的配置和启动都在上面的yaml文件中定义好了，接下来需要逐个创建即可。

创建所需资源

//创建configMap kubectl apply -f configMap.yaml //创建service kubectl apply -f service.yaml //创建statefulSet kubectl apply -f statefulSet.yaml

执行完毕后可以使用以下命令监测创建情况。

kubectl get pods --watch

测试主库

进入pod进行操作

进入到pod mysql-0中，进行测试

kubectl exec -it mysql-0 bash

用mysql-client链接mysql-0

mysql -h mysql-0

创建库、表

//创建数据库test create database test; //使用test库 use test; //创建message表 create table message (message varchar(50)); //查看message表结构 show create table message; 

插入数据

//插入 insert into message value("hello aloofjr"); //查看 select * from message;

测试备库

连接mysql-1

mysql -h mysql-1.mysql

查看库、表结构

//查看数据库列表 show databases; //使用test库 use test; //查看表列表 show tables; //查看message表结构 show create table message;

读取数据

//查看 select * from message;

写入数据

insert into message values("hello world");

此时会报错 ERROR 1290 (HY000): The MySQL server is running with the --super-read-only option so it cannot execute this statement

这是因为mysql-1是一个只读备库，无法进行写操作。

测试mysql-read服务

kubectl run mysql-client-loop --image=mysql:5.7 -i -t --rm --restart=Never --\ bash -ic "while sleep 1; do mysql -h mysql-read -e 'SELECT @@server_id,NOW()'; done"

每秒查询一次数据库，可以观察到，调度到不同的server-id，即pod节点

扩缩容

//扩容至5副本 kubectl scale statefulset mysql --replicas=5 //缩容只2副本 kubectl scale statefulset mysql --replicas=2

清理

kubectl delete statefulset mysql kubectl delete configmap,service,pvc -l app=mysql

总结

上面就是通过k8s部署一个一主多从mysql集群的过程，其中有几个重要知识点：

• 通过configMap可以将配置和镜像解耦
• 通过initContainers在pod启动前，做一些初始化工作
• 通过requests设置pod所需的cpu和memory
• 通过livenessProbe进行pod节点探活
• 通过readnessProbe进行pod可用性检测

下文，我们来学习如何通过k8s部署一个可读写数据库的SpringBoot应用。

本文中用到的yaml文件见我的GitHub仓库AloofJr

更多文章

见我的博客：https://nc2era.com

written by AloofJr，转载请注明出处