k8s实践案例-基于StatefulSet运行Mysql一主多从
创建两个Service:mysql和mysql-read,前者是Headless Service用于StatefulSet Pod解析,写请求需要明确通过mysql-0.mysql访问Master实现;后者用于读请求,读请求可以通过Service转发到任意一个mysql Pod实现。Xtrabackup是用于mysql热备份的开源工具,具有备份速度快、支持备份数据压缩、自动校验备份数据、备份过程不
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下载镜像
先下载xtrabackup镜像
Xtrabackup是用于mysql热备份的开源工具,具有备份速度快、支持备份数据压缩、自动校验备份数据、备份过程不影响业务等特点,是目前使用较广的MySQL备份工具
nerdctl pull ist0ne/xtrabackup:1.0
nerdctl tag ist0ne/xtrabackup:1.0 harbor-server.linux.io/n70/xtrabackup:1.0
nerdctl push harbor-server.linux.io/n70/xtrabackup:1.0 #上传自己的私有仓库
然后下载mysql镜像
nerdctl pull mysql:5.7.39
nerdctl tag mysql:5.7.39 harbor-server.linux.io/n70/mysql:5.7.39
nerdctl push harbor-server.linux.io/n70/mysql:5.7.39
准备mysql配置
将mysql登录密码保存到secret
kubectl create secret generic mysql-root-password --from-literal=password=Passw0rd
将mysql配置文件保存为configmap
apiVersion: v1
kind: ConfigMap
metadata:
name: mysql-conf
data:
#Master 配置文件
master.cnf: |
[mysqld]
log-bin=mysql-bin
skip-name-resolve
#Slave配置文件
slave.cnf: |
[mysqld]
super-read-only
skip-name-resolve
log-bin=mysql-bin
replicate-ignore-db=mysql
创建Service
创建两个Service:mysql和mysql-read,前者是Headless Service用于StatefulSet Pod解析,写请求需要明确通过mysql-0.mysql访问Master实现;后者用于读请求,读请求可以通过Service转发到任意一个mysql Pod实现。
apiVersion: v1
kind: Service
metadata:
name: mysql
spec:
type: ClusterIP
clusterIP: None
selector:
app: mysql
ports:
- name: mysql
port: 3306
targetPort: 3306
---
apiVersion: v1
kind: Service
metadata:
name: mysql-read
spec:
selector:
app: mysql
ports:
- name: mysql
port: 3306
targetPort: 3306
部署mysql
副本数为2,一主一从,部署文件如下:
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: mysql
spec:
selector:
matchLabels:
app: mysql
serviceName: mysql
replicas: 2
template:
metadata:
labels:
app: mysql
spec:
initContainers:
- name: init-mysql
image: harbor-server.linux.io/n70/mysql:5.7.39
env:
- name: MYSQL_ROOT_PASSWORD
valueFrom:
secretKeyRef:
name: mysql-root-password
key: password
command:
- bash
- "-c"
- |
set -ex
# 从Pod的序号,生成server-id
[[ $(cat /etc/hostname) =~ -([0-9]+)$ ]] || exit 1
ordinal=${BASH_REMATCH[1]}
echo [mysqld] > /mnt/conf.d/server-id.cnf
# 由于server-id不能为0,因此给ID加100来避开它
echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf
# 如果Pod的序号为0,说明它是Master节点,从ConfigMap里把Master的配置文件拷贝到/mnt/conf.d目录下
# 否则,拷贝ConfigMap里的Slave的配置文件
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: harbor-server.linux.io/n70/xtrabackup:1.0
env:
- name: MYSQL_ROOT_PASSWORD
valueFrom:
secretKeyRef:
name: mysql-root-password
key: password
command:
- bash
- "-c"
- |
set -ex
# 拷贝操作只需要在第一次启动时进行,所以数据已经存在则跳过
[[ -d /var/lib/mysql/mysql ]] && exit 0
# Master 节点(序号为 0)不需要这个操作
[[ $(cat /etc/hostname) =~ -([0-9]+)$ ]] || exit 1
ordinal=${BASH_REMATCH[1]}
[[ $ordinal == 0 ]] && exit 0
# 使用ncat指令,远程地从前一个节点拷贝数据到本地
ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql
# 执行 --prepare,这样拷贝来的数据就可以用作恢复了
xtrabackup --prepare --target-dir=/var/lib/mysql
volumeMounts:
- name: data
mountPath: /var/lib/mysql
#subPath: mysql
- name: conf
mountPath: /etc/mysql/conf.d
containers:
- name: mysql
image: mysql:5.7
env:
# - name: MYSQL_ALLOW_EMPTY_PASSWORD
# value: "1"
- name: MYSQL_ROOT_PASSWORD
valueFrom:
secretKeyRef:
name: mysql-root-password
key: password
ports:
- name: mysql
containerPort: 3306
volumeMounts:
- name: data
mountPath: /var/lib/mysql
#subPath: mysql
- name: conf
mountPath: /etc/mysql/conf.d
resources:
requests:
cpu: 500m
memory: 1Gi
livenessProbe:
exec:
command:
- "/bin/bash"
- "-c"
- "mysqladmin ping -uroot -p${MYSQL_ROOT_PASSWORD}"
initialDelaySeconds: 30
periodSeconds: 10
timeoutSeconds: 5
readinessProbe:
exec:
command:
- "/bin/bash"
- "-c"
- "mysql -uroot -p${MYSQL_ROOT_PASSWORD} -e 'SELECT 1'"
initialDelaySeconds: 5
periodSeconds: 2
timeoutSeconds: 1
- name: xtrabackup
image: harbor-server.linux.io/n70/xtrabackup:1.0
ports:
- name: xtrabackup
containerPort: 3307
env:
- name: MYSQL_ROOT_PASSWORD
valueFrom:
secretKeyRef:
name: mysql-root-password
key: password
command:
- bash
- "-c"
- |
set -ex
cd /var/lib/mysql
# 从备份信息文件里读取MASTER_LOG_FILE和MASTER_LOG_POS这2个字段的值,用来拼装集群初始化SQL
if [[ -f xtrabackup_slave_info ]]; then
# 如果xtrabackup_slave_info文件存在,说明这个备份数据来自于另一个Slave节点
# 这种情况下,XtraBackup工具在备份的时候,就已经在这个文件里自动生成了“CHANGE MASTER TO”SQL语句
# 所以,只需要把这个文件重命名为change_master_to.sql.in,后面直接使用即可
mv xtrabackup_slave_info change_master_to.sql.in
# 所以,也就用不着xtrabackup_binlog_info了
rm -f xtrabackup_binlog_info
elif [[ -f xtrabackup_binlog_info ]]; then
# 如果只是存在xtrabackup_binlog_info文件,说明备份来自于Master节点,就需要解析这个备份信息文件,读取所需的两个字段的值
[[ $(cat xtrabackup_binlog_info) =~ ^(.*?)[[:space:]]+(.*?)$ ]] || exit 1
rm xtrabackup_binlog_info
# 把两个字段的值拼装成SQL,写入change_master_to.sql.in文件
echo "CHANGE MASTER TO MASTER_LOG_FILE='${BASH_REMATCH[1]}',\
MASTER_LOG_POS=${BASH_REMATCH[2]}" > change_master_to.sql.in
fi
# 如果存在change_master_to.sql.in,就意味着需要做集群初始化工作
if [[ -f change_master_to.sql.in ]]; then
# 但一定要先等MySQL容器启动之后才能进行下一步连接MySQL的操作
echo "Waiting for mysqld to be ready(accepting connections)"
until mysql -h 127.0.0.1 -uroot -p${MYSQL_ROOT_PASSWORD} -e "SELECT 1"; do sleep 1; done
echo "Initializing replication from clone position"
# 将文件change_master_to.sql.in改个名字
# 防止这个Container重启的时候,因为又找到了change_master_to.sql.in,从而重复执行一遍初始化流程
mv change_master_to.sql.in change_master_to.sql.orig
# 使用change_master_to.sql.orig的内容,也就是前面拼装的SQL,组成一个完整的初始化和启动Slave的SQL语句
mysql -h 127.0.0.1 -uroot -p${MYSQL_ROOT_PASSWORD} << EOF
$(< change_master_to.sql.orig),
MASTER_HOST='mysql-0.mysql.default',
MASTER_USER='root',
MASTER_PASSWORD='${MYSQL_ROOT_PASSWORD}',
MASTER_CONNECT_RETRY=10;
START SLAVE;
EOF
fi
# 使用ncat监听3307端口。
# 它的作用是,在收到传输请求的时候,直接执行xtrabackup --backup命令,备份MySQL的数据并发送给请求者
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 --password=${MYSQL_ROOT_PASSWORD}"
volumeMounts:
- name: data
mountPath: /var/lib/mysql
#subPath: mysql
- name: conf
mountPath: /etc/mysql/conf.d
volumes:
- name: conf
emptyDir: {}
- name: config-map
configMap:
name: mysql-conf
volumeClaimTemplates:
- metadata:
name: data
spec:
accessModes:
- "ReadWriteOnce"
storageClassName: managed-nfs-storage
resources:
requests:
storage: 3Gi
limits:
storage: 5Gi
创建完成后查看Pod状态
验证
进入mysql-1验证主从同步状态
在Master插入数据,验证Slave是否同步
扩容一个Slave,验证是否能够正常建立主从关系
进入新创建的mysql-2查看主从同步状态
Slave上也不允许写数据
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