Kubernetes 部署 MySQL 集群

程序员文章站 2022-05-16 21:36:35

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一、配置准备

1. configMap

#application/mysql/mysql-configmap.yaml

apiVersion: v1

kind: ConfigMap

metadata:

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。

2. service

# application/mysql/mysql-services.yaml# Headless service for stable DNS entries of StatefulSet members.apiVersion: v1kind: Servicemetadata:

labels:

app: mysqlspec:

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: v1kind: Servicemetadata:

labels:

app: mysqlspec:

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

3. StatefulSet

#application/mysql/mysql-statefulset.yamlapiVersion: apps/v1kind: StatefulSetmetadata:

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/

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:

volumeClaimTemplates:

- metadata:

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。

二、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

三、测试主库

1. 进入pod进行操作

进入到pod mysql-0中，进行测试

kubectl exec -it mysql-0 bash

2. 用mysql-client链接mysql-0

mysql -h mysql-0

3. 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;

4. 插入数据

//插入

insert into message value("hello aloofjr");

//查看

select * from message;

四、测试备库

1. 连接mysql-1

mysql -h mysql-1.mysql

2. 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;

3. 读取数据

//查看select * from message;

4. 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。

五、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

六、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

七、清理

kubectl delete statefulset mysql

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

八、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

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