【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主多从的MySQL集群。

配置准备

configMap

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#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

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# 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

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#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

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//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。

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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

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kubectl exec -it mysql-0 bash

用mysql-client链接mysql-0

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mysql -h mysql-0

创建库、表

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//创建数据库test
create database test;

//使用test
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

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//插入
insert into message value("hello aloofjr");

//查看
select * from message;

测试备库

连接mysql-1

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mysql -h mysql-1.mysql

查看库、表结构

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//查看数据库列表
show databases;

//使用test
use test;

//查看表列表
show tables;

//查看message表结构
show create table message;

读取数据

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//查看
select * from message;

写入数据

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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

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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

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//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

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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