运维实战案例 容器部分 使用Statefulset部署MySQL主从集群
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运维实战案例 容器部分 使用Statefulset部署mysql主从集群
需求分析
一主多从
模式只能有一个写入端, 多个查询端需要能负载均衡和健康检查- 如何保证
MASTER
端恒定且连接方式不飘逸 - 解决主从机配置文件不同的问题
- 每台机器的配置文件中
server-id
不同, 如何用同一个配置文件模板为所有从机分配各自的配置文件 - 如何进行数据的持久化
解决思路
-
根据
StatefulSet
控制器的特点, 上一个Pod
报告就绪后, 才会开始生成下一个Pod
, 因此我们可以断定, 第一个就绪的Pod
一定是MASTER
端, 且如果MASTER
端初始化出现问题, 整个后续都不会继续. -
根据
Headless Service
的特点, 首先启动的Pod
一定对应的是mysql-0.mysql
, 后续会被Pod
的DNS
自行补全, 因此MASTER
端的唯一性和确定性也可以保证 -
所有
Pod
又可以放入一个新的svc
中管理, 通过ClusterIP
实现负载均衡和健康检查 -
之前我们学过, 在容器创建前依旧会有
Init 容器
存在, 且顺序执行, 将配置文件的放入和处理操作在Init 容器
中执行, 既可以保证容器创建时有符合要求的配置文件,Init 容器
本身顺序执行且必须执行完毕的特性也保证了只要逻辑得当, 生成的配置文件一定是符合要求的 -
两个
Service
实现读写分离 -
借助
Init 容器
实现对配置文件的操作 -
StatefulSet
控制器实现有序建立和定位 -
PVC
动态生成PV
来实现数据持久化
参考教程
注意事项
- 实验采用的设置都不是生产环境下的设置, 并不具备生产环境的安全性
- 重点在于构建的思路
ConfigMap部分
- 通过
ConfigMap
实现将配置模板挂入Pod
中的目的
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
可以看到master.cnf
和slave.cnf
被分别存放, slave.cnf
中包括super-read-only
参数来实现只读, 这一步是为了提供my.cnf
的内容
Service部分
- 创建读写分离所需要的两个服务
- 写服务为
Headless Service
# 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
无头服务为每个Pod
提供一个DNS
解析, 因为服务名为 mysql
, 所以可以通过在同一 Kubernetes 集群和名字中的任何其他 Pod 内解析 <Pod 名称>.mysql
来访问 Pod
, 又因为MASTER
端永远第一个被建立, 因此其解析地址永远为mysql-0.mysql
Read
相关的服务就是普通的服务, 通过ClusterIP
提供负载均衡和健康检查
StatefulSet控制器部分
也是本实验最重要的部分, 可以说以下内容都是通过StatefulSet
的特性来实现的
- 配置文件中
server-id
的有序递增 Pod
创建顺序的有序化- 新生成的
Pod
从上一个Pod
复制数据的实现
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: mysql
spec:
selector:
matchLabels:
app: mysql
serviceName: mysql
replicas: 3
template:
metadata:
labels:
app: mysql
spec:
initContainers:
- name: init-mysql
image: mysql:5.7
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 [[ $ordinal -eq 0 ]]; then
cp /mnt/config-map/master.cnf /mnt/conf.d/
else
cp /mnt/config-map/slave.cnf /mnt/conf.d/
fi
volumeMounts:
- name: conf
mountPath: /mnt/conf.d
- name: config-map
mountPath: /mnt/config-map
- name: clone-mysql
image: gcr.io/google-samples/xtrabackup:1.0
command:
- bash
- "-c"
- |
set -ex
# Skip the clone if data already exists.
[[ -d /var/lib/mysql/mysql ]] && exit 0
# Skip the clone on master (ordinal index 0).
[[ `hostname` =~ -([0-9]+)$ ]] || exit 1
ordinal=$BASH_REMATCH[1]
[[ $ordinal -eq 0 ]] && exit 0
# Clone data from previous peer.
ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql
# Prepare the backup.
xtrabackup --prepare --target-dir=/var/lib/mysql
volumeMounts:
- name: data
mountPath: /var/lib/mysql
subPath: mysql
- name: conf
mountPath: /etc/mysql/conf.d
containers:
- name: mysql
image: mysql:5.7
env:
- name: MYSQL_ALLOW_EMPTY_PASSWORD
value: "1"
ports:
- name: mysql
containerPort: 3306
volumeMounts:
- name: data
mountPath: /var/lib/mysql
subPath: mysql
- name: conf
mountPath: /etc/mysql/conf.d
resources:
requests:
cpu: 500m
memory: 1Gi
livenessProbe:
exec:
command: ["mysqladmin", "ping"]
initialDelaySeconds: 30
periodSeconds: 10
timeoutSeconds: 5
readinessProbe:
exec:
# Check we can execute queries over TCP (skip-networking is off).
command: ["mysql", "-h", "127.0.0.1", "-e", "SELECT 1"]
initialDelaySeconds: 5
periodSeconds: 2
timeoutSeconds: 1
- name: xtrabackup
image: gcr.io/google-samples/xtrabackup:1.0
ports:
- name: xtrabackup
containerPort: 3307
command:
- bash
- "-c"
- |
set -ex
cd /var/lib/mysql
# Determine binlog position of cloned data, if any.
if [[ -f xtrabackup_slave_info && "x$(<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
volumeClaimTemplates:
- metadata:
name: data
spec:
accessModes: ["ReadWriteOnce"]
resources:
requests:
storage: 10Gi
上面的很长很长的资源清单可以拆分为几个部分来看
第一部分
- 生成第一个初始化容器:
init-mysql
, 用MySQL 5.7
的镜像作为母盘构建数据库本体服务的容器 - 采用
创建顺序 + 100
作为server-id
的形式进行配置文件的修改 - 将
conf
和config-map
两个数据盘挂载进容器
第二部分
-
生成第二个初始化容器:
clone-mysql
, 用来进行数据同步, 第一次在带有空PersistentVolume
的副本Pod
上启动时, 会在从属Pod
上执行克隆操作. -
这意味着它将从另一个运行中的
Pod
复制所有现有数据, 使此其本地状态足够一致, 从而可以开始从主服务器复制. -
当新 Pod 作为副本节点加入集合时, 必须假定 MySQL 主节点可能已经有数据. 还必须假设复制日志可能不会一直追溯到时间的开始.
-
用
xtrabackup:1.0
的镜像作为母盘构建数据复制的容器 -
在克隆期间, 源
MySQL
服务器性能可能会受到影响. 为了最大程度地减少对MySQL
主服务器的影响, 该脚本指示每个Pod
从序号较低的Pod
中克隆, 也就是上一个Pod
. 可以这样做的原因是StatefulSet
控制器始终确保在启动Pod N + 1
之前Pod N
已准备就绪. -
这个初始化容器使用
3307
端口进行工作
Init 容器运行完成, 进入主要阶段
第三部分
- 所以实际上的
Pod
由提供MySQL
服务的MySQL
容器和进行辅助的xtrabackup
容器组成 xtrabackup
容器查看查看克隆的数据文件, 确定是否有必要在副本服务器上初始化MySQL
复制- 如果需要, 他将等待
mysqld
准备就绪后复制, 这是用到了上面初始化容器中写好的复制参数 - 在执行了
CHANGE MASTER TO
和START SLAVE
之后, 数据完成同步 - 在同步完成后, 其也会自动寻找
MASTER
端并连接 - 开始复制后,
xtrabackup
容器监听来自其他Pod
的连接, 处理其数据克隆请求. 如果StatefulSet
扩大规模, 或者下一个Pod
失去其PersistentVolumeClaim
并需要重新克隆, 则此服务器将无限期保持运行
至此, 构建步骤完成
操作实录与测试流程
[root@Server2 MySQLStateful]# kubectl get pod -n nfs-client-provisioner
NAME READY STATUS RESTARTS AGE
nfs-client-provisioner-dbd6bcd94-4h6xh 1/1 Running 1 43h
[root@Server2 MySQLStateful]# systemctl enable --now nfs
[root@Server2 mnt]# cd MySQLStateful/
[root@Server2 MySQLStateful]# kubectl apply -f ConfigMap.yaml
configmap/mysql created
[root@Server2 MySQLStateful]# kubectl get cm
NAME DATA AGE
kube-root-ca.crt 1 3d
mysql 2 33s
[root@Server2 MySQLStateful]# kubectl apply -f Services.yaml
service/mysql created
service/mysql-read created
[root@Server2 MySQLStateful]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3d
mysql ClusterIP None <none> 3306/TCP 5s
mysql-read ClusterIP 10.111.252.35 <none> 3306/TCP 5s
[root@Server2 MySQLStateful]# kubectl apply -f StatefulSet.yaml
[root@Server2 MySQLStateful]# kubectl get pod
NAME READY STATUS RESTARTS AGE
mysql-0 2/2 Running 0 28s
mysql-1 2/2 Running 0 19s
mysql-2 0/2 Init:1/2 0 11s
[root@Server2 MySQLStateful]# kubectl get pod
NAME READY STATUS RESTARTS AGE
mysql-0 2/2 Running 0 2m25s
mysql-1 2/2 Running 0 2m16s
mysql-2 2/2 Running 0 2m8s
##运行测试Pod
[root@Server2 MySQLStateful]# kubectl run demo -it --image=mysql:5.7 -- bash
If you don't see a command prompt, try pressing enter.
root@demo:/# exit
exit
Session ended, resume using 'kubectl attach demo -c demo -i -t' command when the pod is running
[root@Server2 MySQLStateful]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
demo 1/1 Running 1 20s 10.244.141.222 server3 <none> <none>
mysql-0 2/2 Running 0 3m18s 10.244.22.20 server4 <none> <none>
mysql-1 2/2 Running 0 3m9s 10.244.141.221 server3 <none> <none>
mysql-2 2/2 Running 0 3m1s 10.244.22.21 server4 <none> <none>
[root@Server2 MySQLStateful]# kubectl attach demo -it
If you don't see a command prompt, try pressing enter.
##连接Master端进行写入测试
root@demo:/# mysql mysql -h mysql-0.mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Welcome to the MySQL monitor. Commands end with ; or \\g.
Your MySQL connection id is 178
Server version: 5.7.30-log MySQL Community Server (GPL)
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\\h' for help. Type '\\c' to clear the current input statement.
mysql> show databases;
+------------------------+
| Database |
+------------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| xtrabackup_backupfiles |
+------------------------+
5 rows in set (0.01 sec)
mysql> create database test;
Query OK, 1 row affected (0.02 sec)
mysql> show databases;
+------------------------+
| Database |
+------------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| test |
| xtrabackup_backupfiles |
+------------------------+
6 rows in set (0.02 sec)
mysql> exit
Bye
##分别连接其他终端进行读取测试, 测试主从复制情况
root@demo:/# mysql mysql -h mysql-1.mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Welcome to the MySQL monitor. Commands end with ; or \\g.
Your MySQL connection id is 195
Server version: 5.7.30 MySQL Community Server (GPL)
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\\h' for help. Type '\\c' to clear the current input statement.
mysql> show databases;
+------------------------+
| Database |
+------------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| test |
| xtrabackup_backupfiles |
+------------------------+
6 rows in set (0.01 sec)
mysql> show slave status/G;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '/G' at line 1
mysql> show slave status\\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: mysql-0.mysql
Master_User: root
Master_Port: 3306
Connect_Retry: 10
Master_Log_File: mysql-0-bin.000005
Read_Master_Log_Pos: 313
Relay_Log_File: mysql-1-relay-bin.000005
Relay_Log_Pos: 530
Relay_Master_Log_File: mysql-0-bin.000005
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 313
Relay_Log_Space: 907
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 100
Master_UUID: d9f1bc4f-b463-11eb-80db-9637abf7b267
Master_Info_File: /var/lib/mysql/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> exit
Bye
root@demo:/# mysql mysql -h mysql-2.mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Welcome to the MySQL monitor. Commands end with ; or \\g.
Your MySQL connection id is 205
Server version: 5.7.30 MySQL Community Server (GPL)
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\\h' for help. Type '\\c' to clear the current input statement.
mysql> show databases;
+------------------------+
| Database |
+------------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| test |
| xtrabackup_backupfiles |
+------------------------+
6 rows in set (0.01 sec)
root@demo:/# mysql mysql -h 10.111.252.35
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Welcome to the MySQL monitor. Commands end with ; or \\g.
Your MySQL connection id is 276
Server version: 5.7.30 MySQL Community Server (GPL)
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\\h' for help. Type '\\c' to clear the current input statement.
mysql> show databases;
+------------------------+
| Database |
+------------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| test |
| xtrabackup_backupfiles |
+------------------------+
6 rows in set (0.00 sec)
mysql> exit
Bye
root@demo:/# exit
exit
Session ended, resume using 'kubectl attach demo -c demo -i -t' command when the pod is running
##查看持续化存储情况
[root@Server2 MySQLStateful]# kubectl get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
data-mysql-0 Bound pvc-c25eede4-6e01-4da5-84aa-fc37296570e1 10Gi RWO managed-nfs-storage 24m
data-mysql-1 Bound pvc-d1f574cb-b8e5-4a3e-8f55-695f8dd36797 10Gi RWO managed-nfs-storage 23m
data-mysql-2 Bound pvc-be316432-2b0c-411f-8554-ac32009c042f 10Gi RWO managed-nfs-storage 12m
[root@Server2 MySQLStateful]# kubectl get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-be316432-2b0c-411f-8554-ac32009c042f 10Gi RWO Delete Bound default/data-mysql-2 managed-nfs-storage 12m
pvc-c25eede4-6e01-4da5-84aa-fc37296570e1 10Gi RWO Delete Bound default/data-mysql-0 managed-nfs-storage 24m
pvc-d1f574cb-b8e5-4a3e-8f55-695f8dd36797 10Gi RWO Delete Bound default/data-mysql-1 managed-nfs-storage 23m
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运维实战案例 容器部分 使用Statefulset部署MySQL主从集群