MariaDB Galera Cluster 部署

2015-07-09 09:57


MariaDB作为Mysql的一个分支,在开源项目中已经广泛使用,例如大热的openstack,所以,为了保证服务的高可用性,同时提高系统的负载能力,集群部署是必不可少的。

MariaDB Galera Cluster 介绍

MariaDB Galera Cluster 是开源的 MariaDB同步多主机集群。它仅支持XtraDB/ InnoDB存储引擎(虽然有对MyISAM实验支持 - 看wsrep_replicate_myisam系统变量)。

主要功能:

  • 同步复制
  • 真正的multi-master,即所有节点可以同时读写数据库
  • 自动的节点成员控制,失效节点自动被清除
  • 新节点加入数据自动复制
  • 真正的并行复制,行级
  • 用户可以直接连接集群,使用感受上与MySQL完全一致

优势:

  • 因为是多主,所以不存在Slavelag(延迟)
  • 不存在丢失事务的情况
  • 同时具有读和写的扩展能力
  • 更小的客户端延迟
  • 节点间数据是同步的,而Master/Slave模式是异步的,不同slave上的binlog可能是不同的

技术:

Galera集群的复制功能基于Galeralibrary实现,为了让MySQL与Galera library通讯,特别针对MySQL开发了wsrep API。

Galera插件保证集群同步数据,保持数据的一致性,靠的就是可认证的复制,工作原理如下图: 

当客户端发出一个commit的指令,在事务被提交之前,所有对数据库的更改都会被 write-set 收集起来,并且将write-set 纪录的内容发送给其他节点。

write-set 将在每个节点进行认证测试,测试结果决定着节点是否应用write-set更改数据。

如果认证测试失败,节点将丢弃 write-set ;如果认证测试成功,则事务提交。

1 安装环境准备

安装MariaDB集群至少需要3台服务器(如果只有两台的话需要特殊配置,请参照官方文档

在这里,我列出试验机器的配置:

操作系统版本:centos7

  • node4:10.128.20.16
  • node5:10.128.20.17
  • node6:10.128.20.18

以第一行为例,node4为 hostname ,10.128.20.16为 ip ,在三台机器修改 /etc/hosts 文件,我的文件如下:

10.128.20.16 node4
10.128.20.17 node5
10.128.20.18 node6

为了保证节点间相互通信,需要禁用防火墙设置(如果需要防火墙,则参照官方网站增加防火墙信息设置)

在三个节点分别执行命令:

systemctl stop firewalld

然后将 /etc/sysconfig/selinux 的 selinux 设置成 disabled ,这样初始化环境就完成了。

2 安装 MariaDB Galera Cluster

[root@node4 ~]# yum install -y mariadb mariadb-galera-server mariadb-galera-common galera rsync
[root@node5 ~]# yum install -y mariadb mariadb-galera-server mariadb-galera-common galera rsync
[root@node6 ~]# yum install -y mariadb mariadb-galera-server mariadb-galera-common galera rsync

3 配置 MariaDB Galera Cluster

初始化数据库服务,只在一个节点进行

[root@node4 mariadb]# systemctl start mariadb
[root@node4 mariadb]# mysql_secure_installation

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MariaDB to secure it, we'll need the current
password for the root user.  If you've just installed MariaDB, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none):
OK, successfully used password, moving on...

Setting the root password ensures that nobody can log into the MariaDB
root user without the proper authorisation.

Set root password? [Y/n]
New password:
Re-enter new password:
Password updated successfully!
Reloading privilege tables..
 ... Success!


By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] n
 ... skipping.

Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] y
 ... Success!

By default, MariaDB comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] n
 ... skipping.

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] y
 ... Success!

Cleaning up...

All done!  If you've completed all of the above steps, your MariaDB
installation should now be secure.

Thanks for using MariaDB!

关闭数据库,修改 /etc/my.cnf.d/galera.cnf

[root@node4 mariadb]# systemctl stop mariadb
[root@node4 ~]# vim /etc/my.cnf.d/galera.cnf

修改以下内容:

[mysqld]
......
wsrep_provider = /usr/lib64/galera/libgalera_smm.so
wsrep_cluster_address = "gcomm://node4,node5,node6"
wsrep_node_name = node4
wsrep_node_address=10.128.20.16
#wsrep_provider_options="socket.ssl_key=/etc/pki/galera/galera.key; socket.ssl_cert=/etc/pki/galera/galera.crt;"

提示:如果不用ssl的方式认证的话,请把 wsrep_provider_options 注释掉。

将此文件复制到node5、node6,注意要把 wsrep_node_name 和 wsrep_node_address 改成相应节点的hostname 和 ip

4 启动 MariaDB Galera Cluster 服务

[root@node4 ~]# /usr/libexec/mysqld --wsrep-new-cluster --user=root &

观察日志:

[root@node4 ~]# tail -f /var/log/mariadb/mariadb.log

150701 19:54:17 [Note] WSREP: wsrep_load(): loading provider library 'none'
150701 19:54:17 [Note] /usr/libexec/mysqld: ready for connections.
Version: '5.5.40-MariaDB-wsrep'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server, wsrep_25.11.r4026

出现 ready for connections ,证明我们启动成功,继续启动其他节点:

[root@node5 ~]# systemctl start mariadb
[root@node6 ~]# systemctl start mariadb

可以查看 /var/log/mariadb/mariadb.log,在日志可以看到节点均加入了集群中。

警告⚠:--wsrep-new-cluster 这个参数只能在初始化集群使用,且只能在一个节点使用。

5 查看集群状态

我们可以关注几个关键的参数:

wsrep_connected = on 链接已开启

wsrep_local_index = 1 在集群中的索引值

wsrep_cluster_size =3 集群中节点的数量

wsrep_incoming_addresses = 10.128.20.17:3306,10.128.20.16:3306,10.128.20.18:3306 集群中节点的访问地址

6 验证数据同步

我们在 node4 上新建数据库 galera_test ,然后在 node5 和 node6 上查询,如果可以查询到 galera_test 这个库,说明数据同步成功,集群运行正常。

[root@node4 ~]# mysql  -uroot  -proot  -e  "create database galera_test"
[root@node5 ~]# mysql  -uroot  -proot  -e  "show databases"
+--------------------+
| Database           |
+--------------------+
| information_schema |
| galera_test        |
| mysql              |
| performance_schema |
+--------------------+
[root@node6 ~]# mysql  -uroot  -proot  -e  "show databases"
+--------------------+
| Database           |
+--------------------+
| information_schema |
| galera_test        |
| mysql              |
| performance_schema |
+--------------------+

至此,我们的 MariaDB Galera Cluster 已经成功部署。

参考文章