简介
Galera Cluster 是一个同步多主数据库集群，可以使得MariDB的所有节点保持同步，Galera为MariaDB提供了同步复制（相对于原生的异步复制）,因此其可以保证HA。在使用InnoDB存储引擎时，还可以支持多主节点功能，这意味着Galera Cluster支持对任何节点的读写操作。
特点
- 真正的多主架构，任何节点都可以进行读写
- 同步复制，各节点间无延迟且节点宕机不会导致数据丢失
- 紧密耦合，所有节点均保持相同状态，节点间无不同数据
- 无需主从切换操作或使用VIP
- 热Standby，在Failover过程中无停机时间（由于不需要Failover）
- 自动节点配置，无需手工备份当前数据库并拷贝至新节点
- 支持InnoDB存储引擎
- 对应于透明，无需更改应用或是进行极小的更改
- 无需进行读写分离
环境搭建
环境准备
三台服务器（操作系统CentOS 7.0）
| 主机名 | IP |
|---|---|
| node-1 | 192.168.2.21 |
| node-2 | 192.168.2.22 |
| node-3 | 192.168.2.23 |
修改SELinux模式
# sed -i 's/^SELINUX=.*/SELINUX=permissive/g' /etc/sysconfig/selinux
# setenforce 0
关闭防火墙
# systemctl stop firewalld
卸载Postfix
安装mysql-wsrep-server包时可能由于Postfix存在导致安装失败，所以先卸载掉该软件包，如系统中需要Postfix提供邮件服务，可以在Galera Cluster部署完成后，重新安装Postfix即可。
# yum remove postfix
集群部署（以下操作在三个节点重复执行）
配置YUM源
# vim /etc/yum.repos.d/mariadb.repo
[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/5.5/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1
安装软件包
# yum -y install MariaDB-client MariaDB-Galera-server galera
修改配置文件
# mv /etc/my.cnf{,.bak}
# vim /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Ensure that the binary log format is set to use row-level replication, as opposed to statement-level replication.
binlog_format=ROW
bind-address=0.0.0.0
# Ensure that the default storage engine is InnoDB
default_storage_engine=innodb
innodb_autoinc_lock_mode=2
innodb_flush_log_at_trx_commit=0
innodb_buffer_pool_size=122M
wsrep_provider=/usr/lib64/galera/libgalera_smm.so
wsrep_provider_options="gcache.size=300M; gcache.page_size=1G"
wsrep_cluster_name="blkart_cluster"
wsrep_cluster_address="gcomm://192.168.2.21,192.168.2.22,192.168.2.23"
wsrep_node_name="node-1"
wsrep_node_address="192.168.2.21"
wsrep_sst_method=rsync
[mysql_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
配置swap空间
# fallocate -l 512M /swapfile
# dd if=/dev/zero of=/swapfile bs=1M count=512
# chmod 600 /swapfile
# ll -a / | grep swapfile
-rw-------. 1 root root 536870912 7月 28 16:07 swapfile
# mkswap /swapfile
# swapon /swapfile
# vim /etc/fstab
/swapfile none swap defaults 0 0
# swapon --summary
Filename Type Size Used Priority
/swapfile file 524284 0 -1
集群初始化
启动第一个节点
# /etc/init.d/mysql start --wsrep-new-cluster
注意： ‘–wsrep-new-cluster’选项只在第一次启动第一个节点时使用！
确认数据库服务启动成功
# mysql -u root -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 9
Server version: 5.5.44-MariaDB-wsrep MariaDB Server, wsrep_25.11.r4026
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]> SHOW STATUS LIKE 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 1 |
+--------------------+-------+
1 row in set (0.00 sec)
注意： 此时不要重启mysql服务!
将其他节点加入集群（在第二及第三个节点执行以下命令）
# systemctl start mysql
# mysql -u root -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 9
Server version: 5.5.44-MariaDB-wsrep MariaDB Server, wsrep_25.11.r4026
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]> SHOW STATUS LIKE 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 3 |
+--------------------+-------+
1 row in set (0.00 sec)
集群测试
复制测试
在node-1连接到数据库
# mysql -u root -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 9
Server version: 5.5.44-MariaDB-wsrep MariaDB Server, wsrep_25.11.r4026
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]> SHOW STATUS LIKE 'wsrep_%';
+---------------------------+------------+
| Variable_name | Value |
+---------------------------+------------+
...
| wsrep_local_state_comment | Synced (6) |
| wsrep_cluster_size | 3 |
| wsrep_ready | ON |
+---------------------------+------------+
MariaDB [(none)]> CREATE DATABASE galeratest;
MariaDB [(none)]> USE galeratest;
MariaDB [(none)]> CREATE TABLE test_table (
-> id INT PRIMARY KEY AUTO_INCREMENT,
-> msg TEXT ) ENGINE=InnoDB;
MariaDB [(none)]> INSERT INTO test_table (msg)
-> VALUES ("Hello my dear cluster.");
MariaDB [(none)]> INSERT INTO test_table (msg)
-> VALUES ("Hello, again, cluster dear.");
在node-2连接到数据库
# mysql -u root -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or g.
Your MariaDB connection id is 9
Server version: 5.5.44-MariaDB-wsrep MariaDB Server, wsrep_25.11.r4026
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
MariaDB [(none)]> USE galeratest;
MariaDB [(none)]> SELECT * FROM test_table;
+----+-----------------------------+
| id | msg |
+----+-----------------------------+
| 1 | Hello my dear cluster. |
| 2 | Hello, again, cluster dear. |
+----+-----------------------------+