双主复制潜在的问题：
双主模型恰巧双方同时操作一组数据，左服务器锁住A字段修改B字段，右服务器锁住B字段修改A字段。双方一同步数据可能出现不一致。
1、在两台服务器上各自建立一个具有复制权限的用户；
mysql
GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO 'repluser'@'192.168.130.%' IDENTIFIED BY 'replpass';
FLUSH PRIVILEGES;
2、修改配置文件；
主服务器A上
service mysqld stop
vim /etc/my.cnf
[mysqld]
server-id = 10
log-bin=/mydata/binlog/log-bin
relay-log = /mydata/relaylog/relay-log
auto-increment-offset = 1
auto-increment-increment = 2
skip-slave-start
service mysqld start
主服务器B上
service mysqld stop
vim /etc/my.cnf
[mysqld]
server-id = 20
log-bin=/mydata/binlog/log-bin
relay-log = /mydata/relaylog/relay-log
auto-increment-offset = 2
auto-increment-increment = 2
skip-slave-start
service mysqld start
3、如果此时两台服务器均为新建立，且无其它写入操作，各服务器只需记录当前自己二进制日志文件及事件位置，以之作为另外的服务器复制起始位置即可
主服务器A上
MariaDB [(none)]> SHOW MASTER STATUS \G;
*************************** 1. row ***************************
File: log-bin.000001
Position: 682
Binlog_Do_DB:
Binlog_Ignore_DB:
1 row in set (0.00 sec)
主服务器B上
MariaDB [(none)]> SHOW MASTER STATUS \G;
*************************** 1. row ***************************
File: log-bin.000001
Position: 682
Binlog_Do_DB:
Binlog_Ignore_DB:
1 row in set (0.00 sec)
4、各服务器接下来指定对另一台服务器为自己的主服务器即可：
主服务器A上
CHANGE MASTER TO MASTER_HOST = '192.168.130.62', MASTER_USER='repluser', MASTER_PASSWORD='replpass',MASTER_LOG_FILE='log-bin.000001', MASTER_LOG_POS=682;
START SLAVE;
SHOW SLAVE STATUS\G;
主服务器B上
CHANGE MASTER TO MASTER_HOST = '192.168.130.61', MASTER_USER='repluser', MASTER_PASSWORD='replpass',MASTER_LOG_FILE='log-bin.000001', MASTER_LOG_POS=682;
START SLAVE;
SHOW SLAVE STATUS\G;
5、各服务器写入数据测试
主服务器A上
CREATE DATABASE testdb;
USE testdb;
CREATE TABLE t1 (ID TINYINT NOT NULL AUTO_INCREMENT PRIMARY KEY,Name VARCHAR(50) NOT NULL);
INSERT INTO t1 (Name) VALUES ('A1'),('A2');
MariaDB [testdb]> SELECT * FROM t1;
+----+------+
| ID | Name |
+----+------+
| 1 | A1 |
| 3 | A2 |
+----+------+
2 rows in set (0.00 sec)
主服务器B上
USE testdb;
INSERT INTO t1 (Name) VALUES ('B1'),('B2');
MariaDB [testdb]> SELECT * FROM t1;
+----+------+
| ID | Name |
+----+------+
| 1 | A1 |
| 3 | A2 |
| 4 | B1 |
| 6 | B2 |
+----+------+
4 rows in set (0.00 sec)
多主，且高可用的解决方案
MMM：Multi Master MySQL
MHA：MySQL HA