环境:
ubuntu18.04.2
mysql5.7.21
---------------master1服务器操作记录---------------
在my.cnf文件的[mysqld]配置区域添加下面内容：
[root@master1 ~]# vim /etc/my.cnf
server-id = 1
log-bin = mysql-bin
sync_binlog = 1
binlog_checksum = none
binlog_format = mixed
auto-increment-increment = 2
auto-increment-offset = 1
slave-skip-errors = all
[root@master1 ~]# cd /usr/local/mysql/support-files
[root@master1 ~]#./mysql.server restart
Shutting down MySQL. SUCCESS!
Starting MySQL.. SUCCESS!
数据同步授权（iptables防火墙开启3306端口）这样I/O线程就可以以这个用户的身份连接到主服务器，并且读取它的二进制日志。
mysql>grant all privileges on *.* to root@'%' identified by "123456";
#grant replication slave,replication client on *.* to root@'192.168.85.%' identified by "123456";
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
最好将库锁住，仅仅允许读，以保证数据一致性；待主主同步环境部署后再解锁；
锁住后，就不能往表里写数据，但是重启mysql服务后就会自动解锁！
mysql> flush tables with read lock; //注意该参数设置后，如果自己同步对方数据，同步前一定要记得先解锁！
Query OK, 0 rows affected (0.00 sec)
查看下log bin日志和pos值位置
mysql> show master status;
+------------------+----------+--------------+--------------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------+-------------------+
| mysql-bin.000004 | 430 | | mysql,information_schema | |
+------------------+----------+--------------+--------------------------+-------------------+
1 row in set (0.00 sec)
---------------master2服务器操作记录---------------
在my.cnf文件的[mysqld]配置区域添加下面内容：
[root@master2 ~]# vim /etc/my.cnf
server-id = 2
log-bin = mysql-bin
sync_binlog = 1
binlog_checksum = none
binlog_format = mixed
auto-increment-increment = 2
auto-increment-offset = 2
slave-skip-errors = all
[root@master1 ~]# cd /usr/local/mysql/support-files
[root@master1 ~]#./mysql.server restart
Shutting down MySQL.. SUCCESS!
Starting MySQL.. SUCCESS!
mysql> grant replication slave,replication client on *.* to root@'192.168.85.%' identified by "123465";
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> flush tables with read lock;
Query OK, 0 rows affected (0.00 sec)
mysql> show master status;
+------------------+----------+--------------+--------------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------+-------------------+
| mysql-bin.000003 | 430 | | mysql,information_schema | |
+------------------+----------+--------------+--------------------------+-------------------+
1 row in set (0.00 sec)
---------------master1服务器做同步操作---------------
mysql> unlock tables; //先解锁，将对方数据同步到自己的数据库中
mysql> slave stop；
mysql> change master to master_host='192.168.85.141',master_user='root',master_password='12346',master_log_file='mysql-bin.000003',master_log_pos=430;
Query OK, 0 rows affected, 2 warnings (0.01 sec)
mysql> start slave;
Query OK, 0 rows affected (0.01 sec)
查看同步状态，如下出现两个“Yes”，表明同步成功！
mysql> show slave status G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 182.148.15.237
Master_User: wang
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003
Read_Master_Log_Pos: 430
Relay_Log_File: mysql-relay-bin.000002
Relay_Log_Pos: 279
Relay_Master_Log_File: mysql-bin.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
.........................
Seconds_Behind_Master: 0
.........................
这样，master1就和master2实现了主从同步，即master1同步master2的数据。
---------------master2服务器做同步操作---------------
mysql> unlock tables; //先解锁，将对方数据同步到自己的数据库中
mysql> slave stop；
mysql> change master to master_host='192.168.85.140',master_user='root',master_password='123456',master_log_file='mysql-bin.000004',master_log_pos=430;
Query OK, 0 rows affected, 2 warnings (0.06 sec)
mysql> start slave;
Query OK, 0 rows affected (0.01 sec)
mysql> show slave status G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 182.148.15.238
Master_User: wang
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000004
Read_Master_Log_Pos: 430
Relay_Log_File: mysql-relay-bin.000002
Relay_Log_Pos: 279
Relay_Master_Log_File: mysql-bin.000004
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
........................
Seconds_Behind_Master: 0
........................
这样，master2就和master1实现了主从同步，即master2也同步master1的数据。
以上表明双方已经实现了mysql主主同步。
当运行一段时间后，要是发现同步有问题，比如只能单向同步，双向同步失效。可以重新执行下上面的change master同步操作，只不过这样同步后，只能同步在此之后的更新数据。下面开始进行数据验证：
-----------------主主同步效果验证---------------------
1）在master1数据库上写入新数据
mysql> unlock tables;
Query OK, 0 rows affected (0.00 sec)
mysql> create database huanqiu;
Query OK, 1 row affected (0.01 sec)
mysql> use huanqiu;
Database changed
mysql> create table if not exists haha (
-> id int(10) PRIMARY KEY AUTO_INCREMENT,
-> name varchar(50) NOT NULL);
Query OK, 0 rows affected (0.04 sec)
mysql> insert into haha values(1,"王士博");
Query OK, 1 row affected (0.00 sec)
mysql> insert into haha values(2,"郭慧慧");
Query OK, 1 row affected (0.00 sec)
mysql> select * from haha;
+----+-----------+
| id | name |
+----+-----------+
| 1 | 王士博 |
| 2 | 郭慧慧 |
+----+-----------+
2 rows in set (0.00 sec)
然后在master2数据库上查看，发现数据已经同步过来了!
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| huanqiu |
| mysql |
| performance_schema |
| test |
+--------------------+
5 rows in set (0.00 sec)
mysql> use huanqiu;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+-------------------+
| Tables_in_huanqiu |
+-------------------+
| haha |
+-------------------+
1 row in set (0.00 sec)
mysql> select * from haha;
+----+-----------+
| id | name |
+----+-----------+
| 1 | 王士博 |
| 2 | 郭慧慧 |
+----+-----------+
2 rows in set (0.00 sec)
2）在master2数据库上写入新数据
mysql> create database hehe;
Query OK, 1 row affected (0.00 sec)
mysql> insert into huanqiu.haha values(3,"周正"),(4,"李敏");
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
然后在master1数据库上查看，发现数据也已经同步过来了!
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| hehe |
| huanqiu |
| mysql |
| performance_schema |
| test |
+--------------------+
6 rows in set (0.00 sec)
mysql> select * from huanqiu.haha;
+----+-----------+
| id | name |
+----+-----------+
| 1 | 王士博 |
| 2 | 郭慧慧 |
| 3 | 周正 |
| 4 | 李敏 |
+----+-----------+
4 rows in set (0.00 sec)
至此，Mysql主主同步环境已经实现。
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