mysql互为主从(双主)配置

　　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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