基于 Gtid 的 MySQL 主从同步实践

民工哥

前几天,有读者在后台留言问我可有基于Gtid的Mysql主从同步的文章,我记得历史文章应该有提及过,也有可能是只是提及,可能没有详细的过程介绍,所以,今天,民工哥就给大家安排一波。

什么是GTID?

  • 1、全局唯一,一个事务对应一个GTID
  • 2、替代传统的binlog+pos复制;使用master_auto_position=1自动匹配GTID断点进行复制
  • 3、MySQL5.6开始支持
  • 4、在传统的主从复制中,slave端不用开启binlog;但是在GTID主从复制中,必须开启binlog
  • 5、slave端在接受master的binlog时,会校验GTID值
  • 6、为了保证主从数据的一致性,多线程同时执行一个GTID

组成

Master_UUID:序列号举例:ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-5ceb0ca3d-8366-11e8-ad2b-000c298b7c9a其实就是master的uuid值;1-5是序列号,每次一个事务完成都会自增1,也就是说下一次为1-6。

工作原理

  • 1、master更新数据时,会在事务前产生GTID,一同记录到binlog日志中。
  • 2、slave端的i/o 线程将变更的binlog,写入到本地的relay log中。
  • 3、sql线程从relay log中获取GTID,然后对比slave端的binlog是否有记录。
  • 4、如果有记录,说明该GTID的事务已经执行,slave会忽略。
  • 5、如果没有记录,slave就会从relay log中执行该GTID的事务,并记录到binlog。
  • 6、在解析过程中会判断是否有主键,如果没有就用二级索引,如果没有就用全部扫描

GTID主从配置

版本:MySQL5.7

配置master

vim /etc/my.cnf
 [client]
 socket=/usr/local/mysql/mysql.sock
 [mysqld]
 basedir=/usr/local/mysql
 datadir=/usr/local/mysql/data
 user=mysql
 pid-file=/usr/local/mysql/data/mysqld.pid
 log-error=/usr/local/mysql/data/mysql.err
 socket=/usr/local/mysql/mysql.sock
 port=3306
 server-id=1
 gtid-mode=ON
 enforce-gtid-consistency=ON
 server-id=1
 binlog_format=row
 log-bin=/usr/local/mysql/data/mysql-bin
systemctl restart mysqld
firewall-cmd --add-port=3306/tcp --permanent
firewall-cmd --reload

配置slave

vim /etc/my.cnf
 [client]
 socket=/usr/local/mysql/mysql.sock
 [mysqld]
 basedir=/usr/local/mysql
 datadir=/usr/local/mysql/data
 user=mysql
 pid-file=/usr/local/mysql/data/mysqld.pid
 log-error=/usr/local/mysql/data/mysql.err
 socket=/usr/local/mysql/mysql.sock
 port=3306
 server-id=2
 gtid-mode=ON
 enforce-gtid-consistency=ON
 server-id=2
 binlog_format=ROW
 log-bin=/usr/local/mysql/data/mysql-bin
 log_slave_updates=ON
 skip-slave-start=1
systemctl restart mysqld
firewall-cmd --add-port=3306/tcp --permanent
firewall-cmd --reload

master授权配置

mysql -uroot -p
mysql> grant replication slave on *.* to 'rep'@'10.0.0.%' identified by '123';
mysql> flush privileges;

slave配置同步

mysql -uroot -p
mysql> change master to master_host='10.0.0.132', master_user='rep',master_password='123',master_port=3306,master_auto_position=1;
mysql> start slave;

查看slave的状态

mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 10.0.0.132
                  Master_User: rep
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 635
               Relay_Log_File: slave-relay-bin.000005
                Relay_Log_Pos: 848
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 635
              Relay_Log_Space: 1308
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
                  Master_UUID: ceb0ca3d-8366-11e8-ad2b-000c298b7c9a
             Master_Info_File: /usr/local/mysql/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-4
            Executed_Gtid_Set: ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-4
                Auto_Position: 1
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)

图片

出现这两个yes表示同步成功

图片

通过slave的状态信息,可以看到GTID的值、Matser\_UUID等信息

查看master状态

mysql> show master status;
+------------------+----------+--------------+------------------+------------------------------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                        |
+------------------+----------+--------------+------------------+------------------------------------------+
| mysql-bin.000003 |      635 |              |                  | ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-4 |
+------------------+----------+--------------+------------------+------------------------------------------+
1 row in set (0.00 sec)

注意对比slave端,Executed\_Gtid\_Set的值应该是一样的。

验证主从

master上

mysql> create database test01;
Query OK, 1 row affected (0.00 sec)

mysql> show master status;
+------------------+----------+--------------+------------------+------------------------------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                        |
+------------------+----------+--------------+------------------+------------------------------------------+
| mysql-bin.000003 |      800 |              |               | ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-5 |
+------------------+----------+--------------+------------------+------------------------------------------+
1 row in set (0.00 sec)

slave上

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| test01             |
+--------------------+
5 rows in set (0.07 sec)

mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 10.0.0.132
                  Master_User: rep
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 800
               Relay_Log_File: slave-relay-bin.000005
                Relay_Log_Pos: 1013
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 800
              Relay_Log_Space: 1473
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
                  Master_UUID: ceb0ca3d-8366-11e8-ad2b-000c298b7c9a
             Master_Info_File: /usr/local/mysql/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-5
            Executed_Gtid_Set: ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-5
                Auto_Position: 1
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)

需要注意的是,GTID的值在完成一次事务后,变成了ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-5(自增1)

排障

思路
  • a、确保master开放3306端口
  • b、最好关闭selinux
  • c、master上授权同步,slave上change master命令指定master的信息不要写错
  • d、UUID问题

图片

如果你出现了上图所示的问题,表示你的master和slave的UUID是一样的,一般这种情况多出现于克隆虚拟机

解决办法:

找到slave上的MySQL数据目录下的auto.cnf文件(这个文件其实是自动生成的mysql服务器的UUID值),将它删除,然后重启MySQL,然后MySQL会重新生成一个UUID。然后停掉slave,重新开启就可以了(我的mysql的数据目录是在/usr/local/mysql/data下,详情查看my.cnf配置文件)

cd /usr/local/mysql/data
rm -f auto.cnf
systemctl restart mysql
[root@slave data]# cat auto.cnf
[auto]
server-uuid=020c7f26-be57-11e8-8e2d-000c29b63bad

通过cat命令查看该文件,发现UUID已经改变

mysql -uroot -p
mysql> stop slave;
mysql> start slave;

总结

排障过程中,注意需要停掉slave,做完修改之后在开启,否则你的修改可能是不会生效的。

来源:https://blog.51cto.com/u_1343...

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