关于 MySQL GTID 复制

MySQL5.7以后都基本用GTID方式复制了,相对于binlog和position号方式,在failover时候减少很多人工切换操作

GTID,global transaction identitifiers,基于全局事务的复制方式,由server_uuid:transaction_id组成,server_uuid在数据库启动过程生成,在/data/auto.cnf中

复制过程:master事务提交时GTID,记录到binlog;然后master的binlog传送到slave的relaylog,slave读取GTID生成gtid_next系统参数;slave校验GTID是否在binlog并进一步应用事务(5.7后是存放在gtid_executed系统表,这样不用开启log_slave_updates参数,从而不用把relaylog记录再记录到binlog,减少slave压力)

下面操作下:

首先主从都配置gtid_mode、enforce_gtid_consistency参数,其中备库多加个log_slave_updates=1

[root@localhost /usr/local/mysql/data]$ cat /etc/my.cnf
[mysqld]
datadir=/usr/local/mysql/data
log_bin=mysql-bin
server_id=1
gtid_mode=on
enforce_gtid_consistency=on
[root@localhost /usr/local/mysql/data]$
 

mysql> show variables like '%gtid%';
+----------------------------------+-----------+
| Variable_name                    | Value    |
+----------------------------------+-----------+
| binlog_gtid_simple_recovery      | ON        |
| enforce_gtid_consistency        | ON        |
| gtid_executed_compression_period | 1000      |
| gtid_mode                        | ON        |
| gtid_next                        | AUTOMATIC |
| gtid_owned                      |          |
| gtid_purged                      |          |
| session_track_gtids              | OFF      |
+----------------------------------+-----------+
8 rows in set (0.00 sec)
 
mysql>

然后将之前异步复制的配置去掉,重新配置slave中主库信息即可

mysql> show variables like '%log_slave_updates%';
+-------------------+-------+
| Variable_name    | Value |
+-------------------+-------+
| log_slave_updates | ON    |
+-------------------+-------+
1 row in set (0.00 sec)
 
mysql> stop slave;
Query OK, 0 rows affected (0.01 sec)
 
mysql> reset slave all;
Query OK, 0 rows affected (0.02 sec)
 
mysql> change master to
    -> master_host='192.0.1.10',
    -> master_user='scott',
    -> master_password='tiger',
    -> master_port=3306,
    -> master_auto_position=1;
Query OK, 0 rows affected, 2 warnings (0.02 sec)
 
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
mysql> show slave status\G
*************************** 1. row ***************************
              Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.0.1.10
                  Master_User: scott
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000004
          Read_Master_Log_Pos: 573
              Relay_Log_File: localhost-relay-bin.000002
                Relay_Log_Pos: 786
        Relay_Master_Log_File: mysql-bin.000004
            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: 573
              Relay_Log_Space: 997
              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: 531fa6d1-627f-11e9-8dc7-000c297887a1
            Master_Info_File: /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: 531fa6d1-627f-11e9-8dc7-000c297887a1:1-2
            Executed_Gtid_Set: 531fa6d1-627f-11e9-8dc7-000c297887a1:1-2
                Auto_Position: 1
        Replicate_Rewrite_DB:
                Channel_Name:
          Master_TLS_Version:
1 row in set (0.00 sec)
 
mysql>
 

测试一下,ok的,主库状态可以看到

mysql> show master status;
+------------------+----------+--------------+------------------+------------------------------------------+
| File            | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                        |
+------------------+----------+--------------+------------------+------------------------------------------+
| mysql-bin.000004 |      573 |              |                  | 531fa6d1-627f-11e9-8dc7-000c297887a1:1-2 |
+------------------+----------+--------------+------------------+------------------------------------------+
1 row in set (0.00 sec)
 
mysql>
 

将slave中log_slave_updates关掉,就能看到mysql.gtid_executed表中记录已执行gtid信息了

mysql> select * from mysql.gtid_executed;
+--------------------------------------+----------------+--------------+
| source_uuid                          | interval_start | interval_end |
+--------------------------------------+----------------+--------------+
| 531fa6d1-627f-11e9-8dc7-000c297887a1 |              1 |            2 |
| 531fa6d1-627f-11e9-8dc7-000c297887a1 |              3 |            3 |
+--------------------------------------+----------------+--------------+
2 rows in set (0.00 sec)
 

由于是基于事务的,所以就有了限制条件: create table select的方式在基于行复制的情况下会被拆分为创建表和insert数据两个事件,某些情况下这两个事件会被分配相同GTID导致后面insert数据部分被忽略而产生错误; 一个事务中既包含InnoDB表又包含MyISAM表会导致可能产生多个gtid,或者表在主从库中存储引擎不一致都会产生gtid复制异常

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