MySQL基于GTID的主从复制

1、什么是GTID？

1、全局唯一，一个事务对应一个GTID2、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binlog5、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

2、组成

Master_UUID:序列号
举例：
ceb0ca3d-8366-11e8-ad2b-000c298b7c9a:1-5
ceb0ca3d-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。

3、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

4、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-binsystemctl restart mysqldfirewall-cmd --add-port=3306/tcp --permanentfirewall-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=1systemctl restart mysqldfirewall-cmd --add-port=3306/tcp --permanentfirewall-cmd --reload

master授权配置

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

slave配置同步

mysql -uroot -pmysql> 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: 0Master_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)

出现这两个yes表示同步成功

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。

5、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: 0Master_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）

6、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

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/datarm -f auto.cnfsystemctl 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 -pmysql> stop slave;mysql> start slave;

e、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。