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基于 Gtid 的 MySQL 主从同步实践
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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)
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。
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
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_13434336/2178937