MySQL5.7 的GTID复制

　　　　　　　　　　　　　　　　　　MySQL5.7 的GTID复制

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　作者：尹正杰 

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　　在MySQL5.6之后其官方推出了GTID复制方式，和传统的基于bin log复制方式有所不同，接下来我们一起来了解一下它！

一.什么是GTID（global transaction identitifiers）

　　GTID复制是完全基于事务的复制，即每个在主库上执行的事务都会被分配到一个唯一的全局ID并记录和应用在主库上。

　　这种复制方式简化了简历slave和master/slave之间的切换工作，因为其完全不需要找当前执行的bin log和log中的位置完成切换。

　　一个GTID是master上执行的任何commit事务所分配的全局唯一ID标识，其由两部分组成。即GTID = source_id:transaction_id。source_id代表主库的server_uuid，transaction_id代表事务按顺序提交的ID,比如第一个提交则是1，第十个提交的事物则是10.

　　GTID集合代表一组GTID.

二.MySQL基于GTID的复制

1>.MySQL基于GTID复制的原理 　　

　　当一个事务在主库提交时，该事务就被赋予了一个GTID，并记录在主库的binary log

　　主库的binary log会被传输到从库的relay log中，从库读取此GTID并生成gtid_next系统参数

　　从库验证此GTID并没有在自己的binary log 中使用，则应用此事物在从库上。

 2>.MySQL5.6和MySQL5.7GTID复制模式之间的区别

　　MySQL5.6的GTID复制模式，slave必须开启binary log和log_slave_updates参数，否则启动就报错，因为需要在binary log找到同步复制的信息（UUID：事务号），注意，开启log_slave_updates参数，是把relay-log里的日志内容再记录到本地的binary log里。

　　但在MySQL5.7里，官方卫做了调整，用一张gtid_executed系统表记录同步复制的信息（UUID：事务号），这样就可以不用开启log_slave_updates参数，减少了从库的压力。

　　从MySQL5.7.4版本开始，GTID会存在在mysql系统库的gtid_executed表中。

[root@node102 ~]# mysql -uroot -pyinzhengjie
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.25-log MySQL Community Server (GPL)

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>
mysql>
mysql>
mysql> USE mysql
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>
mysql> desc gtid_executed;
+----------------+------------+------+-----+---------+-------+
| Field          | Type       | Null | Key | Default | Extra |
+----------------+------------+------+-----+---------+-------+
| source_uuid    | char(36)   | NO   | PRI | NULL    |       |
| interval_start | bigint(20) | NO   | PRI | NULL    |       |
| interval_end   | bigint(20) | NO   |     | NULL    |       |
+----------------+------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql>
mysql> SELECT * FROM gtid_executed;
Empty set (0.00 sec)

mysql>
mysql>  

未开启gtid复制是查看mysql.gtid_executed为空！

#node101.yinzhengjie.org.cn配置gtid生效
[root@node101 ~]#
[root@node101 ~]# cat /etc/my.cnf
[mysqld]
basedir=/yinzhengjie/softwares/mysql/
datadir=/yinzhengjie/softwares/mysql/data/
log-bin=yinzhengjie-mysql-bin
server-id=1
gtid-mode=on
enforce-gtid-consistency=on
[root@node101 ~]#
[root@node101 ~]#
[root@node101 ~]# /etc/init.d/mysql.server restart
Shutting down MySQL............ SUCCESS!
Starting MySQL. SUCCESS!
[root@node101 ~]# 

#node102.yinzhengjie.org.cn配置gtid生效
[root@node102 ~]# /etc/init.d/mysql.server start
Starting MySQL SUCCESS!
[root@node102 ~]# 2019-03-06T14:57:02.069380Z mysqld_safe A mysqld process already exists

[root@node102 ~]#
[root@node102 ~]#
[root@node102 ~]# /etc/init.d/mysql.server restart
Shutting down MySQL.. SUCCESS!
Starting MySQL. SUCCESS!
[root@node102 ~]#
[root@node102 ~]# 

主库和从库都需要修改my.cnf配置文件开启gtid并使之生效！需重启MySQL实例！

[root@node102 ~]# mysql -uroot -pyinzhengjie
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 5.7.25-log MySQL Community Server (GPL)

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>
mysql>
mysql> STOP SLAVE;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> RESET SLAVE ALL;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> CHANGE MASTER TO
    -> MASTER_HOST='node101.yinzhengjie.org.cn',
    -> MASTER_PORT=3306,
    -> MASTER_USER='copy',
    -> MASTER_PASSWORD='yinzhengjie',
    -> MASTER_AUTO_POSITION=1;
Query OK, 0 rows affected, 2 warnings (0.01 sec)

mysql>
mysql> START SLAVE;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql>
mysql>
mysql> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: node101.yinzhengjie.org.cn
                  Master_User: copy
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: yinzhengjie-mysql-bin.000005
          Read_Master_Log_Pos: 154
               Relay_Log_File: node102-relay-bin.000002
                Relay_Log_Pos: 391
        Relay_Master_Log_File: yinzhengjie-mysql-bin.000005
             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: 154
              Relay_Log_Space: 600
              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: b2127a6e-3cf8-11e9-ae0d-000c29fe9bef
             Master_Info_File: /yinzhengjie/softwares/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:
            Executed_Gtid_Set:
                Auto_Position: 1
         Replicate_Rewrite_DB:
                 Channel_Name:
           Master_TLS_Version:
1 row in set (0.00 sec)

mysql> 

从库上重新配置SLAVE相关参数

[root@node101 ~]# mysql -uroot -pyinzhengjie
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.25-log MySQL Community Server (GPL)

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>
mysql> use course
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_course |
+------------------+
| course           |
| dept             |
| score            |
| students         |
| teacher          |
+------------------+
5 rows in set (0.00 sec)

mysql> select * from students;
+-----+-----------+--------+---------+
| sid | sname     | gender | dept_id |
+-----+-----------+--------+---------+
|   1 | Jason Yin | 0      |       1 |
|   2 | Andy      | 0      |       1 |
|   3 | Bob       | 0      |       1 |
|   4 | Ruth      | 1      |       2 |
|   5 | Mike      | 0      |       2 |
+-----+-----------+--------+---------+
5 rows in set (0.00 sec)

mysql>
mysql>
mysql> insert into students values(6,'Jenny',1,1);
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> show master status;
+------------------------------+----------+--------------+------------------+----------------------------------------+
| File                         | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                      |
+------------------------------+----------+--------------+------------------+----------------------------------------+
| yinzhengjie-mysql-bin.000005 |      436 |              |                  | b2127a6e-3cf8-11e9-ae0d-000c29fe9bef:1 |
+------------------------------+----------+--------------+------------------+----------------------------------------+
1 row in set (0.00 sec)

mysql>
mysql>
mysql> show master status;
+------------------------------+----------+--------------+------------------+------------------------------------------+
| File                         | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                        |
+------------------------------+----------+--------------+------------------+------------------------------------------+
| yinzhengjie-mysql-bin.000005 |      718 |              |                  | b2127a6e-3cf8-11e9-ae0d-000c29fe9bef:1-2 |
+------------------------------+----------+--------------+------------------+------------------------------------------+
1 row in set (0.00 sec)

mysql>
mysql> select * from students;
+-----+-----------+--------+---------+
| sid | sname     | gender | dept_id |
+-----+-----------+--------+---------+
|   1 | Jason Yin | 0      |       1 |
|   2 | Andy      | 0      |       1 |
|   3 | Bob       | 0      |       1 |
|   4 | Ruth      | 1      |       2 |
|   5 | Mike      | 0      |       2 |
|   6 | Jenny     | 1      |       1 |
|   7 | DANNY     | 0      |       2 |
+-----+-----------+--------+---------+
7 rows in set (0.00 sec)

mysql> 

主库上插入测试数据

[root@node102 ~]#
[root@node102 ~]# mysql -uroot -pyinzhengjie
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 5.7.25-log MySQL Community Server (GPL)

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>
mysql>
mysql> USE course
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>
mysql> SELECT * FROM students;
+-----+-----------+--------+---------+
| sid | sname     | gender | dept_id |
+-----+-----------+--------+---------+
|   1 | Jason Yin | 0      |       1 |
|   2 | Andy      | 0      |       1 |
|   3 | Bob       | 0      |       1 |
|   4 | Ruth      | 1      |       2 |
|   5 | Mike      | 0      |       2 |
|   6 | Jenny     | 1      |       1 |
|   7 | DANNY     | 0      |       2 |
+-----+-----------+--------+---------+
7 rows in set (0.00 sec)

mysql>
mysql> 

从库上已经同步到了从库

mysql> SELECT * FROM mysql.gtid_executed;　　　　　　　　　　　　　　　　　　　　　　#这张表记录了复制了哪些事物！
+--------------------------------------+----------------+--------------+
| source_uuid                          | interval_start | interval_end |
+--------------------------------------+----------------+--------------+
| b2127a6e-3cf8-11e9-ae0d-000c29fe9bef |              1 |            1 |
| b2127a6e-3cf8-11e9-ae0d-000c29fe9bef |              2 |            2 |
+--------------------------------------+----------------+--------------+
2 rows in set (0.00 sec)

mysql>
mysql> 

　　

三.MySQL使用GTID复制的限制条件

　　由于GTID复制是依赖于事物的，所以MySQL的一些属性不支持。

　　当一个事物中既包含对InnoDB表的操作，也包含对非事物型存储引擎表（MyISAM）的操作时，就会导致一个事物中可能会产生多个GTID的情况；或者是当master和slave的表使用的存储引擎不一样时，都会导致GTID复制功能不正常。

　　CREATE TABLE ... SELECT语句在基于语句复制的环境中是不安全的，在基于行复制的环境中，此语句会被拆分成两个事件，一个是创建表，一个是INSERT数据，在某些情况下这两个事件会被分配相同的GTID，而导致insert的操作被忽略，所以GTID复制不支持CREATE TABLE .... SELECT语句。

[root@node101 ~]# mysql -uroot -pyinzhengjie
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.25-log MySQL Community Server (GPL)

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>
mysql>
mysql> CREATE TABLE temp SELECT * FROM course.students;
ERROR 1786 (HY000): Statement violates GTID consistency: CREATE TABLE ... SELECT.
mysql>
mysql> 

mysql> CREATE TABLE temp SELECT * FROM course.students;

　　CREATE/DROP TEMPORARY TABLE语句在GTID复制环境中不能放在事物中执行，只能单独执行，并且autocommit要开启

　　sql_slave_skip_counter语句是不支持的，如果想要跳过事务，可以使用gitd_exected变量。