基于GTID的复制 简介 基于GTID的复制是MySQL 5.6后新增的复制方式. GTID (global transaction identifier) 即全局事务ID, 保证了在每个在主库上提交的事务在集群中有一个唯一的ID. 在原来基于日志的
基于GTID的复制
简介
基于GTID的复制是MySQL 5.6后新增的复制方式.
GTID (global transaction identifier) 即全局事务ID, 保证了在每个在主库上提交的事务在集群中有一个唯一的ID.
在原来基于日志的复制中, 从库需要告知主库要从哪个偏移量进行增量同步, 如果指定错误会造成数据的遗漏, 从而造成数据的不一致.
而基于GTID的复制中, 从库会告知主库已经执行的事务的GTID的值, 然后主库会将所有未执行的事务的GTID的列表返回给从库. 并且可以保证同一个事务只在指定的从库执行一次.
实战
1、在主库上建立复制账户并授予权限
基于GTID的复制会自动地将没有在从库执行的事务重放, 所以不要在其他从库上建立相同的账号. 如果建立了相同的账户, 有可能造成复制链路的错误.
mysql> create user 'repl'@'172.%' identified by '123456';
注意在生产上的密码必须依照相关规范以达到一定的密码强度, 并且规定在从库上的特定网段上才能访问主库.
mysql> grant replication slave on *.* to 'repl'@'172.%';
查看用户
mysql> select user, host from mysql.user;
+-----------+-----------+
| user | host |
+-----------+-----------+
| prontera | % |
| root | % |
| mysql.sys | localhost |
| root | localhost |
+-----------+-----------+
4 rows in set (0.00 sec)
查看授权
mysql> show grants for repl@'172.%';
+--------------------------------------------------+
| Grants for repl@172.% |
+--------------------------------------------------+
| GRANT REPLICATION SLAVE ON *.* TO 'repl'@'172.%' |
+--------------------------------------------------+
1 row in set (0.00 sec)
2、配置主库服务器
[mysqld]
log_bin = /var/log/mysql/mysql-bin
log_bin_index = /var/log/mysql/mysql-bin.index
binlog_format = row
server_id = 101
gtid_mode = ON
enforce_gtid_consistency = ON
#log_slave_updates = ON
NOTE: 把日志与数据分开是个好习惯, 最好能放到不同的数据分区
enforce_gtid_consistency 强制GTID一致性, 启用后以下命令无法再使用
create table ... select ...
mysql> create table dept select * from departments;
ERROR 1786 (HY000): Statement violates GTID consistency: CREATE TABLE ... SELECT.
因为实际上是两个独立事件, 所以只能将其拆分先建立表, 然后再把数据插入到表中
create temporary table
事务内部不能创建临时表
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> create temporary table dept(id int);
ERROR 1787 (HY000): Statement violates GTID consistency: CREATE TEMPORARY TABLE and DROP TEMPORARY TABLE can only be executed outside transactional context. These statements are also not allowed in a function or trigger because functions and triggers are also considered to be multi-statement transactions.
同一事务中更新事务表与非事务表(MyISAM)
mysql> CREATE TABLE `dept_innodb` (id INT(11) UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT);
Query OK, 0 rows affected (0.04 sec)
mysql> CREATE TABLE `dept_myisam` (id INT(11) UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT) ENGINE = `MyISAM`;
Query OK, 0 rows affected (0.03 sec)
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> insert into dept_innodb(id) value(1);
Query OK, 1 row affected (0.00 sec)
mysql> insert into dept_myisam(id) value(1);
ERROR 1785 (HY000): Statement violates GTID consistency: Updates to non-transactional tables can only be done in either autocommitted statements or single-statement transactions, and never in the same statement as updates to transactional tables.
所以建议选择Innodb作为默认的数据库引擎.
log_slave_updates 该选项在MySQL 5.6版本时基于GTID的复制是必须的, 但是其增大了从服务器的IO负载, 而在MySQL 5.7中该选项已经不是必须项
3、配置从库服务器
master_info_repository 与relay_log_info_repository
在MySQL 5.6.2之前, slave记录的master信息以及slave应用binlog的信息存放在文件中, 即master.info与relay-log.info. 在5.6.2版本之后, 允许记录到table中. 对应的表分别为mysql.slave_master_info与mysql.slave_relay_log_info, 且这两个表均为innodb引擎表.
[mysqld]
log_bin = /var/log/mysql/mysql-bin
log_bin_index = /var/log/mysql/mysql-bin.index
server_id = 102
# slaves
relay_log = /var/log/mysql/relay-bin
relay_log_index = /var/log/mysql/relay-bin.index
relay_log_info_file = /var/log/mysql/relay-bin.info
enforce_gtid_consistency = ON
log_slave_updates = ON
read_only = ON
master_info_repository = TABLE
relay_log_info_repository = TABLE
4、从库数据初始化 - [optional]
先在主库上备份数据
复制代码 代码如下:
mysqldump --single-transaction --master-data=2 --triggers --routines --all-databases --events -u root -p > backup.sql
—master-data=2 该选项将当前服务器的binlog的位置和文件名追加到输出文件中(show master status). 如果为1, 将偏移量拼接到CHANGE MASTER 命令. 如果为2, 输出的偏移量信息将会被注释。
--all-databases 因为基于GTID的复制会记录全部的事务, 所以要构建一个完整的dump这个选项是推荐的
常见错误
当从库导入SQL的时候出现
复制代码 代码如下:
ERROR 1840 (HY000) at line 24: @@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_EXECUTED is empty.
此时进入从库的MySQL Command Line, 使用reset master即可
5、启动基于GTID的复制
现有master@172.20.0.2和slave@172.20.0.3, 并且已经通过mysqldump将数据同步至从库slave中. 现在在从服务器slave上配置复制链路
mysql> change master to master_host='master', master_user='repl', master_password='123456', master_auto_position=1;
Query OK, 0 rows affected, 2 warnings (0.06 sec)
启动复制
mysql> start slave;
启动成功后查看slave的状态
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Queueing master event to the relay log
Master_Host: master
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000002
Read_Master_Log_Pos: 12793692
Relay_Log_File: relay-bin.000002
Relay_Log_Pos: 1027
Relay_Master_Log_File: mysql-bin.000002
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: 814
Relay_Log_Space: 12794106
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: 5096
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: 101
Master_UUID: a9fd4765-ec70-11e6-b543-0242ac140002
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Reading event from the relay log
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set: a9fd4765-ec70-11e6-b543-0242ac140002:1-39
Executed_Gtid_Set: a9fd4765-ec70-11e6-b543-0242ac140002:1-4
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
当Slave_IO_Running, Slave_SQL_Running为YES,
且Slave_SQL_Running_State 为Slave has read all relay log; waiting for more updates时表示成功构建复制链路
6、总结
优点
因为不用手工设置日志偏移量, 可以很方便地进行故障转移
如果启用log_slave_updates那么从库不会丢失主库上的任何修改
缺点
对执行的SQL有一定限制
仅支持MySQL 5.6之后的版本, 而且不建议使用早期5.6版本
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持每日运维。
