Mycat 分库分表实时同步到 GreatSQL
- 2024-01-04 福建
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Mycat 分库分表实时同步到 GreatSQL
这个事情怎么产生的
MyCat 作为经典的分库分表中间件,在长时间内被广泛认为是管理超大 MySQL 数据库集合的有效解决方案。近来接到客户需求,需要将 MyCat 集群迁移到 GreatSQL 中,并且在一段时间内需要实时从 MyCat 中同步数据到 GreatSQL 中,全量同步数据比较容易操作,增量同步有如下两个棘手的问题:
多个 server,不同的库名字,都要同步到 GreatSQL 一个库中,即同步关系如下
server1:db1.tab->gdb:db.tab;
server2:db2.tab->gdb:db.tab;
server3:db3.tab->gdb:db.tab;
ddl 同步多次执行会冲突。当 MyCat 的表中添加一个索引、添加一个字段时,实际上是后端所有 db 都会执行这个 DDL,同步到 GreatSQL 时,多次执行 DDL,复制会异常中断。
为了解决上面两个问题,经过查询资料,发现有两个不常用,官方也不建议使用的功能,刚好能够满足需求
为解决库名映射问题:需要在配置文件中添加参数
replicate_rewrite_db="channel_1:test_rep1->test_rep"
replicate_rewrite_db="channel_2:test_rep2->test_rep"
replicate_rewrite_db="channel_3:test_rep3->test_rep"
为了解决 DDL 同步后重复执行导致复制中断问题,在配置文件中添加
slave-skip-errors=ddl_exist_errors
验证一下
为了简化问题,MyCat 集群咱们就不搭建了,简化为多源同步复制问题。
1.初始化 4 个实例,同步关系如下
2.在 3309 的实例配置文件中,添加库映射关系配置和 DDL 冲突忽略参数
replicate_rewrite_db="channel_3306:test_rep1->test_rep"
replicate_rewrite_db="channel_3307:test_rep2->test_rep"
replicate_rewrite_db="channel_3308:test_rep3->test_rep"
slave-skip-errors=ddl_exist_errors
4.在 3309 实例中,配置三个 channel
greatsql> change master to MASTER_HOST = '172.17.137.91',MASTER_USER = 'greatsql',MASTER_PASSWORD = 'greatsql',MASTER_PORT = 3306,MASTER_AUTO_POSITION = 1 FOR CHANNEL 'channel_3306';
greatsql> change master to MASTER_HOST = '172.17.137.91',MASTER_USER = 'greatsql',MASTER_PASSWORD = 'greatsql',MASTER_PORT = 3307,MASTER_AUTO_POSITION = 1 FOR CHANNEL 'channel_3307';
greatsql> change master to MASTER_HOST = '172.17.137.91',MASTER_USER = 'greatsql',MASTER_PASSWORD = 'greatsql',MASTER_PORT = 3308,MASTER_AUTO_POSITION = 1 FOR CHANNEL 'channel_3308';
greatsql> start slave;
3.检查 channel 配置状态
greatsql> show slave status \G
*************************** 1. row ***************************
Slave_IO_State: Waiting for source to send event
Master_Host: 172.17.137.91
Master_User: greatsql
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: binlog.000002
Read_Master_Log_Pos: 1119
Relay_Log_File: relaylog-channel_3306.000007
Relay_Log_Pos: 397
Relay_Master_Log_File: binlog.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: 1119
Relay_Log_Space: 606
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: 3306
Master_UUID: 5facacd7-9ed6-11ee-b76b-00163e5af5d6
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Replica 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: 49b66af0-9ed6-11ee-ae4f-00163e5af5d6:3,
5a369d0b-9ed6-11ee-b3d1-00163e5af5d6:3,
5facacd7-9ed6-11ee-b76b-00163e5af5d6:1-4,
9a5f9c26-4262-11ee-85fd-00163e5af5d6:1-16571224
Auto_Position: 1
Replicate_Rewrite_DB: (test_rep1,test_rep)
Channel_Name: channel_3306
Master_TLS_Version:
Master_public_key_path:
Get_master_public_key: 0
Network_Namespace:
*************************** 2. row ***************************
Slave_IO_State: Waiting for source to send event
Master_Host: 172.17.137.91
Master_User: greatsql
Master_Port: 3307
Connect_Retry: 60
Master_Log_File: binlog.000002
Read_Master_Log_Pos: 1119
Relay_Log_File: relaylog-channel_3307.000004
Relay_Log_Pos: 1034
Relay_Master_Log_File: binlog.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: 1119
Relay_Log_Space: 1243
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: 3307
Master_UUID: 5a369d0b-9ed6-11ee-b3d1-00163e5af5d6
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Replica 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: 5a369d0b-9ed6-11ee-b3d1-00163e5af5d6:1-2:4
Executed_Gtid_Set: 49b66af0-9ed6-11ee-ae4f-00163e5af5d6:3,
5a369d0b-9ed6-11ee-b3d1-00163e5af5d6:3,
5facacd7-9ed6-11ee-b76b-00163e5af5d6:1-4,
9a5f9c26-4262-11ee-85fd-00163e5af5d6:1-16571224
Auto_Position: 1
Replicate_Rewrite_DB: (test_rep2,test_rep)
Channel_Name: channel_3307
Master_TLS_Version:
Master_public_key_path:
Get_master_public_key: 0
Network_Namespace:
*************************** 3. row ***************************
Slave_IO_State: Waiting for source to send event
Master_Host: 172.17.137.91
Master_User: greatsql
Master_Port: 3308
Connect_Retry: 60
Master_Log_File: binlog.000002
Read_Master_Log_Pos: 1119
Relay_Log_File: relaylog-channel_3308.000004
Relay_Log_Pos: 1034
Relay_Master_Log_File: binlog.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: 1119
Relay_Log_Space: 1243
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: 3308
Master_UUID: 49b66af0-9ed6-11ee-ae4f-00163e5af5d6
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Replica 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: 49b66af0-9ed6-11ee-ae4f-00163e5af5d6:1-2:4
Executed_Gtid_Set: 49b66af0-9ed6-11ee-ae4f-00163e5af5d6:3,
5a369d0b-9ed6-11ee-b3d1-00163e5af5d6:3,
5facacd7-9ed6-11ee-b76b-00163e5af5d6:1-4,
9a5f9c26-4262-11ee-85fd-00163e5af5d6:1-16571224
Auto_Position: 1
Replicate_Rewrite_DB: (test_rep3,test_rep)
Channel_Name: channel_3308
Master_TLS_Version:
Master_public_key_path:
Get_master_public_key: 0
Network_Namespace:
3 rows in set, 1 warning (0.00 sec)
在上面的输出中,可以重点关注如下字段信息,说明 db 转换映射成功
$ MYSQL_PWD=greatsql mysql -ugreatsql -h127.0.0.1 -P3309 -e 'show replica status \G'| grep -wE 'Replica_IO_Running|Replica_SQL_Running|Replicate_Rewrite_DB|Channel_Name'
Replica_IO_Running: Yes
Replica_SQL_Running: Yes
Replicate_Rewrite_DB: (test_rep1,test_rep)
Channel_Name: channel_3306
Replica_IO_Running: Yes
Replica_SQL_Running: Yes
Replicate_Rewrite_DB: (test_rep2,test_rep)
Channel_Name: channel_3307
Replica_IO_Running: Yes
Replica_SQL_Running: Yes
Replicate_Rewrite_DB: (test_rep3,test_rep)
Channel_Name: channel_3308
在 3309 实例中,查询 replica_skip_errors,确认复制异常跳过的错误码,设置为 ddl_exist_errors 会自动转换为如下错误码
greatsql> select @@replica_skip_errors;
+---------------------------------------------------+
| @@replica_skip_errors |
+---------------------------------------------------+
| 1007,1008,1050,1051,1054,1060,1061,1068,1091,1146 |
+---------------------------------------------------+
1 row in set (0.00 sec)
5.数据同步验证
在 3309 库中,创建 database test_rep
这个库需要手动创建,是测试发现映射关系只对库下面的表生效,库不会自动转换创建。
在 3306 库中,创建 database test_rep1,并且创建 tab1 表
$ mysql -ugreatsql -h127.0.0.1 -p -P3306 -s
greatsql> create database test_rep1;
greatsql> use test_rep1;
greatsql> create table tab1(id int primary key auto_increment, cname varchar(10), age int);
在 3307 库中,创建 database test_rep2,并且创建 tab1 表
$ mysql -ugreatsql -h127.0.0.1 -p -P3307 -s
greatsql> create database test_rep2;
greatsql> use test_rep2;
greatsql> create table tab1(id int primary key auto_increment, cname varchar(10), age int);
在 3308 库中,创建 database test_rep3,并且创建 tab1 表
$ mysql -ugreatsql -h127.0.0.1 -p -P3308 -s
greatsql> create database test_rep3;
greatsql> use test_rep3;
greatsql> create table tab1(id int primary key auto_increment, cname varchar(10), age int);
在 3309 中确认 database 及表的同步
$ mysql -ugreatsql -h127.0.0.1 -p -P3309 -s
greatsql> show databases;
Database
information_schema
mysql
performance_schema
sys
test_db
test_rep
test_rep1
test_rep2
test_rep3
greatsql> show tables from test_rep;
Tables_in_test_rep
tab1
greatsql> show tables from test_rep1;
greatsql> show tables from test_rep2;
greatsql> show tables from test_rep3;
从上面的信息可以看出,在 3309 中,3306、3307、3308 中创建的库均按照原有的名字进行了同步,但是表只同步在了 3309 映射的库 test_rep 中。
分别在 3306、3307、3308 中插入一条记录
3306 : insert into test_rep1.tab1 values(1,'a',10);
3307 : insert into test_rep2.tab1 values(2,'b',20);
3308 : insert into test_rep3.tab1 values(3,'c',30);
然后在各自节点查询数据插入情况
$ mysql -ugreatsql -h127.0.0.1 -p -P3306 -s test_rep1 -e 'select * from tab1'
id cname age
1 a 10
$ mysql -ugreatsql -h127.0.0.1 -p -P3307 -s test_rep2 -e 'select * from tab1'
id cname age
2 b 20
$ mysql -ugreatsql -h127.0.0.1 -p -P3308 -s test_rep3 -e 'select * from tab1'
id cname age
3 c 30
$ mysql -ugreatsql -h127.0.0.1 -p -P3309 -s test_rep -e 'select * from tab1'
id cname age
1 a 10
2 b 20
3 c 30
$ mysql -ugreatsql -h127.0.0.1 -p -P3309 -s test_rep1 -e 'select * from tab1'
ERROR 1146 (42S02) at line 1: Table 'test_rep1.tab1' doesn't exist
$ mysql -ugreatsql -h127.0.0.1 -p -P3309 -s test_rep2 -e 'select * from tab1'
ERROR 1146 (42S02) at line 1: Table 'test_rep2.tab1' doesn't exist
$ mysql -ugreatsql -h127.0.0.1 -p -P3309 -s test_rep3 -e 'select * from tab1'
ERROR 1146 (42S02) at line 1: Table 'test_rep3.tab1' doesn't exist
从上面的查询情况可以看出,3306、3307、3308 节点中只有一条记录,并且记录都被同步到了 3309 的 test_rep.tab1 表中,而且在 3309 的 test_rep1、test_rep2、test_rep3 中是没有表存在的。
分别在 3306、3307、3308 给表 tab 创建一个索引
greatsql> alter table tab1 add index idx_cname(cname);
观察 3309 中表的索引情况,可以看到索引 idx_cname 被同步过来了
$ mysql -ugreatsql -h127.0.0.1 -p -P3309 -s
greatsql> use test_rep
greatsql> show create table tab1 \G
*************************** 1. row ***************************
Table: tab1
Create Table: CREATE TABLE `tab1` (
`id` int NOT NULL AUTO_INCREMENT,
`cname` varchar(10) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`age` int DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `idx_cname` (`cname`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
1 row in set (0.00 sec)
分别在 3306、3307、3308 做 update、delete 操作
greatsql> update test_rep1.tab1 set age=110 where id=1;
greatsql> update test_rep2.tab1 set age=120 where id=2;
greatsql> update test_rep3.tab1 set age=130 where id=3;
greatsql> delete from test_rep1.tab1 where id=1;
greatsql> delete from test_rep2.tab1 where id=1;
greatsql> delete from test_rep3.tab1 where id=1;
查看 3309 的数据同步情况,确认数据被清理
$ mysql -ugreatsql -h127.0.0.1 -p -P3309 -s
Welcome to the MySQL monitor. Commands end with ; or \g.
greatsql> select * from test_rep.tab1;
观察 3 个 channel 的同步情况,可以确认三个复制同步均正常
$ mysql -ugreatsql -h127.0.0.1 -p -P3309 -e 'show replica status \G'| grep -E 'Replica_IO_Running|Replica_SQL_Running|Channel_Name'
greatsql: [Warning] Using a password on the command line interface can be insecure.
Replica_IO_Running: Yes
Replica_SQL_Running: Yes
Replica_SQL_Running_State: Replica has read all relay log; waiting for more updates
Channel_Name: channel_3306
Replica_IO_Running: Yes
Replica_SQL_Running: Yes
Replica_SQL_Running_State: Replica has read all relay log; waiting for more updates
Channel_Name: channel_3307
Replica_IO_Running: Yes
Replica_SQL_Running: Yes
Replica_SQL_Running_State: Replica has read all relay log; waiting for more updates
Channel_Name: channel_3308
至此 dml、ddl 同步均验证。
方案缺陷
本方案中,业务访问 MyCat 的表名字,和 server 后端的表名字完全一致,只是库名字不相同,然后 MyCat 代理表名和实际 server 的表名字可以不相同,这种情况下,暂时无法映射处理
MyCat 代理的实际上是多个单独的库,如果这些库之前没有做自增主键步长处理,或者其他一些主键不重复策略,同步过程中,会存在主键冲突导致数据同步中断的情况,需要提前准备处理方案。
最后附上参考资料
Enjoy GreatSQL :)
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版权声明: 本文为 InfoQ 作者【GreatSQL】的原创文章。
原文链接:【http://xie.infoq.cn/article/ce34e844da05bc95e1e54d788】。文章转载请联系作者。
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GreatSQL是由万里数据库维护的MySQL分支,专注于提升MGR可靠性及性能,支持InnoDB并行查询特性,是适用于金融级应用的MySQL分支版本。 社区:https://greatsql.cn/ Gitee: https://gitee.com/GreatSQL/GreatSQL
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