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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;
复制代码
- 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
- 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"
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- 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
复制代码 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
源端口源DB_NAME目标端口目标映射DBchannel_name3306test_rep13309test_repchannel_33063307test_rep23309test_repchannel_33073308test_rep33309test_repchannel_33082.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
复制代码 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;
复制代码 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)
复制代码 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
复制代码 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)
复制代码 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);
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- 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);
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- 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);
复制代码- $ 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;
复制代码 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。
- 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);
复制代码 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
复制代码 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);
复制代码
- 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)
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- 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;
复制代码 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;
复制代码
- 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
复制代码 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
来源:https://www.cnblogs.com/greatsql/p/17944591
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