一、背景
分享一个在项目运维中遇到的一个主从复制限制的一个坑，项目的架构为主集群+灾备集群，每个集群为一主两从模式。主集群到灾备集群的同步为主从复制的方式，根据业务需求灾备集群需要忽略系统库跟某些配置表，所以才会触发此限制，而这个限制如果我们之前没有遇到过，那么排查起来也是相对不易的。
二、限制描述
1、主从同步出现报错
greatsql> show slave status\G*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.xxx.xxx Master_User: repl Master_Port: 3306 Connect_Retry: 60 Master_Log_File: greatsql-bin.000990 Read_Master_Log_Pos: 92274290 Relay_Log_File: greatsql-relay.002963 ----- Relay_Log_Pos: 701548899 Relay_Master_Log_File: greatsql-bin.000988 Slave_IO_Running: Yes Slave_SQL_Running: No Replicate_Do_DB: Replicate_Ignore_DB: mysql,dbscale,dbscale_tmp,information_schema,performance_schema,sys Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: A.ab,B.bc Last_Errno: 1146 Last_Error: Coordinator stopped because there were error(s) in the worker(s). The most recent failure being: Worker 1 failed executing transaction '9e668a93-2618-11ee-93ee-bc16954181bb:47508257' at master log greatdb-bin.000988, end_log_pos 701570116. See error log and/or performance_schema.replication_applier_status_by_worker table for more details about this failure or others, if any. Skip_Counter: 0 Exec_Master_Log_Pos: 701548690 Relay_Log_Space: 2246320360 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: NULLMaster_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 1146 Last_SQL_Error: Coordinator stopped because there were error(s) in the worker(s). The most recent failure being: Worker 1 failed executing transaction '9e668a93-2618-11ee-93ee-bc16954181bb:47508257' at master log greatdb-bin.000988, end_log_pos 701570116. See error log and/or performance_schema.replication_applier_status_by_worker table for more details about this failure or others, if any. Replicate_Ignore_Server_Ids: Master_Server_Id: 1943306 Master_UUID: 9e668a93-2618-11ee-93ee-bc16954181bb Master_Info_File: mysql.slave_master_info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: 230822 14:14:18 Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: 9e668a93-2618-11ee-93ee-bc16954181bb:2-47565802 Executed_Gtid_Set: 30873cfe-8750-11ed-b56f-744aa4073024:1-270,9e668a93-2618-11ee-93ee-bc16954181bb:1-47508256 Auto_Position: 1 Replicate_Rewrite_DB: Channel_Name: Master_TLS_Version:1 row in set (0.00 sec)
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根据 slave status 状态信息可以看出
报错的 GTID 为：'9e668a93-2618-11ee-93ee-bc16954181bb:47508257'
应用的主集群的 binlog 为：greatsql-bin.000988
灾备集群的 relay log 为：greatsql-relay.002963
详细信息查看performance_schema.replication_applier_status_by_worker表
2、查看错误的详细信息
greatsql> select * from performance_schema.replication_applier_status_by_worker\G*************************** 1. row *************************** CHANNEL_NAME: WORKER_ID: 1 THREAD_ID: NULL SERVICE_STATE: OFFLAST_SEEN_TRANSACTION: 9e668a93-2618-11ee-93ee-bc16954181bb:47508257 LAST_ERROR_NUMBER: 1146 LAST_ERROR_MESSAGE: Worker 1 failed executing transaction'9e668a93-2618-11ee-93ee-bc16954181bb:47508257' at master log greatdb-bin.000988,end_log_pos 701570116; Error executing row event: 'Table 'abs_xxx.tmp_xxx_info' doesn't exist'LAST_ERROR_TIMESTAMP: 2023-08-22 14:14:18
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上述信息说明根据performance_schema.replication_applier_status_by_worker表中的详细错误信息可以发现为灾备集群abs_xxx.tmp_xxx_info表不存在，导致同步报错
3、问题分析
3.1、确认灾备集群中目标表是否存在
greatsql> show create table abs_xxx.tmp_xxx_info;ERROR 1146 (42S02): Table 'abs_xxx.tmp_xxx_info' doesn't existgreatsql> desc abs_xxx.tmp_xxx_info;ERROR 1146 (42S02): Table 'abs_xxx.tmp_xxx_info' doesn't exist
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**结论：**灾备集群中目标表的确不存在
3.2、根据主从报错信息解析主集群 binlog，报错的 SQL
解析主集群 binlog
SET @@SESSION.GTID_NEXT= '9e668a93-2618-11ee-93ee-bc16954181bb:47508257'/*!*/;……#230822 14:14:18 server id 1943306 end_log_pos 701570000 Table_map: `abs_xxx`.`tmp_xxx_info` mapped to number 1595# at 701570000#230822 14:14:18 server id 1943306 end_log_pos 701570116 Write_rows: table id 1595 flags: STMT_END_F### INSERT INTO `abs_xxx`.`tmp_xxx_info`### SET### @1=2### @2='自动化'### @3='2300121212120000'### @4='90000000'### @5='1'### @6='202001290231001'### @7='2021-01-31 00:00:00'# at 701570116#230822 14:14:18 server id 1943306 end_log_pos 701570143 Xid = 800998400COMMIT/*!*/;# at 701570143#230822 14:14:18 server id 1943306 end_log_pos 701570204 GTID last_committed=26491 sequence_number=26521 rbr_only=yes/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;
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**结论：**根据复制的报错信息得知具体的 GTID 号以及主集群的 binlog 文件，解析 binlog 得知此事务为一条 INSERT 语句，语句中的目标表与performance_schema.replication_applier_status_by_worker表中信息一致
3.3、寻找主集群目标表 binlog 中是否有建表语句
在同一 binlog 日志中寻找建表语句
SET TIMESTAMP=1692684495/*!*/;CREATE DATABASE IF NOT EXISTS `abs_xxx` /*!40100 DEFAULT CHARACTER SET utf8 COLLATE utf8_bin *//*!*/;……use `information_schema`/*!*/;SET TIMESTAMP=1692684495/*!*/;CREATE TABLE `abs_xxx`.`tmp_xxx_info` ( `ID` int(64) NOT NULL AUTO_INCREMENT, `CUSTOMER_NAME` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `CUSTOMER_NUM` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `PRODIST_SKU_NUM` varchar(64) COLLATE utf8mb4_bin DEFAULT NULL, `STATUS` varchar(64) COLLATE utf8mb4_bin DEFAULT NULL, `AGREEMENT_NUM` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `END_DATE` datetime DEFAULT NULL, PRIMARY KEY (`ID`), KEY `PK_PRODIST_SKU_NUM_AGREEMENT` (`PRODIST_SKU_NUM`) USING BTREE, KEY `IDX_AGREEMENT_NUM` (`AGREEMENT_NUM`) USING BTREE) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin ROW_FORMAT=DYNAMIC/*!*/;# at 475864451
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**结论：**在主集群的 binlog 日志中找到了目标表的建表语句，说明主集群执行 DDL 时并没有关闭 binlog 日志，那么继续查看在灾备集群的中继日志中是否存在 DDL 语句
3.4、解析灾备集群的中继日志，确认是否拉取到灾备集群
#230822 14:08:15 server id 1943306 end_log_pos 475863662 GTID last_committed=16341 sequence_number=16342 rbr_only=noSET @@SESSION.GTID_NEXT= '9e668a93-2618-11ee-93ee-bc16954181bb:47498079'/*!*/;……use `information_schema`/*!*/;SET TIMESTAMP=1692684495/*!*/;CREATE TABLE `abs_xxx`.`tmp_xxx_info` ( `ID` int(64) NOT NULL AUTO_INCREMENT, `CUSTOMER_NAME` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `CUSTOMER_NUM` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `PRODIST_SKU_NUM` varchar(64) COLLATE utf8mb4_bin DEFAULT NULL, `STATUS` varchar(64) COLLATE utf8mb4_bin DEFAULT NULL, `AGREEMENT_NUM` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `END_DATE` datetime DEFAULT NULL, PRIMARY KEY (`ID`), KEY `PK_PRODIST_SKU_NUM_AGREEMENT` (`PRODIST_SKU_NUM`) USING BTREE, KEY `IDX_AGREEMENT_NUM` (`AGREEMENT_NUM`) USING BTREE) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin ROW_FORMAT=DYNAMIC/*!*/;# at 475864660#230822 14:08:15 server id 1943306 end_log_pos 475864512 GTID last_committed=16342 sequence_number=16343 rbr_only=yes/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;
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**结论：**灾备集群的中继日志中存在 DDL 建表语句，说明并不是 IO 线程出了问题
3.5、排查复制配置的忽略库表
Replicate_Ignore_DB: mysql,dbscale,dbscale_tmp,information_schema,performance_schema,sysReplicate_Wild_Ignore_Table: A.ab,B.bc
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**结论：**忽略库表中并不包含目标表，但是根据以上解析日志发现，在主集群 binlog 日志中建表语句之前有个use information_schema/!/; 的语句，此库为同步忽略的系统库，因此触发了 GreatSQL 的规范限制，在忽略库下对未忽略进行操作 Statement 模式下记录语句默认不起作用 （详情：https://dev.mysql.com/doc/refman/5.7/en/replication-options-replica.html#option_mysqld_replicate-do-db）
4、解决同步报错
在灾备集群创建目标表
greatsql> CREATE TABLE `abs_xxx`.`tmp_xxx_info` ( `ID` int(64) NOT NULL AUTO_INCREMENT, `CUSTOMER_NAME` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `CUSTOMER_NUM` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `PRODIST_SKU_NUM` varchar(64) COLLATE utf8mb4_bin DEFAULT NULL, `STATUS` varchar(64) COLLATE utf8mb4_bin DEFAULT NULL, `AGREEMENT_NUM` varchar(256) COLLATE utf8mb4_bin DEFAULT NULL, `END_DATE` datetime DEFAULT NULL, PRIMARY KEY (`ID`), KEY `PK_PRODIST_SKU_NUM_AGREEMENT` (`PRODIST_SKU_NUM`) USING BTREE, KEY `IDX_AGREEMENT_NUM` (`AGREEMENT_NUM`) USING BTREE) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin ROW_FORMAT=DYNAMIC;
greatsql> stop slave;greatsql> start slave;
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**结论：**在灾备集群创建目标表后重启复制恢复成功
三、限制规避
1、第一种规避方式
执行 DDL 时进入目标库
greatsql> use abs_custgreatsql> DDL 语句（CREATE\DROP\ALTER）
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**说明：**在应用连接数据库时有可能默认就是information_schema库，而此环境将系统库全部忽略，所以为了规避类似的问题，请在执行 SQL 语句时请先 use 到目标表的目标库。
2、第二种规避方式
修改主从复制配置，以下步骤为测试环境
关闭灾备集群在复制同步
greatsql> stop slave;Query OK, 0 rows affected, 1 warning (0.03 sec)
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修改忽略库
greatsql> change replication filter Replicate_Ignore_DB=();
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修改忽略表
greatsql> change replication filter replicate_wild_ignore_table =('mysql.%','information_schema.%','sys.%','performance_schema.%');
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启动同步
greatsql> start slave;Query OK, 0 rows affected, 1 warning (0.37 sec)
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测试验证
主集群：
greatsql> use mysqlReading table information for completion of table and column namesYou can turn off this feature to get a quicker startup with -ADatabase changed
greatsql> create table test111.test111(id int primary key);Query OK, 0 rows affected (0.06 sec)
greatsql> show tables;+-------------------+| Tables_in_test111 |+-------------------+| test111 |+-------------------+1 row in set (0.00 sec)
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灾备集群：
greatsql> use test111Reading table information for completion of table and column namesYou can turn off this feature to get a quicker startup with -ADatabase changed
greatsql> show tables;+-------------------+| Tables_in_test111 |+-------------------+| test111 |+-------------------+1 row in set (0.00 sec)
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**说明：**复制配置中参数Replicate_Ignore_DB设置为空，将replicate_wild_ignore_table参数设置为shema_name.%的方式也可以规避类似的问题
四、特别说明
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