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MySQL/TDSQL for MySQL/TDSQL-C Check Details

You need to configure the source database's binlog parameters in compliance with the following requirements. If the verification fails, fix it as instructed in this document.

• The log_bin variable must be set to ON.
• The binlog_format variable must be set to ROW.
• binlog_row_image must be set to FULL.
• If the source database is MySQL 5.6 or later, gtid_mode can be set to only ON or OFF. We recommend you set it to ON, because if it is set to OFF, an alarm will be triggered, and if it is set to ON_PERMISSIVE or OFF_PERMISSIVE, an error will be reported.
• The server_id parameter must be set manually and cannot be 0.
• It is not allowed to set do_db and ignore_db.
• If the source database is a replica instance, the log_slave_updates variable must be set to ON.
• We recommend you retain the binlog of the source database for at least three days; otherwise, the task cannot be resumed from the checkpoint and will fail.

Troubleshooting

Enabling binlog

log_bin controls the binlog switch. You need to enable binlog to log all database table structure and data changes.

If a similar error occurs, fix it as follows:

1. Log in to the source database.

2. Modify the my.cnf configuration file of the source database as follows. As the database needs to be restarted after the log_bin parameter is modified, we recommend you also modify the binlog_format and binlog_row_image parameters based on the verification requirements.

   Note：

   The default path of the my.cnf configuration file is /etc/my.cnf, subject to the actual conditions.

   log_bin = MYSQL_BIN
   binlog_format = ROW
   binlog_row_image = FULL
   

3. Run the following command to restart the source database:

   [$Mysql_Dir]/bin/mysqladmin -u root -p shutdown
   [$Mysql_Dir]/bin/safe_mysqld &
   

Note：

[\$Mysql_Dir] is the installation path of the source database. Replace it with the actual path.
4. Check whether the binlog feature has been enabled.

show variables like '%log_bin%';

The system should display a result similar to the following:

mysql> show variables like '%log_bin%';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| log_bin          | ON    |
+------------------+-------+
| binlog_format    | ROW   |
+------------------+-------+
| binlog_row_image | FULL  |
+------------------+-------+
1 row in set (0.00 sec)

5. Run the verification task again.

Modifying binlog_format parameter

binlog_format specifies one of the following three binlog formats:

• STATEMENT: Each SQL statement that modifies the data will be logged into the binlog of the master. When replicating data, the replica will run the same SQL statements as those in the master. This format can reduce the binlog size. However, the replica may not be able to properly replicate certain functions.
• ROW: The binlog will log the modifications of each data row, and the replica will modify the same data. This format guarantees the correct source-replica replication, but the binlog size will increase.
• MIXED: It is a combination of the above two formats. MySQL will automatically select STATEMENT or ROW format to log each executed SQL statement.

Therefore, to ensure the correct source-replica replication, the binlog_format parameter should be set to ROW. If a similar error occurs, fix it as follows:

Note：

Changes to this parameter can take effect only after all connections to the database are reset. If the source database is a replica, you also need to restart the source/replica sync SQL thread to prevent current business connections from continuing writing data in the mode before modification.

1. Log in to the source database.

2. Run the following command to modify binlog_format.

   set global binlog_format = ROW;
   

3. Restart the thread to make the configuration take effect. Then, run the following command to check whether the parameter modification takes effect:

   show variables like '%binlog_format%';
   

The system should display a result similar to the following:

mysql> show variables like '%binlog_format%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| binlog_format | ROW   |
+---------------+-------+
1 row in set (0.00 sec)

5. Run the verification task again.

Modifying binlog_row_image parameter

The binlog_row_image parameter determines how the binlog logs the pre-image (content before modification) and post-image (content after modification), which directly affects features such as data flashback and source-replica replication.
The binlog_row_image parameter takes effect only if binlog_format is set to ROW. The following describes the effects of specific values:

• FULL: In ROW format, binlog will log all column data information of the pre-image and post-image.
• MINIMAL: In ROW format, if a table has no primary key or unique key, the pre-image will log all columns, and the post-image will log the modified columns. If it has a primary key or unique key, both the pre-image and post-image will only log the affected columns.

Therefore, you need to set binlog_row_image to FULL to make the source database binlog log the full image. If an error occurs, fix it as follows:

Note：

Changes to this parameter can take effect only after all connections to the database are reset. If the source database is a replica, you also need to restart the source/replica sync SQL thread to prevent current business connections from continuing writing data in the mode before modification.

1. Log in to the source database.

2. Run the following command to modify binlog_row_image:

   set global binlog_row_image = FULL;
   

3. Restart the thread to make the configuration take effect. Then, run the following command to check whether the parameter modification takes effect:

   show variables like '%binlog_row_image%';
   

The system should display a result similar to the following:

mysql> show variables like '%binlog_row_image%';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| binlog_row_image | FULL  |
+------------------+-------+
1 row in set (0.00 sec)

4. Run the verification task again.

Modifying gtid_mode parameter

A global transaction identifier (GTID) uniquely identifies a transaction in the binlog. Using GTIDs can prevent disordered data or source-replica inconsistency due to repeated transaction executions.
GTID is a new feature on MySQL 5.6. Therefore, this problem may only occur on MySQL 5.6 or later. DTS only allows you to set gtid_mode to ON or OFF. We recommend you set it to ON; otherwise, an alarm will be triggered during verification.

The alarm does not affect the migration or sync task but affects the business: after GTID is set, during incremental data sync, if HA switch occurs in the source instance, DTS will be switched and restarted, which is almost imperceptible to the task; if GTID is not set, the task will fail after disconnection and cannot be recovered.

Below are the valid values of gtid_mode. When modifying the value, you can only do so in the specified sequence step by step; for example, if you want to change OFF to ON, you should modify the gtid_mode value in the following sequence: OFF > OFF_PERMISSIVE > ON_PERMISSIVE > ON.

• OFF: All new transactions in the master database and all transactions in the replica database must be anonymous.
• OFF_PERMISSIVE: All new transactions in the master database must be anonymous. Transactions in the replica database can be anonymous or GTID transactions but cannot be only GTID transactions.
• ON_PERMISSIVE: All new transactions in the master database must be GTID transactions, and transactions in the replica database can be anonymous or GTID transactions.
• ON: All new transactions in the master database and all transactions in the replica database must be GTID transactions.

If a similar alarm is triggered, fix it as follows:

1. Log in to the source database.

2. Set gtid_mode = OFF_PERMISSIVE on both the source and replica databases.
   On MySQL versions earlier than v5.7.6, you need to modify the parameter in the my.cnf configuration file and restart the database to make the change take effect. On v5.7.6 and later, you can modify the parameter through global naming with no need to restart the database, but you must reset all business connections.

   set global gtid_mode = OFF_PERMISSIVE;
   

3. Set gtid_mode = ON_PERMISSIVE on both the source and replica databases.

   set global gtid_mode = ON_PERMISSIVE;
   

4. Run the following command on each instance node to check whether consumption of anonymous transactions is completed. If the parameter value is 0, the consumption is completed.

   show variables like '%ONGOING_ANONYMOUS_TRANSACTION_COUNT%';
   

The system should display a result similar to the following:

mysql> show variables like '%ONGOING_ANONYMOUS_TRANSACTION_COUNT%';
+-------------------------------------+-------+
| Variable_name                       | Value |
+-------------------------------------+-------+
| Ongoing_anonymous_transaction_count | 0     |
+-------------------------------------+-------+
1 row in set (0.00 sec)

5. Set gtid_mode = ON on both the source and replica databases.

   set global gtid_mode = ON;
   

6. Add the following content to the my.cnf file and restart the database to make the initial values take effect.

   Note：

   The default path of the my.cnf configuration file is /etc/my.cnf, subject to the actual conditions.

   gtid_mode = on
   enforce_gtid_consistency = on
   

7. Run the verification task again.

Modifying server_id parameter

The server_id parameter must be set manually and cannot be set to 0. The system default value of this parameter is 1, but the configuration isn't necessarily correct even if the queried parameter value is 1. You still need to manually set it.

1. Log in to the source database.

2. Run the following command to modify server_id:

   set global server_id = 2;  // We recommend you set it to an integer above 1. The value here is only an example.
   

3. Run the following command to check whether the parameter modification takes effect:

   show global variables like '%server_id%';
   

The system should display a result similar to the following:

mysql> show global variables like '%server_id%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id     | 2     |
+---------------+-------+
1 row in set (0.00 sec)

4. Run the verification task again.

Deleting do_db and ignore_db settings

The binlog logs all executed DDL and DML statements in the database, while do_db and ignore_db are used to set the filter conditions for binlog.

• binlog_do_db: Only the specified databases will be logged in the binlog (all databases will be logged by default).
• binlog_ignore_db: The specified databases will not be logged in the binlog.

After do_db and ignore_db are set, some cross-database operations will not be logged in the binlog, and source-replica replication will be abnormal; therefore, we recommend you not set them. If a similar error occurs, fix it as follows:

1. Log in to the source database.
2. Modify the my.cnf configuration file in the source database to delete do_db and ignore_db settings.

   Note：

   The default path of the my.cnf configuration file is /etc/my.cnf, subject to the actual conditions.

3. Run the following command to restart the source database:

   [$Mysql_Dir]/bin/mysqladmin -u root -p shutdown
   [$Mysql_Dir]/bin/safe_mysqld &
   

Note：

[\$Mysql_Dir] is the installation path of the source database. Replace it with the actual path.
4. Check whether the parameter modification takes effect.

show master status;

The system should display a result similar to the following:

mysql> show master status;
+---------------+----------+--------------+------------------+-------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+---------------+----------+--------------+------------------+-------------------+
| binlog.000011 | 154      |              |                  |                   |
+---------------+----------+--------------+------------------+-------------------+

5. Run the verification task again.

Modifying log_slave_updates parameter

In the source-replica reuse structure, if the log-bin parameter is enabled in the replica database, data operations directly performed in the replica database can be logged in the binlog, but data replications from the source database to the replica database cannot be logged. Therefore, if the replica database is to be used as the source database of another replica database, the log_slave_updates parameter needs to be enabled.

1. Log in to the source database.

2. Add the following content to the my.cnf configuration file of the source database.

   Note：

   The default path of the my.cnf configuration file is /etc/my.cnf, subject to the actual conditions.

   log_slave_updates = ON
   

3. Run the following command to restart the source database:

   [$Mysql_Dir]/bin/mysqladmin -u root -p shutdown
   [$Mysql_Dir]/bin/safe_mysqld &
   

Note：

[\$Mysql_Dir] is the installation path of the source database. Replace it with the actual path.
4. Check whether the configuration takes effect.

show variables like '%log_slave_updates%';

The system should display a result similar to the following:

mysql> show variables like '%log_slave_updates%';
+-------------------+-------+
| Variable_name     | Value |
+-------------------+-------+
| log_slave_updates | ON    |
+-------------------+-------+
1 row in set (0.00 sec)

5. Run the verification task again.