tencent cloud

Feedback

Binlog Parameter Check

Last updated: 2023-08-25 16:23:03

    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 only be set to ON or OFF. We recommend that 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 database, the log_slave_updates variable must be set to ON.
    We recommend that 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:
    The modification of the log_bin parameter only takes effect after the database is restarted. Therefore, if errors are also reported for the binlog_format, server_id, binlog_row_imageandexpire_logs_days` parameters in the verification stage, we recommend that you modify all these parameters before restarting the database so that all the modifications can take effect.
    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
    server_id = 2 //We recommend that you set it to an integer above 1. The value here is only an example
    binlog_row_image = FULL
    expire_logs_days = 3 //Modify the binlog retention period (at least 3 days preferably).
    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 will 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 source/primary database. When replicating data, the replica/secondary database will run the same SQL statements as those in the source/primary database. This format can reduce the binlog size. However, the replica/secondary database may not be able to properly replicate certain functions.
    ROW: The binlog will log the modification of each data row, and the replica/secondary database will modify the same data. This format guarantees the correct source-replica or primary-secondary 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 or primary-secondary 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 only take effect after all connections to the database are reset. If the source database is a replica/secondary database, you also need to restart the source-replica or primary-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 for the configuration to take effect. Then, run the following command to check whether the parameter modification takes effect:
    show variables like '%binlog_format%';
    The system will 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)
    4. 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 or primary-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 the pre-image and post-image column data information.
    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, troubleshoot as follows:
    Note
    Changes to this parameter can only take effect after all connections to the database are reset. If the source database is a replica/secondary database, you also need to restart the source-replica or primary-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 for the configuration to take effect. Then, run the following command to check whether the parameter modification takes effect:
    show variables like '%binlog_row_image%';
    The system will 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 or primary-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 versions. DTS only allows you to set gtid_mode to ON or OFF. We recommend that 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, if HA switch occurs in the source database during incremental data sync, 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 resumed.
    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 source/primary database and all transactions in the replica/secondary database must be anonymous.
    OFF_PERMISSIVE: All new transactions in the source/primary database must be anonymous. Transactions in the replica/secondary database can be anonymous or GTID transactions but cannot only be GTID transactions.
    ON_PERMISSIVE: All new transactions in the source/primary database must be GTID transactions, and transactions in the replica/secondary database can be anonymous or GTID transactions.
    ON: All new transactions in the source/primary database and all transactions in the replica/secondary 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 the source/primary 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 without restarting the database, but you must reset all business connections.
    set global gtid_mode = OFF_PERMISSIVE;
    3. Set gtid_mode = ON_PERMISSIVE on the source/primary 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 will 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 the source/primary 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 0. The default value of this parameter is 1, but the configuration may not be correct even if the queried parameter value is 1. You still need to set it manually.
    1. Log in to the source database.
    2. Run the following command to modify server_id:
    set global server_id = 2; // We recommend that 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 will 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 or primary-replica replication will be abnormal; therefore, this setting is not recommended. 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 will 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 or primary-replica reuse structure, if the log-bin parameter is enabled in the replica/secondary database, data operations directly performed in this database can be logged in the binlog, but data replications from the source/primary database to the replica/secondary database cannot be logged. Therefore, if the replica/secondary database is to be used as the source/primary database of another 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 will 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.
    Contact Us

    Contact our sales team or business advisors to help your business.

    Technical Support

    Open a ticket if you're looking for further assistance. Our Ticket is 7x24 avaliable.

    7x24 Phone Support