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Sync from MySQL/MariaDB/Percona/TDSQL-C MySQL to TencentDB for MariaDB

Last updated: 2024-07-08 17:33:46
    This document describes how to use the data sync feature of DTS to sync data from MySQL/MariaDB/Percona to TencentDB for MariaDB.
    The following deployment modes of the source database are supported:
    Self-built MySQL and TencentDB for MySQL.
    Self-built MariaDB and TencentDB for MariaDB.
    Self-built Percona.
    TencentDB for TDSQL-C MySQL.
    This document describes how to sync data from MariaDB to TencentDB for MariaDB. The requirements and steps of data sync from MySQL, Percona and TDSQL-C MySQL to TencentDB for MariaDB are basically the same.

    Notes

    When DTS performs full data sync, it will occupy some resources in the source instance, which may increase the load of the source instance and the database pressure. If your database has low configurations, we recommend that you sync the data during off-peak hours.
    To avoid duplicate data, make sure that the tables to be synced have a primary key or non-null unique key.
    Sync is implemented without locks by default, during which no global lock (the FTWRL lock) is added to the source database, and only tables without a primary key are locked.
    During data sync, DTS will use the account that executes the sync task to write the system database __tencentdb__ in the source database to record the data comparison information during the sync task.
    To ensure that subsequent data problems can be located, the __tencentdb__ system database in the source database will not be deleted after the sync task ends.
    The __tencentdb__ system database uses a single-threaded connection wait mechanism and occupies a very small space, about 0.01%–0.1% of the storage space of the source database; for example, if the source database is 50 GB, __tencentdb__ will be about 5–50 MB. Therefore, it has almost no impact on the performance of the source database and will not preempt resources.

    Prerequisites

    The source and target databases must meet the requirements for the sync feature and version as instructed in Databases Supported by Data Sync.
    Permissions required of the source database:
    GRANT RELOAD,LOCK TABLES,REPLICATION CLIENT,REPLICATION SLAVE,SHOW VIEW,PROCESS,SELECT ON *.* TO 'account'@'%' IDENTIFIED BY 'password';
    GRANT ALL PRIVILEGES ON `__tencentdb__`.* TO 'account'@'%';
    FLUSH PRIVILEGES;
    Permissions required of the target database: ALTER, ALTER ROUTINE, CREATE, CREATE ROUTINE, CREATE TEMPORARY TABLES, CREATE USER, CREATE VIEW, DELETE, DROP, EVENT, EXECUTE, INDEX, INSERT, LOCK TABLES, PROCESS, REFERENCES, RELOAD, SELECT, SHOW DATABASES, SHOW VIEW, TRIGGER, and UPDATE.

    Application restrictions

    Only basic tables, views, procedures, and functions can be synced.
    When views, procedures, and functions are synced, DTS will check whether user1 corresponding to DEFINER ([DEFINER = user1]) in the source database is the same as the sync account user2, and if not, DTS will change the SQL SECURITY attribute of user1 in the target database from DEFINER to INVOKER ([INVOKER = user1]) after the sync, and set the DEFINER in the target database to the sync account user2 ([DEFINER = sync account user2]). If the view definition in the source database is too complex, the task may fail.
    If the source MySQL database is a non-GTID instance, DTS doesn't support HA switch for it. If it is switched, DTS incremental sync may be interrupted.
    Only data with the following three database engines can be synced: InnoDB, MyISAM, and TokuDB. Tables with other engines will be skipped during sync by default. If there is compressed TokuDB engine data in the source database, the target database must support the compression mode before sync can be performed; otherwise, the task will report an error.
    Correlated data objects must be synced together; otherwise, sync will fail. Common correlations include table referenced by views, view referenced by views, and tables correlated through primary/foreign keys.
    During incremental sync, if the source database has distributed transactions or generates binlog statements in the STATEMENT format, sync will fail.
    If the source database is Alibaba Cloud ApsaraDB RDS for MySQL, then the tables to be synced on v5.6 must have a primary key, while tables on v5.7 and later are unrestricted. If the source database is Amazon RDS for MySQL, then the tables to be synced must have a primary key.
    If the binlog of the source database has a GTID hole, it may compromise the performance of the sync task and cause the task to fail.
    Scenarios that contain both DML and DDL statements in the same transaction are not supported and will trigger errors during task execution.
    Geometry data types are not supported and will trigger errors during task execution.
    The ALTER VIEW statement is not supported and will be skipped during sync.

    Operation restrictions

    During the sync, do not perform the following operations; otherwise, the sync task will fail:
    Do not modify or delete user information (including username, password, and permissions) in the source and target databases and port numbers.
    Do not run distributed transactions in the source database.
    Do not write binlog data in the STATEMENT format into the source database.
    Do not clear binlogs in the source database.
    Do not delete the system table __tencentdb__ during incremental sync.

    Synchronizable SQL Operations

    Operation Type
    SQL Statement
    DML
    INSERT, UPDATE, DELETE
    DDL
    CREATE DATABASE, DROP DATABASE, ALTER DATABASE, CREATE TABLE, ALTER TABLE, DROP TABLE, TRUNCATE TABLE, RENAME TABLE, CREATE VIEW, DROP VIEW, CREATE INDEX, DROP INDEX
    Notes:
    DDL operations involving partitions cannot be synced.
    CREATE TABLE table name AS SELECT is not supported.

    Environment requirements

    Type
    Environment Requirement
    Requirements for the source database
    The source and target databases can be connected.
    Requirements for instance parameters:
    The server_id parameter in the source database must be set manually and cannot be 0.
    row_format for the source databases/tables cannot be set to FIXED.
    The values of the lower_case_table_names variable in both the source and target databases must be the same.
    The connect_timeout variable in the source database must be greater than or equal to 10.
    Requirements for binlog parameters:
    The log_bin variable in the source database must be set to ON.
    The binlog_format variable in the source database must be set to ROW.
    The binlog_row_image variable in the source database must be set to FULL.
    On MySQL 5.6 or later, if the gtid_mode variable is not ON, an alarm will be triggered. We recommend you enable gtid_mode.
    It is not allowed to set do_db and ignore_db.
    If the source instance is a replica database, 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 if it is suspended or interrupted for longer than the time set for binlog retention.
    Foreign key dependency:
    Foreign key dependency can be set to only one of the following two types: NO ACTION and RESTRICT.
    During partial table sync, tables with foreign key dependency must be migrated.
    The environment variable innodb_stats_on_metadata must be set to OFF.
    Requirements for the target database
    The target database version must be later than or equal to the source database version.
    The target database must have sufficient storage space. If you select Full data initialization as the initialization type, the target database space must be at least 1.2 times the space of databases/tables to be synced in the source database.
    The target database cannot have sync objects such as tables and views with the same name as those in the source database.
    The max_allowed_packet parameter of the target database must be set to 4 MB or above.

    Directions

    You can refer to the directions described in Sync from MySQL/MariaDB/Percona to TencentDB for MySQL.
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