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Migrate RDS for MySQL to ApsaraMQ for Kafka

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This topic describes how to use Data Transmission Service (DTS) to migrate data from an RDS for MySQL instance to a Message Queue for Apache Kafka instance.

Prerequisites

  • You have created a source ApsaraDB RDS for MySQL instance and a destination ApsaraMQ for Kafka instance.

    Note

  • The destination ApsaraMQ for Kafka instance must have more storage space than the source ApsaraDB RDS for MySQL instance uses.

  • You have created a topic in the destination ApsaraMQ for Kafka instance to receive the migrated data. For instructions, see Step 1: Create a topic.

Limitations

Note

DTS does not migrate foreign keys from the source database to the destination database. Therefore, operations such as cascade delete in the source database are not migrated to the destination database.

Type

Description

Source database limits

  • Bandwidth requirement: The server hosting the source database must have sufficient outbound bandwidth. Otherwise, migration speed will drop.

  • Each table to migrate must have a primary key or UNIQUE constraint, and the key columns must contain unique values. Otherwise, duplicate records may appear in the destination database.

  • If you select tables as the migration objects and edit them—for example, by mapping column names—a single migration task supports up to 1,000 tables. If you exceed this limit, the task fails with an error when submitted. To fix this, split the tables across multiple tasks or configure a full-database migration task.

  • If you need incremental migration, enable binary logging:

    • Set binlog_format to ROW and binlog_row_image to FULL. Otherwise, the precheck fails and the task cannot start.

      Important

      If your self-managed MySQL source is a dual-master cluster—where each instance acts as both master and slave—enable the log_slave_updates parameter. This ensures DTS can read all binary logs.

    • For RDS for MySQL instances, retain local binary logs for at least three days (seven days recommended). For self-managed MySQL databases, retain local binary logs for at least seven days. If DTS cannot access binary logs, the task fails. In extreme cases, data inconsistency or data loss may occur. Issues caused by binary log retention periods shorter than DTS requires are not covered under the DTS SLA.

      Note

      To set the retention period for local binary logs on an RDS for MySQL instance, see Automatically delete local logs.

  • Operations not allowed on the source database:

    • Do not run DDL operations that change database or table schemas during schema migration or full migration. Otherwise, the migration task fails.

      Note

      During full migration, DTS queries the source database. This creates metadata locks that may block DDL operations on the source database.

    • If you run only full migration, do not write new data to the source instance. Otherwise, source and destination data become inconsistent. To keep data consistent in real time, select schema migration, full migration, and incremental migration.

  • DTS does not migrate data generated by changes that do not write to binary logs. Examples include data restored from physical backups or created by cascade operations.

    Note

    If this occurs, re-run full migration after your business allows it.

  • If your source MySQL database is version 8.0.23 or later and contains invisible hidden columns, DTS cannot read those columns. This may cause data loss.

    Note

    Run ALTER TABLE <table_name> ALTER COLUMN <column_name> SET VISIBLE; to make the hidden column visible. For more information, see Invisible Columns.

Other limits

  • Only data tables are supported as migration objects.

  • DTS does not support migrating INDEX, PARTITION, VIEW, PROCEDURE, FUNCTION, TRIGGER, or FK objects.

  • Before migration, assess the performance of both source and destination databases. Run migration during off-peak business hours. Otherwise, full migration consumes read and write resources on both databases and increases database load.

  • Full migration runs INSERT operations concurrently. This fragments destination tables. After full migration, destination tables require more storage space than source tables.

  • Confirm that DTS migration precision for FLOAT or DOUBLE columns meets your business needs. DTS reads these columns using ROUND(COLUMN,PRECISION). If no precision is defined, DTS uses 38 digits for FLOAT and 308 digits for DOUBLE.

  • DTS tries to recover failed tasks within seven days. Before switching traffic to the destination instance, end or release the task. Or run the revoke command to remove DTS’s write permission on the destination instance account. This prevents automatic recovery from overwriting destination data with source data.

  • Do not write data to the destination database except through DTS, because this can cause data inconsistency between the source and destination databases.

  • If your destination Kafka cluster scales out or scales in during migration, restart the DTS task.

  • If your RDS for MySQL instance has Always-Encrypted enabled, full migration is not supported.

    Note

    RDS for MySQL instances with Transparent Data Encryption (TDE) enabled support schema migration, full migration, and incremental migration.

  • If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters.

    Note

    Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.

Special cases

  • For self-managed MySQL sources:

    • A master–standby switchover on the source database causes the migration task to fail.

    • DTS calculates latency by comparing the timestamp of the last record migrated to the destination database with the current time. If no DML operations run on the source for a long time, latency reporting becomes inaccurate. If latency appears too high, run a DML operation on the source to update the latency value.

      Note

      If you select full-database migration, create a heartbeat table. Update or write to it every second.

    • DTS periodically runs CREATE DATABASE IF NOT EXISTS `test` on the source database to advance the binary log offset.

    • If your source is Amazon Aurora MySQL or another clustered MySQL instance, ensure the domain name or IP address configured for the task—and its DNS resolution—always points to a read–write (RW) node. Otherwise, the migration task may fail.

  • For RDS for MySQL sources:

    • If you need incremental migration, RDS for MySQL instances that do not record transaction logs—such as RDS for MySQL 5.6 read-only instances—are not supported as sources.

    • DTS periodically runs CREATE DATABASE IF NOT EXISTS `test` on the source database to advance the binary log offset.

Billing

Migration type

Channel specification fee

Public traffic fee

Schema migration and full data migration

Free of charge.

You are charged for public traffic if the Access Method for the destination database is set to Public IP Address. For more information, see Billing overview.

Incremental data migration

This is a paid feature. For more information, see Billing overview.

Migration types

  • Schema migration

    DTS migrates the schema definitions of the migration objects from the source database to the destination database.

  • Full migration

    DTS migrates all historical data of the specified migration objects from the source database to the destination database.

  • Incremental migration

    After a full migration is complete, DTS migrates incremental data updates from the source database to the destination database. Incremental migration lets you smoothly migrate data without interrupting your self-managed applications.

SQL operations for incremental migration

Operation type

SQL statement

DML

INSERT, UPDATE, and DELETE

DDL

  • CREATE TABLE, ALTER TABLE, DROP TABLE, RENAME TABLE, and TRUNCATE TABLE

  • CREATE VIEW, ALTER VIEW, and DROP VIEW

  • CREATE PROCEDURE, ALTER PROCEDURE, and DROP PROCEDURE

  • CREATE FUNCTION, DROP FUNCTION, CREATE TRIGGER, and DROP TRIGGER

  • CREATE INDEX and DROP INDEX

Database account permissions

Instance

Schema migration

Full data migration

Incremental data migration

ApsaraDB RDS for MySQL source instance

Read permission on the objects to be migrated.

Procedure

  1. Navigate to the migration task list page for the destination region using one of the following methods.

    From the DTS console

    1. Log on to the Data Transmission Service (DTS) console.

    2. In the navigation pane on the left, click Data Migration.

    3. In the upper-left corner of the page, select the region where the migration instance is located.

    From the DMS console

    Note

    The actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.

    1. Log on to the Data Management (DMS) console.

    2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.

    3. To the right of Data Migration Tasks, select the region where the migration instance is located.

  2. Click Create Task to navigate to the task configuration page.

  3. Configure the source and destination databases.

    Warning

    After you select the source and destination instances, we recommend that you carefully read the limits displayed at the top of the page. Otherwise, the task may fail or data inconsistency may occur.

    Category

    Parameter

    Description

    N/A

    Task Name

    DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.

    Source Database

    Select Existing Connection

    • To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured.

      Note

      In the DMS console, this parameter is named Select a DMS database instance..

    • If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.

    Database Type

    Select MySQL.

    Connection Type

    Select Alibaba Cloud Instance.

    Instance Region

    Select the region of the source RDS for MySQL instance.

    Cross-account

    For migrations within the same Alibaba Cloud account, select No.

    RDS Instance ID

    Select the ID of the source RDS for MySQL instance.

    Database Account

    Enter the database account of the source RDS for MySQL instance. This account must have read permissions on the objects that you are migrating.

    Database Password

    Enter the password for the specified database account.

    Connection method

    Select Non-encrypted or SSL-encrypted as needed. If you set this to SSL-encrypted, you must enable SSL encryption for the RDS for MySQL instance beforehand. For more information, see Use a cloud certificate to quickly enable SSL link encryption.

    Destination Database

    Select Existing Connection

    • To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured.

      Note

      In the DMS console, this parameter is named Select a DMS database instance..

    • If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.

    Database Type

    Select Kafka.

    Connection Type

    Select Alibaba Cloud Instance.

    Instance Region

    Select the region of the target ApsaraMQ for Kafka instance.

    Kafka Instance ID

    Select the ID of the target ApsaraMQ for Kafka instance.

    Connection method

    Select Non-encrypted or SCRAM-SHA-256 based on your business and security requirements.

    Topic

    Select the Topic that will receive the data.

    Use Kafka Schema Registry

    Kafka Schema Registry is a metadata service layer that provides a RESTful interface for storing and retrieving Avro schemas.

    • No: Do not use Kafka Schema Registry.

    • Yes: Use Kafka Schema Registry. You must enter the URL or IP address registered for the Avro schema in Kafka Schema Registry.

  4. After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.

    Note

    • Ensure that the IP address segment of the DTS service is automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add DTS server IP addresses to a whitelist.

    • If the source or destination database is a self-managed database (the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box that appears.

  5. Configure the task objects.

    1. On the Configure Objects page, configure the objects that you want to migrate.

      Parameter

      Description

      Migration Types

      • If you only need a full migration, select both Schema Migration and Full Data Migration.

      • For a seamless, no-downtime migration, select Schema Migration, Full Data Migration, and Incremental Data Migration.

      Note

      • Schema Migration is not supported when the destination Kafka instance's Access Method is Alibaba Cloud Instance.

      • To ensure data consistency, do not write new data to the source instance during migration if you do not select Incremental Data Migration.

      Processing Mode for Existing Destination Tables

      • Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start.

        Note

        If a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping.

      • Ignore Errors and Proceed: Skips the check for tables with the same names.

        Warning

        Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example:

        • If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database:

          • During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated.

          • During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database.

        • If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.

      Data Format in Kafka

      Select the storage format for data migrated to the Kafka instance.

      Kafka Data Compression Format

      Select a compression format for Kafka messages based on your requirements.

      • LZ4 (default): low compression ratio, high compression speed.

      • GZIP: high compression ratio, low compression speed.

        Note

        High CPU consumption.

      • Snappy: medium compression ratio, medium compression speed.

      Policy for Shipping Data to Kafka Partitions

      Select a strategy based on your business requirements.

      Message acknowledgement mechanism

      Select a message acknowledgment mechanism based on your business requirements.

      Topic That Stores DDL Information

      Select the topic for storing DDL information.

      Note

      If no topic is selected, DTS stores DDL information in the data topic by default.

      Capitalization of Object Names in Destination Instance

      You can configure the case sensitivity policy for the names of migrated objects, such as databases, tables, and columns, in the destination instance. By default, DTS default policy is selected. You can also choose to keep the case sensitivity consistent with the default policy of the source or destination database. For more information, see Case sensitivity of object names in the destination database.

      Source Objects

      In the Source Objects box, click the objects to migrate, and then click Right arrow to move them to the Selected Objects box.

      Note

      You can select objects to migrate at the table level.

      Selected Objects

      For this example, no extra configuration is needed. You can use the mapping feature to specify the topic name, partition count, and partition key for each source table in the destination Kafka instance. For more information, see Mapping Information.

      Note

      • Using the object name mapping feature can cause migration failures for dependent objects.

      • To select SQL operations for incremental migration, right-click a migration object in the Selected Objects box and select the desired SQL operations in the dialog box that appears.

    2. Click Next: Advanced Settings to configure advanced parameters.

      Parameter

      Description

      Dedicated Cluster for Task Scheduling

      By default, DTS schedules tasks on a shared cluster. You do not need to select one. If you want more stable tasks, you can purchase a dedicated cluster to run DTS migration tasks.

      Retry Time for Failed Connections

      After the migration task starts, if the connection to the source or destination database fails, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1440 minutes. We recommend that you set the duration to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified duration, the migration task automatically resumes. Otherwise, the task fails.

      Note

      • For multiple DTS instances that share the same source or destination, the network retry time is determined by the setting of the last created task.

      • Because you are charged for the task during the connection retry period, we recommend that you customize the retry time based on your business needs, or release the DTS instance as soon as possible after the source and destination database instances are released.

      Retry Time for Other Issues

      After the migration task starts, if a non-connectivity issue, such as a DDL or DML execution exception, occurs in the source or destination database, DTS reports an error and immediately begins to retry the operation. The default retry duration is 10 minutes. You can customize the retry time to a value from 1 to 1440 minutes. We recommend that you set the duration to more than 10 minutes. If the related operations succeed within the specified retry duration, the migration task automatically resumes. Otherwise, the task fails.

      Important

      The value of Retry Time for Other Issues must be less than the value of Retry Time for Failed Connections.

      Enable Throttling for Full Data Migration

      During full migration, DTS consumes read and write resources on the source and destination databases, which may increase the database load. If required, you can enable throttling for the full migration task. You can set Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) to reduce the load on the destination database.

      Note

      • This configuration item is available only if you select Full Data Migration for Migration Types.

      • You can also adjust the full migration speed after the migration instance is running.

      Enable Throttling for Incremental Data Migration

      If required, you can also choose to set speed limits for the incremental migration task. You can set RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) to reduce the load on the destination database.

      Note

      • This configuration item is available only if you select Incremental Data Migration for Migration Types.

      • You can also adjust the incremental migration speed after the migration instance is running.

      Whether to delete SQL operations on heartbeat tables of forward and reverse tasks

      Choose whether DTS writes heartbeat SQL information to the source database while the instance is running.

      • Yes: Does not write heartbeat SQL information to the source database. The DTS instance may display latency.

      • No: Writes heartbeat SQL information to the source database. This may interfere with source database operations like physical backups and cloning.

      Environment Tag

      You can select an environment tag to identify the instance based on your needs. No selection is required for this example.

      Configure ETL

      Based on your business needs, select whether to configure the ETL feature to process data.

      • Yes: Configures the ETL feature. You must also enter data processing statements in the text box.

      • No: Does not configure the ETL feature.

      Monitoring and Alerting

      Select whether to set alerts and receive alert notifications based on your business needs.

      • No: Does not set an alert.

      • Yes: Configure alerts by setting an alert threshold and an alert contact. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.

  6. Save the task and run a precheck.

    • To view the parameters for configuring this instance when you call the API operation, move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears.

    • If you do not need to view or have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.

    Note

    • Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.

    • If the precheck fails, click View Details next to the failed check item, fix the issue based on the prompt, and then run the precheck again.

    • If a warning is reported during the precheck:

      • For check items that cannot be ignored, click View Details next to the failed item, fix the issue based on the prompt, and then run the precheck again.

      • For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again to skip the alert item and run the precheck again. If you choose to ignore a warning, it may cause issues such as data inconsistency and pose risks to your business.

  7. Purchase an instance.

    1. When the Success Rate is 100%, click Next: Purchase Instance.

    2. On the Purchase page, select the link specification for the data migration instance. For more information, see the following table.

      Category

      Parameter

      Description

      New Instance Class

      Resource Group Settings

      Select the resource group to which the instance belongs. The default value is default resource group. For more information, see What is Resource Management?

      Instance Class

      DTS provides migration specifications with different performance levels. The link specification affects the migration speed. You can select a specification based on your business scenario. For more information, see Data migration link specifications.

    3. After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.

    4. Click Buy and Start. In the OK dialog box that appears, click OK.

      You can view the progress of the migration task on the Data Migration Tasks list page.

      Note

      • If the migration task does not include incremental migration, it stops automatically after the full migration is complete. After the task stops, its Status changes to Completed.

      • If the migration task includes incremental migration, it does not stop automatically. The incremental migration task continues to run. While the incremental migration task is running, the Status of the task is Running.

Mapping information

  1. In the Selected Objects area, hover over the destination topic name at the table level.

  2. Click Edit next to the destination topic name.

  3. In the Edit Table dialog box, configure the mapping information.

    Note

    • The dialog box is named Edit Schema at the database level and Edit Table at the table level. The Edit Schema dialog box has fewer parameters.

    • If you do not migrate the entire database, you cannot modify the Name of target Topic and Number of Partitions parameters in the Edit Schema dialog box.

    Parameter

    Description

    Name of target Topic

    The name of the topic that receives data from the source table. This defaults to the Topic you selected in the Destination Database section during the Configurations for Source and Destination Databases step.

    Important

    • If the destination is a Message Queue for Apache Kafka instance, the specified topic must already exist in the destination instance. Otherwise, the data migration task fails. If the destination is a self-hosted Kafka database and the data migration task includes database and table structure migration, DTS attempts to create the specified topic in the destination database.

    • If you change the Name of target Topic, DTS writes data to the specified topic.

    Filter Conditions

    For more information, see Configure filter conditions.

    Number of Partitions

    The number of partitions in the destination topic.

    Partition Key

    This parameter is available when you set Policy for Shipping Data to Kafka Partitions to Ship Data to Separate Partitions Based on Hash Values of Primary Keys. You can specify one or more columns as the partition key. DTS then calculates a hash value for the specified columns and uses it to distribute rows across partitions in the destination topic.

    Note

    You can select Partition Key only in the Edit Table dialog box.

  4. Click OK.

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