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Synchronize data from ApsaraDB RDS for MySQL to ApsaraMQ for Kafka

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Data Transmission Service (DTS) synchronizes data from an ApsaraDB RDS for MySQL instance to an ApsaraMQ for Kafka instance.

Prerequisites

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

    Note

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

  • Ensure that the storage space of the destination ApsaraMQ for Kafka instance is greater than the storage space used by the source ApsaraDB RDS for MySQL instance.

Precautions

Note

DTS does not synchronize foreign keys from the source database to the destination database. Therefore, cascade operations and delete operations in the source database are not synchronized to the destination database.

Type

Description

Source database limits

  • The tables to synchronize must have a primary key or a unique constraint, and the fields must be unique. Otherwise, duplicate data may appear in the destination database.

  • If you synchronize at the table level and need to edit mappings (such as column name mapping), each synchronization task supports up to 1,000 tables. If you exceed this limit, the task fails with an error. To fix this, split the tables across multiple tasks or configure a full-database synchronization task.

  • Binary logs:

    • ApsaraDB RDS for MySQL enables binary logging by default. Ensure that the binlog_row_image parameter is set to full. Otherwise, the precheck fails and the synchronization task cannot start. For instructions, see Configure instance parameters.

      Important

      • If your source instance is a self-managed MySQL database, enable binary logging and set binlog_format to row and binlog_row_image to full.

      • If your self-managed MySQL database is a dual-primary cluster (where both nodes act as primary and secondary), enable the log_slave_updates parameter so DTS can capture all binary log events. For instructions, see Create an account and configure binary logging for a self-managed MySQL database.

    • The local binary logs for an ApsaraDB RDS for MySQL instance must be retained for at least three days (seven days is recommended). For a self-managed MySQL database, retain local binary logs for at least seven days. Otherwise, DTS may fail to retrieve binary logs, causing the task to fail. In extreme cases, this may cause data inconsistency or data loss. Issues caused by binary log retention periods shorter than DTS requires are not covered under the DTS SLA.

      Note

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

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

    Note

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

  • Data generated by changes that do not write to binary logs—such as data restored from physical backups or created by cascade operations—is not synchronized to the destination database.

    Note

    If this occurs, remove the affected database or table from the synchronization objects. Then add it back. You can do this only if your business allows it. For more information, see Modify synchronization objects.

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

    Note

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

Other limits

  • Assess the performance of both the source and destination databases before starting synchronization. Run synchronization during off-peak hours. Otherwise, full initialization consumes read and write resources on both databases and may increase database load.

  • Full initialization runs INSERT operations concurrently. This fragments destination tables. After full initialization, the tablespace of the destination instance is larger than that of the source instance.

  • If you synchronize one or more tables—not a full database—do not use tools like pt-online-schema-change to perform online DDL operations on the source tables. Otherwise, synchronization fails.

    You can use Data Management (DMS) to perform online DDL operations. For more information, see Online DDL without locking tables.

  • DTS does not support synchronizing indexes, partitions, views, stored procedures, functions, triggers, or foreign keys.

  • Do not write data to the destination database except through DTS while synchronization is running. Otherwise, data inconsistency may occur between the source and destination databases.

  • If the destination Kafka cluster scales out or scales in during synchronization, restart the task.

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

    Note

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

  • 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 a self-managed MySQL source database:

    • If a primary/secondary switchover occurs in the source database during synchronization, the task fails.

    • DTS calculates latency by comparing the timestamp of the last synchronized record with the current time. If no DML operations run for a long time in the source database, latency reporting may become inaccurate. If latency appears too high, run a DML operation in the source database to update the latency.

      Note

      If you select a full database for synchronization, create a heartbeat table. Update or write to this table every second.

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

    • If your source database is Amazon Aurora MySQL or another clustered MySQL instance, ensure the domain name or IP address used in the task configuration—and its DNS resolution—always points to a read/write (RW) node. Otherwise, synchronization may fail.

  • For an ApsaraDB RDS for MySQL source database:

    • Read-only instances—such as ApsaraDB RDS for MySQL 5.6 read-only instances—that do not record transaction logs cannot serve as source databases.

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

Billing

Synchronization type

Pricing

Schema synchronization and full data synchronization

Free of charge.

Incremental data synchronization

Charged. For more information, see Billing overview.

Single record size limit

The maximum size of a single record that can be written to Kafka is 10 MB. If a source row exceeds this limit, DTS interrupts the task because it cannot write the oversized record. In this scenario, we recommend that you do not synchronize the table. If you must synchronize the table, configure the DTS task to include only a subset of its columns, excluding those with large fields. For a running task, first remove the table from the list of synchronized objects. Then, add the table again, but this time, exclude the columns that contain large fields.

Supported synchronization topologies

  • One-way one-to-one synchronization

  • One-way one-to-many synchronization

  • One-way many-to-one synchronization

For details on these synchronization topologies, see Data synchronization topologies.

Supported SQL operations

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

Procedure

  1. Go to the data synchronization task list page in the destination region. You can do this in one of two ways.

    DTS console

    1. Log on to the DTS console.

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

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

    DMS console

    Note

    The actual steps may vary depending 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 DMS console.

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

    3. To the right of Data Synchronization Tasks, select the region of the synchronization instance.

  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, review the Limits 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

    • Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured.

      Note

      In the DMS console, this configuration item is Select a DMS database instance.

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

    Database Type

    Select MySQL.

    Access Method

    Select Alibaba Cloud Instance.

    Instance Region

    Select the region of the source RDS for MySQL instance.

    Replicate Data Across Alibaba Cloud Accounts

    This example synchronizes data 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 for the source RDS for MySQL instance. The account must have read permissions on the objects you want to synchronize.

    Database Password

    Enter the password for the specified database account.

    Encryption

    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

    • Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured.

      Note

      In the DMS console, this configuration item is Select a DMS database instance.

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

    Database Type

    Select Kafka.

    Access Method

    Select Alibaba Cloud Instance.

    Instance Region

    Select the region of the destination Message Queue for Apache Kafka instance.

    Kafka Instance ID

    Select the ID of the destination Message Queue for Apache Kafka instance.

    Encryption

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

    Topic

    From the drop-down list, select the Topic that will receive the synchronized data.

    Use Kafka Schema Registry

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

    • No: Do not use Kafka Schema Registry.

    • Yes: Use Kafka Schema Registry. You must provide the URL or IP address of your Kafka Schema Registry.

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

    Note

    • Ensure that you add the CIDR blocks of the DTS servers (either automatically or manually) to the security settings of both the source and destination databases to allow access. For more information, see Add the IP address whitelist of DTS servers.

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

  5. Configure the task objects.

    1. On the Configure Objects page, specify the objects to synchronize.

      Parameter

      Description

      Synchronization Types

      DTS always selects Incremental Data Synchronization. By default, you must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS initializes the destination cluster with the full data of the selected source objects, which serves as the baseline for subsequent incremental synchronization.

      Note

      If the Access Method for the destination Kafka instance is set to Alibaba Cloud Instance, Schema Synchronization is not supported.

      Processing Mode of Conflicting Tables

      • Precheck and Report Errors: Checks for tables with the same names in the destination database. If any tables with the same names are found, an error is reported during the precheck and the data synchronization task does not start. Otherwise, the precheck is successful.

        Note

        If you cannot delete or rename the table with the same name in the destination database, you can map it to a different name in the destination. For more information, see Database Table Column Name Mapping.

      • Ignore Errors and Proceed: Skips the check for tables with the same name in the destination database.

        Warning

        Selecting Ignore Errors and Proceed may cause data inconsistency and put your business at risk. For example:

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

          • During full data synchronization, DTS retains the destination record and skips the source record.

          • During incremental synchronization, DTS overwrites the destination record with the source record.

        • If the table schemas are inconsistent, data initialization may fail. This can result in only partial data synchronization or a complete synchronization failure. Use with caution.

      Data Format in Kafka

      Select the storage format for data to be synchronized to the Kafka instance.

      Kafka Data Compression Format

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

      • LZ4 (Default): offers a low compression ratio and high compression speed.

      • GZIP: offers a high compression ratio and low compression speed.

        Note

        GZIP compression consumes significant CPU resources.

      • Snappy: offers a medium compression ratio and medium compression speed.

      Policy for Shipping Data to Kafka Partitions

      Select a policy based on your business requirements.

      Message acknowledgement mechanism

      Select a message acknowledgement mechanism based on your business requirements.

      Topic That Stores DDL Information

      From the drop-down list, select a topic to store DDL information.

      Note

      If you do not select a topic, DTS stores DDL information in the data topic by default.

      Capitalization of Object Names in Destination Instance

      Configure the case-sensitivity policy for database, table, and column names in the destination instance. By default, the DTS default policy is selected. You can also choose to use the default policy of the source or destination database. For more information, see Case policy for destination object names.

      Source Objects

      In the Source Objects box, click the objects, and then click 向右 to move them to the Selected Objects box.

      Note

      Objects can be selected at the table level.

      Selected Objects

      No additional configuration is required in this example. Use the mapping feature to set the topic name, topic partition count, and partition key for a source table in the destination Kafka instance. For more information, see Mapping Information.

      Note

      • To select which SQL operations to synchronize at the database or table level, right-click the object in the Selected Objects box and select the operations from the dialog box.

      • Synchronization may fail for objects that depend on a mapped object.

    2. Click Next: Advanced Settings.

      Parameter

      Description

      Dedicated Cluster for Task Scheduling

      By default, DTS uses a shared cluster for tasks, so you do not need to make a selection. For greater task stability, you can purchase a dedicated cluster to run the DTS synchronization task. For more information, see What is a DTS dedicated cluster?.

      Retry Time for Failed Connections

      If the connection to the source or destination database fails after the synchronization task starts, 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 1,440 minutes. We recommend a duration of 30 minutes or more. If the connection is restored within this period, the task resumes automatically. Otherwise, the task fails.

      Note

      • If multiple DTS instances (e.g., Instance A and B) share a source or destination, DTS uses the shortest configured retry duration (e.g., 30 minutes for A, 60 for B, so 30 minutes is used) for all instances.

      • DTS charges for task runtime during connection retries. Set a custom duration based on your business needs, or release the DTS instance promptly after you release the source/destination instances.

      Retry Time for Other Issues

      If a non-connection issue (e.g., a DDL or DML execution error) occurs, DTS reports an error and immediately retries the operation. The default retry duration is 10 minutes. You can also customize the retry time to a value from 1 to 1,440 minutes. We recommend a duration of 10 minutes or more. If the related operations succeed within the set retry time, the synchronization task automatically resumes. Otherwise, the task fails.

      Important

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

      Enable Throttling for Full Data Synchronization

      During full data synchronization, DTS consumes read and write resources from the source and destination databases, which can increase their load. To mitigate pressure on the destination database, you can limit the migration rate by setting Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s).

      Note

      Enable Throttling for Incremental Data Synchronization

      You can also limit the incremental synchronization rate to reduce pressure on the destination database by setting RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s).

      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. No selection is required in this example.

      Configure ETL

      Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values:

      Monitoring and Alerting

      Choose whether to set up alerts. If the synchronization fails or the latency exceeds the specified threshold, DTS sends a notification to the alert contacts.

  6. Save the task and perform a precheck.

    • To view the parameters for configuring this instance via an API operation, hover over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the tooltip.

    • If you have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.

    Note

    • Before a synchronization task starts, DTS performs a precheck. You can start the task only if the precheck passes.

    • If the precheck fails, click View Details next to the failed item, fix the issue as prompted, and then rerun the precheck.

    • If the precheck generates warnings:

      • For non-ignorable warning, click View Details next to the item, fix the issue as prompted, and run the precheck again.

      • For ignorable warnings, you can bypass them by clicking Confirm Alert Details, then Ignore, and then OK. Finally, click Precheck Again to skip the warning and run the precheck again. Ignoring precheck warnings may lead to data inconsistencies and other business risks. Proceed with caution.

  7. Purchase an instance.

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

    2. On the Purchase page, select the billing method and link specifications for the data synchronization instance. For more information, see the following table.

      Category

      Parameter

      Description

      New Instance Class

      Billing Method

      • Subscription: You pay upfront for a specific duration. This is cost-effective for long-term, continuous tasks.

      • Pay-as-you-go: You are billed hourly for actual usage. This is ideal for short-term or test tasks, as you can release the instance at any time to save costs.

      Resource Group Settings

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

      Instance Class

      DTS offers synchronization specifications at different performance levels that affect the synchronization rate. Select a specification based on your business requirements. For more information, see Data synchronization link specifications.

      Subscription Duration

      In subscription mode, select the duration and quantity of the instance. Monthly options range from 1 to 9 months. Yearly options include 1, 2, 3, or 5 years.

      Note

      This option appears only when the billing method is Subscription.

    3. Read and select the checkbox for Data Transmission Service (Pay-as-you-go) Service Terms.

    4. Click Buy and Start, and then click OK in the OK dialog box.

      You can monitor the task progress on the data synchronization page.

Mapping information

  1. In the Selected Objects area, hover over the target Topic name (at the table level).

  2. Click Edit next to the target Topic name.

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

    Note

    • The Edit Schema dialog box appears at the schema level and supports fewer parameters. At the table level, the Edit Table dialog box appears.

    • When not synchronizing an entire database, you cannot modify Name of target Topic or Number of Partitions in the Edit Schema dialog box.

    Parameter

    Description

    Name of target Topic

    The name of the target Topic to which the source table is synchronized. The default value is the Topic selected in the Destination Database section of the Configurations for Source and Destination Databases stage.

    Important

    • If the destination is a Message Queue for Apache Kafka instance, the topic name you specify must exist in the destination Kafka instance. Otherwise, the data synchronization fails. If the destination is a self-managed Kafka cluster and the synchronization task includes schema migration, DTS attempts to create the specified topic in the destination cluster.

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

    Filter Conditions

    For more information, see Set filter conditions.

    Number of Partitions

    The number of partitions for the target topic.

    Partition Key

    You can configure this parameter when Policy for Shipping Data to Kafka Partitions is set to Ship Data to Separate Partitions Based on Hash Values of Primary Keys. Specify one or more columns as the Partition Key to calculate hash values. DTS then ships rows to different partitions based on these hash values.

    Note

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

  4. Click OK.

FAQ

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