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Data Transmission Service:Synchronize data from an ApsaraDB RDS for MySQL instance to an ApsaraMQ for Kafka instance

Last Updated:Oct 30, 2023

This topic describes how to synchronize data from an ApsaraDB RDS for MySQL instance to an ApsaraMQ for Kafka instance by using Data Transmission Service (DTS).

Prerequisites

  • The source ApsaraDB RDS for MySQL instance and the destination ApsaraMQ for Kafka instance are created.

    Note
  • In the destination ApsaraMQ for Kafka instance, a topic is created to receive synchronized data. For more information, see the "Step 1: Create a topic" section of the Step 3: Create resources topic.

  • The available storage space of the destination ApsaraMQ for Kafka instance is larger than the total size of the data in the source ApsaraDB RDS for MySQL instance.

Limits

Note

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

Category

Description

Limits on the source database

  • The tables to be synchronized must have PRIMARY KEY or UNIQUE constraints, and all fields must be unique. Otherwise, the destination database may contain duplicate data records.

  • If you select tables as the objects to be synchronized and you need to edit the tables in the destination database, such as renaming tables or columns, you can synchronize up to 1,000 tables in a single data synchronization task. If you run a task to synchronize more than 1,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to synchronize the tables in batches or configure a task to synchronize the entire database.

  • The following requirements for binary logs must be met:

    • By default, the binary logging feature is enabled. The binlog_row_image parameter must be set to full. Otherwise, error messages are returned during precheck and the data synchronization task cannot be started. For more information, see Modify instance parameters.

      Important
      • If the source database is a self-managed MySQL database, you must enable the binary logging feature and set the binlog_format parameter to row and the binlog_row_image parameter to full.

      • If the source database is a self-managed MySQL database deployed in a dual-primary cluster, you must set the log_slave_updates parameter to ON. This ensures that DTS can obtain all binary logs. For more information, see Create an account for a self-managed MySQL database and configure binary logging.

    • If you perform only incremental data synchronization, the binary logs of the source database must be retained for at least 24 hours. If you perform both full data synchronization and incremental data synchronization, the binary logs of the source database must be retained for at least seven days. Otherwise, DTS may fail to obtain the binary logs, which causes the task to fail, or even data inconsistency and data loss. After full data synchronization is complete, you can set the retention period to more than 24 hours. Make sure that you set the retention period of binary logs based on the preceding requirements. Otherwise, the Service Level Agreement (SLA) of DTS does not guarantee service reliability or performance. For more information about the binary log files of an ApsaraDB RDS for MySQL instance, see Manage binary log files.

Precautions

  • Before you synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. During initial full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the loads on the database servers.

  • During initial full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination database. After initial full data synchronization is complete, the size of the used tablespace of the destination database is larger than that of the source database.

  • If you select one or more tables instead of an entire database as the objects to be synchronized, do not use tools such as pt-online-schema-change to perform online DDL operations on the tables during data synchronization. Otherwise, data may fail to be synchronized.

    You can use Data Management (DMS) to perform online DDL operations. For more information, see Perform lock-free DDL operations.

  • During data synchronization, we recommend that you use only DTS to write data to the destination database. This prevents data inconsistency between the source and destination databases. For example, if you use tools other than DTS to write data to the destination database, data loss may occur in the destination database when you use DMS to perform online DDL operations.

  • During data synchronization, if the destination Kafka instance or cluster is scaled, you must restart the instance or cluster.

Special cases

If the source database is a self-managed MySQL database, take note of the following items:

  • If you perform a primary/secondary switchover on the source database when the data synchronization task is running, the task fails.

  • DTS calculates synchronization latency based on the timestamp of the latest synchronized data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for an extended period of time, the synchronization latency may be inaccurate. If the latency of the data synchronization task is excessively high, you can perform a DML operation on the source database to update the latency.

    Note

    If you select an entire database as the object to be synchronized, you can create a heartbeat table. The heartbeat table is updated or receives data every second.

  • DTS executes the CREATE DATABASE IF NOT EXISTS 'test' statement in the source database as scheduled to move forward the binary log file position.

Billing

Synchronization typeTask configuration fee
Schema synchronization and full data synchronizationFree of charge.
Incremental data synchronizationCharged. For more information, see Billing overview.

Size limit of a single record

The maximum size of a single record that can be written to Kafka is 10 MB. Therefore, if a row of source data exceeds 10 MB, the relevant DTS task will be interrupted because DTS cannot write the record to Kafka. In this scenario, we recommend that you do not synchronize the whole tables that contain large fields but synchronize only some fields of the tables. When you configure a DTS task, you must exclude the records of these large fields. If tables that contain large fields are included in the objects of the task, you must remove the tables, add the tables to the objects again, and then set filter conditions to exclude the large fields.

Supported synchronization topologies

  • One-way one-to-one synchronization

  • One-way one-to-many synchronization

  • One-way many-to-one synchronization

For more information about the synchronization topologies that are supported by DTS, see Synchronization topologies.

SQL operations that can be synchronized

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

Note

This procedure is described based on the new version of the DTS console. In the event of discrepancies in operations between the DTS console and the DTS module in the Data Management (DMS) console, the DMS console takes precedence.

  1. Go to the Data Synchronization Tasks page.

    1. Log on to the DMS console.

    2. In the top navigation bar, click DTS.

    3. In the left-side navigation pane, choose DTS (DTS) > Data Synchronization.

    Note
  2. From the drop-down list to the right of Data Synchronization Tasks, select the region in which you want to create the data synchronization task.

    Note

    If you use the new DTS console, select the region in which you want to create the data synchronization task in the upper-left corner of the page.

  3. Click Create Task. In the Create Task wizard, configure the source and destination databases.

    Warning

    After you configure the source and destination databases, we recommend that you read the limits that are displayed in the upper part of the page. Otherwise, the task may fail or data inconsistency may occur.

    Section

    Parameter

    Description

    N/A

    Task Name

    The name of the task. DTS automatically assigns a name to the task. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.

    Source Database

    Select an existing DMS database instance. (Optional. If you have not registered a DMS database instance, ignore this option and configure database settings in the section below.)

    The database instance that you want to use. You can choose whether to select an existing instance based on your business requirements.

    • If you select an existing instance, DTS automatically populates the parameters for the database.

    • If you do not select an existing instance, you must manually configure parameters for the database.

    Database Type

    The type of the source database. Select MySQL.

    Access Method

    The access method of the source database. Select Alibaba Cloud Instance.

    Instance Region

    The region in which the source ApsaraDB RDS for MySQL instance resides.

    Replicate Data Across Alibaba Cloud Accounts

    Specifies whether to synchronize data across Alibaba Cloud accounts. In this example, No is selected.

    RDS Instance ID

    The ID of the source ApsaraDB RDS for MySQL instance.

    Database Account

    The database account of the source ApsaraDB RDS for MySQL instance. The account must have the read permissions on the objects to be synchronized.

    Database Password

    The password of the database account.

    Encryption

    Specifies whether to encrypt the connection to the database. Select Non-encrypted or SSL-encrypted based on your business requirements. If you select SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the data synchronization task. For more information, see Configure the SSL encryption feature.

    Destination Database

    Select an existing DMS database instance. (Optional. If you have not registered a DMS database instance, ignore this option and configure database settings in the section below.)

    The password of the database account.

    Database Type

    The type of the destination database. Select Kafka.

    Access Method

    The access method of the destination database. Select Express Connect, VPN Gateway, or Smart Access Gateway.

    Note

    DTS does not provide ApsaraMQ for Kafka as an access method. You can use ApsaraMQ for Kafka as a self-managed Kafka cluster to configure data synchronization.

    Instance Region

    The region in which the destination ApsaraMQ for Kafka instance resides.

    Connected VPC

    The ID of the virtual private cloud (VPC) to which the destination ApsaraMQ for Kafka instance belongs.

    Note

    To obtain the VPC ID, perform the following operations: Log on to the ApsaraMQ for Kafka console and go to the Instance Details page of the destination ApsaraMQ for Kafka instance. In the Configuration Information section, view the VPC ID.

    IP address (domain name is not supported)

    An IP address of the default endpoint of the destination ApsaraMQ for Kafka instance.

    Note

    To obtain an IP address, perform the following operations: Log on to the ApsaraMQ for Kafka console and go to the Instance Details page of the destination ApsaraMQ for Kafka instance. In the Endpoint Information section, find the endpoint whose value in the Type column is Default Endpoint. Move the pointer over the endpoint information in the Domain Name column. In the message that appears, obtain an IP address.

    Port Number

    The service port number of the destination ApsaraMQ for Kafka instance. The default port number is 9092.

    Note

    Enter one of the available IP addresses and the port number of the IP address.

    Database Account

    The username and password of the account that you want to use to access the destination ApsaraMQ for Kafka instance. The Database Account and Database Password parameters are required if you enable the access control list (ACL) feature for the ApsaraMQ for Kafka instance.

    Note
    • For more information about how to enable the ACL feature, see Grant permissions to SASL users.

    • Database Account: Go to the Instance Details page of the ApsaraMQ for Kafka instance. On the Manage SASL Users tab, view the username of the account that you want to use.

    • Database Password: On the Manage SASL Users tab, find the account that you want to use and click Copy Password in the Password column.

    Database Password

    Kafka Version

    The version of the destination ApsaraMQ for Kafka instance.

    • If the version of the ApsaraMQ for Kafka instance that is used in this task is 0.10.2, select 0.10.
    • If the version of the ApsaraMQ for Kafka instance that is used in this task is 2.6.2 or 2.2.0, select Later Than 1.0.

    Encryption

    Specifies whether to encrypt the connection to the destination instance. Select Non-encrypted or SCRAM-SHA-256 based on your business and security requirements.

    Topic

    The topic that is used to receive the synchronized data. Select a topic from the drop-down list.

    Topic That Stores DDL Information

    The topic that is used to store the DDL information. Select a topic from the drop-down list. If you do not configure this parameter, the DDL information is stored in the topic that is specified by the Topic parameter.

    Use Kafka Schema Registry

    Specifies whether to use Kafka Schema Registry, which provides a serving layer for your metadata. It provides a RESTful API for storing and retrieving your Avro schemas. Valid values:

    • No: does not use Kafka Schema Registry.

    • Yes: uses Kafka Schema Registry. In this case, you must enter the URL or IP address that is registered in Kafka Schema Registry for your Avro schemas.

  4. If an IP address whitelist is configured for your self-managed database, add the CIDR blocks of DTS servers to the IP address whitelist. Then, click Test Connectivity and Proceed.

    Note

    For more information about the CIDR blocks of DTS servers, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.

  5. Configure the objects to be synchronized and advanced settings.

    Parameter

    Description

    Synchronization Types

    By default, Incremental Data Synchronization is selected. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of selected objects from the source instance to the destination instance. The historical data is the basis for subsequent incremental synchronization.

    Processing Mode of Conflicting Tables

    • Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data synchronization task cannot be started.

      Note

      You can use the object name mapping feature to rename the tables that are synchronized to the destination database. You can use this feature if the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed. For more information, see Map object names.

    • Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.

      Warning

      If you select Ignore Errors and Proceed, data inconsistency may occur, and your business may be exposed to potential risks.

      • If the source and destination databases have the same schemas, and a data record has the same primary key value as an existing data record in the destination database:

        • During full data synchronization, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained.

        • During incremental data synchronization, DTS synchronizes the data record to the destination database. The existing data record in the destination database is overwritten.

      • If the source and destination databases have different schemas, data may fail to be initialized, only some columns are synchronized, or the data synchronization task fails. Operate with caution.

    Data Format in Kafka

    The format in which data is stored in the ApsaraMQ for Kafka instance.

    • If you select DTS Avro, data is parsed based on the schema definition of DTS Avro. For more information, visit GitHub.

    • If you select Canal Json, data is stored in the Canal JSON format. For more information about the related parameters and examples, see the "Canal JSON" section of the Data formats of a Kafka cluster topic.

    Policy for Shipping Data to Kafka Partitions

    The policy for synchronizing data to Kafka partitions. Select a policy based on your business requirements. For more information, see Specify the policy for migrating data to Kafka partitions.

    Capitalization of Object Names in Destination Instance

    The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to ensure that the capitalization of object names is consistent with that in the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.

    Source Objects

    Select one or more objects from the Source Objects section and click the Rightwards arrow icon to add the objects to the Selected Objects section.

    Note

    You can select only tables as the objects to be synchronized.

    Selected Objects

    • To rename an object that you want to synchronize to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.

    • To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.

    Note
    • To select the SQL operations performed on a specific database or table, right-click an object in the Selected Objects section. In the dialog box that appears, select the SQL operations that you want to synchronize. For more information, see the SQL operations that can be synchronized section of this topic.

    • To specify WHERE conditions to filter data, right-click a table in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Use SQL conditions to filter data.

    • If you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be synchronized.

  6. Optional. In the Selected Objects section, move the pointer over the topic name and right-click Edit. In the dialog box that appears, configure the parameters that are described in the following table.

    Parameter

    Description

    Table Name

    The name of the topic to which the data in the source table is synchronized.

    Warning

    The topic must exist in the destination ApsaraMQ for Kafka instance. Otherwise, data synchronization fails.

    Filter Conditions

    • The SQL conditions that are used to filter the data to be synchronized to the destination topic. An SQL condition is a standard SQL WHERE statement. The following operators are supported: =, !=, <, and >. In this example, book_id>1 is used.

    • You can use single quotation marks (' ') in an SQL condition if necessary. For example, you can enter address in('hangzhou','shanghai').

    Number of Partitions

    In this example, you do not need to configure this parameter because the ApsaraMQ for Kafka instance does not support the partitioning feature.

    Partition Key

    If you set the Policy for Shipping Data to Kafka Partitions parameter to Ship Data to Separate Partitions Based on Hash Values of Primary Keys, configure this parameter to specify one or more columns as partition keys to calculate hash values. DTS delivers different rows to each partition of the destination topic based on the calculated hash values.

    Note

    To select Partition Key for columns, you must first clear Synchronize All Tables.

  7. Click Next: Advanced Settings to configure advanced settings.

    Parameter

    Description

    Select the dedicated cluster used to schedule the task

    By default, DTS schedules tasks to shared clusters. You do not need to configure this parameter. You can purchase a dedicated cluster of specified specifications to run DTS synchronization tasks. For more information, see What is a DTS dedicated cluster.

    Set Alerts

    Specifies whether to configure alerting for the data synchronization task. If the task fails or the synchronization latency exceeds the specified threshold, alert contacts will receive notifications. Valid values:

    Retry Time for Failed Connections

    The retry time range for failed connections. If the source or destination database fails to be connected after the data synchronization task is started, DTS immediately retries a connection within the time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.

    Note
    • If you set different retry time ranges for multiple DTS tasks that have the same source or destination database, the shortest retry time range that is set takes precedence.

    • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.

    The wait time before a retry when other issues occur in the source and destination databases.

    The retry time range for other issues. For example, if the DDL or DML operations fail to be performed after the data synchronization task is started, DTS immediately retries the operations within the time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.

    Important

    The value of the The wait time before a retry when other issues occur in the source and destination databases parameter must be smaller than the value of the Retry Time for Failed Connection parameter.

    Enable Throttling for Full Data Migration

    During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and BPS of Full Data Migration parameters for full data synchronization tasks to reduce the pressure on the destination database.

    Note

    This parameter can be configured only if Full Data Synchronization is selected as Synchronization Types.

    Enable Throttling for Incremental Data Synchronization

    You can configure the RPS of Incremental Data Migration and BPS of Incremental Data Migration parameters for incremental data synchronization tasks to reduce the pressure on the destination database.

    Environment Tag

    The environment tag that is used to identify the DTS instance. You can select an environment tag based on your business requirements. In this example, you do not need to configure this parameter.

    Configure ETL

    Specifies whether to configure the extract, transform, and load (ETL) feature. For more information, see What is ETL?. Valid values:
  8. Click Next: Save Task Settings and Precheck in the lower part of the page.

    You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameter settings of the API operation that is called to configure the instance.

    Note
    • Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.

    • If the task fails to pass the precheck, click View Details next to each failed item. After you troubleshoot the issues based on the causes, run a precheck again.

    • If an alert is triggered for an item during the precheck:

      • If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.

      • If an alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.

  9. Wait until the success rate becomes 100%. Then, click Next: Purchase Instance.

  10. On the Purchase Instance page, configure the Billing Method and Instance Class parameters for the data synchronization instance. The following table describes the parameters.

    Section

    Parameter

    Description

    New Instance Class

    Billing Method

    • Subscription: You pay for the instance when you create an instance. The subscription billing method is more cost-effective than the pay-as-you-go billing method for long-term use.

    • Pay-as-you-go: A pay-as-you-go instance is charged on an hourly basis. The pay-as-you-go billing method is suitable for short-term use. If you no longer require a pay-as-you-go instance, you can release the pay-as-you-go instance to reduce costs.

    Resource Group

    The resource group on which the instance is run. Default value: default resource group. For more information, see What is Resource Management?.

    Instance Class

    DTS provides various synchronization specifications that provide different performance. The synchronization speed varies based on the synchronization specifications that you select. You can select a synchronization specification based on your business scenario. For more information, see Specifications of data synchronization instances.

    Subscription Duration

    If you select the subscription billing method, set the subscription duration and the number of instances that you want to create. The subscription duration can be one to nine months, one year, two years, three years, or five years.

    Note

    This parameter is available only if you select the Subscription billing method.

  11. Read and select the check box to agree to the Data Transmission Service (Pay-as-you-go) Service Terms.

  12. Click Buy and Start to start the data synchronization task. You can view the progress of the task in the task list.