Migrate PolarDB-X 2.0 to Message Queue for Apache Kafka

Limitations

Billing

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

Database account permissions

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 PolarDB-X 2.0.
   	Connection Type	Select Alibaba Cloud Instance.
   	Instance Region	Select the region where the source PolarDB-X 2.0 instance is located.
   	Replicate Data Across Alibaba Cloud Accounts	This example demonstrates migration within the same Alibaba Cloud account. Select No.
   	Instance ID	Select the ID of the source PolarDB-X 2.0 instance.
   	Database Account	Enter the database account for the source PolarDB-X 2.0 instance. For information about the required permissions, see Permissions required for database accounts.
   	Database Password	Enter the password for the specified database account.
   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 Express Connect, VPN Gateway, or Smart Access Gateway. Note In this step, the Message Queue for Apache Kafka instance is configured as a self-managed Kafka database.
   	Instance Region	Select the region where the destination Kafka instance is located.
   	Connected VPC	Select the ID of the VPC to which the destination Kafka instance belongs. You can find the VPC ID on the Basic Information page of the Kafka instance.
   	Domain Name or IP	Enter an IP address from the Default Endpoint of the Kafka instance. Note You can obtain the IP address from the Default Endpoint section on the Basic Information page of the Kafka instance.
   	Port	The service port of the Kafka instance. Default: 9092.
   	Database Account	Enter the database account for the destination Kafka instance. Note If the Kafka instance is a VPC instance, you do not need to configure the Database Account and Database Password settings.
   	Database Password	Enter the password for the specified database account.
   	Kafka Version	Select the version that matches your Kafka instance.
   	Connection method	Select Non-encrypted or SCRAM-SHA-256 based on your business and security requirements.
   	Topic	Select the topic to 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 of the Avro schema registered 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 to perform a full migration, select both Schema Migration and Full Data Migration. To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed. If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
      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. If you select DTS Avro, you must parse the data based on the DTS Avro schema definition. For more information, see DTS Avro Schema Definition and DTS Avro Deserialization Example. If you select Canal JSON, see Canal JSON format for parameter descriptions and examples.
      Kafka Data Compression Format	Select the compression format for Kafka messages based on your requirements. LZ4 (Default): Lower compression ratio, higher compression speed. GZIP: Higher compression ratio, lower compression speed. Note This format has high CPU usage. Snappy: Medium compression ratio, medium compression speed.
      Policy for Shipping Data to Kafka Partitions	Select a policy based on your business requirements. Important If the source database is a PolarDB-X 1.0 instance, this feature is not supported.
      Message acknowledgement mechanism	Select a message acknowledgment mechanism based on your business requirements.
      Capitalization of Object Names in Destination Instance	You can configure the case sensitivity policy for the names of schemas, tables, and columns in the destination instance. By default, DTS default policy is selected. You can also select other options to ensure that the case of object names is consistent with the source or destination database. For more information, see Case sensitivity of object names in the destination instance.
      Source Objects	Select one or more objects from the Source Objects section. Click the icon and add the objects to the Selected Objects section. Note The granularity for selecting migration objects is schema, table, and column. If you select only tables or columns as migration objects, other objects such as views, triggers, and stored procedures are not migrated to the destination database.
      Selected Objects	No additional configuration is required for this example. You can use the mapping feature to set the topic name, number of partitions, partition key, and other information for the source table in the destination Kafka instance. For more information, see Map information. Note If you use the object name mapping feature, other objects that depend on the mapped object may fail to be migrated. To select SQL operations for incremental data migration, right-click an 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.
      Environment Tag	You can select environment tags to identify the instance based on your needs. No selection is required for this example.
      Configure ETL	Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: Enables the ETL feature. Enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: Disables the ETL feature.
      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.
      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 the 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 settings

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

2. Click Edit.

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

   Note

   • At the database level, the Edit Schema dialog box appears, which provides fewer parameters. At the table level, the Edit Table dialog box appears.

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

   Parameter	Description
   Name of target Topic	The name of the destination topic for the source table. By default, this is the Topic that you selected for the Destination Database in the Configurations for Source and Destination Databases step. Important If the destination database is a Message Queue for Apache Kafka instance, the topic name that you enter must exist in the destination Kafka instance. Otherwise, the data migration will fail. If the destination database is a self-managed Kafka instance and the task includes a schema migration task, DTS attempts to create the topic that you specify in the destination database. If you change the Name of target Topic, DTS writes data to the topic that you specify.
   Filter Conditions	For more information, see Configure filter conditions.
   Number of Partitions	The number of partitions in the destination topic.
   Partition Key	If the Policy for Shipping Data to Kafka Partitions is set to Ship Data to Separate Partitions Based on Hash Values of Primary Keys, you can configure this parameter. Specify one or more columns as the partition key. DTS calculates a hash value from the key and uses it to distribute rows across the partitions of the destination topic. Note You can select a Partition Key only in the Edit Table dialog box.

4. Click OK.