You can use DTS to track data changes in real time. This feature applies to the following scenarios: lightweight cache updates, business decoupling, asynchronous data processing, and real-time data synchronization of extract, transform, and load (ETL) operations. This topic describes how to track data changes from an Apsara PolarDB for MySQL cluster.

Prerequisites

The binary logging feature is enabled for the Apsara PolarDB for MySQL cluster. For more information, see Enable binlogging.

Precautions

  • DTS does not track data definition language (DDL) operations that are performed by gh-ost or pt-online-schema-change. Therefore, the change tracking client may fail to write the consumed data to the destination tables due to schema conflict.
  • If the source database is used in another task, for example, it is used in a running data migration task, DTS may track data changes of other objects. In this case, you must use the change tracking client to filter the tracked data.

Procedure

  1. Create a change tracking instance. For more information, see Purchase a change tracking instance.
    Note On the buy page, set Source Database to PolarDB and select the region where the source PolarDB cluster resides.
  2. Log on to the DTS console.
  3. In the left-side navigation pane, click Change Tracking.
  4. At the top of the Change Tracking Tasks page, select the region where the change tracking instance resides.Select a region
  5. Find the change tracking instance, and click Configure Channel in the Actions column.
  6. Configure the source database and network type for the change tracking task.Configure the source database and network type
    Section Parameter Description
    N/A Task Name DTS automatically generates a task name. We recommend that you specify an informative name for easy identification. You do not need to use a unique task name.
    Source Database Instance Type The value of this parameter is set to PolarDB Instance and cannot be changed.
    Database Type The value of this parameter is set to PolarDB and cannot be changed.
    Instance Region The region of the source instance. The region is the same as the source region that you selected when you purchased the change tracking instance. You cannot change the value of this parameter.
    PolarDB Instance ID Select the ID of the source PolarDB cluster.
    Database Account Enter the database account of the source PolarDB cluster.
    Note The account must have the REPLICATION SLAVE permission, the REPLICATION CLIENT permission, and the permission to perform SELECT operations on the required objects.
    Database Password Enter the password of the database account.
    Network Type N/A Select the network type of the change tracking instance.
    • Classic

      If you select Classic, no other configurations are required. For more information about the classic network, see Classic network.

    • VPC

      If you select VPC, you must specify the VPC and VSwitch. For more information about VPC, see VPC.

    Note
    • We recommend that you select the same network type as the ECS instance on which the change tracking client is installed For example, if the ECS instance is deployed in a VPC, select VPC as the network type and specify the VPC and VSwitch.
    • If you track data changes over internal networks, the network latency is minimal.
  7. In the lower-right corner of the page, click Set Whitelist and Next.
    Note DTS adds the CIDR blocks of DTS servers to the whitelist of the source PolarDB cluster. This ensures that DTS servers can connect to the source PolarDB cluster.
  8. Select the data change types and objects.Select the data change types and objects
    Parameter Description
    Required Data Types
    • Data Updates

      DTS tracks data updates of the selected objects, including the INSERT, DELETE, and UPDATE operations.

    • Schema Updates

      DTS tracks the create, delete, and modify operations that are performed on all object schemas of the source instance. You must use the change tracking client to filter the tracked data.

    Note
    • If you select a database as the object, DTS tracks data changes of all objects, including new objects in the database.
    • If you select a table as the object, DTS tracks only data changes of this table. In this case, if you want to track data changes of another table, you must add the table to the required objects. For more information, see Modify the objects for change tracking.
    Required Objects

    Select objects from the Required Objects section and click the Right arrow icon to add the objects to the Selected section.

    Note You can select tables or databases as the objects for change tracking.
  9. In the lower-right corner of the page, click Save and Precheck.
    Note
    • Before you can start the change tracking task, a precheck is performed. You can start the change tracking task only after the task passes the precheck.
    • If the task fails to pass the precheck, you can click the Info icon icon next to each failed item to view details. You can troubleshoot the issues based on the causes and run a precheck again.
  10. Close the Precheck dialog box after the following message is displayed: The precheck is passed.

What to do next

After the change tracking task is configured, DTS performs initial change tracking, which takes about 1 minute. After initial change tracking, you can perform the following operations:

  1. Create consumer groups
  2. Use a Kafka client to consume tracked data