You can use Data Transmission Service (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 a Distributed Relational Database Service (DRDS) instance.

Prerequisites

  • The MySQL version of the DRDS instance is MySQL 5.
  • A database is created in the DRDS instance based on an ApsaraDB RDS for MySQL instance that you purchased. DTS does not support databases that are created based on Apsara PolarDB for MySQL clusters or private ApsaraDB RDS for MySQL instances.

Precautions

  • A change tracking channel stores the data that was generated in the last 24 hours and deletes expired data.
  • When the change tracking task is running, do not scale out or scale in the capacity of the DRDS instance, migrate frequently-accessed tables, change shards, or perform data definition language (DDL) operations. Otherwise, the change tracking task fails.

Procedure

  1. Create a change tracking instance. For more information, see Purchase a DTS instance.
    Note On the buy page, set Source Database to DRDS.
  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 for the change tracking task.
    Configure the source database
    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 Select DRDS Instance.
    Database Type The value of this parameter is set to DRDS 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.
    DRDS Instance ID Select the ID of the source DRDS instance.
    Database Name Select the name of the source database in the DRDS instance.
    Database Account Enter the database account of the source RDS instance.
    Database Password Enter the password of the database account.
  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 DRDS instance. This ensures that DTS servers can connect to the source DRDS instance.
  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 required 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 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, click the Info icon icon next to each failed item to view details. Troubleshoot the issues based on the causes and run the 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. After the initial change tracking is complete, you can consume the tracked data. For more information, see Use the SDK demo code to consume tracked data.