ApsaraDB for OceanBase:Synchronize data from OceanBase Database to a RocketMQ instance

Background

Message Queue for Apache RocketMQ is a distributed message-oriented middleware built by Alibaba Cloud based on Apache RocketMQ. It features low latency, high concurrency, and high reliability. The data synchronization capability of the data transmission service enables you to synchronize data between an OceanBase physical table and a RocketMQ data source in real time, extending the message processing capability.

For more information about the data formats for the two types of tenants, see Data formats used when data is transmitted from OceanBase Database to a message queue system.

Prerequisites

• The data transmission service has the privilege to access cloud resources. For more information, see Grant privileges to roles for data transmission.

• You have created a dedicated database user for data synchronization in the source OceanBase database and granted corresponding privileges to the user. For more information, see Create a database user.

Limitations

• The data transmission service supports RocketMQ instances of versions 4.x and 5.x, including commercial and community editions.

• Only physical tables can be synchronized.

• During data synchronization, the data transmission service allows you to drop a table before creating a new one. In other words, you can execute DROP TABLE and then execute CREATE TABLE. The data transmission service does not allow you to create a new table by renaming a table. In other words, you cannot execute RENAME TABLE a TO a_tmp.

• The name of a table to be synchronized, as well as the names of columns in the table, must not contain Chinese characters.

• The data transmission service supports the migration of only objects whose database name, table name, and column name are ASCII-encoded without special characters. The special characters are line breaks, spaces, and the following characters: . | " ' ` ( ) = ; / &

• The data transmission service does not support a standby OceanBase database as the source.

Considerations

• Take note of the following items when an updated row contains a LOB column:

  • If the LOB column is updated, do not use the value stored in the LOB column before the UPDATE or DELETE operation.

    The following data types are stored in LOB columns: JSON, GIS, XML, user-defined type (UDT), and TEXT such as LONGTEXT and MEDIUMTEXT.

  • If the LOB column is not updated, the value stored in the LOB column before and after the UPDATE or DELETE operation is NULL.

• When a data synchronization project is resumed, some data (within the last minute) may be duplicate in the RocketMQ instance, and deduplication is required in downstream systems.

• If the clocks between nodes or between the client and the server are out of synchronization, the latency may be inaccurate during incremental synchronization.

  For example, if the clock is earlier than the standard time, the latency can be negative. If the clock is later than the standard time, the latency can be positive.

Supported source and destination instance types

The following table lists the supported instance types for the source and destination. OceanBase Database has two types of tenants: MySQL and Oracle. The source can be an OceanBase cluster instance or a self-managed database in a virtual private cloud (VPC).

Procedure

1. Log on to the ApsaraDB for OceanBase console and purchase a data synchronization project.

   For more information, see Purchase a data synchronization project.

2. Choose Data Transmission > Data Synchronization. On the page that appears, click Configure for the data synchronization project.

   

   If you want to reference the configurations of an existing project, click Reference Configuration. For more information, see Reference and clear data synchronization project configurations.

3. On the Select Source and Destination page, configure the parameters.

   

   Parameter	Description
   Project Name	We recommend that you set it to a combination of digits and letters. It must not contain any spaces and cannot exceed 64 characters in length.
   Label	Click the field and select a target tag from the drop-down list. You can also click Manage Tags to create, modify, and delete tags. For more information, see Manage data synchronization projects by using tags.
   Source	If you have created an OceanBase data source, select it from the drop-down list. Otherwise, click New Data Source in the drop-down list to create one in the dialog box on the right side. For more information about the parameters, see Create an OceanBase data source. Important The source must not be an OceanBase Database tenant instance.
   Destination	If you have created a RocketMQ data source, select it from the drop-down list. Otherwise, click New Data Source in the drop-down list to create one in the dialog box on the right side. For more information, see Create a RocketMQ data source.

4. Click Next. On the Select Synchronization Type page, specify the synchronization type for the current data synchronization project.

   

   Options for Synchronization Type are Full Synchronization and Incremental Synchronization. The only option for Incremental Synchronization is DML Synchronization. Options for DML Synchronization are Insert, Delete, and Update. You can select the operations based on your business requirements. For more information, see DML synchronization.

5. Click Next. On the Select Synchronization Objects page, select the objects to be synchronized in the current data synchronization project.

   When you synchronize data from an OceanBase database to a RocketMQ instance, you can select multiple tables to map to multiple topics.

   1. In the left-side pane, select the objects to be synchronized.

   2. Click >.

   3. Click the Existing Topics drop-down list in the Map the Object to the Topic dialog box and select the target topic.

      You can also enter the name of an existing topic and select it after it appears.

      

   4. Click OK.

      The data transmission service allows you to import objects by using text. It also allows you to change the topics of the objects, set row filters, and remove a single object or all objects. Objects in the destination database are listed in the structure of Topic > Database > Table.

      

      Operation	Description
      Import Objects	In the list on the right, click Import Objects in the upper-right corner. In the dialog box that appears, click OK. Important This operation will overwrite previous selections. Proceed with caution. In the Import Synchronization Objects dialog box, import the objects to be synchronized. You can import CSV files to set row filter conditions, filter columns, and sharding columns. For more information, see Download and import the settings of synchronization objects. Click Validate. After the validation is passed, click OK.
      Change Topic	The data transmission service allows you to change topics for objects in the destination database. For more information, see Change topics.
      Settings	You can use the WHERE clause to filter data by row, select sharding columns, and select columns to be synchronized. In the Settings dialog box, you can perform the following operations: In the Row Filters section, specify a standard SQL WHERE clause to filter data by row. For more information, see Use SQL conditions to filter data. Select the sharding columns that you want to use from the Sharding Columns drop-down list. You can select multiple fields as sharding columns. This parameter is optional. Unless otherwise specified, select the primary keys as sharding columns. If the primary keys are not load-balanced, select load-balanced fields with unique identifiers as sharding columns to avoid potential performance issues. Sharding columns can be used for the following purposes: Load balancing: Threads used for sending messages can be recognized based on the sharding columns if the destination table supports concurrent writes. Orderliness: The data transmission service ensures that messages are received in order if the values of the sharding columns are the same. The orderliness specifies the sequence of executing DML statements for a column. In the Select Columns section, select the columns to be synchronized. For more information, see Column filtering.
      Remove/Remove All	The data transmission service allows you to remove a single object or all migration objects that are added to the right-side list during data mapping. Remove a single synchronization object In the list on the right, move the pointer over the object that you want to remove, and click Remove to remove the synchronization object. Remove all synchronization objects In the list on the right, click Remove All in the upper-right corner. In the dialog box that appears, click OK to remove all synchronization objects.

6. Click Next. On the Synchronization Options page, configure the parameters.

   

   Parameter	Description
   Incremental Synchronization Start Timestamp	If you have selected Full Synchronization as the synchronization type, the default value of this parameter is the start time of incremental synchronization and cannot be modified. If you have not selected Full Synchronization as the synchronization type, set this parameter to a certain point of time, which is the current system time by default. For more information, see Set an incremental synchronization timestamp.
   Serialization Method	The message format for synchronizing data to the destination RocketMQ instance. Valid values: Default, Canal, DataWorks (version 2.0 supported), SharePlex, DefaultExtendColumnType, Debezium, DebeziumFlatten, and DebeziumSmt. For more information, see Data formats used in serialization methods. Important Only MySQL tenants of OceanBase Database support Debezium, DebeziumFlatten, and DebeziumSmt.
   Partitioning Rules	When you synchronize data to a RocketMQ instance, only Hash is supported. Hash indicates that the data transmission service uses a hash algorithm to select a message queue of RocketMQ based on the value of the primary key or sharding column.
   Business System Identification (Optional)	Identifies the source business system of data. The business system identifier consists of 1 to 20 characters.
   Enter the name of the producer group	Specifies a producer group that can write data into multiple topics.
   Whether to Allow Message Tracing	Specifies whether to allow message tracing. If message tracing is enabled, you can trace the complete project information, including node time and status, of a message in its entire lifecycle from transmission to the RocketMQ server by the producer to consumption by consumers. The message tracing feature provides data support for troubleshooting in the production environment.

7. Click Precheck.

   During the precheck, the data transmission service detects the connection with the destination data source. You can perform the following operations if an error is returned during the precheck:

   • Identify and troubleshoot the problem and then perform the precheck again.

   • Click Skip in the Actions column of the failed precheck item. A dialog box appears, prompting you about the impact. If you want to skip this operation, click OK.

8. After the precheck is passed, click Start Project.

   If you do not need to start the project now, click Save. You can manually start the project on the Synchronization Projects page or by performing batch operations later. For more information about the batch operations, see Perform batch operations on data synchronization projects.

   The data transmission service allows you to modify the synchronization objects when a synchronization project is running. For more information, see View and modify synchronization objects. After the data synchronization project is started, it will be executed based on the selected synchronization types. For more information, see View synchronization details.

If the data synchronization project encounters a running exception due to a network failure or slow startup of processes, you can click Recover on the Synchronization Projects page or on the Details page of the synchronization project.

References

• Create an OceanBase data source

• Create a RocketMQ data source

• Perform batch operations on data synchronization projects

• View the details of a data synchronization project