Create a project to synchronize data from OceanBase Database Community Edition to a RocketMQ instance

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 feature of OceanBase Migration Service (OMS) Community Edition allows you to synchronize data between a physical table in OceanBase Database Community Edition and a RocketMQ data source in real time, extending the message processing capability.

For more information about the data formats for OceanBase Database Community Edition, see Data formats.

Prerequisites

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

Limitations

• OMS Community Edition supports instances of RocketMQ V4.x or V5.x, including RocketMQ Enterprise Edition and RocketMQ Community Edition.

• Only physical tables can be synchronized.

• During data synchronization, OMS Community Edition allows you to drop a table and then create a new one. In other words, you can first execute the DROP TABLE statement and then the CREATE TABLE statement. In OMS, you cannot create a new table by renaming a table. That is, 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 source identifiers and user accounts must be globally unique in OMS Community Edition.

• OMS Community Edition supports the synchronization of only objects whose database name, table name, and column name are ASCII-encoded without special characters. The special characters are line breaks and | " ' ` ( ) = ; / &

• The source cannot be a standby OceanBase database.

Considerations

• 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 duplicated 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.

Procedure

1. Create a data synchronization project.

   1. Log on to the console of OMS Community Edition.

   2. In the left-side navigation pane, click Data Synchronization.

   3. On the Data Synchronization page, click Create Synchronization Project in the upper-right corner.

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

   Parameter	Description
   Synchronization 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.
   Tag	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-CE 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 parameters, see Create a data source of OceanBase Database Community Edition.
   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.

3. Click Next. On the Select Synchronization Type page, select 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.

4. (Optional) Click Next.

   To synchronize data from OceanBase Database Community Edition, you must specify OCP (Optional), Username, and Password for incremental synchronization.

   If you have selected Incremental Synchronization without configuring the required parameters for the source database, the More About Data Sources dialog box appears to prompt you to configure the parameters. For more information about parameters, see Create a data source of OceanBase Database Community Edition.

   After you configure the parameters, click Test Connectivity. After the test succeeds, click Save.

5. Click Next. On the Select Synchronization Objects page, select a synchronization scope.

   When you synchronize data from OceanBase Database Community Edition to a RocketMQ instance, you can synchronize data from multiple tables 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.

      When you synchronize data from OceanBase Database Community Edition to a RocketMQ instance, OMS Community Edition allows you to import objects from text and perform the following operations on the objects in the destination database: change topics, set row filtering conditions, 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. Notice 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 rename databases/tables and set row filtering conditions. For more information, see Download and import the settings of synchronization objects. Click Validate. After the validation succeeds, click OK.
      Change Topic	OMS Community Edition allows you to change topics for objects in the destination. For more information, see Change topics.
      Settings	OMS Community Edition allows you to configure row-based filtering, select sharding columns, and select columns to be synchronized. In the list on the right, move the pointer over the object that you want to set. Click Settings. 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: OMS 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. Click OK.
      Remove/Remove All	During data mapping, OMS allows you to remove one or more selected objects to be migrated to the destination. Remove a single synchronization object In the list on the right of the selection section, move the pointer over the target object, and click Remove. The synchronization object is removed. Remove all synchronization objects In the list on the right of the selection section, 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, specify the following parameters.

   Parameter	Description
   Incremental Synchronization Start Timestamp	This parameter specifies to synchronize data after the synchronization start timestamp. The default value is the current system time. You can select a point in time or enter a timestamp. Notice You can select the current time or a point in time earlier than the current time. This parameter is closely related to the retention period of archive logs. Generally, you can start data synchronization from the current timestamp.
   Serialization Method	The message format for synchronizing data to the RocketMQ instance. Valid values: Default, Canal, Dataworks (V2.0), SharePlex, DefaultExtendColumnType, Debezium, DebeziumFlatten, and DebeziumSmt. For more information, see Data formats. Notice At present, 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 OMS uses a hash algorithm to select the message queue (MQ) for 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	This parameter 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, OMS Community Edition detects the connection with the destination data source. If an error is returned during the precheck:

   • You can identify and troubleshoot the problem and then perform the precheck again.

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

8. Click Start Project. If you do not need to start the project now, click Save to go to the details page of the data synchronization project. You can start the project later as needed.

   OMS Community Edition allows you to modify the synchronization objects during a synchronization project. For more information, see View and modify synchronization objects. After a data synchronization project is started, the synchronization objects will be executed based on the selected synchronization type. For more information, see the "View synchronization details" section in the View details of a data synchronization project topic.

   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.