Create a project to synchronize data from an OceanBase database 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) 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.

Prerequisites

A topic with the partition-ordered messages property is created in your RocketMQ instance.

Limits

• Only physical tables can be synchronized.

• During data synchronization, OMS allows you to delete a table and then create a new one. In other words, you can first perform the drop table a operation and then the create table a_tmp operation without affecting the project. OMS does not allow you to create a table by renaming an existing table. After you perform the rename table a to a_tmp operation, the project cannot be carried out.

• When data transfer is resumed on a link, some data (within the last minute) may be duplicated in the DataHub instance, and deduplication is required in downstream applications.

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

Procedure

1. Create a data synchronization project.

   1. Log on to the OMS console.

   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 Chinese characters, digits, and letters. It must not contain any spaces and cannot exceed 64 characters in length.
   Label	Click the field and select the target tag from the drop-down list. You can 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 a physical OceanBase data source, select it from the drop-down list. If you have not created a data source, click Create Data Source in the drop-down list and create a data source in the dialog box that appears on the right. For more information, see Create a physical OceanBase data source.
   Destination	If you have created a RocketMQ data source, select it from the drop-down list. If you have not created a data source, click Create Data Source in the drop-down list and create a data source in the dialog box that appears on the right. For more information, see Create a RocketMQ data source.

3. Click Next. On the Select Synchronization Type page, specify Synchronization Type and Configuration for the current data synchronization project.

   Synchronization Type and Configuration supports only DML Synchronization in Incremental Synchronization. The DML operations for synchronization are Insert, Delete, and Update.

4. (Optional) Click Next.

   If the source database is an OceanBase database, you must configure the obconfig_url parameter, 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, see Create a physical OceanBase data source.

   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 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.

      When you synchronize data from an OceanBase database to a RocketMQ instance, OMS 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	Steps
      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	In the list on the right, move the pointer over the object that you want to change. Click Change Topic. In the Map Object to Topic dialog box, change the topics to be synchronized. Click OK. Notice The selected topics and tables will be merged into the selected topic. Proceed with caution.
      Settings	You can execute the WHERE clause in OMS to implement row filters and select sharding columns and columns to synchronize. In the list on the right, move the pointer over the object that you want to change. 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. The setting takes effect for both full synchronization and incremental synchronization. Only the data meeting the WHERE condition is synchronized to the destination data source, thereby filtering data by row. If the statement contains a reserved SQL keyword, add an escape character (`). 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 fields with unique identifiers and whose load is balanced as sharding columns. Ensure that the selected sharding columns are correct. An incorrect sharding column will cause data synchronization to fail. 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. If you select all or no columns, OMS will synchronize all columns. Click OK.
      Remove/Remove All	OMS allows you to remove one or more objects from the destination database during data mapping. Remove a single synchronization object In the list on the right of the selection section, hover 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 the 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 archived logs. Generally, you can start data synchronization from the current timestamp.
   Serialization Method	The message format for synchronizing data to a RocketMQ instance. Valid values: Default, Canal, Dataworks (version 2.0 supported), SharePlex, and DefaultExtendColumnType. For more information, see Data formats.
   Enable Intra-Transaction Sequence	Specifies whether to maintain order within a transaction. If this feature is enabled, OMS marks the sequence number for a transaction to be sent to a downstream node. Notice This parameter is valid only for the SharePlex format and is intended for you to obtain the sequence numbers of the DML statements that form a transaction. For example, if a transaction contains 10 DML statements numbered from 1 to 10, OMS will deliver these statements to the destination database in the same order. If this option is enabled, the system performance may be affected. Choose whether to enable it based on the business characteristics.
   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	This parameter specifies whether to allow message tracing. If message tracing is enabled, you can trace the entire link information of a message in the procedure from sending the message to the RocketMQ server to message consumption, including node time and status. The message tracing feature provides data support for troubleshooting in the production environment.

7. Click Precheck.

   During the precheck, OMS detects the connection with the destination data source. If an error is returned:

   • You can troubleshoot the error and run the precheck again.

   • You can also click Skip in the Actions column of the precheck item that returns the error. Then, a dialog box appears, indicating the impact that may be caused if you choose to skip this check item. If you want to continue, click OK in the dialog box.

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 allows you to modify synchronization objects when a data synchronization project is running. 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 data access fails due to a network failure or the slow startup of processes, go to the project list or the project details page and click Restore.