Synchronize data from 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) allows you to synchronize data between an OceanBase physical table and a RocketMQ data source in real time, extending the message processing capability. This topic describes how to synchronize data from OceanBase Database to a RocketMQ instance.

For more information about the data formats for the two types of tenants, see Data formats.

Prerequisites

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

• OMS supports RocketMQ instances of versions 4.x and 5.x, including commercial and community editions.

• Only physical tables can be synchronized.

• During data synchronization, OMS allows you to drop a table before creating a new one. In other words, you can execute DROP TABLE and then execute CREATE TABLE. In OMS, you cannot 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.

• Data source identifiers and user accounts must be globally unique in OMS.

• OMS supports the synchronization of only objects whose database name, table name, and column name are ASCII-encoded and do not contain special characters. The special characters are line breaks, spaces, and the following characters: . | " ' ` ( ) = ; / & \.

• OMS does not support a standby OceanBase database as the source.

Considerations

• During incremental synchronization from OceanBase Database V4.x, if the STORED attribute is not marked for a generated column, the column value synchronized to the target database is NULL. As a result, the data of this column received by the downstream system is not as expected.

• 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 data transmission is resumed for a task, some data (transmitted within the last minute) may be duplicated in the RocketMQ instance. Therefore, 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.

• If you select only Incremental Synchronization when you create a data synchronization task, OMS requires that the local incremental logs in the source database be retained for more than 48 hours.

  ​If you select Full Synchronization and Incremental Synchronization when you create the data synchronization task, OMS requires that the local incremental logs of the source database be retained for at least seven days. Otherwise, the data synchronization task may fail or the data in the source and target databases may be inconsistent because OMS cannot obtain incremental logs.

Procedure

1. Create a data synchronization task.

   

   1. Log in to the OMS console.

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

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

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

   Parameter	Description
   Task 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.
   Source	If you have created an OceanBase data source, which can be a physical data source or an ApsaraDB for OceanBase data source, select it from the drop-down list. Otherwise, click New Data Source in the drop-down list and create one in the dialog box that appears on the right. For more information about the parameters, see Create a physical OceanBase data source or Create an ApsaraDB for OceanBase data source.
   Target	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 and create one in the dialog box that appears on the right. For more information, see Create a RocketMQ data source.
   Tag	Click the field and select a tag from the drop-down list. This parameter is optional. You can also click Manage Tags to create, modify, and delete tags. For more information, see Use tags to manage data synchronization tasks.

3. Click Next. On the Select Synchronization Type page, specify the synchronization types for the current data synchronization task.

   

   The supported synchronization types are Full Synchronization and Incremental Synchronization. Incremental Synchronization supports only the DML Synchronization option. The supported DML operations are INSERT, DELETE, and UPDATE. Select the options based on your business needs. For more information, see Configure DDL/DML synchronization.

4. (Optional) Click Next.

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

   After you configure the parameters, click Test Connection. After the test succeeds, click OK.

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

   You can select Specify Objects or Match Rules to specify the synchronization objects. The following procedure describes how to specify synchronization objects by using the Specify Objects option. For information about the procedure for specifying synchronization objects by using the Match Rules option, see the Configure matching rules for data migration/synchronization from a database to a Message Queue instance section in the Configure matching rules topic.

   Note

   If you have selected DDL Synchronization in the Select Synchronization Type step, we recommend that you select Match Rules to specify synchronization objects. This way, all new objects that meet the specified rules will be synchronized. If you select Specify Objects to specify synchronization objects, new or renamed objects will not be synchronized.

   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 Select Synchronization Objects section, select Specify Objects.

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

   3. Click >.

      

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

      

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

   5. Click OK.

      Note

      OMS automatically filters out unsupported tables. For information about the SQL statements for querying table objects, see SQL statements for querying table objects.

   OMS allows you to import objects from text files, change the topics of the objects, set row-based filtering, or remove a single object or all objects. Objects in the target database are listed in the structure of Topic > Database > Table.

   Note

   When you select Match Rules to specify synchronization objects, object renaming is implemented based on the syntax of the specified matching rules. In the operation area, you can only set filter conditions and select sharding columns and the columns to be synchronized. For more information, see Configure matching rules.

   

   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 filter conditions. For more information, see Download and import the settings of synchronization objects. Click Validate. After the validation succeeds, click OK.
   Change topics	OMS allows you to change the topic for objects in the target database. For more information, see Change the topic.
   Configure settings	OMS 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 key 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 target 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 one or all objects	OMS allows you to remove a single object or all objects to be synchronized to the target database 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 following parameters.

   • Full synchronization

     The following parameters are displayed only if you have selected Full Synchronization on the Select Synchronization Type page.

     

     Parameter	Description
     Full Synchronization Rate Limit	You can choose whether to limit the full synchronization rate as needed. If you choose to limit the full synchronization rate, you must specify the records per second (RPS) and bytes per second (BPS). The RPS specifies the maximum number of data rows synchronized to the target database per second during full synchronization, and the BPS specifies the maximum amount of data in bytes synchronized to the target database per second during full synchronization. Note The RPS and BPS values specified here are only for throttling. The actual full synchronization performance is subject to factors such as the settings of the source and target databases and the instance specifications.
     Full Synchronization Resource Configuration	You can select Small, Medium, or Large to use the corresponding default values of Read Concurrency, Write Concurrency, and Memory. You can also customize the resource configurations for full synchronization. By setting the resource configuration for the Full-Import component, you can limit the resource consumption of a task in the full synchronization phase. Notice In the case of custom configurations, the minimum value is 1, and only integers are supported.

   • Incremental synchronization

     The following parameters are displayed only if you have selected Incremental Synchronization on the Select Synchronization Type page.

     

     Parameter	Description
     Incremental Synchronization Rate Limit	You can choose whether to limit the incremental synchronization rate as needed. If you choose to limit the incremental synchronization rate, you must specify the RPS and BPS. The RPS specifies the maximum number of data rows synchronized to the target database per second during incremental synchronization, and the BPS specifies the maximum amount of data in bytes synchronized to the target database per second during incremental synchronization. Note The RPS and BPS values specified here are only for throttling. The actual incremental synchronization performance is subject to factors such as the settings of the source and target databases and the instance specifications.
     Incremental Log Pull Resource Configuration	You can select Small, Medium, or Large to use the corresponding default value of Memory. You can also customize the resource configurations for incremental log pull. By setting the resource configuration for the Store component, you can limit the resource consumption of a task in log pull in the incremental synchronization phase. Notice In the case of custom configurations, the minimum value is 1, and only integers are supported.
     Incremental Data Write Resource Configuration	You can select Small, Medium, or Large to use the corresponding default values of Write Concurrency and Memory. You can also customize the resource configurations for incremental data write. By setting the resource configuration for the Incr-Sync component, you can limit the resource consumption of a task in data writes in the incremental synchronization phase. Notice In the case of custom configurations, the minimum value is 1, and only integers are supported.
     Incremental Record Retention Time	The duration that incremental parsed files are cached in OMS. A longer retention period results in more disk space occupied by the Store component.
     Incremental Synchronization Start Timestamp	If you have selected Full Synchronization as the synchronization type, the default value of this parameter is the task startup time and cannot be modified. If you did not select 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.

   • Advanced options

     

     Parameter	Description
     Serialization Method	The message format for synchronizing data to a RocketMQ instance. Valid values: Default, Canal, Dataworks (version 2.0 supported), SharePlex, DefaultExtendColumnType, Debezium, DebeziumFlatten, and DebeziumSmt. For more information, see Data formats. Notice At present, only MySQL-compatible tenants of OceanBase Database support Debezium, DebeziumFlatten, and DebeziumSmt.
     Partitioning Rules	The rule for synchronizing data from the source database to a RocketMQ instance. At present, it can be set only to Hash. 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. This parameter is displayed only when Serialization Method is set to Dataworks. The business system identifier consists of 1 to 20 characters.

   • Target

     

     Parameter	Description
     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 task information, including the 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.

   If the parameter settings on the page cannot meet your requirements, you can click Parameter Configuration in the lower part of the page to configure more specific settings. You can also reference an existing task or component template.

   

7. Click Precheck.

   During the precheck, OMS detects the connection with the target data source. If an error is returned during the precheck, you can perform the following operations:

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

   • Click Skip in the Actions column of a failed precheck item. In the dialog box that prompts the consequences of the operation, click OK.

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

   OMS allows you to modify the synchronization objects when the data synchronization task is running. For more information, see View and modify synchronization objects. After the data synchronization task is started, it will be executed based on the selected synchronization types. For more information, see the View synchronization details section in the View details of a data synchronization task topic.

   If the data synchronization task encounters an execution exception due to a network failure or slow startup of processes, you can click Recover on the Synchronization Tasks or Details page of the synchronization task.