Configuring a Job for Synchronizing Data from DMS for Kafka to OBS

Supported Source and Destination Database Versions

Database Account Permissions

Before you use DataArts Migration for data synchronization, ensure that the source and destination database accounts meet the requirements in the following table. The required account permissions vary depending on the synchronization task type.

Supported Synchronization Objects

The following table lists the objects that can be synchronized using different links in DataArts Migration.

Important Notes

In addition to the constraints on supported data sources and versions, connection account permissions, and synchronization objects, you also need to pay attention to the notes in the following table.

Procedure

This section uses real-time synchronization from DMS for Kafka to OBS as an example to describe how to configure a real-time data migration job. Before that, ensure that you have read the instructions described in Check Before Use and completed all the preparations.

1. Create a real-time migration job by following the instructions in Creating a Real-Time Migration Job and go to the job configuration page.
2. Select the data connection type. Select DMS Kafka for Source and OBS for Destination.
   Figure 1 Selecting the data connection type
   

3. Select a job type. The default migration type is Real-time. The migration scenarios include Single table and Entire DB.
   Figure 2 Setting the migration job type
   
   

   For details about synchronization scenarios, see Synchronization Scenarios.

4. Configure network resources. Select the created DMS for Kafka and OBS data connections and the migration resource group for which the network connection has been configured.
   Figure 3 Selecting data connections and a migration resource group
   
   

   If no data connection is available, click Create to go to the Manage Data Connections page of the Management Center console and click Create Data Connection to create a connection. For details, see Configuring DataArts Studio Data Connection Parameters.

5. Configure source parameters.
   • Select the Kafka topics to be synchronized in different migration scenarios based on the following table.

     Table 5 Selecting the Kafka topics to be synchronized

     Synchronization Scenario	Configuration Method
     Single table	Enter a Kafka topic to be migrated. Figure 4 Entering a Kafka topic
     Entire DB	Select the Kafka topics to be migrated. Figure 5 Selecting Kafka topics

   • Data Format
     Format of the message content in the source Kafka topic. DataArts Migration can process the following types of messages:

     • JSON: Messages can be parsed in JSON format.
     • CSV: Messages can be parsed using specified separators in CSV format.
     • TEXT: The entire message is synchronized as text.
   • Consumer Group ID

     A consumer subscribes to a topic. A consumer group consists of one or more consumers. DataArts Migration allows you to specify the Kafka consumer group to which a consumption action belongs.

   • Source Kafka Attributes

     You can set Kafka attributes and add the properties. prefix. The job will automatically remove the prefix and transfer the attributes to the Kafka client. For details about the parameters, see the configuration descriptions in the Kafka documentation.

6. Configure destination parameters.
   Figure 6 Configuring destination OBS parameters
   
   • File Storage Format

     Format of the files to be written to OBS. Parquet, SequenceFile, and TextFile are supported.

   • File Compression Mode
     Compression mode of the data to be written to OBS files. By default, data is not compressed. The following compression modes are supported:

     • Parquet format: UNCOMPRESSED or SNAPPY
     • SequenceFile format: UNCOMPRESSED, SNAPPY, GZIP, LZ4, or BZIP2.
     • TextFile format: UNCOMPRESSED
   • OBS Path

     Path for storing OBS files. You can enter the #{source_Topic_name} built-in variable so that topics at the source can be written to different paths. An example path is obs://bucket/dir/test.db/prefix_#{source_Topic_name}_suffix/.

   • Global Advanced Settings
     You can configure the parameters in the following table to enable some advanced functions.

     Table 6 OBS advanced parameters

     Parameter	Type	Default Value	Unit	Description
     auto-compaction	boolean	false	N/A	Whether to compact merge files. Data is written to a temporary file first. This parameter specifies whether to compact the generated temporary files after the checkpoint is complete. Enabling this function reduces the number of small files in some scenarios, but greatly slows down the synchronization.

7. Refresh the mapping between the source table and destination table. Click Edit Destination Field to check the fields to be written to the destination and configure partition fields as needed.
   Figure 7 Mapping between source and destination tables
   
   • Partition Field

     After you configure partition fields, a partition directory is automatically generated when data is written to OBS. The directory name is in Partition field=Partition value format. In addition, the field selection sequence affects the partition level. For example, if par1 and par2 are selected as partition fields, par1 is a level-1 partition and par2 is a level-2 partition. A maximum of five levels of partitions are supported.

   • Edit Destination Field
     DataArts Migration automatically parses source messages based on the selected source message format and generates corresponding fields. You can customize the names, types, and values of the fields.

     • Field Name: name of the field to be written to the destination OBS file. The name must contain at least one letter and can contain underscores (_) and hyphens (-), but cannot contain only digits.
     • Field Type: type of the field to be written to the destination OBS file. The following types are supported: STRING, BOOLEAN, INTEGER, LONG, FLOAT, DOUBLE, SHORT, DECIMAL, DATE, and TIMESTAMP.
     • Field Value: value source of the field to be written to the destination OBS file

       Table 7 Destination field value obtaining mode

       Type	Value
       Manually assigned value	Any character
       Built-in variable	Kafka metadata, including six fields: __key__, __value__, __Topic__, __partition__, __offset__, and __timestamp__.
       Source table field	Any field parsed from the source Kafka topic message NOTE: If the source Kafka message is in nested JSON format, this link can parse field values at different levels (including arrays whose subscript indexes start from 1). The following is an example of the JSON content: { "col1": "1", "col2": "2", "level1": { "level2": [ { "level3": "test" } ] } } You can obtain test using level1.level2[1].level3 and use it as the value of a field at the destination.
       UDF	Flink built-in function used to transform data. The following are examples: CONCAT(CAST(NOW() as STRING), `col_name`) DATE_FORMAT(NOW(), 'yy') Note that the field name must be enclosed in backquotes. For details about the built-in functions of Flink, see the official Flink documentation.

8. Configure task parameters.

   Table 8 Task parameters

   Parameter	Description	Default Value
   Execution Memory	Memory allocated for job execution, which automatically changes with the number of CPU cores	8GB
   CPU Cores	Value range: 2 to 32 For each CPU core added, 4 GB execution memory and one concurrency are automatically added.	2
   Maximum Concurrent Requests	Maximum number of jobs that can be concurrently executed. This parameter does not need to be configured and automatically changes with the number of CPU cores.	1
   Adding custom attributes	You can add custom attributes to modify some job parameters and enable some advanced functions. For details, see Job Performance Optimization.	N/A

9. Submit and run the job.

   After configuring the job, click Submit in the upper left corner to submit the job.

   Figure 8 Submitting the job
   

   After submitting the job, click Start on the job development page. In the displayed dialog box, set required parameters and click OK.

   Figure 9 Starting the job
   

   Table 9 Parameters for starting the job

   Parameter	Description
   Offset Parameter	Earliest: Data consumption starts from the earliest offset of the Kafka topic. Latest: Data consumption starts from the latest offset of the Kafka topic. Start/End time: Data consumption starts from the offset of the Kafka topic obtained based on the time.
   Time	This parameter is required if Offset is set to Start/End time. It specifies the start time of synchronization. NOTE: If you set a time earlier than the earliest offset of Kafka messages, data consumption starts from the earliest offset by default.

10. Monitor the job.

    On the job development page, click Monitor to go to the Job Monitoring page. You can view the status and log of the job, and configure alarm rules for the job. For details, see Real-Time Migration Job O&M.

    Figure 10 Monitoring the job
    

Performance Optimization

If the synchronization speed is too slow, rectify the fault by referring to Job Performance Optimization.