Data Transmission Service:Synchronize data from an ApsaraDB RDS for MySQL instance to a Tablestore instance

Precautions

• During initial full data synchronization, DTS consumes the read and write resources of the source and destination databases. This may increase the loads of the database servers. Before you synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours.

• DTS does not synchronize data definition language (DDL) operations. If a DDL operation is performed on a table in the source database during data synchronization, you must perform the following steps: Remove the table from the selected objects, remove the table from the Tablestore instance, and then add the table to the selected objects again. For more information see Remove an object from a data synchronization task and Add an object to a data synchronization task.

• You can synchronize up to 64 tables to the Tablestore instance. If you want to synchronize more than 64 tables to the Tablestore instance, you can disable the limit for the destination Tablestore instance.

• The names of the tables and columns to be synchronized must comply with the naming conventions of the Tablestore instance.

  • The name of a table or an index can contain letters, digits, and underscores (_). The name must start with a letter or underscore (_).

  • The name of a table or an index must be 1 to 255 characters in length.

Billing

Initial synchronization types

Before you begin

1. Create a RAM user and grant the AliyunOTSFullAccess permission on Tablestore to the RAM user.

   1. Log on to the RAM console.

   2. Create a RAM user.

   3. In the left-side navigation pane, choose Identities > Users.

   4. On the Users page, find the RAM user and click Add Permissions in the Actions column.

      

   5. In the dialog box that appears, enter AliyunOTSFullAccess in the search box, and click the policy name to add the policy to the Selected section.

      

   6. Click OK.

   7. Click Complete.

2. Create an AccessKey pair for the RAM user. For more information, see Create an AccessKey pair.

3. Optional:If you need to configure a data synchronization task as a RAM user, you must grant the AliyunDTSDefaultRole permission to the RAM user. For more information, see Authorize DTS to access Alibaba Cloud resources.

   Note

   If you use an Alibaba Cloud account to configure a data synchronization task, skip this step.

Procedure

1. Purchase a data synchronization instance. For more information, see Purchase a DTS instance.

   Note

   On the buy page, set Source Instance to MySQL, set Destination Instance to Tablestore, and set Synchronization Topology to One-way Synchronization.

2. Log on to the Data Transmission Service (DTS) console.

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

4. In the upper part of the Data Synchronization Tasks page, select the region in which the destination instance resides.

5. Find the data synchronization task and click Configure Task in the Actions column.

6. Configure the source and destination databases.

   

   Section	Parameter	Description
   N/A	Synchronization Task Name	The task name that DTS automatically generates. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to use a unique task name.
   Source Instance Details	Instance Type	Select RDS Instance.
   	Instance Region	The source region that you selected on the buy page. The value of this parameter cannot be changed.
   	Instance ID	The ID of the source ApsaraDB RDS for MySQL instance.
   	Database Account	The database account of the source ApsaraDB RDS instance. The account must have the SELECT permission on the objects to be synchronized and the REPLICATION CLIENT, REPLICATION SLAVE permission, and SHOW VIEW permissions. Note If the database engine of the source ApsaraDB RDS instance is MySQL 5.5 or MySQL 5.6, you do not need to configure the Database Account or Database Password parameter.
   	Database Password	The password of the database account.
   	Encryption	Select Non-encrypted or SSL-encrypted. If you want to select SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS instance before you configure the data synchronization task. For more information, see Use a cloud certificate to enable SSL encryption. Important The Encryption parameter is available only within regions in the Chinese mainland and the China (Hong Kong) region.
   Destination Instance Details	Instance Type	Select Tablestore.
   	Instance Region	The destination region that you selected on the buy page. The value of this parameter cannot be changed.
   	Instance ID	The ID of the destination Tablestore instance.
   	AccessKeyId	The AccessKey ID. For more information, see Create an AccessKey pair.
   	AccessKeySecrect	The AccessKey secret.

7. In the lower-right corner of the page, click Set Whitelist and Next.

   If the source or destination database is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB instance, DTS automatically adds the CIDR blocks of DTS servers to the IP address whitelist of the instance. If the source or destination database is a self-managed database hosted on an Elastic Compute Service (ECS) instance, DTS automatically adds the CIDR blocks of DTS servers to the security group rules of the ECS instance, and you must make sure that the ECS instance can access the database. If the self-managed database is hosted on multiple ECS instances, you must manually add the CIDR blocks of DTS servers to the security group rules of each ECS instance. If the source or destination database is a self-managed database that is deployed in a data center or provided by a third-party cloud service provider, you must manually add the CIDR blocks of DTS servers to the IP address whitelist of the database to allow DTS to access the database. For more information, see Add the CIDR blocks of DTS servers.

   Warning

   If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of the database or instance, or to the ECS security group rules, security risks may arise. Therefore, before you use DTS to synchronize data, you must understand and acknowledge the potential risks and take preventive measures, including but not limited to the following measures: enhancing the security of your username and password, limiting the ports that are exposed, authenticating API calls, regularly checking the whitelist or ECS security group rules and forbidding unauthorized CIDR blocks, or connecting the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

8. Configure the synchronization policy and the objects to be synchronized.

   1. Configure the synchronization policy.

      

      Parameter	Description
      Initial Synchronization	Select Initial Schema Synchronization, Initial Full Data Synchronization, and Initial Incremental Data Synchronization. For more information, see Initial synchronization types.
      Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the destination database does not contain tables that have the same names as those in the source database, the precheck is passed. Otherwise, an error is returned during precheck and the data synchronization task cannot be started. Note You can use the object name mapping feature to rename the tables that are synchronized to the destination database. You can use this feature if the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed. For more information, see Rename an object to be synchronized. Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases. Warning If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to potential risks. During initial data synchronization, DTS does not synchronize the data records that have the same primary keys as the data records in the destination database. This occurs if the source and destination databases have the same schema. However, DTS synchronizes these data records during incremental data synchronization. If the source and destination databases have different schemas, initial data migration may fail. In this case, only specific columns are migrated, or the data migration task fails.
      Merge Tables	Yes: In online transaction processing (OLTP) scenarios, sharding is implemented to speed up the response to business tables. You can merge multiple source tables that have the same schema into a single destination table. This feature allows you to synchronize data from multiple tables in the source database to a single table in the Tablestore instance. Note DTS adds a column named __dts_data_source to the destination table in the Tablestore instance. This column is used to record the data source. The data type of this column is VARCHAR. DTS specifies the column values based on the following format: <Data synchronization instance ID>:<Source database name>.<Source table name>. Such column values allow DTS to identify each source table. For example, dts********:dtstestdata.customer1 indicates that the source table is customer1. If you set this parameter to Yes, all selected source tables in the task are merged into the destination table. If you do not need to merge specific source tables, you can create a separate data synchronization task for these tables. No: the default value.
      Operation Types	The types of operations that you want to synchronize based on your business requirements. All operation types are selected by default.
      Processing Policy of Dirty Data	The processing policy for handling data write errors: Skip Block
      Data Write Mode	Update Row: The PutRowChange operation is performed to update rows in the Tablestore instance. Overwrite Row: The UpdateRowChange operation is performed to overwrite rows in the Tablestore instance.
      Batch Write Operation	The operation used to write multiple rows of data to the Tablestore instance. BulkImportRequest: Data is written offline. BatchWriteRowRequest: Data is written in batches. To achieve higher read and write efficiency and reduce your costs of using the Tablestore instance, we recommend that you select BulkImportRequest.
      More
      └ Queue Size	The length of the queue for writing data to the Tablestore instance.
      └ Thread Quantity	The number of callback threads for writing data to the Tablestore instance.
      └ Concurrency	The maximum number of concurrent threads for the Tablestore instance.
      └ Buckets	The number of concurrent buckets for incremental and sequential writes. To improve the concurrent write capability, you can set this parameter to a relatively larger value. Note The value must be less than or equal to the maximum number of concurrent threads.

   2. Select the objects to be synchronized.

      

      Setting

      Description

      Select the objects to be synchronized

      Select one or more tables from the Available section and click the icon to add the tables to the Selected section. Up to 64 tables can be selected. By default, after an object is synchronized to the destination instance, the name of the object remains unchanged. You can use the object name mapping feature to rename the objects that are synchronized to the destination instance. For more information, see Rename an object to be synchronized. Warning If you set Merge Tables to Yes in Step 8 and select multiple source tables, you must use the object name mapping feature to change their names to the same table name in the Tablestore instance. Otherwise, data inconsistency may occur.

   3. Click Next.

9. Optional:In the Selected section, move the pointer over a table, and then click Edit. In the Edit Table dialog box, set the data type of each column in the Tablestore instance.

   

10. Configure the primary key columns of the tables that you want to synchronize to the Tablestore instance.

    

    Note

    For more information about primary keys of Tablestore instances, see Primary keys.

11. In the lower-right corner of the page, click Next: Precheck and Start Task.

    Note

    • Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.

    • If the task fails to pass the precheck, you can click the icon next to each failed item to view details. After you troubleshoot the issues based on the causes, run a precheck again.

12. Close the Precheck dialog box after the following message is displayed: Precheck Passed. Then, the data synchronization task starts.

13. Wait until the initial synchronization is complete and the data synchronization task enters the Synchronizing state.

    You can view the status of the data synchronization task on the Data Synchronization Tasks page.