Data Transmission Service:Synchronize data from an ApsaraDB for MongoDB instance to a Lindorm instance

Prerequisites

• An ApsaraDB for MongoDB instance that resides in the Germany (Frankfurt) region is created.

• The ApsaraDB for MongoDB instance is deployed in the replica set or sharded cluster architecture.

  Important

  If the source instance is an ApsaraDB for MongoDB sharded cluster instance, endpoints are assigned to the shard nodes and the shard nodes share the same account and password. For more information, see Apply for an endpoint for a shard node or the ConfigServer node in a sharded cluster instance.

• A Lindorm instance is created, whose available storage space is larger than the total size of the data in the source ApsaraDB for MongoDB instance. The wide table engine is used for the Lindorm instance. For more information, see Create an instance.

  Note

  The available storage space of the destination instance is 10% larger than the total size of data in the source instance. This is a recommended prerequisite.

• A wide table is created in the Lindorm instance. For more information, see Use Lindorm-cli to connect to and use LindormTable and Use Lindorm Shell to connect to LindormTable.

  Note

  If the wide table is created by calling the Apache HBase API, we recommend that you create column mappings. For more information, see the Example of adding column mappings for a table created by calling the Apache HBase API section of this topic.

Usage notes

Billing

Synchronization types

Permissions required for database accounts

Procedure

1. Go to the Data Synchronization Tasks page.

   1. Log on to the DMS console.

   2. In the top navigation bar, move the pointer over Data Development.

   3. Choose DTS (DTS) > Data Synchronization.

   Note

   • The actual operation may vary depending on the mode and layout of DMS. For more information, see Simple mode and Customize the layout and style of the DMS console.

   • You can also go to the Data Synchronization Tasks page of the new DTS console.

2. On the right side of Data Synchronization Tasks, select the region in which the data synchronization instance resides.

   Note

   If you use the new DTS console, select the region in which you want to create the data synchronization task in the top navigation bar.

3. Click Create Task. On the Create Task page, configure the source and destination databases. The following table describes the parameters.

   Section	Parameter	Description
   N/A	Task Name	The name of the DTS task. DTS automatically generates a task name. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.
   Source Database	Select an existing DMS database instance. (Optional. If you have not registered a DMS database instance, ignore this option and configure database settings in the section below.)	The database instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the database. If you do not select an existing instance, you must configure the following database information.
   	Database Type	The type of the source database. Select MongoDB.
   	Access Method	The access method of the source database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the source ApsaraDB for MongoDB instance resides.
   	Replicate Data Across Alibaba Cloud Accounts	Specifies whether data is synchronized across Alibaba Cloud accounts. In this example, No is selected.
   	Architecture	The architecture in which the source instance is deployed. In this example, Replica Set is selected. Note If the source ApsaraDB for MongoDB instance is deployed in the Sharded Cluster architecture, you must configure the Shard account and Shard password parameters.
   	Instance ID	The ID of the source ApsaraDB for MongoDB instance.
   	Authentication Database	The name of the authentication database that stores database accounts and passwords of the source ApsaraDB for MongoDB instance. If you did not change the name before, the default value is admin.
   	Database Account	The database account of the source ApsaraDB for MongoDB instance. For more information about the required permissions, see the Permissions required for database accounts section of this topic.
   	Database Password	The password that is used to access the database instance.
   Destination Database	Select an existing DMS database instance. (Optional. If you have not registered a DMS database instance, ignore this option and configure database settings in the section below.)	The database instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the database. If you do not select an existing instance, you must configure the following database information.
   	Database Type	The type of the destination database. Select Lindorm.
   	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the destination Lindorm instance resides.
   	Instance ID	The ID of the destination Lindorm instance.
   	Database Account	The database account of the destination Lindorm instance. For more information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
   	Database Password	The password that is used to access the database instance.

4. In the lower part of the page, click Test Connectivity and Proceed.

   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 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 database is deployed 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 whitelist of the database to allow DTS to access the database. For more information, see the CIDR blocks of DTS servers section of the Add the CIDR blocks of DTS servers topic.

   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.

5. Configure the objects to be synchronized and the advanced settings.

   Parameter	Description
   Synchronization Types	By default, Incremental Data Synchronization is selected. You can select only Full Data Synchronization. You cannot select Schema Synchronization. After the precheck is complete, DTS synchronizes the historical data of the selected objects from the source database to the destination database. The historical data is the basis for subsequent incremental synchronization.
   Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains collections that have the same names as the collections in the source database. If the source and destination databases do not contain collections that have identical collection names, the precheck is passed. Otherwise, an error is returned during the precheck, and the data synchronization task cannot be started. Note If the source and destination databases have collections with identical names and the collections in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the collections that are synchronized to the destination database. For more information, see Rename an object to be synchronized. Ignore Errors and Proceed: skips the precheck for identical collection 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. If a data record in the destination database has the same primary key value or unique key value as a data record in the source database, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained. Data may fail to be initialized, only specific columns are synchronized, or the data synchronization task fails.
   Capitalization of Object Names in Destination Instance	The capitalization of database names and collection names in the destination instance. By default, DTS default policy is selected. You can select other options to ensure that the capitalization of object names is consistent with the default capitalization of object names in the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.
   Source Objects	Select one or more objects from the Source Objects section and click the icon to add the objects to the Selected Objects section. Note You can select collections as the objects to be synchronized.
   Selected Objects	If the wide table in the destination database is created by executing SQL statements, you must add additional columns to the wide table based on the objects to be synchronized from the source database. Columns that exist in the source database but are not added to the wide table are not synchronized to the destination database. Edit the database name. In the Selected Objects section, right-click the database that contains the collections to be synchronized. In the Edit Schema dialog box, enter the database name that you want to use in the Lindorm instance in the Schema Name field. Optional. Select the operations that you want to synchronize during incremental data synchronization in the Select DML Operations to Be Synchronized section. Click OK. Edit table names. In the Selected Objects section, right-click the collection that you want to synchronize. In the Edit Table Name dialog box, enter the table name that you want to use in the Lindorm instance in the Table Name field. Optional. You can specify conditions to filter data. For more information, see Specify filter conditions. Optional. Select the operations that you want to synchronize during incremental data synchronization in the Select DML Operations to Be Synchronized section. Specify the columns to be synchronized from the source ApsaraDB for MongoDB instance. In the Appended Column section, click + Add Column. Configure the Column Name parameter. Note Enter the column names that you want to use in the destination table in the Lindorm instance. If the destination table is created by executing SQL statements, specify these column names as the value of the Column Name parameter. If the destination table is created by calling the Apache HBase API and additional columns are required, you must create column mappings before you edit column names. For more information, see the Example of adding column mappings for a table created by calling the Apache HBase API section of this topic. Take note of the following rules when you specify the Column Name parameter: If a column is a primary key, specify ROW as the column name. If a column is not a primary key, specify the Column Name parameter in the Column family:Column name format. Example: person:name. Set the data type for each column. Optional. Set the data length and precision for each column. Enter bson_value() expressions in the Assign Value column. For more information, see the Example of value assignment section of this topic. Important You must specify the field and subfield of each column in the corresponding bson_value() expression based on the hierarchical relationship. Otherwise, data loss may occur or the task may fail. Repeat the preceding steps to map the columns of the source table onto the columns of the destination table. Click OK.

6. Click Next: Advanced Settings to configure advanced settings.

   Parameter	Description
   Dedicated Cluster for Task Scheduling	By default, DTS schedules tasks to shared clusters. You do not need to configure this parameter. If you want to improve the stability of data synchronization tasks, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.
   Set Alerts	Specifies whether to configure alerting for the data synchronization task. If the task fails or the synchronization latency exceeds the specified threshold, alert contacts will receive notifications. Valid values: No: does not enable alerting. Yes: configures alerting. In this case, you must also configure the alert threshold and alert notification settings. For more information, see the Configure monitoring and alerting when you create a DTS task section of the Configure monitoring and alerting topic.
   Retry Time for Failed Connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data synchronization task is started, DTS immediately retries a connection within the time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set this parameter to a value greater than 30. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails. Note If you specify different retry time ranges for multiple data synchronization tasks that have the same source or destination database, the shortest retry time range takes precedence. When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
   Retry Time for Other Issues	The retry time range for other issues. For example, if the DDL or DML operations fail to be performed after the data synchronization task is started, DTS immediately retries the operations within the time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set this parameter to a value greater than 10. If the failed operations are successfully performed within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails. Important The value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
   Enable Throttling for Full Data Migration	During full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the load on the database servers. You can configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters for full data synchronization tasks to reduce the load on the destination database server. Note This parameter is displayed only if Full Data Synchronization is selected for the Synchronization Types parameter.
   Enable Throttling for Incremental Data Synchronization	Specifies whether to enable throttling for incremental data synchronization. You can enable throttling for incremental data synchronization based on your business requirements. To configure throttling, you must configure the RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s) parameters. This reduces the load on the destination database server.
   Environment Tag	The environment tag that is used to identify the DTS instance. You can select an environment tag based on your business requirements. In this example, you do not need to configure this parameter.
   Configure ETL	Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: configures the ETL feature. You can enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: does not configure the ETL feature. Note If the destination table in the Lindorm instance is created by calling the Apache HBase API, take note of the following items: You must specify the columns to be synchronized and those not to be synchronized in the ETL script. By default, the top-level fields of the specified documents in the ETL task are stored in the f column family of the table created by calling the Apache HBase API during data synchronization. The following code shows how to write data rows of columns other than _id and name as dynamic columns to the destination table. For more information, see the Example of configuring an ETL task for a table created by calling the Apache HBase API section of this topic. script:e_expand_bson_value("*", "_id,name") If you want to add additional columns and use the ETL feature, make sure that the Lindorm instance does not contain duplicate data. DTS does not synchronize the additional columns or columns that are not contained in the ETL task to the destination database.

7. Save the task settings and run a precheck.

   • To view the parameters to be specified when you call the relevant API operation to configure the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.

   • If you do not need to view or have viewed the parameters, click Next: Save Task Settings and Precheck in the lower part of the page.

   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 data synchronization task fails the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, rerun the precheck.

   • If an alert is triggered for an item during the precheck:

     • If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issue. Then, run a precheck again.

     • If an alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.

8. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.

9. On the buy page, configure the Billing Method and Instance Class parameters for the data synchronization instance. The following table describes the parameters.

   Section	Parameter	Description
   New Instance Class	Billing Method	Subscription: You pay for a subscription when you create a data synchronization instance. The subscription billing method is more cost-effective than the pay-as-you-go billing method for long-term use. Pay-as-you-go: A pay-as-you-go instance is billed on an hourly basis. The pay-as-you-go billing method is suitable for short-term use. If you no longer require a pay-as-you-go data synchronization instance, you can release the instance to reduce costs.
   	Resource Group Settings	The resource group to which the data synchronization instance belongs. Default value: default resource group. For more information, see What is Resource Management?
   	Instance Class	DTS provides instance classes that vary in synchronization speed. You can select an instance class based on your business requirements. For more information, see Instance classes of data synchronization instances.
   	Subscription Duration	If you select the subscription billing method, specify the subscription duration and the number of data synchronization instances that you want to create. The subscription duration can be one to nine months, one year, two years, three years, or five years. Note This parameter is available only if you select the Subscription billing method.

10. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.

11. Click Buy and Start. In the dialog box that appears, click OK.

    You can view the progress of the task in the task list.

12. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.

Example of adding column mappings for a table created by calling the Apache HBase API

In this example, SQL Shell is used.

1. Create a column mapping for the table created by calling the Apache HBase API:

   ALTER TABLE test MAP DYNAMIC COLUMN f:_mongo_id_ HSTRING/HINT/..., person:name HSTRING, person:age HINT;

2. Create a secondary index for the table created by calling the Apache HBase API:

   CREATE INDEX idx ON test(f:_mongo_id_);

Example of configuring an ETL task for a table created by calling the Apache HBase API

A document in the source ApsaraDB for MongoDB instance

{
  "_id" : 0,
  "person" : {
    "name" : "cindy0",
    "age" : 0,
    "student" : true
  }
}

ETL syntax

script:e_expand_bson_value("*", "_id")

Synchronization result

Example of value assignment

Data structure of the source ApsaraDB for MongoDB instance

{
  "_id":"62cd344c85c1ea6a2a9f****",
  "person":{
    "name":"neo",
    "age":"26",
    "sex":"male"
  }
}

Schema of the destination table in the Lindorm instance.

Configuration of additional columns