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.

• 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

  • The objects that you create must comply with the Quotas and limits.

  • 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. Use one of the following methods to go to the Data Synchronization page and select the region in which the data synchronization instance resides.

   DTS console

   1. Log on to the DTS console.

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

   3. In the upper-left corner of the page, select the region in which the data synchronization task resides.

   DMS console

   Note

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

   1. Log on to the DMS console.

   2. In the top navigation bar, move the pointer over Data + AI and choose DTS (DTS) > Data Synchronization.

   3. From the drop-down list to the right of Data Synchronization Tasks, select the region in which the data synchronization instance resides.

2. Click Create Task to go to the task configuration page.

3. Configure the source and destination databases. The following table describes the parameters.

   Category	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 Existing Connection	If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections. Note In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list. If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, 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.
   	Migration Method	The method used to synchronize incremental data from the source database. Select a method based on your business requirements. Valid values: Oplog (recommended): This option is available if the oplog feature is enabled for the source database. Note By default, the oplog feature is enabled for both self-managed MongoDB databases and ApsaraDB for MongoDB instances. This feature allows you to synchronize incremental data at a low latency because of a fast log pulling speed. Therefore, we recommend that you select Oplog for the Migration Method parameter. ChangeStream: This option is available if change streams are enabled for the source database. For more information, see Change Streams. Note If the source database is an inelastic Amazon DocumentDB cluster, you can set the Migration Method parameter only to ChangeStream. If you select Sharded Cluster for the Architecture parameter, you do not need to 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.
   	Encryption	Specifies whether to encrypt the connection to the source database. You can select Non-encrypted, SSL-encrypted, or Mongo Atlas SSL based on your business requirements. The options available for the Encryption parameter are determined by the values selected for the Access Method and Architecture parameters. The options displayed in the DTS console prevail. Note If the Architecture parameter is set to Sharded Cluster, and the Migration Method parameter is set to Oplog for the ApsaraDB for MongoDB database, the Encryption parameter SSL-encrypted is unavailable. If the source database is a self-managed MongoDB database that uses the Replica Set architecture, the Access Method parameter is not set to Alibaba Cloud Instance, and the Encryption parameter is set to SSL-encrypted, you can upload a certification authority (CA) certificate to verify the connection to the source database.
   Destination Database	Select Existing Connection	If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections. Note In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list. If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, 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.

4. Click Test Connectivity and Proceed in the lower part of the page.

   Note

   • Make sure that the CIDR blocks of DTS servers can be automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add the CIDR blocks of DTS servers.

   • If the source or destination database is a self-managed database and its Access Method is not set to Alibaba Cloud Instance, click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

5. Configure the objects to be synchronized.

   1. In the Configure Objects step, configure the objects that you want to synchronize.

      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	Retain the default settings.
      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 fields to be synchronized from the source ApsaraDB for MongoDB instance. By default, DTS maps the data of a collection to be synchronized and configures an expression in the Assign Value column. You must check whether the expression meets your requirements and specify the Column Name, Type, Length, and Precision parameters. In the bson_value() expression of the Assign Value column, view the field name of the row of data in the ApsaraDB for MongoDB instance. The field in "" is the field name in the ApsaraDB for MongoDB instance. For example, if the expression is bson_value("age"), age is the field name of the row of data in the ApsaraDB for MongoDB instance. Optional: You can delete fields that do not need to be synchronized. Note Click the icon after the row of data to delete fields that do not need to be synchronized. Specify the fields to be synchronized. Perform one of the following procedures based on whether the bson_value() expression meets your requirements. The expression meets field requirements Configure the Column Name parameter. Note Enter the name of the column in the table that is used to receive data in the destination 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. Select a data Type for each column. Important Make sure that the data type of the destination table is compatible with the data in the source ApsaraDB for MongoDB instance. Optional: Specify a data length and a precision for each column. Repeat the preceding steps to map the columns of the source table onto the columns of the destination table. The expression does not meet field requirements Note For example, fields with hierarchical relationships such as parent-child structure. In the Actions column, click the icon after the row of the data. Click + New Column. Configure the Column Name, Type, Length, and Precision parameters. Enter the bson_value() expression in the Assign Value field. For more information, see the Example of value assignment section of this topic. Important You must assign bson_value("_id") to the primary key column of the destination table. 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.

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

      Parameter	Description
      Dedicated Cluster for Task Scheduling	By default, DTS schedules the task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data synchronization instances, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.
      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 Synchronization	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 You can configure this parameter only if Full Data Synchronization is selected for the Synchronization Types parameter.
      Only one data type for primary key _id in a table of the data to be synchronized	Whether the data type for primary key _id in a collection of the data to be synchronized is unique. Valid value: Note Specify this parameter based on your business requirements. Otherwise, data may be lost. This parameter is displayed only if Full Data Synchronization is selected for the Synchronization Types parameter. Yes: The data type is unique. During full data synchronization, DTS does not scan the data type for primary key _id of the data to be synchronized from the source database. DTS synchronizes only the data of the primary key for a data type in a single collection. No: The data type is not unique. During full data synchronization, DTS scans the data type for primary key _id of the data to be synchronized from the source database and synchronizes all data to be synchronized.
      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.
      Monitoring and Alerting	Specifies whether to configure alerting for the data synchronization instance. 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.

6. 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.

7. Purchase an instance.

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

   2. On the buy page, configure the Billing Method and Instance Class parameters for the data synchronization task. 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.

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

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

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

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

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

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

Example of value assignment

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