Data Transmission Service:Migrate data from an ApsaraDB for MongoDB instance to an ApsaraDB RDS for MySQL instance

Prerequisites

• If the source database is a ApsaraDB for MongoDB sharded cluster, you must apply for endpoints for all shard nodes. The shard nodes in a sharded cluster instance must share the same account password and endpoint. For more information about how to apply for an endpoint, see Apply for an endpoint for a shard or ConfigServer component.

• The destination ApsaraDB RDS for MySQL instance is created. The available storage space of this instance is larger than the total size of data in the source database. For more information, see Create an ApsaraDB RDS for MySQL instance.

  Note

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

• A database and a table that has a primary key column are created in the destination ApsaraDB RDS for MySQL instance to receive data. For more information, see Manage databases.

  Important

  • Make sure that the data type of the destination table is compatible with the data in the source ApsaraDB for MongoDB instance. For example, if the _id field of the ApsaraDB for MongoDB instance is of the ObjectId type, the data type of the ApsaraDB RDS for MySQL instance must be varchar.

  • Do not name the columns of the destination table in the ApsaraDB RDS for MySQL instance as _id or _value.

Usage notes

Billing overview

Migration types

Permissions required for database accounts

Procedure

1. Use one of the following methods to go to the Data Migration page and select the region in which the data migration instance resides.

DTS console

1. Log on to the DTS console.

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

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

DMS console

Note

The actual operation 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 Development > DTS (DTS) > Data Migration .

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

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

3. Optional. Click New Configuration Page in the upper-right corner of the page.

Note

• Skip this step if the Back to Previous Version button is displayed in the upper-right corner of the page.

• Specific parameters in the new and previous versions of the configuration page may be different. We recommend that you use the new version of the configuration page.

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

   Category	Configuration	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	The 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 use an existing instance, you must configure the database information below. Note You can register a database with DTS on the Database Connections page or the new configuration page. For more information, see Manage database connections. In the DMS console, you can select an existing database from the Select a DMS database instance. drop-down list. You can also click Add DMS Database Instance or go back to the homepage of the DMS console to register a database with DMS. For more information, see Register an Alibaba Cloud database instance and Register a database hosted on a third-party cloud service or a self-managed database.
   	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	In this example, a database instance of the current Alibaba Cloud account is used. Select No.
   	Architecture	The architecture of the source ApsaraDB for MongoDB instance. In this example, Replica Set is selected. Note If the source database is an ApsaraDB for MongoDB Sharded Cluster instance, you must specify Shard account and Shard password.
   	Migration Method	Select the method for incremental data migration based on your actual situation. Oplog (recommended): If the source database has enabled Oplog, this option is supported. Note Local self-managed MongoDB and ApsaraDB for MongoDB have Oplog enabled by default. When migrating incremental data using this method, the delay of the incremental migration task is small (the speed of pulling logs is fast). Therefore, it is recommended to select Oplog. ChangeStream: If the source database has enabled Change Streams (Change Streams), this option is supported. Note When the source database is Amazon DocumentDB (non-elastic cluster), only ChangeStream is supported. When the Architecture of the source database is selected as Sharded Cluster, there is no need to fill in the Shard account and Shard password.
   	Instance ID	The ID of the source ApsaraDB for MongoDB instance.
   	Authentication Database	The name of the authentication database that stores the database accounts and passwords of the source ApsaraDB for MongoDB instance. If you did not change the name before, the default value admin is used.
   	Database Account	The database account of the source ApsaraDB for MongoDB 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.
   	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	The 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 use an existing instance, you must configure the database information below. Note You can register a database with DTS on the Database Connections page or the new configuration page. For more information, see Manage database connections. In the DMS console, you can select an existing database from the Select a DMS database instance. drop-down list. You can also click Add DMS Database Instance or go back to the homepage of the DMS console to register a database with DMS. For more information, see Register an Alibaba Cloud database instance and Register a database hosted on a third-party cloud service or a self-managed database.
   	Database Type	The type of the destination database. Select MySQL.
   	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the destination ApsaraDB RDS for MySQL instance resides.
   	Replicate Data Across Alibaba Cloud Accounts	In this example, a database instance of the current Alibaba Cloud account is used. Select No.
   	RDS Instance ID	The ID of the destination ApsaraDB RDS for MySQL instance.
   	Database Account	The database account of the destination ApsaraDB RDS for MySQL instance. For 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.
   	Encryption	Specifies whether to encrypt the connection to the source database instance. Select Non-encrypted or SSL-encrypted based on your business requirements. If you want to set this parameter to SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the DTS task. For more information, see Use a cloud certificate to enable SSL encryption.

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

   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.

6. Configure the objects to be migrated.

   1. On the Configure Objects page, configure the objects that you want to migrate.

      Configuration	Description
      Migration Types	To perform only full data migration, select only Full Data Migration. To ensure service continuity during data migration, select Full Data Migration and Incremental Data Migration. Note If you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
      Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains collections that have the same names as collections in the source database. If the source and destination databases do not contain collections that have identical names, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started. Note If the source and destination databases contain 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 migrated to the destination database. For more information, see Map object names. 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 consistency is not ensured and your business may be exposed to potential risks. DTS does not migrate data records that have the same primary keys as data records in the destination database. Data may fail to be initialized, only specific columns are migrated, or the data migration task fails.
      Capitalization of Object Names in Destination Instance	The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of 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. Click the icon to add the objects to the Selected Objects section. Note You can select collections as the objects to be migrated.
      Selected Objects	Modify the database name. In the Selected Objects section, right-click the database to which the collections to be migrated belong. Change the value of Database Name to the name of the schema that is used to receive data in the destination ApsaraDB RDS for MySQL instance. Click OK. Modify table names. In the Selected Objects section, right-click the collection to which the collections to be migrated belong. Change the value of Table Name to the name of the table that is used to receive data in the destination ApsaraDB RDS for MySQL instance. Optional: You can specify conditions to filter data. For more information, see Specify filter conditions. Optional: In the Select DDL and DML Operations to Be Synchronized section, you can select the operations that you want to migrate during incremental data migration. Specify the fields to be migrated from the source ApsaraDB for MongoDB instance. By default, DTS maps the data of a collection to be migrated 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. 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. 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 migrated. Note Click the icon after the row of data to delete fields that do not need to be migrated. Specify the fields to be migrated. Perform one of the following procedures based on whether the bson_value() expression meets you 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 ApsaraDB RDS for MySQL instance. 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. For more information about data type mappings, see the Data type mapping section of this topic. 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 + Add 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. 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.

      Configuration	Description
      Dedicated Cluster for Task Scheduling	By default, DTS schedules the data migration task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data migration tasks, 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 migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1,440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later 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 the earliest opportunity after the source database and destination instance are released.
      Retry Time for Other Issues	The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration 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	Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must 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. This reduces the loads of the destination database server. Note You can configure this parameter only if you select Full Data Migration for the Migration Types parameter.
      Only one data type for primary key _id in a single table	Whether the data type of the primary key _id is unique within the same collection of the data to be migrated. Note This can be configured only when Migration Types is set to Full Data Migration. Yes: Unique. During the full migration phase, DTS will not scan the data type of the primary key in the data to be migrated from the source database. No: Not unique. During the full migration phase, DTS will scan the data type of the primary key in the data to be migrated from the source database.
      Enable Throttling for Incremental Data Migration	Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server. Note You can configure this parameter only if you select Incremental Data Migration for the Migration Types parameter.
      Environment Tag	You can select an environment tag to identify the instance based on your actual situation. In this example, no environment tag is selected.
      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.
      Monitoring and Alerting	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values: No: does not configure 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.

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 migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.

   • If the task fails to pass the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.

   • 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 issues. Then, run a precheck again.

     • If the 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. Purchase an instance.

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

   2. On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

      Section	Parameter	Description
      New Instance Class	Resource Group	The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?
      	Instance Class	DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Instance classes of data migration instances.

   3. Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.

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

   5. You can view the progress of the task on the Data Migration page.

Data type mapping

Example of value assignment

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