Data Transmission Service:Synchronize data from an ApsaraDB for MongoDB instance to an AnalyticDB for MySQL 3.0 cluster

Prerequisites

• An endpoint is available for each shard node if the source is an ApsaraDB for MongoDB sharded cluster instance. The account usernames and passwords of the shards are the same. For more information, see Apply for an endpoint for a shard node or the ConfigServer node in a sharded cluster instance.

• A destination AnalyticDB for MySQL 3.0 cluster is created. The available storage space of the cluster is larger than the used storage space of the source ApsaraDB for MongoDB instance. For more information, see Create a cluster.

  Note

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

• A database that is used to receive data and a table that has a primary key column are created in the destination AnalyticDB for MySQL 3.0 cluster. For more information, see CREATE DATABASE and CREATE TABLE.

  Important

  • Make sure that the data type of the destination table is compatible with the data on the source ApsaraDB for MongoDB instance. For example, if the _id field on the ApsaraDB for MongoDB instance is of the ObjectId type, the data type in the AnalyticDB for MySQL 3.0 cluster must be varchar.

  • Do not name the columns in the destination table in the AnalyticDB for MySQL 3.0 cluster as _id or _value.

• The multi-statement feature is enabled for the destination AnalyticDB for MySQL 3.0 cluster by running the SET ADB_CONFIG ALLOW_MULTI_QUERIES=true; command.

  Note

  Only AnalyticDB for MySQL clusters of V3.1.9.3 or later support the multi-statement feature. For more information, see Update the minor version of a cluster.

Usage notes

Billing

Synchronization types

Permissions required by 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	Select the region of the ApsaraDB for MongoDB instance.
   	Replicate Data Across Alibaba Cloud Accounts	In this example, a database 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 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	Select the ID of the source ApsaraDB for MongoDB instance.
   	Authentication Database	Enter the name of the database to which the database account on the source ApsaraDB for MongoDB instance belongs. If the account has not been modified, enter the default name admin.
   	Database Account	Enter the database account of the source ApsaraDB for MongoDB instance. For more information about the permissions required by the account, see Permissions required by database accounts.
   	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 AnalyticDB for MySQL 3.0.
   	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
   	Instance Region	Select the region of the destination AnalyticDB for MySQL 3.0 cluster.
   	Instance ID	Select the ID of the destination AnalyticDB for MySQL 3.0 cluster.
   	Database Account	Enter the database account of the destination AnalyticDB for MySQL 3.0 cluster. For more information about the permissions required by the account, see Permissions required by database accounts.
   	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.
      DDL and DML Operations to Be Synchronized	Select the instance DDL and DML operations that you want to synchronize during incremental data synchronization. Note To synchronize DDL and DML operations in collections, right-click the Selected Objects and select the operations in the dialog box that appears.
      Merge Tables	Yes: In online transaction processing (OLTP) scenarios, sharding is implemented to speed up the response to business tables. In online analytical processing (OLAP) scenarios, you can store a large volume of data in a single table. This makes your SQL queries more efficient. 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 destination database. For more information, see Enable the multi-table merging feature. Note After you select multiple tables from the source database, you must change the names of these tables to the name of the destination table by using the object name mapping feature. For more information, see Map object names. DTS adds a column named __dts_data_source to the destination table. This column is used to record the data source. The data type of this column is TEXT. The values of this column are in the following format: data synchronization instance ID:source database name:source schema name:source table name. This allows DTS to identify each source table. Example: dts********:dtstestdata:testschema:customer1. If you set this parameter to Yes, all the 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. Warning We recommend that you do not perform DDL operations to change the schemas of source databases or tables. Otherwise, data inconsistency occurs or the data synchronization task fails. No: This value is selected by default.
      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 source and destination databases do not contain tables that have identical table 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 contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are synchronized to the destination database. For more information, see Map object names. 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. If the source and destination databases have the same schema and 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: During full data synchronization, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained. During incremental data synchronization, DTS synchronizes the data record to the destination database. The existing data record in the destination database is overwritten. If the source and destination databases have different schemas, data may fail to be initialized. In this case, only some columns are synchronized, or the data synchronization instance fails. Proceed with caution.
      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	Edit the schema name. In the Selected Objects list, right-click the database to which the collection to be synchronized belongs. Set Schema Name to the name of the database that receives data in the destination AnalyticDB for MySQL 3.0 cluster. Optional. In the Select DDL and DML Operations to Be Synchronized section, select the operations that you want to synchronize. Click OK. Edit table names. Right-click the collection in the Selected Objects list. Set Table Name to the name of the table that receives data in the destination AnalyticDB for MySQL 3.0 cluster. Optional. Configure filter conditions for full data synchronization. For more information, see Set filter conditions. Optional. In the Select DDL and DML Operations to Be Synchronized section, select the operations that you want to synchronize. 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. 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 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 AnalyticDB for MySQL 3.0 cluster. 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.

      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.
      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 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.
      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.
      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 value assignment

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