Data Transmission Service (DTS) supports synchronizing data from a source MongoDB instance without shard key fields to a MongoDB sharded cluster architecture and specifying default values for shard keys. This topic uses ApsaraDB for MongoDB (ReplicaSet architecture) as the source and ApsaraDB for MongoDB (sharded cluster architecture) as the destination to describe the synchronization steps.
Prerequisites
The destination ApsaraDB for MongoDB (sharded cluster architecture) has been created. For more information, see Create a sharded cluster instance.
NoteIf the source is a sharded cluster architecture ApsaraDB for MongoDB, you need to apply for connection addresses for all Shard nodes, and ensure that the accounts and passwords of each Shard are consistent. For application methods, see Apply for Shard or ConfigServer node connection addresses.
For supported versions, see Synchronization solution overview.
The storage space of the destination ApsaraDB for MongoDB is larger than that of the source ApsaraDB for MongoDB. It is recommended that the storage space of the destination is 10% larger than that of the source.
According to business needs, create the databases and collections that need to be sharded in the destination ApsaraDB for MongoDB, configure data sharding, enable the Balancer, and perform pre-sharding. For more information, see Set data sharding to fully utilize Shard performance and How to handle uneven data distribution in MongoDB sharded cluster architecture.
NoteConfiguring data sharding can prevent data from being synchronized to the same Shard, which would otherwise hinder cluster performance. Enabling the Balancer and performing pre-sharding can prevent data skew issues.
Notes
Type | Description |
Source database limitations |
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Other limitations |
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Special cases | When the source database is a self-managed MongoDB:
Note If the synchronization object is selected as the entire database, you can also create a heartbeat that periodically updates or writes data every second. |
Billing
Synchronization type | Task configuration fee |
Schema synchronization and full data synchronization | Free of charge. |
Incremental data synchronization | Charged. For more information, see Billing overview. |
Synchronization types
Synchronization type | Description |
Schema synchronization | DTS synchronizes the schemas of the selected objects from the source ApsaraDB for MongoDB instance to the destination ApsaraDB for MongoDB instance. |
Full data synchronization | DTS synchronizes the historical data of the selected objects from the source ApsaraDB for MongoDB instance to the destination ApsaraDB for MongoDB instance. Note DTS supports full data synchronization for the following types of objects: databases and collections. |
Incremental data synchronization | DTS synchronizes incremental data from the source ApsaraDB for MongoDB instance to the destination ApsaraDB for MongoDB instance. Use oplogA DTS task does not synchronize incremental data from databases that are created after the task starts to run. DTS synchronizes incremental data generated by the following operations:
Use change streamsDTS synchronizes incremental data generated by the following operations:
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Permissions required for database accounts
Database | Required permissions | Creation and authorization method |
Source ApsaraDB for MongoDB | Read permissions for the databases to be synchronized, config database, admin database, and local database. | |
Destination ApsaraDB for MongoDB | dbAdminAnyDatabase permission, readWrite permission for the destination database, read permission for the local database, and read permission for the config database. |
Procedure
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
Log on to the DTS console.
In the left-side navigation pane, click Data Synchronization.
In the upper-left corner of the page, select the region in which the data synchronization instance resides.
DMS console
NoteThe 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.
Log on to the DMS console.
In the top navigation bar, move the pointer over Data Development and choose
.From the drop-down list to the right of Data Synchronization Tasks, select the region in which the data synchronization instance resides.
Click Create Task to go to the task configuration page.
Optional. Click New Configuration Page in the upper-right corner of the page.
NoteSkip 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.
Configure the source and destination databases. The following table describes the parameters.
Category
Configuration
Description
None
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 database that you want to use. You can choose whether to use an existing database based on your business requirements.
If you select an existing database, DTS automatically populates the parameters for the database.
If you do not select an existing database, you must configure the following database information.
NoteIn the DTS console, 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
Select MongoDB.
Access Method
Select Alibaba Cloud Instance.
Instance Region
Select the region where the source ApsaraDB for MongoDB instance resides.
Replicate Data Across Alibaba Cloud Accounts
This example is for synchronization between the same Alibaba Cloud account. Select No.
Architecture
This example selects Replica Set.
Replica Set: Achieves high availability and read/write splitting by deploying multiple nodes. For more information, see ReplicaSet architecture.
Sharded Cluster: Provides three components: Mongos, Shard, and ConfigServer. You can freely choose the number and configuration of Mongos and Shard. For more information, see Sharded cluster architecture.
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.
NoteBy 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.
NoteIf 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 instance ID of the source ApsaraDB for MongoDB.
Authentication Database
Enter the name of the database to which the database account of the source ApsaraDB for MongoDB instance belongs. If it has not been modified, the default is admin.
Database Account
Enter the database account of the source ApsaraDB for MongoDB instance. For permission requirements, see Permissions required for 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.
NoteIf 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 database that you want to use. You can choose whether to use an existing database based on your business requirements.
If you select an existing database, DTS automatically populates the parameters for the database.
If you do not select an existing database, you must configure the following database information.
NoteIn the DTS console, 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
Select MongoDB.
Access Method
Select Alibaba Cloud Instance.
Instance Region
Select the region where the destination ApsaraDB for MongoDB instance resides.
Replicate Data Across Alibaba Cloud Accounts
In this example, a database of the current Alibaba Cloud account is used. Select No.
Architecture
This example requires selecting Sharded Cluster.
Instance ID
Select the instance ID of the destination ApsaraDB for MongoDB.
Authentication Database
Enter the name of the database to which the database account of the destination ApsaraDB for MongoDB instance belongs. If it has not been modified, the default is admin.
Database Account
Enter the database account of the destination ApsaraDB for MongoDB. For permission requirements, see Permissions required for database accounts.
Database Password
The password that is used to access the database.
Encryption
Specifies whether to encrypt the connection to the destination 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.
NoteIf the destination database is an ApsaraDB for MongoDB instance and the Architecture parameter is set to Sharded Cluster, the Encryption parameter SSL-encrypted is unavailable.
If the destination 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 CA certificate to verify the connection to the destination database.
Click Test Connectivity and Proceed in the lower part of the page.
NoteMake 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.
Configure the objects to be synchronized.
In the Configure Objects step, configure the objects that you want to synchronize.
Configuration
Description
Synchronization Types
The synchronization types. By default, Incremental Data Synchronization is selected. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of the selected objects from the source database to the destination cluster. 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.
NoteIf 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.
WarningIf 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.
Synchronization Topology
Select One-way Synchronization.
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 ensure that the capitalization of object names is consistent with that 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.
NoteThe granularity of selecting synchronization objects is database or collection.
Selected Objects
To specify the database name in the destination MongoDB (sharded cluster architecture) for receiving data:
Right-click the desired database under Selected Objects, and within the Edit Schema dialog box that appears, update the Schema Name to match the destination MongoDB database name (sharded cluster architecture) that will receive the data. For more information, see Single mapping of database table columns.
To specify the collection name in the destination MongoDB (sharded cluster architecture) for receiving data:
Right-click the collection under Selected Objects, and in the pop-up Edit Table dialog box, rename the Table Name to match the collection name in the destination MongoDB, which utilizes a sharded cluster architecture, to facilitate data reception.
ImportantOnly when the granularity of the synchronization object is a collection can you specify the collection for receiving data.
NoteIf you need to establish filter conditions for data (note that filter conditions are supported during the full synchronization phase but not during the incremental synchronization phase), right-click the table you want to sync in Selected Objects, and define the filter conditions in the dialog box that appears. For instructions on how to configure these conditions, see Set filter conditions.
If you use the object name mapping feature (specifying the database or collection for receiving data), it may cause synchronization failures for other objects that depend on this object.
Click Next: Advanced Settings to configure advanced settings.
Configuration
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 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 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.
NoteIf 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.
ImportantThe 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.
NoteThis parameter is displayed only if Full Data Synchronization is selected for the Synchronization Types parameter.
Only one data type for primary key _id in a single table
Whether the data type for primary key
_id
in a collection of the data to be synchronized is unique. Valif value:NoteThis 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.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.
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
You can select an environment tag to identify the instance based on your actual situation. This example does not require selection.
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 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.
Click Next Step: Data Verification to configure data verification.
For more information about how to use the data verification feature, see Configure a data verification task.
Click Next: Configure Database and Table Fields to set the default value for the ShardKey.
Click Set Default Value in the corresponding row of the target collection.
NoteIf the Number of Shard Keys is 0 for a Table Name(collection), this indicates that the target collection does not contain a shard key, and setting a default value is unnecessary.
Select the Shard key default value type.
NoteThe current Shard key default value type supports only string and int data types.
Set the Default Value for the ShardKey.
ImportantThe set ShardKey default value will only take effect when the version of the destination MongoDB (sharded cluster architecture) is lower than 4.4.
You must assign default values to all ShardKeys within the objects slated for synchronization. If not, an alert will be triggered during the Precheck phase, potentially causing the task to fail.
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.
NoteBefore 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.
Purchase an instance.
Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
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.
NoteThis parameter is available only if you select the Subscription billing method.
Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the dialog box that appears, click OK.
You can view the progress of the task in the task list.