Synchronize data from AnalyticDB for PostgreSQL to Alibaba Cloud Message Queue for Kafka - Data Transmission Service

Data Transmission Service (DTS) supports data synchronization from an AnalyticDB for PostgreSQL instance to Alibaba Cloud Message Queue for Kafka.

Note

This feature is in invitational preview. To use this feature, submit a ticket.

Scope

A topic has been created in the destination Alibaba Cloud Message Queue for Kafka instance to receive the synchronized data. For more information, see Step 1: Create a topic.
The storage space of the destination Alibaba Cloud Message Queue for Kafka instance must be larger than the storage space used by the source AnalyticDB for PostgreSQL instance.

Usage notes

Source database limits

Type	Limit
Before synchronization	Bandwidth requirements: To ensure the synchronization speed, make sure that the outbound bandwidth of the source database server is at least 100 Mb/s. Kernel version: The kernel version of the source AnalyticDB for PostgreSQL instance must be 7.2.1.4 or later. Parameter settings: Logical replication: You must enable logical replication. To do this, set the `wal_level` parameter to `logical`. High-availability configuration: If the source instance is a High-availability Edition, you must also set the `hot_standby`, `hot_standby_feedback`, and `sync_replication_slots` parameters to `on`. This prevents the synchronization task from being interrupted by a primary/standby switchover. Account permissions: The synchronization account must have read permissions on the objects to be synchronized and the `REPLICATION` permission. You can run the `ALTER USER your_user WITH REPLICATION;` command to grant the required permissions. Impact of long-running transactions: During incremental synchronization, uncommitted long-running transactions in the source database can cause write-ahead log (WAL) files to accumulate and eventually exhaust the disk space. Object limits: Naming conventions: The name of the database to be synchronized cannot contain a hyphen (-), such as `dts-testdata`. Primary key or UNIQUE constraint: The tables to be synchronized must have a primary key or a UNIQUE constraint. The values in the constraint columns must be unique. Otherwise, duplicate data may exist in the destination database. Partitioned tables: The schema of partitioned tables cannot be synchronized. After a partitioned table is synchronized, the partition information is lost when the table schema is synchronized to the destination. All tables are created as non-partitioned tables by default. Number of databases per task: A sync task can synchronize only one database. To synchronize multiple databases, create a separate sync task for each database. Task configuration scale: To edit more than 5,000 tables in a task, such as for column name mapping, create multiple tasks in batches or configure synchronization for the entire database. This avoids request errors when you submit the task. Unsupported object types: Synchronization of tables that inherit across schemas, temporary tables, internal system triggers, some functions (C language functions and internal functions for PROCEDURE and FUNCTION), and plugins (EXTENSION) is not supported. Supported object types: Synchronization of primary keys, UNIQUE constraints, CHECK constraints, and some custom data types (COMPOSITE, ENUM, and RANGE) is supported.
During synchronization	DDL operation limits: During schema synchronization and full synchronization, do not perform DDL operations to change the database or table schema. Otherwise, the data synchronization task fails. Note During full synchronization, DTS queries the source database. This creates metadata locks, which may block DDL operations on the source database. DDL synchronization support: Synchronization of DDL operations on the source database is not supported. After the DTS task starts, new tables created in the source and their subsequent data changes will not be synchronized to the destination. If needed, create a new synchronization link. Connection information changes: While the task is running, do not modify the endpoint or zone of the AnalyticDB for PostgreSQL instance. Otherwise, the sync task fails.

Destination database limits

Type	Limit
Before synchronization	Performance impact assessment: Full synchronization consumes read and write resources on both the source and destination databases, which may increase the database load. We recommend that you run synchronization tasks during off-peak hours, for example, when the CPU load is below 30%. Single message size: Kafka limits the size of a single message to 10 MB. If a single row of data from the source database exceeds this limit after conversion, the task is interrupted. Therefore, when you configure the task, filter out columns that contain large objects. If the task is already running, you must modify the synchronization objects. Remove the table, click Modify Synchronization Objects again, re-add the table, and then filter out the large object columns to prevent them from being synchronized.
During synchronization	Destination database scale-out/in: If the destination Kafka cluster is scaled out or in while the task is running, such as by adding or removing broker nodes, you must restart the DTS sync task for the changes to take effect. External data writes: To ensure data consistency, do not write data from sources other than the DTS task to the destination Kafka cluster during synchronization. This may cause data inconsistency or task failure. Storage space growth: During full synchronization, DTS performs concurrent write operations, which can cause data fragmentation in the destination. As a result, the storage usage of the destination may be greater than that of the source after synchronization is complete. Task restart behavior: For tasks that include both full and incremental synchronization, restarting the task may re-run the full synchronization phase. Instance failure: Recovery mechanism: DTS helpdesk will try to recover the instance within 8 hours. During the recovery process, the instance may be restarted or the DTS task parameters may be adjusted. Your database parameters will not be modified. Data overwriting risk: To prevent automatic recovery from accidentally overwriting data in the destination database, stop or release sync tasks that are no longer needed after you switch your business to the destination database.
Supported SQL operations	`INSERT`, `UPDATE`, and `DELETE`.
Supported objects for synchronization	Basic objects: `SCHEMA` and `TABLE` Note Includes `PRIMARY KEY`, `UNIQUE KEY`, `DATATYPE` (built-in data types), and `DEFAULT CONSTRAINT`. Other objects: `VIEW`, `INDEX`, `PROCEDURE`, `FUNCTION`, `RULE`, `SEQUENCE`, `AGGREGATE`, `OPERATOR`, and `DOMAIN`.

Billing description

Synchronization type	Task configuration fee
Schema synchronization and full data synchronization	Free of charge.
Incremental synchronization	Charged. For more information, see Billing overview.

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
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.
Click Create Task to go to the task 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	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	Select AnalyticDB for PostgreSQL.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the source AnalyticDB for PostgreSQL instance resides.
	Replicate Data Across Alibaba Cloud Accounts	This example shows synchronization within the same Alibaba Cloud account. Select No.
	Instance ID	Select the instance ID of the source AnalyticDB for PostgreSQL instance.
	Database Name	Enter the name of the database that contains the data to be synchronized in the source AnalyticDB for PostgreSQL instance.
	Database Account	Enter the database account of the source AnalyticDB for PostgreSQL instance. The account must have read permissions on the objects to be synchronized.
	Database Password	The password that is used to access the 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	Select Kafka.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination Alibaba Cloud Message Queue for Kafka instance resides.
	Kafka Instance ID	Select the ID of the destination Alibaba Cloud Message Queue for Kafka instance.
	Encryption	Based on your business and security requirements, select Non-encrypted or SCRAM-SHA-256.
	Topic	From the drop-down list, select the topic to receive data.
	Use Kafka Schema Registry	Kafka Schema Registry is a metadata service layer that provides a RESTful interface for storing and retrieving Avro schemas. No: Do not use Kafka Schema Registry. Yes: Use Kafka Schema Registry. You must enter the URL or IP address where the Avro schema is registered in Kafka Schema Registry.

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 DTS server IP addresses to a whitelist.
- 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.

Note

Schema Synchronization is not supported when the Access Method for the destination Kafka instance is Alibaba Cloud Instance.

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.

Data Format in Kafka

Select the required data storage format for synchronization to the Kafka instance.

If you select DTS Avro, you need to parse the data according to the DTS Avro schema definition. For more information, see DTS Avro schema definition and DTS Avro deserialization example.
If you select Canal JSON, see Canal JSON for parameter descriptions and examples.

Kafka Data Compression Format

Select the required compression format for Kafka messages.

LZ4 (default): Offers a lower compression ratio and a higher compression speed.
GZIP: Offers a higher compression ratio and a lower compression speed.
Note
This format consumes more CPU resources.
Snappy: Offers a medium compression ratio and a medium compression speed.

Policy for Shipping Data to Kafka Partitions

Select a policy as required.

Message acknowledgement mechanism

Select a message acknowledgment mechanism as required.

Topic That Stores DDL Information

From the drop-down list, select the topic to store DDL information.

Note

If you do not select a topic, DDL information is stored in the topic that receives data by default.

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.

Note

You can select objects to synchronize at the table level.

Selected Objects

No additional configuration is required in this example. You can use the mapping feature to set the topic name, number of partitions for the topic, or column names for the source table in the destination Kafka instance.

Click to expand and view how to configure object information in the destination Kafka instance

In the Selected Objects section, hover the mouse pointer over the destination topic name at the table level.
Click Edit, which appears next to the destination topic name.

In the Edit Table dialog box that appears, configure the mapping information.

Note

At the database level, the Edit Schema dialog box appears, which has fewer parameters. At the table level, the Edit Table dialog box appears.
If you synchronize objects at a granularity other than the entire database, you cannot modify Destination Database Name (Name of target Topic) or Number of Partitions in the Edit Schema dialog box.

Configuration	Description
Name of target Topic	The name of the destination topic to which the source table is synchronized. By default, this is the Topic that you select in the Destination Database section during the Configurations for Source and Destination Databases step. Important If the destination database is an ApsaraMQ for Kafka instance, the topic name that you enter must exist in the destination Kafka instance. Otherwise, the data synchronization task fails. If the destination database is a self-managed Kafka cluster and the synchronization task includes schema synchronization, DTS attempts to create the topic that you enter in the destination database. If you change the Name of target Topic, data is written to the topic that you specify.
Filter Conditions	For more information, see Set filter conditions.
Number of Partitions	The number of partitions for the destination topic to which data is written.
Column	Edit the column names for the data that is written to the destination topic.

Note

To select the SQL operations to be synchronized at the database or table level, right-click the object in the Selected Objects section and select the desired SQL operations in the dialog box that appears.
If you use the object name mapping feature, other objects that depend on the mapped object may fail to be synchronized.

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 instances, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.
Enable Encryption For Data Transmission	Enabling encrypted transmission may affect DTS synchronization performance. Select whether to enable this feature based on your production and security requirements. No (default) Yes
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.
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 as required. No selection is required for this example.
Scene Label	You can select a scenario tag to identify the usage scenario of the instance as required. Scenario tags do not affect the normal operation of the task. No selection is required for this example.
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.

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.

Purchase the 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 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.

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.

FAQ

Can I modify the Kafka Data Compression Format?
Yes. You can use the Modify Synchronization Objects feature to modify the format.
Can I modify the Message acknowledgement mechanism?
Yes. You can use the Modify Synchronization Objects feature to modify the mechanism.

Scope

Usage notes

Source database limits

Destination database limits

Billing description

Procedure

DTS console

DMS console

FAQ