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Data Transmission Service:Synchronize data from an ApsaraDB RDS for MySQL instance to a Function Compute function

Last Updated:Dec 29, 2023

You can use Data Transmission Service (DTS) to synchronize full data or incremental data from an ApsaraDB RDS for MySQL instance to a Function Compute function. You can write function code to further process the data that is synchronized to the function.

Prerequisites

  • The source ApsaraDB RDS for MySQL instance is created. For more information, see Create an ApsaraDB RDS for MySQL instance.

  • The destination service and the function are created and the Handler Type parameter is set to Event Handler for the function. For more information about how to create a function, see Quickly create a function.

Limits

Category

Description

Limits on the source database

  • The tables to be synchronized must have PRIMARY KEY or UNIQUE constraints, and all fields must be unique.

  • The size of a single data entry in the source database cannot exceed 16 MB. Otherwise, DTS cannot write the data to the destination function and an error is reported. If you do not want to migrate all fields, you can use the extract, transform, and load (ETL) feature to filter out large-size data entries.

  • If you select tables as the objects to be synchronized, up to 1,000 tables can be synchronized in a single data synchronization task. If you run a task to synchronize more than 1,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to synchronize the tables or configure a task to synchronize the entire database.

  • The following requirements for binary logs must be met:

    • By default, the binary logging feature is enabled. The binlog_row_image parameter must be set to full. Otherwise, error messages are returned during the precheck and the data synchronization task cannot be started. For more information, see Modify instance parameters.

      Important
      • If the source database is a self-managed MySQL database, you must enable the binary logging feature and set the binlog_format parameter to row and the binlog_row_image parameter to full.

      • If the source database is a self-managed MySQL database deployed in a dual-primary cluster, you must set the log_slave_updates parameter to ON. This ensures that DTS can obtain all binary logs. For more information, see Create an account for a self-managed MySQL database and configure binary logging.

    • For an incremental data synchronization task, the binary logs of the source database are retained for at least 24 hours. For a full and incremental data synchronization task, the binary logs of the source database are retained for at least seven days. Otherwise, DTS may fail to obtain the binary logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. After the full data synchronization is complete, you can set the retention period to more than 24 hours. Make sure that you configure the retention period of binary logs based on the preceding requirements. Otherwise, the service level agreement (SLA) of DTS does not guarantee service reliability or performance. For more information about how to manage the binary log files of an ApsaraDB RDS for MySQL instance, see Manage binary log files.

Other limits

  • The mapping feature is not supported.

  • Cross-region data synchronization is not supported.

  • Before you synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. During initial full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers.

  • During initial full data synchronization, INSERT operations are concurrently performed. In this case, you must set the Instance Concurrency parameter of the destination function to a relatively large value. For more information, see Configure instance concurrency.

  • If you select one or more tables instead of an entire database as the objects to be synchronized, do not use tools such as pt-online-schema-change to perform online DDL operations on the tables during data synchronization. Otherwise, data may fail to be synchronized. You can use Data Management (DMS) to perform online DDL operations. For more information, see Perform lock-free DDL operations.

  • We recommend that you specify different destination functions for different DTS tasks. Otherwise, errors may occur in the data of the destination function.

Special cases

  • If the source database is a self-managed MySQL database, take note of the following items:

    • If you perform a primary/secondary switchover on the source database when the data synchronization task is running, the task fails.

    • DTS calculates the synchronization latency based on the timestamp of the latest synchronized data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for an extended period of time, the synchronization latency may be inaccurate. If the latency of the data synchronization task is excessively high, you can perform a DML operation on the source database to update the latency.

      Note

      If you select an entire database as the object to be synchronized, you can create a heartbeat table. The heartbeat table is updated or receives data every second.

    • DTS executes the CREATE DATABASE IF NOT EXISTS 'test' statement in the source database as scheduled to move forward the binary log file position.

  • If the source database is an Apsara RDS for MySQL instance, take note of the following item:

    The source Apsara RDS for MySQL instance cannot be a read-only ApsaraDB RDS for MySQL instance that does not record transaction logs, such as an ApsaraDB RDS for MySQL V5.6 instance.

Billing

Synchronization type

Task configuration fee

Full data synchronization

Free of charge.

Incremental data synchronization

Charged. For more information, see Billing overview.

SQL operations that support data synchronization

Operation type

SQL statement

DML

INSERT, UPDATE, and DELETE

DDL

  • CREATE TABLE, ALTER TABLE, DROP TABLE, RENAME TABLE, and TRUNCATE TABLE

  • CREATE VIEW, ALTER VIEW, and DROP VIEW

  • CREATE PROCEDURE, ALTER PROCEDURE, and DROP PROCEDURE

  • CREATE FUNCTION, DROP FUNCTION, CREATE TRIGGER, and DROP TRIGGER

  • CREATE INDEX and DROP INDEX

Permissions required for database accounts

Database

Required permissions

References

Source ApsaraDB RDS for MySQL instance

The read permissions on the objects to be synchronized.

Create an account on an ApsaraDB RDS for MySQL instance and Modify the permissions of a standard account on an ApsaraDB RDS for MySQL instance.

Note

If the source database account that you use is not created and authorized in the ApsaraDB RDS console, make sure that the account has the REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT permissions.

Procedure

  1. Go to the Data Synchronization Tasks page.

    1. Log on to the DMS console.

    2. In the top navigation bar, click DTS.

    3. In the left-side navigation pane, choose DTS (DTS) > Data Synchronization.

    Note
  2. From the drop-down list to the right of Data Synchronization Tasks, select the region in which you want to create the data synchronization task.

    Note

    If you use the new DTS console, select the region in which you want to create the data synchronization task in the upper-left corner of the page.

  3. Click Create Task. On the Create Task wizard page, configure the source and destination databases.

    Section

    Parameter

    Description

    N/A

    Task Name

    The name of the task. DTS automatically assigns a name to the task. 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 an existing DMS database instance. (Optional. If you have not registered a DMS database instance, ignore this option and configure database settings in the section below.)

    The database instance that you want to use. You can choose whether to select 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 select an existing instance, you must manually configure parameters for the database.

    Database Type

    The type of the source database. Select MySQL.

    Access Method

    The access method of the source database. Select Alibaba Cloud Instance.

    Instance Region

    The region in which the source ApsaraDB RDS for MySQL instance resides.

    Replicate Data Across Alibaba Cloud Accounts

    Specifies whether to synchronize data across Alibaba Cloud accounts. In this example, No is selected.

    RDS Instance ID

    The ID of the source ApsaraDB RDS for MySQL instance.

    Database Account

    The database account of the source 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 of the database account.

    Encryption

    Specifies whether to encrypt the connection to the database. Select Non-encrypted or SSL-encrypted based on your business requirements. If you select SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the data synchronization task. For more information, see Configure the SSL encryption feature.

    Destination Database

    Select an existing DMS database instance. (Optional. If you have not registered a DMS database instance, ignore this option and configure database settings in the section below.)

    The database instance that you want to use. You can choose whether to select 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 select an existing instance, you must manually configure parameters for the database.

    Database Type

    The type of the destination database. Select Function Compute.

    Access Method

    The access method of the destination database. Select Alibaba Cloud Instance.

    Instance Region

    The region in which the destination database resides. By default, the value is the same as that of the Instance Region parameter of the source database and cannot be changed.

    Service

    The name of the service to which the destination function belongs.

    Function

    The destination function that receives the synchronized data.

    Service Version and Alias

    The version or alias of the service. Configure this parameter based on your business requirements.

    • If you select Default Version, the value of the Service Version parameter is fixed to LATEST.

    • If you select Specified Version, you must configure the Service Version parameter.

    • If you select Specified Alias, you must configure the Service Alias parameter.

    Note

    For more information about the terms of Function Compute, see Terms.

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

    If the source or destination database is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB instance, DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the instance. If the source or destination database is a self-managed database hosted on an Elastic Compute Service (ECS) instance, DTS automatically adds the CIDR blocks of DTS servers to the security group rules of the ECS instance, and you must ensure that the ECS instance can access the database. If the source or destination database is a self-managed database that is deployed in a data center or provided by a third-party cloud service provider, you must manually add the CIDR blocks of DTS servers to the whitelist of the database to allow DTS to access the database. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.

    Warning

    If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of the database or instance, or to the ECS security group rules, security risks may arise. Therefore, before you use DTS to synchronize data, you must understand and acknowledge the potential risks and take preventive measures, including but not limited to the following measures: enhancing the security of your username and password, limiting the ports that are exposed, authenticating API calls, regularly checking the whitelist or ECS security group rules and forbidding unauthorized CIDR blocks, or connecting the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

  5. Configure the objects to be synchronized and advanced settings.

    Parameter

    Description

    Synchronization Types

    By default, Incremental Data Synchronization is selected. If you want to synchronize historical data, you must also select Full Data Synchronization.

    Data Format

    The format in which the data that is synchronized to the destination function is stored. Only the Canal Json format is supported.

    Note

    For more information about the parameters of the Canal JSON format, see the "Canal Json" section of the Data formats of a Kafka cluster topic.

    Source Objects

    Select one or more objects from the Source Objects section and click the Rightwards arrow icon to add the objects to the Selected Objects section.

    Note

    Select databases or tables as the objects to be synchronized.

    Selected Objects

    In the Selected Objects section, check the data that you want to synchronize.

    Note

    To remove a selected object, select the objects that you want to remove in the Selected Objects section and click the zuoyi icon.

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

    Parameter

    Description

    Select the dedicated cluster used to schedule the task

    By default, DTS schedules tasks to shared clusters. You do not need to configure this parameter. You can purchase a dedicated cluster of specified specifications to run DTS synchronization tasks. For more information, see What is a DTS dedicated cluster.

    Set Alerts

    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:

    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 the 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 set different retry time ranges for multiple DTS tasks that have the same source or destination database, the shortest retry time range that is set 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.

    The wait time before a retry when other issues occur in the source and destination databases.

    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 the 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 The wait time before a retry when other issues occur in the source and destination databases parameter must be smaller than the value of the Retry Time for Failed Connection parameter.

    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 configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and BPS of Full Data Migration parameters for full data synchronization tasks to reduce the pressure on the destination database.

    Note

    This parameter can be configured only if Full Data Synchronization is selected as Synchronization Types.

    Enable Throttling for Incremental Data Synchronization

    You can configure the RPS of Incremental Data Migration and BPS of Incremental Data Migration parameters for incremental data synchronization tasks to reduce the pressure on the destination database.

    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, no environment tag is selected.

    Configure ETL

    Specifies whether to configure the extract, transform, and load (ETL) feature. For more information, see What is ETL?. Valid values:
  7. Click Next: Save Task Settings and Precheck in the lower part of the page.

    You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameter settings of the API operation that is called to configure the instance.

    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 task fails to pass the precheck, click View Details next to each failed item. After you troubleshoot the issues based on the causes, 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 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.

  8. Wait until the success rate becomes 100%. Then, click Next: Purchase Instance.

  9. On the Purchase Instance 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 the instance when you create an 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 charged 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 instance, you can release the pay-as-you-go instance to reduce costs.

    Resource Group

    The resource group on which the instance is run. Default value: default resource group. For more information, see What is Resource Management?.

    Instance Class

    DTS provides various synchronization specifications that provide different performance. The synchronization speed varies based on the synchronization specifications that you select. You can select a synchronization specification based on your business scenario. For more information, see Specifications of data synchronization instances.

    Subscription Duration

    If you select the subscription billing method, set the subscription duration and the number of 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.

  10. Read and select the check box to agree to the Data Transmission Service (Pay-as-you-go) Service Terms.

  11. Click Buy and Start to start the data synchronization task. You can view the progress of the task in the task list.

What to do next

Formats of data received by the destination function

The data received by the destination function is of the Object type. Incremental data of the source database is stored in the Records field in the array format. Each element in the array indicates a data record of the Object type. The following table describes the fields in the data records of the Object type.

Note

A destination function receives data that records the following two types of SQL operations:

  • DDL data: operations on data schema changes.

  • DML data: operations on data management.

Field

Type

Description

isDdl

Boolean

Indicates whether the operation is a DDL operation. Valid values:

  • True

  • False

type

String

The type of the SQL operation.

  • Valid values for DML operations: DELETE, UPDATE, and INSERT

  • Valid value for DDL operations: DDL

Important

During full data synchronization, the value of the field is fixed to INIT.

database

String

The name of the source MySQL database.

table

String

The name of the table in the source MySQL database.

pkNames

String

The name of the primary key contained in the table.

es

Long

The time when the operation is performed on the source database. The value is a 13-bit UNIX timestamp. Unit: millisecond.

Note

You can use a search engine to obtain a UNIX timestamp converter.

ts

Long

The time when the operation starts to be performed on the destination database. The value is a 13-bit UNIX timestamp. Unit: millisecond.

Note

You can use a search engine to obtain a UNIX timestamp converter.

data

Object Array

The array that contains only one element of the Object type. The key of the element is the column name, and the value of the element is the value contained in the column.

old

Object Array

The array in which the original data is stored. The format of the field is the same as that of the data field.

Important

This field is available and has the same format as the data field only if the value of the type field is DELETE.

sql

String

  • If the value of the type field is DELETE, UPDATE, or INSERT, no value is returned for the sql field.

  • If the value of the type field is DDL, the executed SQL statement is returned for the sql field.

id

Int

The serial number of the operation.

Examples of DDL operations and data received by the destination function

Modify a table

SQL statement

ALTER TABLE `demoTable` 
	ADD COLUMN `address` varchar(20) NULL AFTER `sex`
;

Data received by the destination function

{
	'Records': [{
		'type': 'DDL',
		'serverId': '27142679',
		'es': 1690000000000,
		'sql': '/* Query from DMS-WEBSQL-0-Eid_15682857722282385K by user 14xxxxxxxx */ ALTER TABLE `demoDatabase`.`DDL` \n\tADD COLUMN `address` varchar(20) NULL AFTER `sex`',
		'database': 'demoDatabase',
		'id': 63151,
		'isDdl': True,
		'table': 'demoTable',
		'ts': 1690000000000
	}]
}

Examples of DML operations and data received by the destination function

Insert data

SQL statement

INSERT INTO demoTable VALUES("xiaoming", 10, "man");

Data received by the destination function

{
	'Records': [{
		'data': [{
			'sex': 'man',
			'name': 'xiaoming',
			'age': '10'
		}],
		'pkNames': ['name'],
		'type': 'INSERT',
		'serverId': '27142678',
		'es': 1690000000000,
		'sql': '',
		'database': 'demoDatabase',
		'sqlType': {
			'sex': 253,
			'name': 253,
			'age': 3
		},
		'mysqlType': {
			'sex': 'varchar',
			'name': 'varchar',
			'age': 'int'
		},
		'id': 62051,
		'isDdl': False,
		'table': 'demoTable',
		'ts': 1690000000000
	}]
}

Update data

SQL statement

UPDATE `demoDatabase`.`demoTable` SET `age`=11 WHERE `name`='xiaoming';

Data received by the destination function

{
	'Records': [{
		'data': [{
			'sex': 'man',
			'name': 'xiaoming',
			'age': '11'
		}],
		'pkNames': ['name'],
		'old': [{
			'sex': 'man',
			'name': 'xiaoming',
			'age': '10'
		}],
		'type': 'UPDATE',
		'serverId': '27142679',
		'es': 1690000000000,
		'sql': '',
		'database': 'demoDatabase',
		'sqlType': {
			'sex': 253,
			'name': 253,
			'age': 3
		},
		'mysqlType': {
			'sex': 'varchar',
			'name': 'varchar',
			'age': 'int'
		},
		'id': 62373,
		'isDdl': False,
		'table': 'demoTable',
		'ts': 1690000000000
	}]
}

Delete data

SQL statement

DELETE FROM `demoDatabase`.`demoTable` WHERE `name`='xiaoming';

Data received by the destination function

{
	'Records': [{
		'data': [{
			'sex': 'man',
			'name': 'xiaoming',
			'age': '11'
		}],
		'pkNames': ['name'],
		'type': 'DELETE',
		'serverId': '27142679',
		'es': 1690000000000,
		'sql': '',
		'database': 'demoDatabase',
		'sqlType': {
			'sex': 253,
			'name': 253,
			'age': 3
		},
		'mysqlType': {
			'sex': 'varchar',
			'name': 'varchar',
			'age': 'int'
		},
		'id': 62635,
		'isDdl': False,
		'table': 'demoTable',
		'ts': 1690000000000
	}]
}