How do I migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraMQ for Kafka instance? - Data Transmission Service

This topic describes how to migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraMQ for Kafka instance by using Data Transmission Service (DTS).

Prerequisites

The source ApsaraDB RDS for MySQL instance and destination ApsaraMQ for Kafka instance are created.
Note
- For more information about how to create an ApsaraDB RDS for MySQL instance, see Create an ApsaraDB RDS for MySQL instance.
- For more information about the supported database versions, see Overview of data migration scenarios.
The available storage space of the destination ApsaraMQ for Kafka instance is larger than the total size of the data in the source ApsaraDB RDS for MySQL instance.
In the destination ApsaraMQ for Kafka instance, a topic is created to receive migrated data. For more information, see the "Step 1: Create a topic" section of the Step 3: Create resources topic.

Limits

Note

DTS does not migrate foreign keys in the source database to the destination database. Therefore, the cascade and delete operations of the source database are not migrated to the destination database.

Category	Description
Limits on the source database	Bandwidth requirements: The server to which the source database belongs must have sufficient outbound bandwidth. Otherwise, the data migration speed decreases. The tables to be migrated must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records. If you select tables as the objects to be migrated and you need to edit the tables in the destination database, such as renaming tables or columns, up to 1,000 tables can be migrated in a single data migration task. If you run a task to migrate more than 1,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to migrate the tables in batches, or configure a task to migrate the entire database. If you want to migrate incremental data, make sure that the following requirements are met: The binary logging feature is enabled in the ApsaraDB RDS console. For more information, see Modify instance parameters. The binlog_format parameter is set to row and the binlog_row_image parameter is set to full. Otherwise, error messages are returned during the precheck and the data migration task cannot be started. Important If the source database is a self-managed MySQL database that is 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. The local binary logs of the source database must be stored for at least seven days. Otherwise, DTS may fail to obtain the binary logs, which causes the task to fail, or even data inconsistency and data loss. Make sure that you configure the retention period of binary logs based on the preceding requirements. Otherwise, the SLA of DTS does not guarantee service reliability or performance. For more information about the binary log files of an ApsaraDB RDS for MySQL instance, see Manage binary log files. Limits on operations that are performed on the source database: During schema migration and full data migration, do not perform DDL operations to change the schemas of databases or tables. Otherwise, the data migration task fails. If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data inconsistency may occur between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Limits on the destination database	Before you configure a data migration task, you must create a Kafka cluster of version 0.10.1.0 to 2.0. You can select only tables as the objects to be migrated. Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. During full data migration, DTS uses read and write resources of the source and destination databases. This may increase the loads on the database servers. During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination database. After full data migration is complete, the size of used tablespace of the destination database is larger than that of the source database. Make sure that the precision settings for columns of the FLOAT or DOUBLE data type meet your business requirements. DTS uses the `ROUND(COLUMN,PRECISION)` function to retrieve values from columns of the FLOAT or DOUBLE data type. If you do not specify a precision, DTS sets the precision for columns of the FLOAT data type to 38 digits and the precision for columns of the DOUBLE data type to 308 digits. DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads to the destination database, you must stop or release the failed tasks. You can also execute the `REVOKE` statement to revoke the write permissions from the accounts that are used by DTS to access the destination database. Otherwise, the data in the source database overwrites the data in the destination database after a failed task is resumed. We recommend that you do not use tools other than DTS to write data to the destination database. Otherwise, data inconsistency may occur between the source and destination databases. If the destination Kafka cluster is upgraded or downgraded during data migration, you must restart the cluster.
Special cases	If the source database is a self-managed MySQL database, take note of the following limits: If you perform a primary/secondary switchover on the source database when the data migration task is running, the task fails. DTS calculates migration latency based on the timestamp of the latest migrated 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 migration latency may be inaccurate. If the latency of the data migration 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 migrated, 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 runs on an ApsaraDB RDS for MySQL instance: If you want to migrate incremental data, you cannot use a read-only ApsaraDB RDS for MySQL instance that does not record transaction logs, such as an ApsaraDB RDS for MySQL V5.6 instance, as the source instance.

Billing rules

Migration type	Task configuration fee	Internet traffic fee
Schema migration and full data migration	Free of charge.	Charged only when data is migrated from Alibaba Cloud over the Internet. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Schema migration
DTS migrates the schemas of objects from the source database to the destination database.
Full data migration
DTS migrates the existing data of objects from the source database to the destination database.
Incremental data migration
After full data migration is complete, DTS migrates incremental data from the source database to the destination database. Incremental data migration allows data to be migrated smoothly without interrupting the services of self-managed applications during data migration.

SQL operations that can be incrementally migrated

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

Instance	Schema migration	Full data migration	Incremental data migration
The source ApsaraDB RDS for MySQL instance	The read permissions on the objects to be migrated.

Procedure

Go to the Data Migration Tasks page.
1. Log on to the Data Management (DMS) console.
2. In the top navigation bar, click DTS.
3. In the left-side navigation pane, choose DTS (DTS) > Data Migration.
Note
- 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.
- You can also go to the Data Migration Tasks page of the new DTS console.
From the drop-down list next to Data Migration Tasks, select the region in which the data migration instance resides.
Note If you use the new DTS console, you must select the region in which the data migration instance resides in the upper-left corner.

Click Create Task. In the Create Task wizard, configure the source and destination databases.

Warning

After you configure the source and destination databases, we recommend that you read the limits that are displayed in the upper part of the page. Otherwise, the task may fail or data inconsistency may occur.

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	If you select an existing instance, DTS automatically populates the parameters for the instance. If you do not select an existing instance, you must configure parameters for the source 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 migrate 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. The account must have the read permissions on the objects to be migrated.
	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	The database instance that you want to use. You can determine whether to select an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the instance. If you do not select an existing instance, you must configure parameters for the source database.
	Database Type	The type of the destination database. Select Kafka.
	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
	Instance Region	The region in which the destination ApsaraMQ for Kafka instance resides.
	Kafka Instance ID	The ID of the destination ApsaraMQ for Kafka instance.
	Encryption	Specifies whether to encrypt the connection to the destination instance. Select Non-encrypted or SCRAM-SHA-256 based on your business and security requirements.
	Topic	The topic that is used to receive the migrated data. Select a topic from the drop-down list.
	Topic That Stores DDL Information	The topic that is used to store the DDL information. Select a topic from the drop-down list. If you do not configure this parameter, the DDL information is stored in the topic that is specified by the Topic parameter.
	Use Kafka Schema Registry	Specifies whether to use Kafka Schema Registry. Kafka Schema Registry provides a serving layer for your metadata. It provides a RESTful API to store and retrieve your Avro schemas. Valid values: No Yes If you select Yes for this parameter, you must enter the URL or IP address that is registered in Kafka Schema Registry for your Avro schemas.

If an IP address whitelist is configured for your self-managed database, add the CIDR blocks of DTS servers to the IP address whitelist. Then, click Test Connectivity and Proceed.
Note
For more information about the CIDR blocks of DTS servers, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
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 IP address 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 make sure that the ECS instance can access the database. If the self-managed database is hosted on multiple ECS instances, you must manually add the CIDR blocks of DTS servers to the security group rules of each ECS instance. 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 IP address whitelist of the database to allow DTS to access the database. For more information, see the "CIDR blocks of DTS servers" section of the Add the CIDR blocks of DTS servers to the security settings of on-premises databases topic.
Warning
If the public CIDR blocks of DTS servers are automatically or manually added to the IP address whitelist of a database instance or to the security group rules of an ECS instance, security risks may arise. Therefore, before you use DTS to migrate 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 account and password, limiting the ports that are exposed, authenticating API calls, regularly checking the IP address whitelist or ECS security group rules and forbidding unauthorized CIDR blocks, and connecting the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

Configure the objects to be migrated and advanced settings.

Parameter	Description
Migration Types	To perform only full data migration, select Schema Migration and Full Data Migration. To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains 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 migration task cannot be started. Note You can use the object name mapping feature to rename the tables that are migrated to the destination database. You can use this feature if the source and destination databases contain tables that have identical table names and the tables in the destination database cannot be deleted or renamed. 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 the following potential risks: If the source and destination databases have the same schemas, DTS does not migrate data records that have the same primary key values as data records in the destination database. If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.
Data Format in Kafka	The format in which data is stored in the destination ApsaraMQ for Kafka instance. If you select DTS Avro, data is parsed based on the schema definition of DTS Avro. For more information, visit GitHub. If you select Canal Json, data is stored in the Canal JSON format. For more information about the related parameters and examples, see the Canal Json section of the "Data formats of a Kafka cluster" topic.
Policy for Shipping Data to Kafka Partitions	The policy for migrating data to Kafka partitions. Select a policy based on your business requirements. For more information, see Specify the policy for migrating data to Kafka partitions.
Capitalization of Object Names in Destination Instance	The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that 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 only tables as the objects to be migrated.
Selected Objects	In this example, you do not need to configure this parameter. You can use the object name mapping feature to specify the information about the destination ApsaraMQ for Kafka instance, such as the name of the topic to which the data in the source table is migrated, number of partitions in the topic, and partition keys. For more information, see the Use the object name mapping feature section of this topic. Note If you use the object name mapping feature to rename an object, other objects that depend on the object may fail to be migrated. To migrate DML or DDL operations performed on an object during incremental migration, right-click the object in the Selected Objects section. In the dialog box that appears, select the DML and DDL operations that you want to migrate. For more information, see the SQL operations that can be incrementally migrated section of this topic.

Click Next: Advanced Settings to configure advanced settings.

Parameter or setting	Description
Select the dedicated cluster used to schedule the task	By default, DTS schedules the data migration task to the shared cluster if you do not specify a dedicated cluster. You can also purchase and specify a dedicated cluster of the required specifications to run the data migration task. For more information, see What is a DTS dedicated cluster.
Set Alerts	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts will receive notifications. Valid values: No: does not configure alerting. Yes: configures alerting. If you select Yes, you must also specify the alert threshold and alert contacts. For more information, see Configure monitoring and alerting.
Retry Time for Failed Connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later takes precedence. When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at 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 DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Important The value of the 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 Connections parameter.
Enable Throttling for Full Data Migration	Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters. This reduces the loads of the destination database server. Note This parameter is displayed only when Full Data Migration is selected as Migration Types.
Enable Throttling for Incremental Data Migration	Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server. Note This parameter is displayed only when Incremental Data Migration is selected as Migration Types.
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 added.
Configure ETL	Specifies whether to configure 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 synchronization task. No: does not configure the ETL feature.
Whether to delete SQL operations on heartbeat tables of forward and reverse tasks	Specifies whether to write SQL operations on heartbeat tables to the source database while the DTS instance is running. Yes: does not write SQL operations on heartbeat tables. In this case, a latency of the DTS instance may be displayed. No: writes SQL operations on heartbeat tables. In this case, specific features such as physical backup and cloning of the source database may be affected.

In the lower part of the page, click Next: Save Task Settings and Precheck.
You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameters to be specified when you call the relevant API operation to configure the DTS task.
Note
- Before you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.
- If the task fails to pass the precheck, click View Details next to each failed item. After you troubleshoot the issues based on the error message, you can run a precheck again.
- If an alert is triggered for an item during the precheck:
  If the alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.
  If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur and your business may be exposed to potential risks.
Wait until the success rate becomes 100%. Then, click Next: Purchase Instance.

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

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

Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.
Click Buy and Start to start the data migration task. You can view the progress of the task in the task list.

Use the object name mapping feature

In the Selected Objects section, move the pointer over the topic name.
Right-click Edit.

In the dialog box that appears, configure the parameters that are described in the following table.

Parameter	Description
Table Name	The name of the topic to which the data in the source table is migrated. Important The topic must exist in the destination ApsaraMQ for Kafka instance. Otherwise, data migration fails.
Filter Conditions	For more information, see Set filter conditions.
Number of Partitions	The number of partitions in the topic to which the data is migrated.
Partition Key	If you set the Policy for Shipping Data to Kafka Partitions parameter to Ship Data to Separate Partitions Based on Hash Values of Primary Keys, configure this parameter to specify one or more columns as partition keys to calculate hash values. DTS delivers different rows to each partition of the destination topic based on the calculated hash values. Note To select Partition Key for columns, you must first clear Synchronize All Tables.

Click OK.