Migrate RDS for MySQL to Alibaba Cloud Elasticsearch-Data Transmission Service(DTS)-阿里云帮助中心

Prerequisites

A destination Elasticsearch instance is created. For more information, see Create an Alibaba Cloud Elasticsearch instance.
For a full data migration, the destination instance must have more storage space than the source database uses.

Limitations

Note

DTS migrates foreign keys during schema migration.
During full and incremental data migration, DTS temporarily disables constraint checks and foreign key cascades at the session level. Cascade updates or deletes on the source database while the task runs may cause data inconsistency.

Type	Description
Source database limitations	Tables to be migrated must have a primary key or unique constraint, and the fields in the key or constraint must be unique. Otherwise, duplicate data may appear in the destination database. When you migrate data at the table level with edits such as column name mapping, a single task supports up to 5,000 tables. To migrate more than 5,000 tables, split them into multiple tasks or migrate the entire database in a single task. Otherwise, task submission may fail. If you need incremental migration, enable binary logging: Set binlog_format to ROW and binlog_row_image to FULL. Otherwise, the precheck fails and the task cannot start. Important If your self-managed MySQL source is a dual-master cluster—where each instance acts as both master and slave—enable the log_slave_updates parameter. This ensures DTS can read all binary logs. For RDS for MySQL instances, retain local binary logs for at least three days (seven days recommended). For self-managed MySQL databases, retain local binary logs for at least seven days. If DTS cannot access binary logs, the task fails. In extreme cases, data inconsistency or data loss may occur. Issues caused by binary log retention periods shorter than DTS requires are not covered under the DTS SLA. Note To set the retention period for local binary logs on an RDS for MySQL instance, see Automatically delete local logs. During the schema migration phase, do not perform DDL operations on the source database. Otherwise, the data migration task will fail. If you need incremental migration, RDS for MySQL instances that do not record transaction logs—such as RDS for MySQL 5.6 read-only instances—are not supported as sources. DTS does not migrate data generated by changes that do not write to binary logs. Examples include data restored from physical backups or created by cascade operations. Note If this occurs, re-run full migration after your business allows it. If your source MySQL database is version 8.0.23 or later and contains invisible hidden columns, DTS cannot read those columns. This may cause data loss. Note Run `ALTER TABLE <table_name> ALTER COLUMN <column_name> SET VISIBLE;` to make the hidden column visible. For more information, see Invisible Columns.
Other limitations	DTS does not support migrating indexes, partitions, views, procedures, functions, or triggers. Do not migrate data to a destination index that contains parent-child relationships or a Join field type mapping. This may cause task exceptions or query failures in the destination database. If you need to add a column to a table being migrated, first modify the mapping for the corresponding index in the Elasticsearch instance, then perform the DDL operation in the source database, and finally pause and restart the data migration task. Before you start data migration, evaluate the performance of the source and destination databases. We recommend that you perform the migration during off-peak hours because DTS consumes read and write resources on both databases during a full migration, which may increase their load. During a full migration, DTS runs concurrent INSERT operations that cause table fragmentation in the destination database. As a result, tables in the destination database may use more storage space than those in the source database after the migration completes. DTS attempts to resume failed migration tasks within seven days. Before you switch your workloads to the destination database, stop or release the task, or use the `revoke` statement to revoke write permissions from the DTS account on the destination database. Otherwise, the task may automatically resume and overwrite data in the destination database. If data migrated from a MySQL instance to an Elasticsearch instance contains null characters, they are converted to the LONG data type before being written to the Elasticsearch instance, which causes the task to fail. If data migrated from a MySQL instance to an Elasticsearch instance contains location information with latitude and longitude values stored in reverse order, an error occurs when writing the data to the Elasticsearch instance. Development and test specifications of Elasticsearch instances are not supported. If your RDS for MySQL instance has Always-Encrypted enabled, full migration is not supported. Note RDS for MySQL instances with Transparent Data Encryption (TDE) enabled support schema migration, full migration, and incremental migration. If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters. Note Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.
Special cases	For self-managed MySQL sources: A master–standby switchover on the source database causes the migration task to fail. DTS calculates latency by comparing the timestamp of the last record migrated to the destination database with the current time. If no DML operations run on the source for a long time, latency reporting becomes inaccurate. If latency appears too high, run a DML operation on the source to update the latency value. Note If you select full-database migration, create a heartbeat table. Update or write to it every second. DTS periodically runs CREATE DATABASE IF NOT EXISTS `test` on the source database to advance the binary log offset. If your source is Amazon Aurora MySQL or another clustered MySQL instance, ensure the domain name or IP address configured for the task—and its DNS resolution—always points to a read–write (RW) node. Otherwise, the migration task may fail. For RDS for MySQL sources: If you need incremental migration, RDS for MySQL instances that do not record transaction logs—such as RDS for MySQL 5.6 read-only instances—are not supported as sources. DTS periodically runs CREATE DATABASE IF NOT EXISTS `test` on the source database to advance the binary log offset.

Note

If a synchronization object of DTS is an index alias in the destination Elasticsearch instance, data inconsistency may occur when the actual index that the alias points to changes. For example, when data is written, the index alias points to Index A. If the alias later points to Index B during a subsequent synchronous delete operation, the data on Index A cannot be deleted. As a result, data deleted from the source can still be queried in the destination.

Billing

Migration type	Instance configuration fee	Internet traffic fee
Schema migration and full data migration	Free of charge.	When the Access Method parameter of the destination database is set to Public IP Address, you are charged for Internet traffic. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Schema migration

DTS migrates the schema definitions of the migration objects from the source database to the destination database.
Full migration

DTS migrates all historical data of the specified migration objects from the source database to the destination database.
Incremental migration

After a full migration is complete, DTS migrates incremental data updates from the source database to the destination database. Incremental migration lets you smoothly migrate data without interrupting your self-managed applications.

Supported SQL operations for incremental migration

Type	SQL statement
DML	INSERT, UPDATE, and DELETE Note Using an UPDATE statement to remove a column is not a supported operation.

Database account permissions

Database	Schema migration	Full data migration	Incremental data migration	Actions
ApsaraDB RDS for MySQL instance	`SELECT` privilege	`SELECT` privilege	`REPLICATION CLIENT`, `REPLICATION SLAVE`, `SHOW VIEW`, and `SELECT` privileges	Create an account
Elasticsearch cluster	The database account (typically `elastic`) requires read and write privileges.

Data type mapping

A source database and an Elasticsearch instance support different data types that cannot always be mapped directly. During structure initialization, DTS maps data types based on those supported by the target Elasticsearch instance. For more information, see Data type mapping for structure initialization.

Note
During the DTS schema migration process, DTS does not set the dynamic parameter in mapping. The behavior of this parameter depends on the settings of your Elasticsearch instance. If your source data is of the JSON type, you must ensure that for a specific key, its corresponding values have the same data type across all rows in a table. Otherwise, DTS may encounter synchronization issues. For more information, see dynamic.

The mapping between Elasticsearch and a relational database varies by Elasticsearch version.

Important

Starting with Elasticsearch 7.0, an index no longer supports multiple types, and types were completely removed in Elasticsearch 8.0. By default, when you configure a synchronization or migration task, DTS maps a table from a relational database to an index in Elasticsearch. You can change this mapping when you configure the objects to synchronize or migrate.

Elasticsearch 7.0 and later

Elasticsearch	Relational database
index	table
document	row
field	column
mapping	schema

Versions before Elasticsearch 7.0

Elasticsearch	Relational database
index	database
type	table
document	row
field	column
mapping	schema

Procedure

Navigate to the migration task list page for the destination region using one of the following methods.
From the DTS console
1. Log on to the Data Transmission Service (DTS) console.
2. In the navigation pane on the left, click Data Migration.
3. In the upper-left corner of the page, select the region where the migration instance is located.
From the DMS console

Note
The actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.
1. Log on to the Data Management (DMS) console.
2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.
3. To the right of Data Migration Tasks, select the region where the migration instance is located.
Click Create Task to navigate to the task configuration page.

Configure the source and destination databases.

Category	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.
Source Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select MySQL.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the source ApsaraDB RDS for MySQL instance is located.
	Replicate Data Across Alibaba Cloud Accounts	To migrate data within the same Alibaba Cloud account, select No.
	RDS Instance ID	Select the ID of the source ApsaraDB RDS for MySQL instance.
	Database Account	Enter the database account for the source ApsaraDB RDS for MySQL instance. For information about the required permissions, see Permissions required for database accounts.
	Database Password	Enter the password for the specified database account.
	Encryption	Select Non-encrypted or SSL-encrypted as needed. If you set this to SSL-encrypted, you must enable SSL encryption for the RDS for MySQL instance beforehand. For more information, see Use a cloud certificate to quickly enable SSL link encryption.
Destination Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select Elasticsearch.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination Elasticsearch instance is located.
	Type	Select Cluster Edition or Serverless based on your requirements.
	Instance ID	Select the ID of the destination Elasticsearch instance.
	Database Account	Enter the account used to connect to the Elasticsearch instance. This is the Username you specified when creating the instance. The default account is elastic.
	Database Password	Enter the password for the specified database account.
	Encryption	Select HTTP or HTTPS as needed.

After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.
Note
- Ensure that the IP address segment of the DTS service is 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 (the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box that appears.

Configure the task objects.

On the Configure Objects page, configure the objects that you want to migrate.

Parameter	Description
Migration Types	If you only need to perform a full migration, select both Schema Migration and Full Data Migration. To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed. If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
Processing Mode for Existing Destination Tables	Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start. Note If a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping. Ignore Errors and Proceed: Skips the check for tables with the same names. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example: If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database: During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated. During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database. If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.
Index Name	If you select Table Name, the index created in the destination Elasticsearch instance has the same name as the table. If you select Database Name_Table Name, the index name in the destination Elasticsearch instance is a concatenation of the database name, an underscore (_), and the table name. Note The index name mapping configuration applies to all tables.
Case Policy for Destination Object Names	You can configure the case sensitivity policy for the names of migrated objects, such as databases, tables, and columns, in the destination instance. By default, DTS default policy is selected. You can also choose to keep the case sensitivity consistent with the default policy of the source or destination database. For more information, see Case sensitivity of object names in the destination database.
Source Objects	In the Source Objects pane, click the object that you want to migrate, and then click the icon to move the object to the Selected Objects pane.
Selected Objects	To modify the field names after migration, right-click the corresponding table name in the Selected Objects pane, set the index name and type name for the table in the destination Elasticsearch instance, and then click OK. For more information, see Map a single table and its columns. Note The only special character supported for index names and type names is the underscore (_). You can set SQL filter conditions. Only data that meets these conditions will be migrated to the destination instance. For more information, see Filter task data by using SQL conditions.

Click Next: Advanced Settings to configure advanced parameters.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules tasks on a shared cluster. You do not need to select one. If you want more stable tasks, you can purchase a dedicated cluster to run DTS migration tasks.
Retry Time for Failed Connections	After the migration task starts, if the connection to the source or destination database fails, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1440 minutes. We recommend that you set the duration to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified duration, the migration task automatically resumes. Otherwise, the task fails. Note For multiple DTS instances that share the same source or destination, the network retry time is determined by the setting of the last created task. Because you are charged for the task during the connection retry period, we recommend that you customize the retry time based on your business needs, or release the DTS instance as soon as possible after the source and destination database instances are released.
Retry Time for Other Issues	After the migration task starts, if a non-connectivity issue, such as a DDL or DML execution exception, occurs in the source or destination database, DTS reports an error and immediately begins to retry the operation. The default retry duration is 10 minutes. You can customize the retry time to a value from 1 to 1440 minutes. We recommend that you set the duration to more than 10 minutes. If the related operations succeed within the specified retry duration, the migration task automatically resumes. Otherwise, the task fails. Important The value of Retry Time for Other Issues must be less than the value of Retry Time for Failed Connections.
Shard Configuration	Set the number of primary and replica shards for the index based on the maximum shard configuration of indexes in the destination Elasticsearch instance.
String Index	Specifies how strings are indexed in the destination Elasticsearch instance. analyzed: The string is first analyzed and then indexed. You must also select a specific analyzer. For information about analyzer types and their functions, see Analyzers. not_analyzed: The string is not analyzed and is indexed by using its original value. no: The string is not indexed.
Time Zone	Specifies the time zone applied when DTS migrates time-based data types (such as DATETIME and TIMESTAMP) to the destination Elasticsearch instance. Note If the time-based data in the destination instance does not require a time zone, you must set the document type (type) for these data types in the destination instance in advance.
DOCID	By default, the DOCID is the primary key of the table. If the table has no primary key, the DOCID is an ID column automatically generated by Elasticsearch.
Environment Tag	Select an environment tag to identify the instance. This parameter is optional for this example.
Configure ETL	Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: Enables the ETL feature. Enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: Disables the ETL feature.
Whether to delete SQL operations on heartbeat tables of forward and reverse tasks	Choose whether DTS writes heartbeat SQL information to the source database while the instance is running. Yes: Does not write heartbeat SQL information to the source database. The DTS instance may display latency. No: Writes heartbeat SQL information to the source database. This may interfere with source database operations like physical backups and cloning.
Monitoring and Alerting	Select whether to set alerts and receive alert notifications based on your business needs. No: Does not set an alert. Yes: Configure alerts by setting an alert threshold and an alert contact. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.

After you complete the preceding configurations, click Next: Configure Database and Table Fields at the bottom of the page to set the _routing policy and the value of _id for the tables to be migrated in the destination Elasticsearch.

Type	Description
Set _routing	Configures _routing to store documents on a specific shard in the destination Elasticsearch instance. For more information, see _routing. Select Yes to use a custom column for routing. Select No to use the _id value for routing. Note If the destination Elasticsearch instance is version 7.x, you must select No.
_routing Column	Select the column to be used for routing. Note This parameter is required only if you select Yes for Set _routing.
Value of _id	Select the column to be used as the document ID.

Save the task and run a precheck.
- To view the parameters for configuring this instance when you call the API operation, move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears.
- If you do not need to view or have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note
- Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.
- If the precheck fails, click View Details next to the failed check item, fix the issue based on the prompt, and then run the precheck again.
- If a warning is reported during the precheck:
  
  For check items that cannot be ignored, click View Details next to the failed item, fix the issue based on the prompt, and then run the precheck again.
  
  For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again to skip the alert item and run the precheck again. If you choose to ignore a warning, it may cause issues such as data inconsistency and pose risks to your business.

Purchase the instance.

When the Success Rate reaches 100%, click Next: Purchase Instance.

On the Purchase page, select the link specification for the data migration instance. For more information, see the following table.

Category	Parameter	Description
New Instance Class	Resource Group Settings	Select the resource group to which the instance belongs. The default value is default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides migration specifications with different performance levels. The link specification affects the migration speed. You can select a specification based on your business scenario. For more information, see Data migration link specifications.

After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the OK dialog box that appears, click OK.

You can view the progress of the migration task on the Data Migration Tasks list page.
Note
- If the migration task does not include incremental migration, it stops automatically after the full migration is complete. After the task stops, its Status changes to Completed.
- If the migration task includes incremental migration, it does not stop automatically. The incremental migration task continues to run. While the incremental migration task is running, the Status of the task is Running.