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

Prerequisites

  • The destination Elasticsearch cluster is created. For more information, see Create an Alibaba Cloud Elasticsearch cluster.
  • The available storage space of the destination Elasticsearch cluster is larger than the total size of the data in the ApsaraDB RDS for MySQL instance. This ensures a successful full data migration.

Limits

Category Description
Limits on the source instance
  • 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 want to edit the tables (such as renaming tables or columns) in the destination cluster, you can migrate up to 5,000 tables in a single data migration task. If you run a task to migrate more than 5,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to migrate the tables or configure a task to migrate the entire instance.
  • The binary logging feature must be enabled for the ApsaraDB RDS for MySQL instance. The binlog_format parameter must be set to row and the binlog_row_image parameter must be set to full. For more information, see View the parameters of an ApsaraDB RDS for MySQL instance. Otherwise, error messages are returned during precheck and the data migration task cannot be started.
  • For an incremental data migration task, binary logs of the source instance must be stored for more than 24 hours. For a full data and incremental data migration task, binary logs of the source instance must be stored for at least seven days. After full data migration is complete, you can set the retention period to more than 24 hours. Otherwise, DTS may fail to obtain the binary logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. Make sure that you set the retention period of binary logs in accordance with the preceding requirements. Otherwise, the SLA of DTS does not ensure service reliability and performance. For more information about binary log files of an ApsaraDB RDS for MySQL instance, see View and delete the binary log files of an ApsaraDB RDS for MySQL instance.

  • Limits on operations: During schema migration, do not perform DDL operations to change the schemas of databases or tables. Otherwise, the data migration task fails.
Other limits
  • If you want to add columns to a table in the source instance, modify the mappings of the index that corresponds to the table in the Elasticsearch cluster. Then, perform DDL operations on the source table, pause the data migration task, and then start the task again.
  • Before you migrate data, evaluate the impact of data migration on the performance of the source instance and destination cluster. We recommend that you migrate data during off-peak hours. During full data migration, DTS uses the read and write resources of the source instance and destination cluster. This may increase the loads on the database servers.
  • During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination cluster. After full data migration is complete, the size of used tablespace of the destination cluster is larger than that of the source instance.
  • DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads to the destination cluster, stop or release the data migration task. You can also execute the REVOKE statement to revoke the write permissions from the accounts that are used by DTS to access the destination cluster. Otherwise, the data in the source instance overwrites the data in the destination cluster after the task is resumed.

Billing

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 Pricing.
Incremental data migration Charged. For more information, see Pricing.

Migration types

  • Schema migration

    DTS migrates the schemas of required objects from the source database to the destination database.

  • Full data migration

    DTS migrates historical data of required 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 you to ensure service continuity when you migrate data between self-managed databases.

SQL operations that support incremental data migration

Operation type SQL statement
DML INSERT, UPDATE, and DELETE

Data type mappings

The data types of MySQL databases and Elasticsearch clusters do not have one-to-one correspondence. During initial schema synchronization, DTS converts the data types of the source database into the data types of the destination database. For more information, see Data type mappings between heterogeneous databases.

Permissions required for database accounts

Database type Schema migration Full data migration Incremental data migration References
ApsaraDB RDS for MySQL instance The SELECT permission The SELECT permission The REPLICATION SLAVE, REPLICATION CLIENT, SHOW VIEW, and SELECT permissions Create an account on an ApsaraDB RDS for MySQL instance
Elasticsearch instance The database account must have the read and write permissions on the objects to be migrated. The default database account in Elasticsearch clusters is elastic.

Procedure

  1. Go to the Data Migration Tasks page.
    1. Log on to the DMS console.
    2. In the top navigation bar, move the pointer over DTS.
    3. Choose DTS (DTS) > Data Migration.
  2. In the drop-down list next to Data Migration Tasks, select the region in which your data migration instance resides.
    Note If you use the new DTS console, you must select the region in which your data migration instance resides in the upper-left corner.
  3. Click Create Task. On the page that appears, configure the source and destination databases.
    Section Parameter Description
    N/A Task Name

    DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to use a unique task name.

    Source Database Select Instance
    Select whether to use an existing instance.
    • If you use an existing instance, DTS automatically applies the parameter settings of the instance.
    • If you do not use an existing instance, you must configure the following parameters.
    Database Type Select MySQL.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select 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 Select the ID of the source ApsaraDB RDS for MySQL instance.
    Database Account Enter the database account of the source ApsaraDB RDS for MySQL instance. For information about the permissions that are required for the account, see Permissions required for database accounts.
    Database Password

    Enter the password of the database account.

    Encryption

    Select Non-encrypted or SSL-encrypted based on your business requirements. If you want to 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 SSL encryption for an ApsaraDB RDS for MySQL instance.

    Destination Database Select Instance
    Select whether to use an existing instance.
    • If you use an existing instance, DTS automatically applies the parameter settings of the instance.
    • If you do not use an existing instance, you must configure the following parameters.
    Database Type Select Elasticsearch.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select the region in which the destination Elasticsearch cluster resides.
    Instance ID Select the ID of the destination Elasticsearch cluster.
    Database Account Enter the username that is used to connect to the Elasticsearch cluster. This account is the Username that you specified when you created the Elasticsearch cluster. The default database account in Elasticsearch clusters is elastic.
    Database Password

    Enter the password of the database account.

  4. In the lower part of the page, click Test Connectivity and Proceed.
    Warning
    • 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. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases. 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.
    • If the CIDR blocks of DTS servers are automatically or manually added to the whitelist or ECS security group rules, 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 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.
    • After the DTS task is complete or released, we recommend that you manually detect and remove the added CIDR blocks from the whitelist or ECS security group rules.
  5. Select objects for the task and configure advanced settings.
    • Basic Settings
      Parameter Description
      Task Stages
      • 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 Incremental Data Migration is not selected, we recommend that you do not write data to the source instance during data migration. This ensures data consistency between the source and destination instances.
      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 identical table names, the precheck is passed. Otherwise, an error is returned during 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 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 consistency is not guaranteed and your business may be exposed to potential risks.
        • If the source and destination databases have the same schema, DTS does not migrate data records that have the same primary keys 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.
      Index Name
      • If you select Table Name, the index created in the destination Elasticsearch cluster uses the same name as the table in the ApsaraDB RDS for MySQL instance.

      • If you select Database Name_Table Name, the index created in the destination Elasticsearch cluster is concatenated in the format of DatabaseName_TableName.

      Note The index name mapping rule takes effect for all tables.
      Capitalization of Object Names in Destination Instance

      Specify 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 of 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 Rightwards arrow icon to add the objects to the Selected Objects section.

      Note The time field supports the TIMESTAMP data type. If the time field of the source instance is 0, the time field of the destination cluster is automatically converted to null.
      Selected Objects
      • To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.
      • To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
      Note If you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be migrated.
    • Advanced Settings
      Parameter Description
      Set Alerts
      Specify whether to set alerts for the data migration task. If the task fails or the migration latency exceeds the threshold, the alert contacts will receive notifications.
      • Select No if you do not want to set alerts.
      • Select Yes to set alerts. In this case, you must also set the alert threshold and alert contacts.
      Retry Time for Failed Connection
      The retry time range for failed connections. If the data migration task fails, DTS immediately retries a connection within the time range. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the parameter to a value greater than 30. If DTS reconnects to the source instance and destination cluster within the specified time range, DTS resumes the data migration task. Otherwise, the data migration task fails.
      Note
      • If you set different retry time ranges for multiple data migration tasks that have the same source instance or destination cluster, the value that is set 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 needs. You can also release the DTS instance at your earliest opportunity after the source instance and destination cluster are released.
      Shard Configuration The number of primary shards and replica shards based on the shard configuration of indexes of the destination Elasticsearch cluster.
      String Index
      Set the method that is used to index the migrated strings in the destination Elasticsearch cluster.
      • analyzed: indicates that the strings are analyzed before indexing. You must select a specific analyzer. For more information about the analyzer types, see Built-in analyzer reference.
      • not analyzed: indicates that the strings are indexed with the original values.
      • no: indicates that the strings are not indexed.
      Time Zone
      The time zone of the date and time data types such as DATETIME and TIMESTAMP, which you can select during the data migration to the destination Elasticsearch cluster.
      Note If the date and time data types in the destination cluster do not need a time zone, you must specify the document type for the date and time data types.
      DOCID

      The default value of the parameter is the primary key of the table in the Elasticsearch cluster. If the table does not have a primary key, the value of the parameter is the ID column that is automatically generated by Elasticsearch.

      Configure ETL
      Specify whether you want to enable the ETL feature. For more information, see What is ETL?.
      • If you select Yes, the ETL feature is enabled. You must specify a policy in the text box.
      • If you select No, the ETL feature is disabled.
  6. In the lower part of the page, click Next: Configure Database and Table Fields. On the page that appears, set the _routing policy and _id value of the tables that you want to migrate to the destination Elasticsearch cluster.
    Category Description
    Set _routing. Specifies whether to store a document on a specific shard of the destination Elasticsearch cluster. For more information, see _routing.
    • If you select Yes, you can specify custom columns for routing.
    • If you select No, the _id value is used for routing.
    Note If the version of the destination Elasticsearch cluster is 7.x, you must select No.
    _routing Column Select the column that is used for routing.
    Note This parameter is required only when the Set _routing parameter is set to Yes.
    Value of _id Select the column that is used to store the IDs of documents.
  7. In the lower part of the page, click Next: Save Task Settings and Precheck.
    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, you can click the Info icon icon next to each failed item to view details.
      • You can troubleshoot the issues based on the causes and run a precheck again.
      • If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
  8. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
  9. On the Purchase Instance page, specify the Instance Class parameter for the data migration instance. The following table describes the parameter.
    Section Parameter Description
    Parameters Instance Class

    DTS provides several instance classes that have different performance in migration speed. You can select an instance class based on your business scenario. For more information, see Specifications of data migration instances.

  10. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
  11. Click Buy and Start to start the data migration task. You can view the progress of the task in the task list.