Data Transmission Service:Migrate data from a PolarDB-X 2.0 instance to an Elasticsearch cluster

Prerequisites

• The source PolarDB-X 2.0 instance that is compatible with MySQL 5.7 is created.
• The destination Elasticsearch cluster is created. For more information, see Create an Alibaba Cloud Elasticsearch cluster.
• The engine versions of the source instance and the destination cluster are supported. For more information, see Overview of data migration scenarios.
• The available storage space of the destination PolarDB-X 2.0 instance is larger than the total size of the data in the source Elasticsearch instance.

Limits

Billing

Migration types

• Schema migration

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

• Full data migration

  DTS migrates the 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 can be incrementally migrated

Mappings

The MySQL data types supported by PolarDB-X 2.0 do not exactly match the data types supported by Elasticsearch. DTS converts the data types of the source database to those of the Elasticsearch cluster during schema migration based on the data type mappings between heterogeneous databases. For more information, see Data type mappings between heterogeneous databases.

Permissions required for database accounts

Procedure

1. 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 You can also configure the settings by using the new DTS console.
2. From the drop-down list to the right of Data Migration Tasks, select the region in which your data migration instance resides.
   Note If you use the new DTS console, 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.
   Warning After you select the source and destination instances, we recommend that you read the limits displayed at the top of the page. This helps you create and run the data migration task.

   Section	Parameter	Description
   N/A	Task Name	The name of the task. DTS automatically generates a task name. We recommend that you specify a descriptive name to identify the task. You do not need to specify a unique task name.
   Source Database	Select Instance	The instance that you want to use. You can choose whether to use an existing instance based on your business requirements. 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 set parameters for the database.
   	Database Type	The type of the source database. Select PolarDB-X 2.0.
   	Access Method	The access method of the source database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the source PolarDB-X 2.0 instance resides.
   	Instance ID	The ID of the source PolarDB-X 2.0 instance.
   	Database Account	The database account of the source PolarDB-X 2.0 instance. For more information about the permissions that are required for the account, see Permissions required for database accounts.
   	Database Password	The password of the database account.
   Destination Database	Select Instance	The instance that you want to use. You can choose whether to use an existing instance based on your business requirements. 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 set parameters for the database.
   	Database Type	The type of the destination database. Select Elasticsearch.
   	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the destination Elasticsearch cluster resides.
   	Instance ID	The ID of the destination Elasticsearch cluster.
   	Database Account	The database account of the destination Elasticsearch cluster. For more information about the permissions that are required for the account, see Permissions required for database accounts.
   	Database Password	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 of the database, Alibaba Cloud database instance, 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 of the database, Alibaba Cloud database instance, or ECS security group rules.
5. Select objects for the task and configure advanced 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 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 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 ensured, 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	Table Name If you select Table Name, the created index name in the destination Elasticsearch cluster is the same as the table name. In this example, order is used. Database Name_Table Name If you select Database Name_Table Name, the created index name in the destination Elasticsearch cluster is in the format of Database name_Table name. In this example, dtstest_order is used.
   Source Objects	Select one or more objects from the Source Objects section. Click the icon and add the objects to the Selected Objects section. Note You can select columns, tables, or schemas as the objects to be migrated. If you select tables or columns as the objects to be migrated, DTS does not migrate other objects such as views, triggers, or stored procedures to the destination database.
   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. To specify WHERE conditions to filter data, right-click an object in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Use SQL conditions to filter data. To select the SQL operations performed on a specific database or table, right-click an object in the Selected Objects section. In the dialog box that appears, select the SQL operations that you want to migrate. For more information about the SQL operations that can be migrated, see SQL operations that can be incrementally migrated.

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

   Parameter	Description
   Set Alerts	Specifies 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. Valid values: No: does not set alerts. Yes: sets alerts. If you select Yes, you must also set the alert threshold and alert contacts.
   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 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 and destination databases within the specified retry 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 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.
   Shard Configuration	The number of primary shards and replica shards based on the shard configuration of indexes of the destination Elasticsearch cluster.
   String Index	The method used to compile the strings to the indexes of the destination Elasticsearch cluster. analyzed: 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: The strings are indexed with the original values. no: The strings are not indexed.
   Time Zone	The time zone of the date and time data types such as DATETIME and TIMESTAMP. You can select a time zone 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	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 data 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, latency of the DTS instance may be displayed. No: writes SQL operations on heartbeat tables. In this case, features such as physical backup and cloning of the source database may be affected.

7. 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.

   Parameter	Description
   Set _routing	Specifies whether to store a document on a specified 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.
   Value of _id	Primary key column Multiple columns are merged into one composite primary key. Business key If you select a business key, you must also specify the business key column.

8. 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 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.
9. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
10. On the Purchase Instance page, specify the Instance Class parameter for the data migration instance. The following table describes the parameter.

    Section	Parameter	Description
    New Instance Class	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.

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

Check the index and data

After the state of the data migration task changes to Running, you can use the data visualization tool Kibana to connect to the Elasticsearch cluster. This way, you can check whether the index is created and data is migrated as expected. For more information about how to log on to the Kibana console, see Log on to the Kibana console.