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

Prerequisites

• The source PolarDB-X 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 synchronization scenarios.

• The available storage space of the destination Elasticsearch cluster is larger than the total size of the data in the source PolarDB-X instance.

Limits

Billing

Supported synchronization topologies

• One-way one-to-one synchronization

• One-way one-to-many synchronization

• One-way many-to-one synchronization

For more information about the synchronization topologies that are supported by DTS, see Synchronization topologies.

SQL operations that can be synchronized

Mappings

The MySQL data types supported by PolarDB-X do not match the data types supported by Elasticsearch. DTS converts the data types of the source database to those of the Elasticsearch cluster during schema synchronization based on the data type mappings for schema synchronization. For more information, see Data type mappings for initial schema synchronization.

Procedure

1. Go to the Data Synchronization 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 Synchronization.

   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 Synchronization Tasks page of the new DTS console.

2. On the right side of Data Synchronization Tasks, select the region in which the data synchronization instance resides.

   Note

   If you use the new DTS console, you must select the region in which the data synchronization instance resides in the top navigation bar.

3. Click Create Task. In the Create Data Synchronization Task wizard, configure the source and destination databases. The following table describes the parameters.

   Warning

   After you configure the source and destination databases, we recommend that you read the Limits that are displayed on the page. Otherwise, the task may fail or data inconsistency may occur.

   Section	Parameter	Description
   N/A	Task Name	The name of the DTS task. DTS automatically generates a task name. 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	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 instance resides.
   	Instance ID	The ID of the source PolarDB-X instance.
   	Database Account	The database account of the source PolarDB-X instance. The account must have the SELECT permission on the objects to be synchronized, and the REPLICATION CLIENT and REPLICATION SLAVE permissions. Note For more information about how to grant the permissions to the database account, see Data synchronization tools for PolarDB-X.
   	Database Password	The password that is used to access the database.
   Destination 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. The default database account in Elasticsearch clusters is elastic and must have the read and write permissions on the objects to be synchronized.
   	Database Password	The password that is used to access the database.

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 instance or an 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 make sure that the ECS instance can access the database. If the database is deployed 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 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 topic.

   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	The synchronization types. By default, Incremental Data Synchronization is selected. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of the selected objects from the source database to the destination cluster. The historical data is the basis for subsequent incremental synchronization.
   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 synchronization task cannot be started. Note If the source and destination databases contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are synchronized to the destination database. 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 potential risks. If the source and destination databases have the same schema and a data record in the destination database has the same primary key value or unique key value as a data record in the source database: During full data synchronization, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained. During incremental data synchronization, DTS synchronizes the data record to the destination database. The existing data record in the destination database is overwritten. If the source and destination databases have different schemas, data may fail to be initialized. In this case, only some columns are synchronized, or the data synchronization task fails. Proceed with caution.
   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. DatabaseName_TableName 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 and click the icon to add the objects to the Selected Objects section. Note You can select columns, tables, or databases as objects to synchronize. If you select tables or columns as the objects to be synchronized, DTS does not synchronize other objects such as views, triggers, and stored procedures to the destination database.
   Selected Objects	To rename an object that you want to synchronize to the destination instance, right-click the object in the Selected Objects section. For more information, see the "Map the name of a single object" section of the Map object names topic. To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see the "Map multiple object names at a time" section of the Map object names topic. Note To select the SQL operations performed on a specific database or table, perform the following steps: In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to synchronize. For more information about the SQL operations that can be synchronized, see the SQL operations that can be synchronized section of this topic. 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 Specify filter conditions. If you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be synchronized.

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

   Parameter	Description
   Monitoring and Alerting	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: No: does not enable alerting. Yes: configures alerting. In this case, you must also configure the alert threshold and alert notification settings. For more information, see the "Configure monitoring and alerting when you create a DTS task" section of the Configure monitoring and alerting topic.
   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 this 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 specify different retry time ranges for multiple data synchronization tasks that have the same source or destination database, the shortest retry time range 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 synchronization 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.

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 synchronize to the destination Elasticsearch cluster.

   Category	Description
   Set _routing	Specifies whether to store a document on a shard of the destination Elasticsearch cluster. For more information, see _routing. Valid values: Yes: You can specify custom columns for routing. 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 Composite primary keys are merged into one column. Business key If you select a business key, you must specify the business key column.

8. Save the task settings and run a precheck.

   • To view the parameters to be specified when you call the relevant API operation to configure the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.

   • If you do not need to view or have viewed the parameters, click Next: Save Task Settings and Precheck in the lower part of the page.

   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 data synchronization task fails the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, rerun the precheck.

   • 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 issue. 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.

9. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.

10. On the buy 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 a subscription when you create a data synchronization 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 billed 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 data synchronization instance, you can release the instance to reduce costs.
    	Resource Group Settings	The resource group to which the data synchronization instance belongs. Default value: default resource group. For more information, see What is Resource Management?
    	Instance Class	DTS provides instance classes that vary in synchronization speed. You can select an instance class based on your business requirements. For more information, see Instance classes of data synchronization instances.
    	Subscription Duration	If you select the subscription billing method, specify the subscription duration and the number of data synchronization 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.

11. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.

12. Click Buy and Start. In the dialog box that appears, click OK.

    You can view the progress of the task in the task list.

Check the index and data

After the state of the data synchronization 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 synchronized as expected. For more information about how to log on to the Kibana console, see Log on to the Kibana console.