Data Transmission Service：Synchronize 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 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 2.0 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 2.0 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 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 Configure the DMS console based on your business requirements.
   • You can also go to the Data Synchronization Tasks page of the new DTS console.
2. From the drop-down list to the right 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. 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 in the upper part of the page. This helps you create and run the data synchronization task.

   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	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. 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 Permissions required for an account to synchronize data.
   	Database Password	The password of the database account.
   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 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, DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the 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 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 need to manually add the CIDR blocks of DTS servers to the whitelist of the self-managed database on the ECS instance to allow DTS to access the database. 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 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.
   • After the DTS task is complete or released, we recommend that you manually remove the CIDR blocks of DTS servers from the whitelist or ECS security group rules. You must remove the IP address whitelist group whose name contains dts from the whitelist of the Alibaba Cloud database instance or the security group rules of the ECS instance. For more information about the CIDR blocks that you must remove from the whitelist of the self-managed databases that are deployed in data centers or databases that are hosted on third-party cloud services, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.

5. Select objects for the task and configure advanced settings.

   Parameter	Description
   Task Stages	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 database. 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 You can use the object name mapping feature to rename the tables that are synchronized 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 inconsistency may occur, and your business may be exposed to potential risks. If the source and destination databases have the same schemas, and a data record has the same primary key value as an existing data record in the destination 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.
   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 the objects to be synchronized. If you select tables or columns as the objects to be synchronized, DTS does not synchronize other objects such as views, triggers, or 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 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 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 Use SQL conditions to filter data. 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
   Set Alerts	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 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 when you create a DTS task.
   Retry Time for Failed Connection	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 the 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 set different retry time ranges for multiple DTS 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 the 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.
   

   Parameter	Description
   Set _routing	Specifies whether to store a document on a 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 synchronization task, DTS performs a precheck. You can start the data synchronization 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 analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.
   • If an alert is generated for an item during the precheck, perform the following operations based on the scenario:
     • In scenarios where you cannot ignore the alert item, click View Details next to the failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.
     • In scenarios where you can ignore the alert item, click Confirm Alert Details next to the failed item. 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 Purchase Instance 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 the instance when you create an 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 charged 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 instance, you can release the pay-as-you-go instance to reduce costs.
    	Instance Class	DTS provides several instance classes that have different performance in synchronization speed. You can select an instance class based on your business scenario. For more information, see Specifications of data synchronization instances.
    	Subscription Duration	If you select the subscription billing method, set the subscription duration and the number of instances that you want to create. The subscription duration can be one to nine months or one to three years. Note This parameter is displayed only if you select the subscription billing method.

11. Read and select the check box for Data Transmission Service (Pay-as-you-go) Service Terms.
12. Click Buy and Start to start the data synchronization task. 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.