Elasticsearch：Use DTS to synchronize data from MySQL to Alibaba Cloud Elasticsearch in real time

Enable the Auto Indexing feature for the Elasticsearch cluster.

Create a database and a table. Then, insert data into the table.

You can use an ApsaraDB RDS database or a self-managed database that is created on your on-premises machine. In this example, an ApsaraDB RDS for MySQL database is used. For information about how to create an ApsaraDB RDS for MySQL database and create a table in the database, see General workflow to use ApsaraDB RDS for MySQL.

In this example, the following ApsaraDB RDS for MySQL database is created, and the following SQL statements are executed to create a table in the database and insert data into the table.

• Create an ApsaraDB RDS for MySQL database

  test_logstash

• Create a table in the database and insert data into the table

  -- create table
  CREATE TABLE `es_test` (
      `id` bigint(32) NOT NULL,
      `name` varchar(32) NULL,
      `age` bigint(32) NULL,
      `hobby` varchar(32) NULL,
      PRIMARY KEY (`id`)
  ) ENGINE=InnoDB
  DEFAULT CHARACTER SET=utf8;
  
  -- insert data
  INSERT INTO `es_test` (`id`,`name`,`age`,`hobby`) VALUES (1,'user1',22,'music');
  INSERT INTO `es_test` (`id`,`name`,`age`,`hobby`) VALUES (2,'user2',23,'sport');
  INSERT INTO `es_test` (`id`,`name`,`age`,`hobby`) VALUES (3,'user3',43,'game');
  INSERT INTO `es_test` (`id`,`name`,`age`,`hobby`) VALUES (4,'user4',24,'run');
  INSERT INTO `es_test` (`id`,`name`,`age`,`hobby`) VALUES (5,'user5',42,'basketball');

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.

On the Data Synchronization page, click Create Task. Then, create and configure a data synchronization task as prompted.

1. Configure the source database and destination database.

   Category	Parameter	Description
   None	Task Name	DTS automatically generates a task name. You do not need to use a unique task name. We recommend that you use an informative name for easy identification.
   Source Database	Database Type	The source database type. Select MySQL.
   	Access Method	The access method of the source database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the source MySQL database resides.
   	Replicate Data Across Alibaba Cloud Accounts	In this example, No is selected because data is synchronized within the same Alibaba Cloud account.
   	RDS Instance ID	The ID of the source ApsaraDB RDS for MySQL instance.
   	Database Account	The account that is used to connect to the ApsaraDB RDS for MySQL database from which you want to synchronize data. The account must be granted read permissions on the database.
   	Database Password	The password that is used to connect to the ApsaraDB RDS for MySQL database. Enter the password that corresponds to the username specified by Database Account.
   	Encryption	Specifies whether to encrypt the connection to the source ApsaraDB RDS for MySQL database. Valid values: Non-encrypted and SSL-encrypted. If you 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 the SSL encryption feature.
   Destination Database	Database Type	The destination database type. Select Elasticsearch.
   	Access Method	The access method of the destination Elasticsearch cluster. The value of this parameter is fixed as Alibaba Cloud Instance.
   	Instance Region	The region in which the destination Elasticsearch cluster resides. We recommend that you select the region in which the source ApsaraDB RDS for MySQL database resides.
   	Instance ID	The ID of the destination Elasticsearch cluster.
   	Database Account	The username that is used to connect to the destination Elasticsearch cluster. The default username is elastic.
   	Database Password	The password that is used to connect to the destination Elasticsearch cluster. Enter the password that corresponds to the username specified by Database Account.

2. Configure the objects from which you want to synchronize data.

   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 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 If the source and destination databases contain identical table 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 the following 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 system creates an index that has the same name as the table in the Elasticsearch cluster. In this example, the index name is es_test. Database Name_Table Name If you select Database Name_Table Name, the system creates an index whose name is in the format of Database name_Table name. In this example, the index name is test_logstash_es_test.
   Source Objects	Select one or more objects from the Source Objects section and click the icon to move the objects to the Selected Objects section.
   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.

3. Configure field mappings and change the names of fields that are synchronized.

   If you want to change the names of fields that are synchronized, you can click the name of the table to which the fields belong in the Selected Objects list, and specify the name of the index and the name of the index type in the Elasticsearch cluster for the table. After the configuration is complete, click OK. The following table describes the parameters that are configured in this example. You can retain the default values for other parameters that are not described in the following table. For more information, see Map the name of a single object.

   Parameter	Description
   Index Name	The name of the destination index. You can specify a name based on your business requirements. For information about the concept of an index, see Terms. Important The name that you enter must be unique in the Elasticsearch cluster. Otherwise, the index already exists error message appears.
   Type Name	The name of the destination index type. You can specify a name based on your business requirements. For information about the concept of an index type, see Terms.
   Filter Conditions	You can specify SQL conditions to filter data. Only data that meets the specified conditions can be synchronized to the destination Elasticsearch cluster. For more information, see Set filter conditions.
   Parameter	Select the column parameter and parameter value. For more information, see Mapping parameters. Important If you set index to false for a field that you added, the field cannot be queried. For more information, see index.

4. Configure advanced parameters.

   In this example, default values are retained for the advanced parameters. The following table describes the advanced parameters.

   Parameter	Description
   Select the dedicated cluster used to schedule the task	By default, DTS schedules the data synchronization task by using a public cluster. You do not need to specify a node in a public cluster for task scheduling. If you want to use a dedicated cluster, you must purchase one first, and make sure that the dedicated cluster can successfully run before you can select it. You can purchase a dedicated cluster to run DTS tasks such as data migration tasks, data synchronization tasks, and subscription tasks. Dedicated clusters can isolate resources for your DTS tasks from the resources used by DTS instances of other users. Compared with DTS instances in public clusters, DTS instances in dedicated clusters have higher stability and better performance.
   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. In this case, you must also configure the alert threshold and alert contacts. For more information, see Configure monitoring and alerting.
   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 the number of replica shards for each primary shard. You can specify the numbers based on the default shard configuration of the destination Elasticsearch cluster. By default, an index in an Elasticsearch cluster whose version is earlier than V7.X has five primary shards and one replica shard for each primary shard. By default, an index in an Elasticsearch cluster whose version is V7.X or later has one primary shard and one replica shard for the primary shard. Important The number of shards and the size of each shard are important factors that affect the stability and performance of an Elasticsearch cluster. You must appropriately configure shards for indexes in an Elasticsearch cluster. For information about how to plan shards for indexes, see Evaluate specifications and storage capacity.
   String Index	The method used to index strings that are synchronized to the destination Elasticsearch cluster. Valid values: analyzed: indicates that the strings are analyzed before indexing. You must select an analyzer. For information about the analyzer types, reference 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	If you synchronize data of a date or time data type such as DATETIME or TIMESTAMP, you can select a time zone. Note If the date and time data type in the destination Elasticsearch 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 this parameter is the primary key of the table in the destination Elasticsearch cluster. If the table does not have a primary key, the value of this parameter is the ID column that is automatically generated by Elasticsearch.
   Configure ETL	The ETL configuration feature does not support changes on table schemas in a destination. If changes on table schemas are required, you must make the changes in the destination before the data synchronization task starts. If you change the existing ETL-related configurations, the data synchronization task may be interrupted, or historical data may be changed. Make sure that your business is not affected if you change the existing ETL-related configurations. If you change the existing ETL-related configurations and restart the data synchronization task, the new configurations take effect only for incremental data that is generated after the restart. The new configurations do not take effect for historical data. For more information about how to make ETL-related configurations, see Configure ETL in a data migration or data synchronization task.

5. Configure the routing policy and the value of the _id field in the Elasticsearch cluster for the table from which you want to synchronize data.

   The following table describes the parameters that are configured in this example.

   Parameter	Description
   Set _routing	Specifies whether to store a document on a specific 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.

After the configuration is complete, save the data synchronization task, perform a pre-check on the task, and purchase a DTS instance to start the data synchronization task.

On the Console tab, run the following command to query the full data that is synchronized to the destination Elasticsearch cluster:

GET /es_test_index/es_test_type/_search

Insert a data record into the source table and view the synchronization result of the data record in the destination Elasticsearch cluster.

INSERT INTO `test_logstash`.`es_test` (`id`,`name`,`age`,`hobby`) VALUES (6,'user6',30,'dance');