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Data Transmission Service:Synchronize data from an ApsaraDB RDS for MySQL instance to an Elasticsearch cluster

更新時間:Oct 17, 2023

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

Prerequisites

Precautions

Category

Description

Limits on the source database

  • The tables to be synchronized 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 synchronized and you need to edit the tables in the destination database, such as renaming tables or columns, you can synchronize up to 1,000 tables in a single data synchronization task. If you run a task to synchronize more than 1,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to synchronize the tables in batches or configure a task to synchronize the entire database.

  • The following requirements for binary logs must be met:

    • By default, the binary logging feature is enabled. The binlog_row_image parameter must be set to full. Otherwise, error messages are returned during precheck and the data synchronization task cannot be started. For more information, see Modify instance parameters.

      Important
      • If the source database is a self-managed MySQL database, you must enable the binary logging feature and set the binlog_format parameter to row and the binlog_row_image parameter to full.

      • If the source database is a self-managed MySQL database deployed in a dual-primary cluster, you must set the log_slave_updates parameter to ON. This ensures that DTS can obtain all binary logs. For more information, see Create an account for a self-managed MySQL database and configure binary logging.

    • If you perform only incremental data synchronization, the binary logs of the source database must be retained for at least 24 hours. If you perform both full data synchronization and incremental data synchronization, the binary logs of the source database must be retained for at least seven days. Otherwise, DTS may fail to obtain the binary logs, which causes the task to fail, or even data inconsistency and data loss. After full data synchronization is complete, you can set the retention period to more than 24 hours. Make sure that you set the retention period of binary logs based on the preceding requirements. Otherwise, the Service Level Agreement (SLA) of DTS does not guarantee service reliability or performance. For more information about the binary log files of an ApsaraDB RDS for MySQL instance, see Manage binary log files.

Other limits

  • Before you synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. During initial full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the loads on the database servers.

  • During initial full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination database. After initial full data synchronization is complete, the size of the used tablespace of the destination database is larger than that of the source database.

  • If you select one or more tables instead of an entire database as the objects to be synchronized, do not use tools such as pt-online-schema-change to perform online DDL operations on the tables during data synchronization. Otherwise, data may fail to be synchronized.

    You can use Data Management (DMS) to perform online DDL operations. For more information, see Perform lock-free DDL operations.

  • To add columns to a table that you want to synchronize, perform the following operations: Modify the mappings of the table in the Elasticsearch cluster, perform DDL operations in the source MySQL database, and then pause and start the data synchronization task.

  • During data synchronization, we recommend that you use only DTS to write data to the destination database. This prevents data inconsistency between the source and destination databases. For example, if you use tools other than DTS to write data to the destination database, data loss may occur in the destination database when you use DMS to perform online DDL operations.

  • If a table that you want to synchronize contains empty strings, the data that contains empty strings in the table is written to the Elasticsearch cluster as data of the LONG type. In this case, the data synchronization task fails.

  • If a table that you want to synchronize contains latitude and longitude values that are stored in reverse, an error occurs when the data in the table is written to the Elasticsearch cluster.

Special cases

If the source database is a self-managed MySQL database, take note of the following items:

  • If you perform a primary/secondary switchover on the source database when the data synchronization task is running, the task fails.

  • DTS calculates synchronization latency based on the timestamp of the latest synchronized data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for an extended period of time, the synchronization latency may be inaccurate. If the latency of the data synchronization task is excessively high, you can perform a DML operation on the source database to update the latency.

    Note

    If you select an entire database as the object to be synchronized, you can create a heartbeat table. The heartbeat table is updated or receives data every second.

  • DTS executes the CREATE DATABASE IF NOT EXISTS 'test' statement in the source database as scheduled to move forward the binary log file position.

Billing

Synchronization typeTask configuration fee
Schema synchronization and full data synchronizationFree of charge.
Incremental data synchronizationCharged. For more information, see Billing overview.

SQL operations that can be synchronized

Operation type

SQL statement

DML

INSERT, UPDATE, and DELETE

Permissions required for database accounts

Database

Required permission

References

The source ApsaraDB RDS for MySQL instance

Read permissions on the objects to synchronize

Create an account on an ApsaraDB RDS for MySQL instance and Modify the permissions of a standard account on an ApsaraDB RDS for MySQL instance.

The destination Elasticsearch cluster

The username (elastic by default) and the logon password that were set when the Elasticsearch cluster was created.

Note

If the source database account that you use is not created and authorized by using the ApsaraDB RDS for MySQL console, make sure that the account has the REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT permissions.

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 cluster. For more information, see Data type mappings for schema synchronization.

Term mappings

ElasticsearchRelational database
indexdatabase
typetable
documentrow
fieldcolumn
mappingschema

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
  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.

    Category

    Parameter

    Description

    N/A

    Task Name

    The name of the task. DTS automatically assigns a name to the task. 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

    Select an existing DMS database instance

    The database instance that you want to use. You can choose whether to select an existing instance based on your business requirements.

    • If you select an existing instance, DTS automatically populates the parameters for the database.

    • If you do not select an existing instance, you must manually configure parameters for the database.

    Database Type

    The type of the destination instance. Select MySQL.

    Access Method

    The access method of the destination instance. Select Alibaba Cloud Instance.

    Instance Region

    Select the region where the source ApsaraDB RDS for MySQL instance resides.

    Replicate Data Across Alibaba Cloud Accounts

    Specifies whether data is synchronized 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

    The database account of the source ApsaraDB RDS for MySQL instance. For information about the permissions that are required for the account, see the "Permissions required for database accounts" section of this topic.

    Database Password

    The password of the database account.

    Encryption

    Specifies whether to encrypt the connection to the database. Select Non-encrypted or SSL-encrypted based on your business requirements. 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

    Select an existing DMS database instance

    The database instance that you want to use. You can choose whether to select an existing instance based on your business requirements.

    • If you select an existing instance, DTS automatically populates the parameters for the database.

    • If you do not select an existing instance, you must manually configure parameters for the database.

    Database Type

    The type of the destination database. Select Elasticsearch.

    Access Method

    The access method of the destination instance. Select Alibaba Cloud Instance.

    Instance Region

    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

    The password of the database account.

  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 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, and you must ensure that the ECS instance can 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. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.

    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 objects to be synchronized and advanced settings.

    Parameter

    Description

    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

      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, only some columns are synchronized, or the data synchronization task fails. Operate with caution.

    • Precheck and Report Errors: checks whether the destination database contains collections that have the same names as collections in the source database. If the source and destination databases do not contain collections that have identical collection 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 collections that are synchronized to the destination database. You can use this feature if the source and destination databases contain collections that have identical names and the collections in the destination database cannot be deleted or renamed. For more information, see Rename an object to be synchronized.

    • Ignore Errors and Proceed: skips the precheck for identical collection 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.

      • DTS does not synchronize data records that have the same primary key values as data records in the destination database.

      • Data may fail to be initialized, only some columns are synchronized, or the data synchronization task fails.

    • 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.

    • 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, only some columns are synchronized, or the data synchronization task fails. Operate with caution.

    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 Database name_Table name.

    Note The index name mapping rule takes effect for all tables.

    Capitalization of Object Names in Destination Instance

    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 ensure that the capitalization of object names is consistent with that in 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

    You can select tables or databases as objects to synchronize. If you select tables 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

    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. For more information, see Map object names.

    Note

    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 Use SQL conditions to filter data.

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

    Parameter

    Description

    Select the dedicated cluster used to schedule the task

    By default, DTS schedules the data synchronization task to the shared cluster if you do not specify a dedicated cluster. You can purchase a dedicated cluster of specified specifications to run DTS synchronization tasks. For more information, see What is a DTS dedicated cluster.

    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:

    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 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 your earliest opportunity after the source and destination instances are released.

    The wait time before a retry when other issues occur in the source and destination databases.

    The retry time range for other issues. For example, if the DDL or DML operations fail to be performed after the data synchronization task is started, DTS immediately retries the operations within the time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.

    Important

    The value of the The wait time before a retry when other issues occur in the source and destination databases parameter must be smaller than the value of the Retry Time for Failed Connection parameter.

    Enable Throttling for Full Data Migration

    During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and BPS of Full Data Migration parameters for full data synchronization tasks to reduce the pressure on the destination database.

    Note

    This parameter can be configured only if Full Data Synchronization is selected as Synchronization Types.

    Enable Throttling for Incremental Data Synchronization

    You can configure the RPS of Incremental Data Migration and BPS of Incremental Data Migration parameters for incremental data synchronization tasks to reduce the pressure on the destination database.

    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.

    String Index

    The method used to index strings that are synchronized to the destination Elasticsearch cluster. Valid values:

    • 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 of the DATETIME or TIMESTAMP type to be synchronized to the 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

    No configuration is required. 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

    Specifies whether to configure the extract, transform, and load (ETL) feature. For more information, see What is ETL?. Valid values:
  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.

    Type

    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.No

    _routing Column

    The column that is used for routing.

    Note

    This parameter is required only if the Set _routing parameter is set to Yes.

    Value of _id

    The column that is used to store the IDs of documents.

  8. Click Next: Save Task Settings and Precheck in the lower part of the page.

    You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameter settings of the API operation that is called to configure the instance.

    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 troubleshoot the issues based on the causes, run a precheck again.

    • 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 issues. 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 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.

    Resource Group

    The resource group on which the instance is run. Default value: default resource group. For more information, see What is Resource Management?.

    Instance Class

    DTS provides various synchronization specifications that provide different performance. The synchronization speed varies based on the synchronization specifications that you select. You can select a synchronization specification 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, 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 the check box to agree to the 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.