This topic describes how to synchronize data from a PolarDB-X V2.0 instance to an Elasticsearch cluster by using Data Transmission Service (DTS).
- The source PolarDB-X V2.0 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.
- Engine versions of the source instance and the destination cluster meet the data synchronization requirements. For more information about the supported data synchronization scenarios, 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 V2.0 instance.
|Limits on the source database||
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 synchronization topologies, see Synchronization topologies.
SQL operations that can be synchronized
|Operation type||SQL statement|
|DML||INSERT, UPDATE, and DELETE|
The MySQL data types supported by PolarDB-X V2.0 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 the schema synchronization based on the data type mappings for schema synchronization. For more information, see Data type mappings for schema synchronization.
- Go to the Data Synchronization page of the new DTS console.
- In the upper-left corner of the page, select the region where the data synchronization
- 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 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 Select PolarDB-X 2.0. Access Method Select Cloud Instance. Instance Region The region where the source PolarDB-X V2.0 instance resides. Instance ID The ID of the source PolarDB-X V2.0 instance. Database Account The database account of the source PolarDB-X V2.0 instance. The database account must have the SELECT permission on the objects to synchronize and the REPLICATION SLAVE and REPLICATION CLIENT permissions. DTS automatically grants these permissions to the database account. Database Password
Enter the password of the database account.
Destination Database Database Type Select Elasticsearch. Access Method Select Cloud Instance. Instance Region The region where 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 read and write permissions on the objects to synchronize. Database Password
Enter the password of the database account.
- In the lower part of the page, click Test Connectivity and Proceed.
- Select objects for the task and configure advanced settings.
- Basic Settings
Parameter Description Task Stages
Incremental Data Synchronization is selected by default. You must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS synchronizes the historical data of the selected objects from the source instance 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 identical table names, the precheck is passed. Otherwise, an error is returned during 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 consistency is not guaranteed and your business may be exposed to potential risks.
- If the source and destination databases have the same schema, and a data record has
the same primary key 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.
- If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database:
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.
If you select DatabaseName_TableName, the created index name in the destination Elasticsearch cluster is in the format of databasename_tablename. In this example, dtstest_order is used.
Select one or more objects from the Source Objects section and click the icon to move the objects to the Selected Objects section.Note You can select columns, tables, or databases as the objects to be synchronized.
Rename Databases and Tables
- 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.
You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.
Select the SQL operations to be synchronized 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, see SQL operations that can be synchronized.
- Advanced Settings
Parameter Description Set AlertsSpecify whether to set alerts for the data synchronization task. If the task fails or the synchronization latency exceeds the threshold, the alert contacts will receive notifications.
- Select No if you do not want to set alerts.
- Select Yes to set alerts. In this case, you must also set the alert threshold and alert contacts.
Retry Time for Failed ConnectionSpecify the retry time for failed connections. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the retry time to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.Note
- If multiple DTS instances have the same source or destination database, the lowest value takes effect. For example, the retry time is set to 30 minutes for Instance A and 60 minutes for Instance B, DTS retries failed connections at an interval of 30 minutes.
- When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time based on your business needs. 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: indicates that the strings are indexed with the original values.
- no: indicates that 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.
- Basic Settings
- 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 Specify whether you want to store a document on a specified shard of the destination Elasticsearch cluster. For more information, see _routing.
Note If the version of the destination Elasticsearch cluster is 7.4, you must select No.
- If you select Yes, you can specify custom columns for routing.
- If you select No, the _id value is used for routing.
Value of _id
- Primary key column
Composite primary keys are merged into one column.
- Business key
If you select a business key, you must also specify the business key column.
- 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 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.
- Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
- On the Purchase Instance page, specify the Billing Method and Instance Class parameters for the data synchronization
instance. The following table describes the parameters.
Section Parameter Description Parameters Billing Method
- Subscription: You can pay for your subscription when you create an instance. We recommend that you select the subscription billing method for long-term use because it is more cost-effective than the pay-as-you-go billing method. You can save more costs with longer subscription periods.
- Pay-as-you-go: A pay-as-you-go instance is billed on an hourly basis. We recommend that you select the pay-as-you-go billing method for short-term use. If you no longer require your pay-as-you-go instance, you can release it 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 Length If you select the subscription billing method, set the subscription length and the number of instances that you want to create. The subscription length can be one to nine months or one to three years.Note This parameter is available only if you select the subscription billing method.
- Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
- 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 data synchronization task enters the Running state, 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.