MySQL Synchronization to Alibaba Cloud PolarDB-X

NineData data replication supports full data synchronization and incremental data synchronization between self-built MySQL and self-built MySQL data sources.

Feature Introduction

NineData data replication supports high-performance replication of structure, full data, and incremental data between data sources. For certain data sources, it also provides bidirectional replication, enabling the quick construction of geo-distributed active-active business architectures.

• Structure: Supports the replication of object structures between homogeneous and heterogeneous data sources, greatly reducing the barrier to data replication between two sources.
• Full Data: Achieves row-level concurrent batch replication through intelligent data sharding, effectively ensuring replication performance. The independently developed novel breakpoint resume technology ensures the accuracy of data in tables without primary keys.
• Incremental Data: Supports DML and DDL incremental data replication for all object types. By leveraging technologies such as row-level concurrency and hotspot merging, it delivers robust replication performance.
• Bidirectional Real-time Data Replication (only between MySQL instances): Direct bidirectional replication of data between multiple nodes ensures that all node data remains up-to-date.

With the above features, it is easy and efficient to achieve scenarios such as full|incremental data replication, full|incremental data migration, full|incremental data synchronization, data integration, and seamless migration without downtime, providing enterprises with flexible and reliable data replication solutions.

Prerequisites

• The source and target data sources have been added to NineData. For instructions on how to add them, see Add Data Source.

• The source data source is MySQL, with a version of 5.1 or above.

• The target data source is Alibaba Cloud PolarDB-X.

• The source data source must have Binlog enabled, and the Binlog-related parameters are set as follows:

  • binlog_format=ROW
  • binlog_row_image=FULL
  tip

  If the source data source is a replica, to ensure complete Binlog logs are obtained, the log_slave_updates parameter also needs to be enabled.

Usage Limitations

• The data replication function is only for the user databases in the data source, and the system databases will not be replicated. For example: information_schema, mysql, performance_schema, sys databases in MySQL type data sources will not be replicated.
• The account for source data must have SELECT (for replicate database structure and full data), SHOW VIEW (for replicate views), and REPLICATION CLIENT, REPLICATION SLAVE (for replicate incremental data) privileges on the objects to be replicated. The account for target must have DML and DDL privileges.
• Before performing data synchronization, user need to evaluate the performance of the source data source and the target data source, and it is recommended to perform data synchronization during off-peak time. Otherwise, the full data initialization will occupy a certain amount of read and write resources of the source data source and the target data source, increasing database load.
• During the synchronization process, if the source data contains views, functions, stored procedures, triggers, and events, after synchronizing to the target data source, the definer of the above objects information will be modified in the target data source to the account that accesses the target data source in the current synchronization task.
• It is necessary to ensure that each table in the synchronization object has a primary key or unique constraint, and the column name is unique, otherwise the same data may be synchronized repeatedly.
• During the synchronization process, if there are triggers in the source, the system will not synchronize the triggers until the incremental synchronization ends.

Operation Steps

Commercialization Notice

NineData’s data replication product has been commercialized. You can still use 10 replication tasks for free, with the following considerations:

• Among the 10 replication tasks, you can include 1 Incremental task, with a specification of Micro.

• Tasks with a status of Terminated do not count towards the 10-task limit. If you have already created 10 replication tasks and want to create more, you can terminate previous replication tasks and then create new ones.

• When creating replication tasks, you can only select the Spec you have purchased. Specifications that have not been purchased will be grayed out and cannot be selected. If you need to purchase additional specifications, please contact us through the customer service icon at the bottom right of the page.

1. Log in to the NineData Console.

2. Click on Replication in the left navigation bar.

3. On the Replication page, click on Create Replication in the top right corner.

4. On the Source & Target tab, configure according to the table below and click on Next.

   Parameter	Description
   Name	Enter the name of the data synchronization task. To facilitate subsequent search and management, please use meaningful names as much as possible. Up to 64 characters are supported.
   Source	The data source where the synchronization object is located.
   Target	The data source that receives the synchronization object.
   Type	Choose the content that needs to be copied to the target data source. Full: Syncs all objects and data from the source data source, i.e., full data replication. The switch on the right is for toggling periodic full replication. For more information, please refer to Periodic Full Replication. Incremental: After full sync, perform incremental sync based on the log of the source data source. The icon represents incremental operation type configuration (not supported by some replication links). You can deselect certain operation types as needed. Once deselected, these operations will be ignored during incremental synchronization.
   If target table already exists	Pre-Check Error and Stop Task: Stop the task when the target object already exists during the pre-inspection stage. Ignore the existing data and append : Ignore and append write when the target object already exists during the pre-inspection stage. Clear the existing data before write: Delete and rewrite when the target object already exists during the pre-inspection stage.

5. On the Objects tab, configure the following parameters, then click on Next.

   Parameter	Description
   Replication Objects	Choose the content that needs to be copied. You can select All Objects to copy all content from the source database, or you can select Customized Object, select the content that needs to be copied in the Source Object list, and click > to add to the right Target Object list.

   If you need to create multiple replication chains with the same replication object, you can create a configuration file and import it when creating a new task. Click on Import Config in the top right corner, then click Download Template to download the configuration file template to your local machine, edit it, and then click Upload to upload the configuration file to achieve batch import. Configuration file description:

   Parameter	Description
   source_table_name	The source table name where the object to be synchronized is located.
   destination_table_name	The target table name that receives the synchronized object.
   source_schema_name	The source Schema name where the object to be synchronized is located.
   destination_schema_name	The target Schema name that receives the synchronized object.
   source_database_name	The source database name where the object to be synchronized is located.
   target_database_name	The target database name that receives the synchronized object.
   column_list	The list of fields that need to be synchronized.
   extra_configuration	Additional configuration information can be set here: column_rules: Used to define column mapping and value rules. Field descriptions: column_name: Original column name. destination_column_name: Target column name. column_value: Value to assign, which can be an SQL function or a constant. filter_condition: Used to specify row-level filtering conditions; only rows that meet the criteria will be copied.

   tip

   • An example of the extra_configuration content is as follows:

     {
       "extra_config": {
         "column_rules": [
           {
             "column_name": "created_time", // Original column name to map.
             "destination_column_name": "migrated_time", // Target column name mapped to "migrated_time".
             "column_value": "current_timestamp()" // Change the column value to the current timestamp.
           }
         ],
         "filter_condition": "id != 0" // Only rows where ID is not 0 will be synchronized.
       }
     }

   • For a complete example of the configuration file, refer to the downloaded template.

6. On the "Mapping" tab, the system defaults to selecting the database with the same name in the target data source. If it does not exist, you need to manually select the target database. The table name and column name in the target database need to be consistent with the synchronization object. If they are not consistent, you can also manually map the table name and column name, and then click on Save and Pre-Check. If there are updates in the source and target data sources during the configuration mapping stage, you can click on the Refresh Metadata button in the top right corner of the page to refresh the information from the source and target data sources.

   You can also perform the following operations:

   • Click on the Mapping & Filtering on the right side of the page to customize the column names after they are synchronized to the target data source.

   • On the Mapping & Filtering page, click on Data Filter, and configure the filtering conditions through comparison expressions. Only data that meets the filtering conditions will be synchronized to the target data source. For example, if you set the filtering condition to emp_no>=10005, then data in the emp_no column that is less than 10005 will not be synchronized to the target data source.

   • Click on the icon next to "Target Table" to search for table names and replace them with target names.

   • Enter the table name in the Search Table text box at the top right to quickly locate the target table.

   • Click Batch Configuration in the upper right corner to define general rules in bulk (such as converting table and column name case, adding prefixes or suffixes, replacements, etc.), enabling unified mapping configuration for a large number of tables and columns.

7. On the Pre-check tab, wait for the system to complete the pre-inspection, and after the pre-inspection is passed, click on Launch.

   tip

   • You can check Enable data consistency comparison. After the synchronization task is completed, automatically start data consistency comparison based on the source data source to ensure data consistency on both sides. It starts when the incremental data is first consistent with the source data source and Delay is 0 seconds. You can click on View Details to view the synchronization delay on the Details page.

     

   • If the pre-inspection does not pass, you need to click on Details in the Actions column on the right side of the target inspection item, troubleshoot the cause of the failure, manually fix it, and then click on Check Again to re-execute the pre-inspection until it passes.

   • If the Result is Warning for the inspection item, it can be fixed or ignored according to the specific situation.

8. On the Launch page, it prompts Launch Successfully, and the synchronization task starts running. At this time, you can perform the following operations:

   • Click on View Details to view the execution of each stage of the synchronization task.
   • Click on Back to list to return to the Replication task list page.

View Synchronization Results

1. Log in to the NineData Console.

2. Click on Replication > Data Replication in the left navigation bar.

3. On the Replication page, click the Task ID of the target synchronization task, and the page description is as follows.

   

   No.	Function	Description
   1	Synchronization Delay	The data synchronization delay between the source and target data sources. 0 seconds indicate no delay between the two ends. At this point, you can choose to switch the business to the target data source to achieve a smooth migration.
   2	Configure Alerts	After configuring alerts, the system will notify you through your chosen method when the task fails. For more information, please refer to Introduction to Operations Monitoring.
   3	More	Pause: Pause the task, only available for tasks in the running status. Duplicate: Create a new replication task with the same configuration as the current task. Terminate: End tasks that are not completed or in listening mode (i.e., incremental synchronization). After terminating the task, it cannot be restarted, please proceed with caution. If the synchronization object includes triggers, trigger replication options will pop up, please choose as needed. Delete: Delete the task, the task cannot be recovered after deletion, please proceed with caution.
   4	Full Replication (displayed in scenarios including full replication)	Display the progress and detailed information of full replication. Click on Monitor on the right side of the page: View various monitoring metrics during the full replication process. During the full replication process, you can also click on Flow Control Settings on the right side of the monitoring metrics page to limit the rate of writing to the target data source per second. The unit is rows/second. Click on Log on the right side of the page: View the execution logs of full replication. Click on the on the right side of the page: View the latest information.
   5	Incremental Replication (displayed in scenarios including incremental replication)	Display various monitoring metrics for incremental replication. Click on View Threads on the right side of the page: View the operations currently being executed by the replication task, including: Thread ID: The replication task is executed by multiple threads, displaying the current thread number. Execute SQL: Details of the SQL statement currently being executed by the current thread. Response Time: The response time of the current thread, if this value increases, it indicates that the current thread may be stuck due to some reason. Event Time: The timestamp when the current thread started. Status: The status of the current thread. Click on Flow Control Settings on the right side of the page: Limit the rate of writing to the target data source per second. The unit is rows/second. Click on Log on the right side of the page: View the execution logs of incremental replication. Click on the on the right side of the page: View the latest information.
   6	Modify Objects	Display the modification records of synchronization objects. Click on Modify Objects on the right side of the page to configure synchronization objects. Click on the on the right side of the page: View the latest information.
   7	Data Comparison	Display the results of the comparison between the source and target data sources. If you have not enabled data comparison, please click on Enable Comparison in the page. Click on Re-compare on the right side of the page: Re-initiate a comparison between the current source and target data. Click on Stop on the right side of the page: After the comparison task starts, you can click this button to immediately stop the comparison task. Click on Log on the right side of the page: View the execution logs of consistency comparison. Click on Monitor on the right side of the page (only displayed during data comparison): View the trend chart of comparison RPS (records compared per second). Click on Details to view records from earlier times. Click on in the Actions column on the right side of the comparison list (only displayed under the Data tab when inconsistencies are found): View the comparison details between the source and target ends. Click on in the Actions column on the right side of the comparison list (displayed when inconsistencies are found): Generate change SQL, you can directly copy this SQL to the target data source for execution, modifying the inconsistent content.
   8	Expand	Display detailed information of the current replication task.

Appendix: Pre-Check Item List

Check Items	Check Contents
Verify if there are no primary key tables in the source database	Check if the object to be migrated does not have a primary key or unique key
Source datasource connection check	Check the status of the gateway of the source datasource, database connectable, and verify the username and password
Target datasource connection check	Check the status of the gateway of the target datasource, database connectable, and verify the username and password
Source database privilege check	Check whether the account privileges of the source database meet the requirements
Source database log_slave_updates check	When the source database is a slave, check whether log_slave_updates is ON
Source and target datasource version check	Check whether the source and target database versions are compatible
Check if the source database has Binlog enabled	Check if the source database has Binlog enabled
Source database binlog format check	Check whether the binlog format of the source database is 'ROW'
Source database binlog_row_image check	Check whether the binlog_row_image of the source database is 'FULL'
Cyclic replication check	Check for replication loops
Check the read-only status of the source database instance	Check the read-only status of the source database instance

Related Documentation

Data Replication Introduction