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.

Log in to the NineData Console.
In the left navigation pane, click Replication > Data Replication.
On the Replication page, click Create Replication in the upper-right corner.

On the Source & Target tab, configure the parameters in the following table, and click Next.

Parameter	Description
Name	Enter a name for the data synchronization task. To make the task easier to find and manage later, use a meaningful name. Up to 64 characters are supported.
Source	The data source that contains the objects to synchronize.
Target	The data source that receives the synchronized objects.
Target Object Name	Select the case conversion rule for object names after they are migrated from the source to the target. Convert all to Lowercase: Regardless of the naming rule on the source, all target names are lowercase. Consistent with Source: Keep the naming rule of the source. Convert all to Uppercase: Regardless of the naming rule on the source, all target names are uppercase.
Replication Mode	Select the replication mode. Uni-directional: A unidirectional data replication task from the source data source to the target data source. Bi-directional: A bidirectional incremental data replication task between the source and target data sources.
Type	Required when Replication Mode is Bi-directional.Select the replication type. Full: Synchronize all objects and data from the source data source, namely full data replication. The switch on the right enables periodic full replication. For more information, see Periodic Full Replication. Incremental: After full synchronization is complete, perform incremental synchronization based on the logs of the source data source.The icon is used to configure incremental operation types. You can clear specific operation types as needed. Cleared operation types will be ignored during incremental synchronization.
Forward Type	Required when Replication Mode is Bi-directional. Select the forward replication type. Full: Synchronize all objects and data from the source data source, namely full data replication. Incremental: After full synchronization is complete, perform incremental synchronization based on the logs of the source data source.The icon is used to configure incremental operation types. You can clear specific operation types as needed. Cleared operation types will be ignored during incremental synchronization.
Incremental Started	Required only when Type is Incremental. From Started: Use the current replication task start time as the baseline for incremental replication. Customized Time: Select the point in time from which incremental replication starts. You can select a time zone based on the region of your business. If the configured time point is earlier than the current replication task start time and DDL operations occurred during that period, the replication task will fail.
Forward Incremental Started	Required only when Forward Type is Incremental. From Started: Use the current replication task start time as the baseline for incremental replication. Customized Time: Select the point in time from which incremental replication starts. You can select a time zone based on the region of your business. If the configured time point is earlier than the current replication task start time and DDL operations occurred during that period, the replication task will fail.
Reverse Type	The replication type from the target data source to the source data source. This parameter is displayed only when Replication Mode is Bi-directional. Only Incremental is supported, and it is selected by default and cannot be disabled.
Spec (Unavailable only when Schema is selected)	The specification of the replication task. A larger specification provides a higher replication rate. Hover over the icon to view the rate and configuration information of each specification. Each specification shows the available quantity and total quantity. When the available quantity is 0, the specification is grayed out and cannot be selected.
Target Table Exists Data (Required when Full is selected)	Pre-Check Error and Stop Task: Stop the task when data is detected in the target table during the precheck stage. Ignore existing target data and append to it.: When data is detected in the target table during the precheck stage, ignore that data and append other data. Clear target existing data before write: When data is detected in the target table during the precheck stage, delete that data and write it again.
Incremental data conflict handling strategy for target table (Required when Incremental is selected)	Runtime error: During incremental replication, report an error when target data already exists and wait for manual intervention. Do not update target data: During incremental replication, do not write data when target data already exists, and continue subsequent tasks. Update target data: During incremental replication, overwrite the target data when target data already exists.

On the Objects tab, configure the following parameters, and click Next.

Parameter	Description
Replication Objects	Select the content to replicate. You can select All Objects to replicate all content in the source database, or select Customized Object, select the content to replicate in the Source Object list, and click > to add it to the Target Object list on the right.

If you need to create multiple replication links with the same replication objects, you can create a configuration file and import it when creating a task. Click Import Config in the upper-right corner, click Download Template to download the configuration file template, edit the file, and then click Upload to upload it for batch import. Configuration file description:

Parameter	Description
`source_table_name`	The source table name of the object to synchronize.
`destination_table_name`	The target table name that receives the synchronized object.
`source_schema_name`	The source schema name of the object to synchronize.
`destination_schema_name`	The target schema name that receives the synchronized object.
`source_database_name`	The source database name of the object to synchronize.
`target_database_name`	The target database name that receives the synchronized object.
`column_list`	The list of columns to synchronize.
`extra_configuration`	Additional configuration information. You can configure the following information here: `column_rules`: Defines column mappings and value rules. Field descriptions: `column_name`: Original column name. `destination_column_name`: Specifies the target column name. `column_value`: Specifies the column value, which can be an SQL function or a constant value. `filter_condition`: Specifies row-level data filtering conditions. Only rows that meet the conditions are replicated.

tip

The following is an example of extra_configuration:

{
  "extra_config":{
    "column_rules":[
      {
        "column_name": "created_time", // Specifies the original column name to be mapped.
        "destination_column_name": "migrated_time", // Maps the target column name to "migrated_time".
        "column_value": "current_timestamp()" // Changes the column value to the current timestamp.
      }
    ],
    "filter_condition": "id != 0" // Only rows whose ID is not 0 are synchronized.
  }
}

For a complete example of the configuration file, see the downloaded template.

On the "Mapping" tab, choose different operations based on the selected replication type, and click Save and Pre-Check. If the source and target data sources are updated during mapping configuration, click Refresh Metadata in the upper-right corner of the page to refresh the source and target data source information.
- Includes Schema: Configure the table name after synchronization to the target data source.
- Does not include Schema: The system selects the database with the same name in the target data source by default. If no such database exists, you need to manually select the target database. The table names and column names in the target database must match the synchronization objects. If they do not match, you can manually map the table names and column names.
You can also perform the following operations:
- Click Mapping & Filtering on the right side of the page to customize the column names after synchronization to the target data source.
- On the Mapping & Filtering page, click Data Filter to configure filtering conditions by using comparison expressions. Only data that meets the filtering conditions is synchronized to the target data source. For example, if the filtering condition is set to emp_no>=10005, data whose emp_no column value is less than 10005 is not synchronized to the target data source.
- Click the icon to the right of "Target Table" to search for a table name and replace it with the target name.
- Enter a table name in the Search Table text box in the upper-right corner to quickly locate the target table.
- Click Batch Configuration in the upper-right corner to define common rules in batches, such as table name and column name case conversion, prefix or suffix addition, and replacement, so that mapping configuration can be applied uniformly to a large number of tables and columns.

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.

On the Pre-check tab, wait for the system to complete the precheck. After the precheck is passed, click Launch.
- You can select Enable data consistency comparison. After the synchronization task is complete, a data consistency comparison task based on the source data source automatically starts to ensure data consistency between both ends. Based on the selected Type, Enable data consistency comparison starts at the following times:
  - Full: Starts after full replication is complete.
  - Full+Incremental, Incremental: Starts when incremental data is consistent with the source data source for the first time and Delay is 0 seconds. You can click View Details and view the synchronization delay on the Details page.
- If the precheck fails, click Details in the Actions column on the right of the failed check item, troubleshoot the cause, manually fix the issue, and then click Check Again to run the precheck again until it passes.
- Check items whose Result is Warning can be fixed or ignored depending on the situation.
On the Launch page, the Launch Successfully prompt appears, indicating that the synchronization task has started. You can then perform the following operations:
- Click View Details to view the execution status of each stage of the synchronization task.
- Click Back to list to return to the Replication task list page.

View Synchronization Results

Log in to the NineData Console.
Click on Replication > Data Replication in the left navigation bar.

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

result_sybase

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.
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

Data Replication Introduction

MySQL Synchronization to Alibaba Cloud PolarDB-X

Feature Introduction​

Prerequisites​

Usage Limitations​

Operation Steps​

View Synchronization Results​

Appendix: Pre-Check Item List​

Related Documentation​