MySQL Replication to TiDB

NineData data replication supports data migration or synchronization between MySQL and TiDB data sources.

Feature Introduction

NineData data replication supports high-performance replication of structure, full data, and incremental data between data sources. For MySQL 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 incremental data replication of full object types DML|DDL, combined with transaction-level concurrency, hotspot merging, and other technologies to provide robust replication performance while ensuring transaction consistency.
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 must be added to NineData. See Add Data Source for instructions on how to add them.
The source data source must have Binlog enabled, and the Binlog-related parameters set as follows:
- binlog_format=ROW
- binlog_row_image=FULL
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If the source data source is a slave, to ensure the complete Binlog log is 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.

Operations

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 task, with a specification of Micro.
Tasks with a status of 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 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.
Click on in the left navigation bar.
On the page, click on the in the top right corner.

On the tab, configure according to the table below, and click on .

Parameter	Description
	Enter the name of the data synchronization task. For easy retrieval and management, use a meaningful name, up to 64 characters.
	The data source where the sync object is located.
	The data source that receives the sync object.
	Choose the content to be copied to the target data source. : Only syncs the table structure of the source data source, without syncing data. : 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. : 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.
	(selected when is selected) : Stop the task when a table with the same name is detected during precheck. : Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, ignore this table with the same name. If you are also performing data replication, data will be appended to this table with the same name without overwriting existing data. : Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, delete the table with the same name in the target database and replicate the table structure based on the source database. If you are also performing data replication, data will be written after the table structure replication is completed. (optional when performing both structure and data replication): Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, keep the table structure in the target database and, when data replication starts, clear the data in the table with the same name and then replicate from the original table. (required when is not selected) : Stop the task when data exists in the target table during precheck. : Ignore this part of the data when data is detected in the target table during precheck and append other data. : Delete this part of the data when data is detected in the target table during precheck and rewrite it.

On the tab, configure the following parameters, and then click on .

Parameter	Description
	Choose what to copy. You can choose to copy all contents of the source database, or choose to select the contents to be copied in the list and click > to add them to the right list.

If you need to create multiple identical replication links, you can create a configuration file and import it when creating a new task. Click at the top right corner, then click Download Template to download the configuration file template to your local machine. After editing, click to upload the configuration file for batch import.

Parameter	Description
`source_table_name`	Name of the source table containing the objects to be synchronized.
`destination_table_name`	Name of the target table receiving the synchronized objects.
`source_schema_name`	Name of the source schema containing the objects to be synchronized.
`destination_schema_name`	Name of the target schema receiving the synchronized objects.
`source_database_name`	Name of the source database containing the objects to be synchronized.
`target_database_name`	Name of the target database receiving the synchronized objects.
`column_list`	List of columns to be synchronized.
`extra_configuration`	Additional configuration information, where you can configure the following: Column Mapping: `column_name`, `destination_column_name` Column Value: `column_value` Data Filtering: `filter_condition`

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An example of the extra_configuration content is as follows:

{
    "column_name": "created_time", // Original column name to be mapped
    "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 synchronize rows where ID is not 0.
}

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

On the tab, select different actions based on the selected replication type. If updates occur in the source and target data sources during the configuration mapping phase, you can click the button in the upper right corner of the page to refresh the information of the source and target data sources.
- Includes : Configure the table name after the target table is synchronized to the target data source, and click .
- Excludes : The system automatically selects the same name database in the target data source by default. If it does not exist, you need to manually select the target database. The table names and column names in the target database need to be consistent with the sync objects. If they are not consistent, you can manually map the table names and column names.
You can click on on the right side of the page to customize the name of the columns after synchronization to the target data source. In addition, you can set to configure filter conditions through comparison expressions. Only data that meets the filter conditions will be synchronized to the target data source. For example, setting the filter condition to emp_no>=10005 means that data with emp_no less than 10005 will not be synchronized to the target data source.
On the tab, wait for the system to complete the precheck. After the precheck passes, click on .
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- You can check . After the sync task is completed, automatically initiate data consistency comparison based on the source data source to ensure data consistency on both ends. Depending on your choice of , the timing of starting is as follows:
  - : Initiated after structure replication is completed.
  - + , : Initiated after full replication is completed.
  - + + , : Initiated when the incremental data is first consistent with the source data source and is 0 seconds. You can click on to view the synchronization delay on the page.
- If the precheck fails, click on on the right side of the target check item to investigate the cause of the failure, manually fix it, and then click to re-execute the precheck until it passes.
- Items in with can be repaired or ignored depending on the specific situation.
On the page, when prompted with , the sync task begins to run. At this point, you can perform the following operations:
- Click on to view the execution status of each stage of the sync task.
- Click on to return to the task list page.

View Synchronization Results

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

On the page, click on the of the target synchronization task, the page details are as follows.

result

Number	Function	Description
1	Sync Delay	The data synchronization delay between the source data source and the target data source. 0 seconds means there is no delay between the two ends, at which point you can choose to switch the business to the target data source for smooth migration.
2	Configure Alerts	After configuring alerts, the system will notify you in the way you choose when the task fails. For more information, please refer to Operations Monitoring Introduction.
3	More	: Pause the task, only tasks with Running status are selectable. : Create a new replication task with the same configuration as the current task. : End tasks that are unfinished or listening (i.e., in incremental synchronization). Once the task is terminated, it cannot be restarted, so please proceed with caution. If the synchronization objects contain triggers, a trigger replication option will pop up, please select as needed. : Delete the task. Once the task is deleted, it cannot be recovered, so please proceed with caution.
4	Structure Replication (displayed in scenarios involving structure replication)	Displays the progress and detailed information of structure replication. Click on on the right side of the page: View the execution logs of structure replication. Click on on the right side of the page: View the latest information. Click on in the column on the right side of the target object in the list: View SQL playback.
5	Full Replication (displayed in scenarios involving full replication)	Displays the progress and detailed information of full replication. Click on on the right side of the page: View various monitoring indicators during full replication. During full replication, you can also click on on the right side of the monitoring indicator page to limit the rate of writing to the target data source per second. The unit is rows/second. Click on on the right side of the page: View the execution logs of full replication. Click on on the right side of the page: View the latest information.
6	Incremental Replication (displayed in scenarios involving incremental replication)	Displays various monitoring indicators of incremental replication. Click on on the right side of the page: View the operations currently being executed by the current replication task, including: : Replication tasks are executed in multiple threads, displaying the current thread number in progress. : Details of the SQL statement currently being executed by the current thread. : The response time of the current thread. If this value increases, it indicates that the current thread may be stuck for some reason. : The timestamp when the current thread was started. : The status of the current thread. Click on 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 on the right side of the page: View the execution logs of incremental replication. Click on on the right side of the page: View the latest information.
7	Modify Object	Displays the modification records of synchronization objects. Click on on the right side of the page to configure the synchronization objects. Click on on the right side of the page: View the latest information.
8	Data Comparison	Displays the comparison results between the source data source and the target data source. If you have not enabled data comparison, please click on on the page. Click on on the right side of the page: Re-initiate the comparison between the current source and target data sources. Click on on the right side of the page: After the comparison task starts, you can click this button to stop the comparison task immediately. Click on on the right side of the page: View the execution logs of consistency comparison. Click on (displayed only in data comparison): View the trend chart of RPS (records per second) comparison. Click on to view earlier records. Click on in the column on the right side of the comparison list (displayed under the tab only in the case of inconsistency): View details of the comparison between the source and target sides. Click on in the column on the right side of the comparison list (displayed only in the case of inconsistency): Generate change SQL. You can directly copy this SQL to the target data source to execute and modify the inconsistent content.
9	Expand	Display detailed information of the current replication task. Common Options: : Export the current task's database and table configuration, allowing for quick import when creating a new replication task. This helps rapidly establish multiple replication links with the same replication objects. : Configure the alarm strategy for the current task.

Appendix: Pre-check Item Overview

Check Item	Check Content

Introduction to Data Replication

MySQL Replication to TiDB

Feature Introduction​

Prerequisites​

Usage Limitations​

Operations​

View Synchronization Results​

Appendix: Pre-check Item Overview​

Related Documents​