MySQL to MySQL

NineData Data Replication supports full data replication and incremental replication between self-managed MySQL data sources.

Overview

Use this workflow to migrate data between MySQL databases and keep the target database updated with source changes.

Before you begin

• Add the source and target data sources to NineData. For details, see Add Data Source.

• The supported MySQL source versions range from 5.1 to 9.0.

• The source data source must have Binlog enabled, with the following parameters:

  • binlog_format=ROW

  • binlog_row_image=FULL

    tip

    If the source data source is a standby database, enable log_slave_updates to capture the complete Binlog.

Restrictions

• Data replication applies only to user databases in the data source. System databases are not replicated. For example, MySQL system databases such as information_schema, mysql, performance_schema, and sys are not replicated.
• The source account must have SELECT privileges for schema and full data replication, SHOW VIEW privileges for view replication, and REPLICATION CLIENT and REPLICATION SLAVE privileges for incremental replication. The target account must have DML and DDL privileges.
• Before starting data synchronization, evaluate the performance of the source and target data sources. Run synchronization during off-peak hours when possible. Otherwise, full data initialization consumes read and write resources on both data sources and increases database load.
• If the source data source contains views, functions, stored procedures, triggers, or events, the definer information of these objects is changed on the target data source to the account used by the current synchronization task to access the target data source.
• Make sure every table in the synchronization objects has a primary key or unique constraint, and that column names are unique. Otherwise, duplicate rows may be synchronized.
• If triggers exist in the source data source, NineData synchronizes the triggers only after incremental synchronization ends.

Procedure

1. Sign in to the NineData Console.

2. In the left navigation pane, click Replication > Data Replication.

3. On the Replication page, click Create Replication.

4. On the Source & Target tab, configure the fields in the 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.
   Datahub Project	Select the target Datahub Project. Data from the source data source will be written to the specified Project.
   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. Schema: Synchronize only the database and table schemas of the source data source, without synchronizing data. 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. Schema: Synchronize only the database and table schemas of the source data source, without synchronizing data. 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.
   If target table already exists (Required when Schema is selected)	Pre-Check Error and Stop Task: Stop the task when a table with the same name is detected during the precheck stage. Skip and Continue Task: When a table with the same name is detected during the precheck stage, display a message and continue the task. During schema replication, ignore the table with the same name. If you also perform data replication, data is appended to the table with the same name and existing data is not overwritten. Delete Objects and Rewrite: When a table with the same name is detected during the precheck stage, display a message and continue the task. During schema replication, delete the table with the same name in the target database and replicate the table schema again based on the source database. If you also perform data replication, data is written after schema replication is complete.
   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.

5. On the Objects tab, configure the parameters in the table, 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.
   Blacklist	Click Add to add a blacklist record, and select the database or object to add to the blacklist. The selected content will not be replicated. This is used to exclude specific databases or objects when performing full-database replication for Customized Object or Full Instance. Left drop-down list: Select the database name to add to the blacklist. Right drop-down list: Select objects in the corresponding database. You can click multiple objects to select them. Leave it empty to add the entire database to the blacklist. To add multiple databases to the blacklist, click the Add button below to add another row.

   To create multiple replication tasks with the same replication objects, import a configuration file. Click Import Config, click Download Template to download the template, edit the file, and then click Upload to upload it and import the objects in bulk. The configuration file uses these fields:

   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. This field supports: 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

   • Example of extra_configuration:

     {
       "extra_config":{
         "column_rules":[
           {
              "column_name": "created_time",
              "destination_column_name": "migrated_time",
              "column_value": "current_timestamp()"
           }
         ],
          "filter_condition": "id != 0"
       }
     }

     In this example, created_time is mapped to migrated_time, the target column value is changed to current_timestamp(), and only rows whose id value is not 0 are synchronized.

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

6. On the "Mapping" tab, configure the mapping that matches the selected replication type, then click Save and Pre-Check. If source or target metadata changes while you configure mappings, click Refresh Metadata to refresh the metadata.

   • 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, select the target database manually. The table names and column names in the target database must match the synchronization objects. If they do not match, map the table names and column names manually.

   You can also perform these actions:

   • Click Mapping & Filtering 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 to quickly locate the target table.
   • Click Batch Configuration to define common rules in batches, such as table name and column name case conversion, prefix or suffix addition, and replacement. Use this option to apply mapping configuration to many tables and columns at the same time.

7. On the Pre-check tab, wait for the system to complete the precheck. After the precheck passes, click Launch.

   • Select Enable data consistency comparison to start a data consistency comparison task based on the source data source after synchronization completes. Based on the selected Type, Enable data consistency comparison starts at these times:

     • Schema: Starts after schema replication is complete.
     • Schema+Full: Starts after full replication is complete.
     • Full: Starts after full replication is complete.
     • Schema+Full+Incremental, Incremental: Starts when incremental data is consistent with the source data source for the first time and Delay is 0 seconds. Click View Details to view synchronization delay on the Details page.

   • If the precheck fails, click Details in the Actions column for the failed check item, review the cause, fix the issue, and then click Check Again to run the precheck again until it passes.

   • Items with Warning in Result can be fixed or ignored as needed.

8. On the Launch page, the Launch Successfully message appears, indicating that the synchronization task has started. You can then perform these actions:

   • 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 replication results

1. Sign in to the NineData Console.

2. In the navigation menu, click Replication > Data Replication.

3. On the Replication page, click the Task ID of the target synchronization task. The task details page shows the following information.

   

   Number	Function	Description
   1	Sync Delay	The synchronization delay between the source and target data sources. 0 seconds means the target has caught up with the source, so you can switch traffic based on your migration plan.
   2	Configure Alerts	When the task fails, the system notifies the selected channel through the configured alert.
   3	More	Pause: Pause the task. Only tasks with Running status are selectable. Duplicate: Create a new replication task with the same configuration as the current task. Terminate: Terminate tasks that are incomplete or still listening (that is, in incremental synchronization). After a task is terminated, it cannot be restarted, so proceed with caution. If the synchronization objects contain triggers, trigger replication options appear for selection. Delete: Delete the task. Once deleted, it cannot be recovered, so proceed with caution.
   4	Structure Replication (displayed in scenarios involving structure replication)	Displays the progress and detailed information of structure replication. Click Log to view the execution logs of structure replication. Click the to view the latest information. Click View DDL in the Actions column for the target object in the list to view SQL replay.
   5	Full Replication (displayed in scenarios involving full replication)	Displays the progress and detailed information of full replication. Click Monitor to view various monitoring indicators during full replication. During full replication, you can also click Flow Control Settings on the monitoring page to limit the rate of writing to the target data source per second. The unit is rows/second. Click Log to view the execution logs of full replication. Click the to view the latest information.
   6	Incremental Replication (displayed in scenarios involving incremental replication)	Displays incremental replication indicators. Click View Threads to view the operations currently being executed by the current replication task, including: Thread ID: Replication tasks are executed in multiple threads, and this shows 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 for some reason. Event Time: The timestamp when the current thread was started. Status: The status of the current thread. Click Flow Control Settings to limit the rate of writing to the target data source per second. The unit is rows/second. Click Log to view the execution logs of incremental replication. Click the to view the latest information.
   7	Modify Object	Displays the modification records of synchronization objects. Click Modify Objects to configure the synchronization objects. Click the to view the latest information.
   8	Data Comparison	Displays the comparison results between the source and target data sources. If data comparison is not enabled, click Enable Comparison on the page to enable it. Click Re-compare to rerun the comparison for the current source and target data sources. Click Stop to stop the comparison task immediately after it starts. Click Log to view the execution logs of consistency comparison. Click Monitor (displayed only in data comparison) to view the trend chart of RPS (records per second) comparison. Click Details to view earlier records. Click the in the Actions column in the comparison list (displayed under the Data tab only when inconsistencies are found) to view details of the comparison between the source and target data sources. Click the in the Actions column in the comparison list (displayed only when inconsistencies are found): Generate change SQL. You can copy this SQL to the target data source and run it to fix the mismatch.
   9	Expand	Displays detailed information of the current replication task. Common actions: Export table configuration: Export the current task's database and table configuration so you can quickly import it when creating another replication task with the same objects. Alert Rules: Configure alerts for the current task.

Appendix: Precheck items

Check item	What NineData checks
Target database data existence check	Check whether the object to be replicated not empty in the target database
Objects with the same name in the target database existence check	Check whether the object to be replicated already exists in the target database
Existence check for the Definer of non-table objects	Check whether the definer of view, trigger, procedure, function, event exists in the target database
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
Target databse privilege check	Check whether the account privileges of the target database meet the requirements
Source database privilege check	Check whether the account privileges of the source database meet the requirements
Source and target datasource collation check	Check whether the collations of the source and target databases are compatible
Target datasource trigger check	Check the existence of triggers on the target database
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'
Source and target datasource time zone check	Check whether the timezones of the source and target databases match
Source and target datasource character set check	Check whether the character set of the source and target databases are compatible
Source and target datasource SQL_MODE check	Check whether the SQL_MODE of the source and target databases are compatible
Source and target datasource case-sensitive check	Check whether the case-sensitive configurations of the source database and the target database are compatible
Source datasource and target datasource explicit_defaults_for_timestamp check	Check whether the explicit_defaults_for_timestamp of the source database and the target database are compatible
Source database procedure and function check	Check that the source database has been granted privileges to obtain the definitions of procedures and functions

Related documents

• Introduction to Data Replication