From MySQL to MySQL¶
Supported Source and Destination Databases¶
Source DB | Destination DB |
|---|---|
|
|
Prerequisites¶
You have logged in to the DRS console.
For details about the DB types and versions supported by real-time synchronization, see Real-Time Synchronization.
Suggestions¶
Caution
When a task is being started or in the full synchronization phase, do not perform DDL operations on the source database. Otherwise, the task may be abnormal.
To keep data consistency before and after the synchronization, ensure that no data is written to the destination database during the synchronization.
The success of database synchronization depends on environment and manual operations. To ensure a smooth synchronization, perform a synchronization trial before you start the synchronization to help you detect and resolve problems in advance.
Start your synchronization task during off-peak hours. A less active database is easier to synchronize successfully. If the data is fairly static, there is less likely to be any severe performance impacts during the synchronization. If you have to synchronize data during peak hours, you can select Yes for Flow Control to adjust the synchronization speed.
If network bandwidth is not limited, the query rate of the source database increases by about 50 MB/s during full synchronization, and two to four CPUs are occupied.
To ensure data consistency, tables to be synchronized without a primary key may be locked for 3s.
The data being synchronized may be locked by other transactions for a long period of time, resulting in read timeout.
Due to the inherent characteristics of MySQL, in certain scenarios the performance may be negatively affected. For example, if the CPU resources are insufficient and the storage engine is TokuDB, the read speed on tables may be decreased by 10%.
When DRS concurrently reads data from a database, it will use about 6 to 10 sessions. The impact of the connections on services must be considered.
If you read a table, especially a large table, during the full migration, the exclusive lock on that table may be blocked.
Data-Level Comparison
To obtain accurate comparison results, compare data at a specified time point during off-peak hours. If it is needed, select Start at a specified time for Comparison Time. Due to slight time difference and continuous operations on data, data inconsistency may occur, reducing the reliability and validity of the comparison results.
For many-to-one synchronization tasks that involve the synchronization of the same table, DDL operations cannot be performed on source databases. Otherwise, all synchronization tasks fail.
Precautions¶
Before creating a synchronization task, read the following notes:
Type | Restrictions |
|---|---|
Database permissions |
|
Synchronization object |
|
Source database |
|
Destination database |
|
Precautions |
|
Procedure¶
On the Data Synchronization Management page, click Create Synchronization Task.
On the Create Synchronization Instance page, specify the task name, description, and the synchronization instance details, and click Next.
Table 3 Task and recipient description¶ Parameter
Description
Region
The region where the synchronization instance is deployed. You can change the region.
Project
The project corresponds to the current region and can be changed.
Task Name
The task name must start with a letter and consist of 4 to 50 characters. It can contain only letters, digits, hyphens (-), and underscores (_).
Description
The description consists of a maximum of 256 characters and cannot contain special characters
!=<>'&"\Table 4 Synchronization instance settings¶ Parameter
Description
Data Flow
Choose Self-built to self-built.
Source DB Engine
Select MySQL.
Destination DB Engine
Select MySQL.
Network Type
The Public network is used as an example. Available options: Public network and VPN or Direct Connect
Instance Type
DRS instance type. The value can be single or primary/standby.
primary/standby: This architecture provides HA, improving the reliability of DRS instances. After the primary and standby instances are created, the DRS creates an active subtask and a standby subtask at the same time. If the task on the active node is abnormal, the DRS automatically starts the task on the standby node to continue the synchronization, improving the reliability of the synchronization task.
Single: The single-node deployment architecture is used, which is cost-effective.
VPC
Select an available VPC.
Synchronization Instance Subnet
Select the subnet where the synchronization instance is located. You can also click View Subnet to go to the network console to view the subnet where the instance resides.
By default, the DRS instance and the destination DB instance are in the same subnet. You need to select the subnet where the DRS instance resides and ensure that there are available IP addresses. To ensure that the synchronization instance is successfully created, only subnets with DHCP enabled are displayed.
Security Group
Select a security group. You can use security group rules to allow or deny access to the instance.
Synchronization Mode
Select Incremental.
Full+Incremental
This synchronization mode allows you to synchronize data in real time. After a full synchronization initializes the destination database, an incremental synchronization parses logs to ensure data consistency between the source and destination databases.
Note
If you select Full+Incremental, data generated during the full synchronization will be continuously synchronized to the destination database, and the source remains accessible.
Incremental
Through log parsing, incremental data generated on the source database is synchronized to the destination database.
During synchronization, the source database continues to provide services for external systems with zero downtime.
AZ
Select the AZ where you want to create the DRS instance. Selecting the one housing the source or destination database can provide better performance.
If Instance Type is set to primary/standby, you can specify Primary AZ and Standby AZ.
Tags
This setting is optional. Adding tags helps you better identify and manage your tasks. Each task can have up to 20 tags.
After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.
Note
If a task fails to be created, DRS retains the task for three days by default. After three days, the task automatically ends.
On the Configure Source and Destination Databases page, wait until the synchronization instance is created. Then, specify source and destination database information and click Test Connection for both the source and destination databases to check whether they have been connected to the synchronization instance. After the connection tests are successful, select the check box before the agreement and click Next.
Table 5 Source database settings¶ Parameter
Description
IP Address or Domain Name
The IP address or domain name of the source database.
Port
The port of the source database. Range: 1 - 65535
Database Username
The username for accessing the source database.
Database Password
The password for the database username.
SSL Connection
SSL encrypts the connections between the source and destination databases. If SSL is enabled, upload the SSL CA root certificate.
Note
The maximum size of a single certificate file that can be uploaded is 500 KB.
If SSL is disabled, your data may be at risk.
Table 6 Destination database settings¶ Parameter
Description
IP Address or Domain Name
The IP address or domain name of the destination database.
Port
The port of the destination database. Range: 1 - 65535
Database Username
The username for accessing the destination database.
Database Password
The password for the database username.
SSL Connection
SSL encrypts the connections between the source and destination databases. If SSL is enabled, upload the SSL CA root certificate.
Note
The maximum size of a single certificate file that can be uploaded is 500 KB.
If the SSL certificate is not used, your data may be at risk.
Note
The username and password of the source and destination databases are encrypted and stored in DRS, and will be cleared after the task is deleted.
On the Set Synchronization Task page, select the synchronization policy, objects, and data format, and click Next.
Table 7 Synchronization mode and object¶ Parameter
Description
Conflict Policy
The conflict policy refers to the conflict handling policy during incremental synchronization. By default, conflicts in the full synchronization phase are ignored. Select any of the following conflict policies:
Ignore
The system will skip the conflicting data and continue the subsequent synchronization process.
Report error
The synchronization task will be stopped and fail.
Overwrite
Conflicting data will be overwritten.
Filter DROP DATABASE
During real-time synchronization, executing DDL operations on the source database may affect the synchronization performance. To reduce the risk of synchronization failure, DRS allows you to filter out DDL operations. Currently, only the delete operations on databases can be filtered by default.
If you select Yes, the database deletion operation performed on the source database is not synchronized during data synchronization.
If you select No, related operations are synchronized to the destination database during data synchronization.
Synchronize
Supports index synchronization. You can determine whether to synchronize indexes based on the service requirements. If you deselect Normal index, DDL statements related to index adding will be filtered out in the incremental phase. If the DDL statements contain other operations, they may also be filtered out.
Start Point
The position where the incremental log was created based on the source log. It allows you to perform resumable data transfer.
For an incremental synchronization task, the start point must be in the standard format. You can run the show master status command in the source database to obtain the start point.
If GTID mode is disabled, the format of the start point is File:Position (for example, mysql-bin.014734:8937).
After the GTID is enabled, the format of the start point is File:Position; Executed_Gtid_Set (for example, mysql-bin.014734:8937;ea352a82-e9a0-11ea-b650-fa163e1e82ed:1-23377228, 8404bb4b-cc96-11ea-ae7f-fa163ead1b99:1-59684135)
Synchronization Object
Select Tables, Databases, or Import object file as required.
Note
To quickly select the desired database objects, you can use the search function.
If there are changes made to the source databases or objects, click in the upper right corner to update the objects to be synchronized.
If an object name contains spaces, the spaces before and after the object name are not displayed. If there are two or more consecutive spaces in the middle of the object name, only one space is displayed.
The name of the selected synchronization object cannot contain spaces.
On the Process Data page, set the filtering rules for data processing.
If you do not need to set a processing rule, select No processing and click Next.
If you need to set data processing rules, configure related filtering rules by referring to Processing Data.
On the Check Task page, check the synchronization task.
If any check fails, review the cause and rectify the fault. After the fault is rectified, click Check Again.
If all check items are successful, click Next.
Note
You can proceed to the next step only when all checks are successful. If there are any items that require confirmation, view and confirm the details first before proceeding to the next step.
On the Confirm Task page, specify Start Time, confirm that the configured information is correct, and click Submit to submit the task.
Table 8 Task startup settings¶ Parameter
Description
Started Time
Set Start Time to Start upon task creation or Start at a specified time based on site requirements.
Note
After a synchronization task is started, the performance of the source and destination databases may be affected. You are advised to start a synchronization task during off-peak hours.
After the task is submitted, you can view and manage it on the Data Synchronization Management page.
You can view the task status. For more information about task status, see Task Statuses.
You can click
in the upper-right corner to view the latest task status.